,transcriber's ,note ,italic text displayed as3 italic ,bold text displayed as3 bold ,,pitman',s ,,technical ,,primer ,,series ,edited by ,r4 ,e4 ,,neale1 ,b4,sc41 ,hons4 7,lond47 ,a4,c4,g4,i41 ,a4,m4,i4,e4,e4 ,,pneumatic ,,conveying ,,pitman',s ,,technical ,,primers ,edited by ,r4 ,e4 ,,neale1 ,b4,sc4 7,hons471 ,a4,c4,g4,i41 ,a4,m4,i4,e4,e4 ,in each book of the series the fundamental principles of some sub-division of engineering technology are treated in a practical manner1 providing the student with a handy survey of the particular branch of technology with which he is concerned4 ,each #bs4 #f;d4 net4 ,,the ,,steam ,,locomotive4 ,by ,e4 ,l4 ,,ahrons1 ,m4,i4,mech4,e4 ,,belts ,,for ,,power ,,transmission4 ,by ,w4 ,g4 ,,dunkley1 ,b4,sc4 ,,water-,,power ,,engineering4 ,by ,f4 ,f4 ,,fergusson1 ,a4,m4,i4,c4,e4 ,,photographic ,,technique4 ,by ,l4 ,j4 ,,hibbert1 ,f4,r4,p4,s4 ,,hydro-,,electric ,,development4 ,by ,j4 ,w4 ,,meares1 ,m4,inst4,c4,e4 ,,the ,,electrification ,,of ,,railways4 ,by ,h4 ,f4 ,,trewman1 ,m4,a4 ,,continuous-,,current ,,armature ,,winding4 ,by ,f4 ,m4 ,,denton4 ,,municipal ,,engineering4 ,by ,h4 ,,percy ,,boulnois1 ,m4,inst4,c4,e4 ,,foundrywork4 ,by ,,ben ,,shaw and ,,james ,,edgar4 ,,patternmaking4 ,by ,,ben ,,shaw and ,,james ,,edgar4 ,,the ,,electric ,,furnace4 ,by ,,frank ,j4 ,,moffett1 ,b4,a41 ,m4,i4,e4,e4 ,,small ,,single-,,phase ,,transformers4 ,by ,e4 ,t4 ,,painton1 ,b4,sc4 ,,pneumatic ,,conveying4 ,by ,e4 ,g4 ,,phillips1 ,m4,i4,e4,e41 ,a4,m4,i4,mech4,e4 ,,boiler ,,inspection ,,and ,,maintenance4 ,by ,r4 ,,clayton4 ,,electricity ,,in ,,steel ,,works4 ,by ,w4 ,,macfarlane1 ,b4,sc4 ,,modern ,,central ,,stations4 ,by ,c4 ,w4 ,,marshall1 ,b4,sc4 ,,steam ,,locomotive ,,construction ,,and ,,maintenance4 ,by ,e4 ,l4 ,,ahrons1 ,m4,i4,mech4,e41 ,m4,i4,loco4,e4 ,,high ,,tension ,,switchgear4 ,by ,h4 ,e4 ,,poole1 ,b4,sc41 ,a4,c4,g4,i4 ,,high ,,tension ,,switchboards4 ,by the ,same ,author4 ,,power ,,factor ,,correction4 ,by ,a4 ,e4 ,,clayton1 ,b4,sc41 ,a4,k4,c4 ,,tool ,,and ,,machine ,,setting4 ,by ,p4 ,,gates4 ,,tidal ,,power4 ,by ,a4 ,,struben1 ,o4,b4,e41 ,a4,m4,i4,c4,e4 ,,sewers ,,and ,,sewerage4 ,by ,h4 ,g4 ,,whyatt1 ,m4,inst4,c4,e4 ,m4,r4,s4,i4 ,,elements ,,of ,,illuminating ,,engineering4 ,by ,a4 ,p4 ,,trotter1 ,m4,inst4,c4,e4 ,,coal-,,cutting ,,machinery4 ,by ,g4 ,e4 ,f4 ,,eagar1 ,m4,inst4,min4,e4 ,,grinding ,,machines ,,and ,,their ,,use4 ,by ,t4 ,r4 ,,shaw1 ,m4,i4,mech4,e4 ,,electro-,,deposition ,,of ,,copper4 ,by ,c4 ,w4 ,,denny1 ,a4,m4,i4,e4,e4 ,,directive ,,wireless ,,telegraphy4 ,by ,l4 ,h4 ,,walter1 ,m4,a4 ,,testing ,,of ,,continuous-,,current ,,machines4 ,by ,c4 ,f4 ,,smith1 ,d4,sc41 ,m4,i4,e4,e4 ,,electrical ,,transmission ,,of ,,energy4 ,by ,w4 ,m4 ,,thornton1 ,d4,sc4 ,,steam ,,engine ,,valves ,,and ,,valve ,,gear4 ,by ,e4 ,l4 ,,ahrons1 ,m4,i4,mech4,e4 ,,mechanical ,,handling ,,of ,,goods4 ,by ,c4 ,h4 ,,woodfield4 ,,industrial ,,and ,,power ,,alcohol4 ,by ,r4 ,c4 ,,farmer1 ,d4,sc4 ,,position ,,and ,,direction ,,finding4 ,by ,l4 ,h4 ,,walter1 ,m4,a41 ,a4,m4,i4,e4,e4 ,,high ,,tension ,,transformers4 ,by ,w4 ,t4 ,,taylor1 ,m4,inst4,c4,e4 ,,london3 ,,sir ,,isaac ,,pitman ,,sons1 ,,ltd4 ,illustration3 ,frontispiece ,,intake ,,end ,,of ,,pneumatic ,,conveyor4 ,adjustable to follow rise and fall of vessel on tidal waters4 ,,pneumatic ,,conveying ,a ,,concise ,,treatment ,,of ,,the ,,principles1 ,,methods ,,and ,,applications ,,of ,,pneumatic ,,conveyance ,,of ,,materials ,,with ,,special ,,reference ,,to ,,the ,,conveying ,,and ,,elevating ,,of ,,heavy ,,solid ,,materials ,,for ,,engineers1 ,,works ,,managers1 ,,and ,,students ,,by ,e4 ,g4 ,,phillips ,m4,i4,e4,e41 ,a4,m4,i4,,mech4,e4 ,illustration3 ,,pitman',s ,,technical ,,primers ,,london ,,sir ,,isaac ,,pitman ,,sons1 ,,ltd4 ,,parker ,,street1 ,,kingsway1 ,w4,c4#b ,,bath1 ,,melbourne1 ,,toronto1 ,,new ,,york #aiba ,,printed ,,by ,,sir ,,isaac ,,pitman ,,sons1 ,,ltd4 ,,bath1 ,,england ,,preface ,pneumatic ,conveying has recently attracted great and widespread interest amongst engineers and others interested in the economical handling of materials4 ,the information hitherto available on the subject has1 however1 been so meagre and so indefinite that the author offers this concise treatment of principles1 methods and applications in order that those who are anxious to avail themselves of this flexible means of transportation may know just how1 and why1 it is worthy of their attention4 ,the high cost of labour1 coupled with the desire to improve the condition of the worker who has had to work in a dust-laden atmosphere of an objectionable1 or even poisonous nature1 will create such a demand for pneumatic conveying plant that present day methods of transportation will be revolutionized in many branches of industry4 ,the author has had three years' experience with one of the first pneumatic plants erected in this country1 for use with coal1 ashes1 and flue dust1 and he has conducted numerous experiments on other materials1 such as sand1 oxide1 potatoes1 various chemicals1 etc41 and has endeavoured to add his quota to the information available for the benefit of other engineers and works managers4 ,experiments proved that with certain materials the discharger was the weak link in the chain1 as wet sticky materials entering at a high velocity 8packed0 tight and would not discharge freely4 ,this led to experiments which1 with the valuable assistance of ,mr4 ,h4 ,b4 ,clarke1 ,a4,m4,i4,e4,e41 resulted in overcoming this difficulty by means which are described fully in ,chapter ,,vi4 ,no attempt has been made to go fully into the questions of domestic vacuum cleaners1 removing dust from manufacturing processes1 etc4 ,the chief aim has been rather to bring into prominence the flexibility and other advantages of moving air as a means of conveying and elevating heavy solid materials which hitherto it has been thought could not be handled in this manner4 ,the author gladly acknowledges the interest and information given by the following firms and individuals ,mr4 ,h4 ,b4 ,clarke1 ,a4,m4,i4,e4,e42 ,messrs4 ,ashwell ,nesbit2 ,boby1 ,ltd42 ,h4 ,j4 ,h4 ,king ,co41 ,ltd42 ,the ,lamson ,store ,service ,co42 and the ,sturtevant ,engineering ,co41 ,ltd4 ,e4 ,g4 ,,phillips4 ,,nottingham4 ,,contents ,,chap4 ,,page ,,preface vii ,i4 ,,systems ,,and ,,applications ,,of ,,pneumatic ,,conveying #a ,,ii4 ,,details ,,of ,,plant--,,pumps1 ,,exhausters ,,and ,,air ,,filters #aj ,,iii4 ,,details ,,of ,,plant 7,,contd47--,,dischargers1 ,,pipe ,,lines ,,and ,,suction ,,nozzles #bh ,,iv4 ,,typical ,,installations ,,for ,,grain #de ,v4 ,,pneumatic ,,coal ,,handling ,,plants #ed ,,vi4 ,,the ,,induction ,,conveyor #fb ,,vii4 ,,steam ,,jet ,,conveyors #gb ,,viii4 ,,miscellaneous ,,applications ,,of ,,pneumatic ,,conveying #hj ,,bibliography #aje ,,index #ajg ,,illustrations ,,fig4 ,,page ,intake end of ,pneumatic ,conveyor1 with rise and fall adjustment ,frontispiece #a4 ,king's pneumatic system4 ,steam-driven air pump #ab #b4 ,sturtevant rotary blower #ag #c4 ,nash 8,hydro-,turbo0 exhauster #ai #d4 ,sturtevant 8,cyclone0 dust separator #ba #e4 ,automatic bag filter #bc #f4 ,mollers' air filter #bd #g4 ,sturtevant wet filter #bf #h4 ,fixed discharger with glass receiver #cj #i4 ,sturtevant patent junction #cc #aj4 ,course taken by material round bend #ce #aa4 ,segment-back bend #ce #ab4 ,lobster bend #ce #ac4 ,king full-way junction valve #cg #ad4 ,suction nozzles for high pressure systems #dj #ae4 ,sturtevant equipment removing wood refuse from double tenoning machine #da #af4 ,sturtevant equipment removing dust from sand papering machines #db #ag1 #ah4 ,ancient and ,modern #df #ai4 ,typical grain-handling plant #dg #bj4 ,floating pneumatic transport plant #di #ba4 ,portable pneumatic plant on railway truck #ej #bb4 ,portable railway plant in operation #eb #bc4 ,pneumatic unloading of coal #ee #bd4 ,discharger for coal conveying plant #eg #be4 ,brady steam jet ash conveyor #ge #bf4 ,typical ,lamson inter-communication carrier #hb #bg4 ,tube central in wholesale drug house #hg #bh4 ,lamson distributing station #hh #bi4 ,stationary turbo-exhauster with dust separator #ia #cj4 ,portable turbo-exhauster #ia #ca4 ,suction cleaning for railway carriage cushions #ic #cb4 ,sturtevant equipment for office cleaning #ic #cc1 #cd4 ,air-lift pumping #ih ,,pneumatic ,,conveying ,,chapter ,i ,,systems ,,and ,,applications ,,of ,,pneumatic ,,conveying ,conveying by mechanical means has existed for many centuries1 and is one of the earliest forms of man's ingenuity towards labour saving as we know it to-day4 ,the pneumatic conveyance of materials from one position to another1 either horizontally or vertically1 is the most recent form of automatic handling of solid substances4 ,genesis and ,applications of ,pneumatic ,conveying4 ,the need of water for human consumption and for irrigation purposes caused the ancient inventor to carry out nearly all his experiments with that substance1 and the first instance we have of anything approaching pneumatic conveying is the well known injector in which steam is passed through one pipe1 placed at right angles to a second pipe1 at such a velocity as to reduce the pressure in the second pipe to below the atmospheric pressure4 ,the excess of atmospheric pressure over the reduced pressure in the second pipe then drives up the latter the material 7in this case water7 in which the end of the pipe is submerged4 ,this invention is about a century old1 if it emanated from the ,marquis ,mammonry d',eclet1 in #ahah1 as is usually believed4 ,the first practical application of this invention to other than liquid materials is supposed to have been in connection with the conveying of cotton in a loose form1 as an improvement upon the manual shifting of large bales4 ,this development was made about #ahfg1 and after this date great progress was made1 principally in connection with the handling of grain1 wheat1 malt1 etc41 and largely owing to the work of an ,american named ,a4 ,k4 ,williams4 ,at the present day it is hardly possible to enumerate all the successful schemes for the pneumatic handling of materials4 ,in addition to installations for the conveyance of materials such as those mentioned above is the pneumatic tube1 for conveying papers1 messages and cash in offices and between shop counter and cash desk1 etc4 ,also1 there is the suction cleaner1 ranging in application from the handling of refuse and dust from saw mills and woodworking machinery to the removal of fine abrasive and poisonous particles in certain manufacturing processes4 ,small suction cleaners are1 of course1 now quite familiar domestic appliances4 ,the sand-blasting machine is really another example of a self contained pneumatic conveyor on a small scale4 ,ashes1 coal1 oranges1 sugar1 chemicals1 spent oxide1 iron ore1 spent tanning bark1 and many other materials are now actually transported1 elevated or conveyed pneumatically1 and it must here be acknowledged that the first really successful plant in this country was due entirely to the initiative and inventive genius of ,mr4 ,frederic ,eliot ,duckham1 late ,chief ,engineer to the ,millwall ,dock ,co41 who in #ahhh commenced experiments in grain-handling by suction4 ,in #ahib he produced a very successful floating plant for unloading ships into land silos1 and this installation was the prototype of many similar plants which were placed in commission all over the world4 ,many improvements have been carried out and numerous patents issued for pneumatic handling apparatus1 but the original scheme as designed by ,mr4 ,duckham has never been departed from seriously4 ,fundamental ,principles and ,components4 ,the pneumatic conveyance of materials along pipes is most easily understood when the equipment is considered as a pump producing a high velocity stream of air in which the material to be transported is floating1 and with which it is carried through the pipe system4 ,it is necessary fully to understand this1 as it is otherwise difficult to realize how it can be possible to lift solids at the rate of #ajj tons or more per hour1 several hundred feet up a pipe in which the vacuum does not exceed about #g inches mercury column 7say1 #aa lb4 per sq4 in4 absolute74 ,a modern pneumatic conveying plant of the suction type comprises3 7#a7 ,an exhauster1 or an air pump1 of either the reciprocating or the rotary type4 7#b7 ,a suction nozzle4 7#c7 ,a discharger1 whereby the material is extracted from the pipe line at the desired position1 without 8breaking0 or losing the vacuum4 7#d7 ,one or more appliances for filtering the air and extracting any foreign material which may have been carried over from the discharger and which would damage the cylinder walls of the exhauster if allowed to enter the plant4 ,it is necessary here to mention that all pneumatic conveying is not done by exhausting1 but frequently by the use of pressure1 that is1 that the air is not sucked along the transport line but is actually blown in under pressure by fans1 air compressors1 or rotary blowers1 according to the circumstances4 ,the suction system is preferable when it is required to convey materials from several outlying points to one central storage bunker or area4 ,on the other hand1 the pressure system is less expensive in first cost1 when it is required to transport from one central point to numerous outlying plants in the area to be served4 ,a combination of the suction and pressure systems is now being developed for the handling of materials in cases where neither the 8suction0 nor the 8blowing0 scheme alone can be said to be successful4 ,this combined system is known as the induction system and is discussed in ,chapter ,,vi4 ,advantages over ,mechanical ,conveyors4 ,the reasons why pneumatic methods for elevating and conveying are now receiving such attention are to be found in the advantages of pneumatic over mechanical conveying4 ,these may be summarized as follows3 ,economy in labour2 flexibility of plant both in design and operation2 elimination of dust and its harmful effects on the employees2 and in many instances the recovery of dust which is valuable and which would otherwise represent a serious financial loss4 ,wear and tear on moving parts is reduced to a minimum4 ,all obstacles such as buildings1 roads1 rivers1 railways1 etc41 can be overcome easily since the conveyor is 8only a pipe40 ,should circumstances not permit of a straight single run for such appliances as bucket elevators1 it is usually necessary to bag and cart the material from one position to another1 but this is avoided by pneumatic elevating and conveying1 because the pipe can be carried up or down1 round corners1 over or under roads1 etc4 ,hundreds of instances still exist in which loose material in barges is shovelled into bags1 which are lifted by an ordinary friction hoist into a building over the quay-side4 ,the sacks are wheeled by manual labour into the building1 and emptied into hoppers or silos1 the empty bags being lowered again for a further cycle of operations4 ,this costly multiple handling may be obviated by the erection of a small pipe line which will automatically feed itself at one end1 and discharge evenly and continuously into the receptacle provided4 ,the whole of the 8moving parts0 may be situated in one position1 which enables them to be carefully inspected1 oiled and kept in repair1 etc4 ,cranes1 hoists1 telphers1 and belt conveyors all have their special spheres of usefulness1 but no other plant can claim all the advantages of the pneumatic system as outlined above4 ,pneumatic ,conveying ,systems4 ,as mentioned above there are three main systems of pneumatic conveying1 viz4-- 7#a7 ,conveying by air above atmospheric pressure4 7#b7 ,conveying by air below atmospheric pressure4 7#c7 ,conveying by air above and below atmospheric pressure1 by a combination of 7#a7 and 7#b71 known as the induction system4 ,although these are the main headings under which the subject may be considered1 they must be sub-divided further as follows-- 7#a7 ,conveying above ,atmospheric ,pressure4 7a7 ,low pressure systems using single-stage centrifugal fans1 and suitable for conveying such materials as wool1 cotton1 bark1 chopped straw1 paper clippings1 sawdust1 shavings1 jute1 and fibrous materials of many kinds4 7b7 ,high pressure systems using multi-stage fans and blowers of the rotary type or positive design1 and suitable for conveying materials of a denser nature such as dry sand1 sugar1 etc41 also for pneumatic despatch tubes4 7#b7 ,air ,suction ,systems4 7a7 ,large pipe systems using ordinary steel plate centrifugal fans1 and applied to handling the waste products and injurious dust in many industries1 such materials being sawdust and shavings from woodworking machinery2 emery dust from grinding wheels2 dust and lint from polishing mops2 leather dust from heel and sole scouring plants2 starch dust in confectionery works2 colour dust in works manufacturing pigments2 and bronze dust in printing works4 ,many other examples will no doubt occur to the reader4 7b7 ,small pipe systems using multi-stage centrifugal fans or rotary blowers4 ,under this section the most important plants are undoubtedly those for domestic vacuum cleaning4 ,large stationary plants for this purpose are installed in many hotels1 offices1 buildings1 workshops1 theatres1 large private houses1 etc4 7c7 ,heavy commercial systems in which the fan is replaced by a reciprocating exhauster1 producing currents of air suitable for conveying such materials as coal1 ashes1 sugar1 leather tanning bark1 ores1 granite chippings1 wood blocks1 oranges1 etc41 which it would be impossible1 or undesirable1 to pass through a fan4 7#c7 ,induction ,system4 ,a compressed air injector is used to produce a partial vacuum on the suction or inlet end of the pipe system1 and to produce a pressure above atmospheric at the delivery end1 thus avoiding the necessity for a discharger4 ,this system1 which is suitable for use with heavy sticky materials--such as hot sugar1 saturated sand1 finely ground heavy ores1 spent oxide as used in gas works1 etc4--is now being developed so as to make possible pneumatic conveyance of all manner of materials which are unsuitable for passing through the discharger1 or air lock1 of a suction system4 ,factors influencing ,design4 ,in the strict sense of the term1 8pneumatic conveying0 really implies the conveyance of a quantity of material from one point to another1 using air as the conveying agent4 ,as will be seen from the above1 the subject also embraces the removal of comparatively light dust produced in many industrial processes4 ,although the same name is implied in both cases1 the methods to be adopted vary1 and each case must be considered on its own merits4 ,with regard to a conveying plant proper1 the points for consideration in the initial stages are as follows-- 7#a7 ,the nature of the material to be handled and the quantity required in a given time4 7#b7 ,the size of the largest and smallest pieces of materials and the density of the material4 7#c7 ,the distance over which the material is to be conveyed4 7#d7 ,the difference in level between the point at which the material is fed into the system1 and the point where it is delivered4 7#e7 ,the method and regularity of feeding the material into the system4 7#f7 ,the means to be adopted for separating the material from the conveying air at the desired point of delivery4 ,there is a very important distinction between plants in which the material passes through the fan or blower and those in which the conveying is carried out entirely under suction4 ,the latter system has many advantages1 but it carries with it the necessity of providing automatic delivery of the material without seriously impairing the suction4 ,in order to accomplish this1 some form of 8air lock0 is required1 and a necessary feature of this is a device with close-fitting surfaces or more or less air-tight valves4 ,the simpler plan is undoubtedly to pass the material through the fan1 as there is then no question of breaking the suction in order to get the material out of the system4 ,it is common practice to convey for long distances such materials as wood chippings and sawdust1 cotton1 jute1 wool1 esparto grass1 paper chippings and many other materials4 ,in all cases1 however1 the designer is confronted with the problem of separating the material from the air1 and in many instances to do this satisfactorily is more difficult than the actual conveying2 especially is this so with certain sticky materials or materials which will readily 8pack0 or build up when entering any mechanical discharger at the high velocity necessary in the suction system4 ,,chapter ,,ii ,,details ,,of ,,plant ,,pumps1 ,,exhausters ,,and ,,air ,,filters ,a pneumatic conveying plant of practically any type comprises the following five main components3 7#a7 ,a pump or exhauster to create a partial vacuum in the pipe line and so induce a high velocity air current in which the material will be conveyed4 7#b7 ,an air filter in which any light dust carried over beyond the receiver is trapped1 to prevent its entering the exhauster where it would quickly damage the piston rings and cylinder walls of reciprocating pumps4 7#c7 ,a main receiver or discharger1 and occasionally one or more subsidiary receivers1 in which the conveyed material is extracted from the system and discharged into the receptacle or on to a dump as required4 7#d7 ,the pipe line1 junctions1 etc41 to connect the point of supply with the desired point of delivery4 7#e7 ,the suction nozzle through which the material enters the system1 together with the 8free air0 which is to act as the conveying medium4 ,pumps and ,exhausters4 ,the type of apparatus used for creating the flow of air varies according to the ideas of the numerous makers of the plants4 ,it must be remembered that for a pump working under the conditions required for pneumatic plants it is not a high vacuum that is required2 the most important function is to handle very large quantities of air at a comparatively low vacuum4 ,the most efficient type of plant for dealing with large quantities of air is certainly the reciprocating pump1 although several makers are now devoting a lot of attention to the multi-stage turbine type of blower1 or exhauster4 ,the probability is that this type may shortly be as efficient as the reciprocating pump1 and if so it is almost sure to be used extensively1 as it has distinct advantages in other directions compared with the cylinder and piston type4 ,this remark has special reference to the high pressure system for conveying sand1 coal1 sugar1 etc41 and does not apply to the 8small pipe system0 detailed later4 ,in dealing with ashes1 flue dust1 crushed iron ore1 and similar abrasive materials1 it is essential that the air passing through the pump should be filtered thoroughly so that no dust should enter the cylinders and cut the walls and piston rings4 ,the turbo-blower1 having no rubbing surfaces1 would suffer little or no damage from a small percentage of dust1 hence the filtering equipment might be less elaborate and less costly4 ,no lubrication would be necessary in the rotary pump 7except1 of course1 at the bearings71 hence no difficulties would arise owing to oil acting as a dust trap1 as is sometimes the case in reciprocating pumps with defective air filters4 ,illustration3 ,,fig4 #a4--,,king',s ,,pneumatic ,,system4 ,,steam-,,driven ,,air ,,pump4 ,,key ,,to ,,fig4 #a4 ,a cylinder of double-acting steam engine driving the whole machine4 ,b semi-rotary valve controlling admission of steam to ,a4 ,c steam gland for piston rod connecting ,l and ,m4 ,d ,corliss-type air-inlet valves with semi-rotary motion4 ,these valves are alternately open to the pipe system and the air cylinder ,e when the piston is travelling in one direction1 and are closed 7both to cylinder and air pipe7 directly the piston reverses its travel4 ,e cylinder of double-acting air pump4 ,f valve gear for operating the ,corliss valves1 ,d this gear is driven by a pin out of centre on the flywheel4 ,g cross-head and slide4 ,h big-end bearing and crank4 ,i flywheels on the main shaft4 ,j eccentric and strap operating the valve1 ,b1 on the steam cylinder4 ,k leather air-outlet valves held on two sides by metal strips4 ,the leathers are opened by air pressure on the exhaust stroke1 and are drawn on to their gridiron seatings during the inlet stroke4 ,l steam piston4 ,m air piston4 ,note4--,if preferred1 the steam cylinder may be omitted and the air pump driven by electric motor direct-coupled or geared to the main shaft4 ,belt drive on to the flywheels or special pulley is possible but not advisable4 ,typical ,reciprocating ,pump4 ,fig4 #a shows the general construction of a vertical steam-driven air pump such as is generally used in present day plants4 ,the pump shown has a stroke of #ad ins41 with an air-cylinder diameter of #bh ins4 ,the machine is a dry air pump1 and is fitted with ,corliss inlet valves and special leather exhaust valves3 it is fitted with ring-oiling bearings and automatic continuous lubrication1 and under test it shows a mechanical efficiency of #gh per cent4 from power input to air horse-power delivered4 ,such a pump is suitable for a plant handling #bj to #be tons per hour and1 if preferred1 the pump may be driven through gearing from an electric motor on the same bed-plate4 ,rotary ,blowers and ,exhausters4 ,the turbine blower and exhauster depend entirely upon centrifugal force for their power to compress or exhaust air or gas1 etc4 ,the use of centrifugal force makes this type of machine resemble the centrifugal water-pump1 but radical differences in design have to be introduced1 seeing that water is not compressible1 whereas air is capable of compression1 and alterations are also necessary1 due to the great difference in specific gravity of the two substances4 ,owing to the very low specific gravity of air1 the machine must run at a much higher speed than would be required with water to develop a given pressure4 ,the high speed of the steam turbine has given impetus to the design of large exhausters on the turbine principle4 ,it will be recognized that1 when air is made to flow steadily along a conduit or pipe of gradually diminishing cross-sectional area1 the velocity of the air must increase correspondingly1 in order that the constant quantity may flow through the smaller section of pipe4 ,increasing the velocity will diminish the pressure due to the greater kinetic energy to increase the velocity4 ,the converse is the result of passing air at constant pressure through a channel gradually increasing from a smaller to a larger area1 the velocity being then reduced and the pressure increased4 ,now if a number of impellers be mounted turbine fashion on a high speed shaft1 and the casing be so designed that the area between stages gradually increases1 the air will enter the first stage and will be caught up by the impeller and accelerated until it leaves ,no4 #a impeller at a higher pressure and velocity4 ,leaving the casing through a diffuser which gradually increases in area the velocity is transformed into pressure in the diffuser4 ,the air therefore travels to the second stage with its initial pressure plus the pressure due to the conversion of velocity in the first diffuser4 ,this process may be repeated stage by stage until almost any desired pressure is obtained4 ,as there are no rubbing surfaces in this type of machine it is particularly suitable for the work under consideration1 and when developed for efficient running in small sizes it will be very effective in 8booming0 pneumatic conveying4 ,sturtevant ,blower or ,exhauster4 ,the ,sturtevant ,engineering ,co41 ,ltd41 has developed a special rotary blower or exhauster suitable for use with pneumatic conveying installations and1 although this machine has not a water-seal for surfaces under pressure 7as in the ,nash ,hydro-,turbo described below71 it has a number of distinctive points1 and the discharge of the air1 or the intake of air1 as the case may be1 occurs at a more nearly constant pressure and with smaller pulsations than with any other rotary blower known to the writer4 ,the sectional diagrams 7,fig4 #b7 show the four successive stages in the movement of the rotors4 ,in position 7#a71 chamber ,d has been filled with air1 while chamber ,e is discharging air against pressure in the delivery pipe4 ,in position 7#b71 chamber ,d is cut off from the inlet1 and the air in it is being carried round4 ,blade ,c has entered pocket ,z1 which is filled with air under pressure2 this air1 however1 in turn is released into pocket ,y through leakage passage ,o4 ,continued rotation carries the rotors ,a1 ,b and ,c to position 7#c71 and the remaining pressure in ,z is now being transferred to ,x by leakage passage ,n4 ,as the fourth position is reached1 chamber ,f is filling and pocket ,y is discharging its air4 ,when further rotation brings impeller blade ,b into the discharge passage1 the air in space ,d will be delivered from the blower4 ,after leaving position 7#d71 the rotors again reach a position similar to that shown at 7#a71 and the cycle is then repeated4 ,illustration3 ,,fig4 #b4--,,sturtevant ,,rotary ,,blower4 ,a study of the above will convince the reader that this blower is ingenious and very suitable for the class of work under investigation4 ,for certain conditions the ,roots blower and the multifarious types of drum pumps or blowers can be used1 seeing that it is quantity rather than pressure that is required1 but it is essential that the most reliable and efficient exhauster should be installed in accordance with the conditions for each installation1 bearing in mind always the questions of dust1 speed1 lubrication1 etc4 ,nash ,hydro-,turbine4 ,an entirely new type of rotary exhauster was recently illustrated in the ,chemical ,age1 and a study of ,fig4 #c will show the principle of this pump4 ,this pump was built just before the war by ,messrs4 ,siemens-,schuckert1 and similar pumps are now being introduced by the ,nash ,engineering ,co4 7,u4,s4,a471 and are known as the ,nash ,hydro-,turbine4 ,this exhauster has a cylindroid external casing1 inside which is a shaft carried on the two end brackets and having mounted upon it a crude type of water-wheel4 ,it should be noted here that this arrangement has the effect of bringing the edges of the wheel into a position of eccentricity in relation to the inside of the external casing4 ,the wheel shaft is connected directly to a high speed electric motor1 and when the pump is running the water which is fed into the casing is thrown by centrifugal force to the periphery of the casing and thus forms certain air pockets into which the air of the system is drawn4 ,the air is now locked between the hub of the wheel and the sheet of water surrounding the outside of the wheel4 ,as the wheel revolves1 the air in each pocket in turn is compressed into a smaller capacity and eventually1 when it arrives opposite the outlet point1 it at once escapes into the atmosphere due to its additional pressure4 ,illustration3 ,,fig4 #c4--,,nash 8,,hydro-,,turbo0 ,,exhauster4 ,tracing the wheel right round we then find that another pocket is formed into which the air is again sucked1 and so the cycle of operations continues1 two compressions and extractions occurring per revolution of the spindle4 ,for many materials such a pump has the great advantage that the water acts as a wet filter and traps all the dust in suspension which can be washed out in the form of sludge4 ,where the dust is valuable this characteristic would be a disadvantage1 but it is very useful in plants dealing with corrosive and abrasive materials4 ,lubrication4 ,the lubrication of cylinders in the reciprocating type of pump has been mentioned in connection with the necessity for taking special care in filtering all dust from the air pulled over from the discharger4 ,ordinary oil makes a sticky surface to which any dust adheres readily1 and the two combined make an abrasive mixture which will quickly score and damage the walls of the cylinders4 ,one firm1 at least1 has gone a long way towards removing this trouble by inserting pieces of solid graphite into the piston3 this provides dry lubrication and produces a very smooth surface on which dust finds great difficulty in obtaining a 8footing40 ,the use of 8,aquadag0 is also fairly successful3 this lubricant consists of deflocculated graphite in such very fine particles that they will remain in suspension in water even without mechanical agitation4 8,aquadag0 is fed into the cylinders in the same way as oil and deposits its graphite in the pores of the cylinder walls1 whilst the water is atomized and blown out with the air4 ,the turbine exhauster solves the problem by eliminating the necessity for internal lubrication1 and the perfect filtering of the air is then not so important4 ,air ,filters4 ,it is impossible to deal with practically any granular material without carrying over more or less dust beyond the discharger1 and to obviate the damage and inconvenience which would result from allowing this to enter the exhauster1 an air filter is fitted between the discharger and the pump4 ,many types of air filters have been introduced1 and representative examples are described below4 ,illustration3 ,,fig4 #d4--,,sturtevant 8,,cyclone0 ,,dust ,,separator4 8,cyclone0 ,separators4 ,for such materials as grain1 malt1 etc41 the ordinary type of cyclone separator is frequently mounted inside the receiver4 ,this separator consists of an inverted cone3 the dust laden air enters at the top and the heavy material circulates inside1 and gradually falls to the bottom from which it is discharged into suitable containers 7see ,fig4 #d74 ,the cyclone is an excellent separator1 and has the advantage that it is self-cleaning1 and offers little or no resistance to the flow of air1 but so large a cone would be required to separate very fine dusts that it frequently becomes impossible to use this type of plant4 ,bag ,filters4 ,an alternative type of air filter is the ordinary bag filter1 which consists of a number of closely woven fabric 8stockings0 in a cast iron container4 ,the air is led into the casing so that it passes down through the inside of the tubes1 through the fabric1 where it deposits the greater proportion of the dust1 and then out to the atmosphere4 ,naturally1 after working a certain period1 the fabric becomes choked with deposited dust1 and it is then necessary to dislodge the dust by shaking the 8stocking0 somewhat violently4 ,this is usually carried out by a mechanically operated vibrating apparatus1 but cleaning is done more effectively and time is saved if the air is shut off from the filter while the dust is dislodged4 ,this is done most conveniently by having two similar filters installed1 working in parallel2 then1 when cleaning becomes necessary1 all the air is passed through each filter in turn1 whilst the other is cleaned4 ,the bags or tubes hang vertically in the casing1 and as the air is brought in at the top and discharged in a downward vertical direction1 it naturally discharges the heavier material straight into the bottom of the casing1 owing to the inertia of the heavy particles and the high velocity of the incoming air4 ,illustration3 ,,fig4 #e4--;,,automatic ,,bag ,,filter4 ,showing filter bags through the open access doors ,fig4 #e illustrates a ,sturtevant automatic bag filter4 ,in this case the air is brought in at the bottom4 ,the cleaning of the bags is effected automatically4 ,at frequent intervals and in rotation1 each section of bags is cut off automatically from the supply of dust-laden air by closing the outlet valve of that section4 ,at the same time1 that section is opened to the atmosphere at the top1 causing a reverse current of air downwards4 ,the bags are then agitated automatically and the dust adhering to the fabric drops1 and is blown into the discharge hopper below4 ,the opening and closing of the valves is accomplished by a simple mechanism driven by the pulley shown at the top of the illustration4 ,where the amount of dust to be handled is large and continuous it can be extracted from the hopper by a worm or screw conveyor1 or1 as in some other patterns1 by a rotary valve placed in the bottom of the hopper4 ,illustration3 ,,fig4 #f4--,,mollers' ,,air ,,filter4 ,mollers' ,air ,filter4 ,this apparatus consists of separate fabric pockets mounted on a frame4 ,the pockets are rectangular and taper towards the top4 ,referring to ,fig4 #f1 ,a is the frame on which the fabric is stretched1 and ,b is the fabric pocket4 ,as many of these units as necessary are mounted side by side in an adjustable frame1 each unit having fixing and tension bolts4 ,this arrangement permits a filter of any desired capacity to be built up quickly1 and facilitates repairs and cleaning of filter bags4 ,wet ,filters4 ,the type of filtering apparatus used for dealing with poisonous material1 emery dust from grinding wheels1 sand from sand-blasting apparatus1 etc41 is usually of the wet type1 of which ,fig4 #g is a good example4 ,this apparatus consists of a tank having a wire shelf on which a layer of coke is supported4 ,the tank is partially filled with water1 the level of which is regulated by an overflow4 ,the dust-laden air impinges on the surface of the water1 and the major portion of the dust is trapped by being driven actually into the water4 ,the dust particles too light to be brought into contact with the water are compelled to pass through the coke screen and are there arrested4 ,if necessary1 the scheme can be made to deal with finer dusts by having the coke constantly sprayed with water4 ,the dust is reclaimed from the tank in the form of sludge or mud through the door or valve provided for that purpose4 ,illustration3 ,,fig4 #g4--,,sturtevant ,,wet ,,filter4 ,another type of air filter which might be developed in connection with the pneumatic handling of material consists of a very slowly revolving drum or cylinder1 which is fitted with a continuous corrugated tape running spirally from the centre to the extreme edge of the casing4 ,the space between the corrugated sheets is very small1 and as a stream of water is continually running over and around the divisions1 the air passing through the very tortuous path provided is bound to come into contact with these wet surfaces and give up its dust or other contamination1 which is washed off when it arrives at the bottom of the cylinder4 ,naturally1 this or any other wet filter would not be used where the recovery of dust in dry form was desired4 ,another form of wet filter consists of a chamber of suitable proportions 7according to the amount of air to be cleansed71 fitted with racks in which are placed strips of glass at an angle of #de to the flow of air1 and at #ij to one another4 ,the glass strips have a serrated or prismatic face1 and the air carries the dust forward into the angles of the glass4 ,a very fine water spray keeps the glass moist and eventually trickles down to the drain channels1 washing the glass in its course4 ,the development of apparatus for air-washing has received considerable attention during recent years1 owing to the necessity of having pure1 dust-free air for ventilating turbo-generators1 etc41 and no difficulty should present itself in obtaining satisfactory results for pneumatic conveying plants1 except in cases when the collection and retention of dust is required4 ,in these cases the bag or fabric sheet filter is the only type available4 ,,chapter ,,iii ,,details ,,of ,,plant--7,contd47 ,,dischargers1 ,,pipe ,,lines ,,and ,,suction ,,nozzles ,dischargers4 ,the advocates of 8blowing0 material1 instead of 8sucking0 it through the pipe1 often lay great stress on the alleged difficulties of extracting the material from the system without allowing air leakage4 ,this1 however1 has been overcome successfully by several designers and is not the serious difficulty so frequently suggested1 providing that the material is suitable for this means of treatment4 ,the only exception to this is1 when the high velocity at which the material enters the discharger--say1 #de to #ej ft4 per sec4--causes it to pack or bind so that it will not fall by gravity into the rotary valves and then out into the storage bins4 ,the function of the discharger is to cause the incoming material to lose its velocity and to fall into a compartment which can eventually be discharged after it has been moved from the low pressure to which the chamber itself is subjected4 ,this is best accomplished by the use of a rotary valve1 somewhat similar to a paddle-wheel1 which is revolved slowly but continuously4 ,this wheel can be placed either vertically or horizontally at the bottom of the receiving chamber2 the material enters the large chamber above1 loses its velocity1 drops by gravity1 is caught in the box formed by the revolving paddle-wheel1 and gradually is carried forward out of the chamber1 eventually passing over an aperture through which it again gravitates to the bunker1 silo1 or other container4 ,probably the horizontal type of rotary valve is preferable because1 owing to the increased surface exposed to the vacuum1 the 8suction0 effect assists in holding the valve up to its seat4 ,when dealing with such materials as malt and grain1 it is an advantage to be able to inspect the material entering the receiver1 and at least one maker secures this advantage by constructing the chamber of a glass cylinder to which are bolted cast iron top and bottom pieces carrying the necessary pipe connections and discharge valves4 ,fig4 #h illustrates this construction and also shows fairly clearly the method of driving or revolving the discharge valves4 ,the top flange of the valve has a worm wheel tooth cut around its periphery and the actuating worm engages in this wheel1 thereby obtaining a large reduction in speed4 ,in other words1 the worm can be driven by a light1 high speed belt and pulley1 and still revolve the valve at a very low speed2 such gearing is smooth1 silent running1 and altogether admirable for such a purpose as the one under consideration4 ,illustration3 ,,fig4 #h4--;,,fixed ,,discharger ,,with ,,glass ,,receiver4 ,a very common form of separator1 which is used almost invariably on plants dealing with wood shavings1 sawdust and similar materials1 is known as the cyclone or centrifugal separator4 ,this is usually constructed with a sheet steel body with the inlet for the dust-laden air at the top1 and so arranged that the air enters tangentially4 ,inside there is a smaller cylinder of sheet steel forming an air outlet1 and the laden air sweeps round the annular space between the body and the inner cylinder4 ,this results in a whirling action and the material entrained in the air is projected by centrifugal force against the side of the separator body4 ,in some instances an internal ledge1 or plate of 8corkscrew0 form1 leads the material downwards towards the outlet at the bottom of the separator4 ,in the case of some of the denser materials which can be conveyed by air1 it is sufficient to connect the discharge pipe to an open bin or chamber1 the material in such cases being heavy enough to separate itself by the action of gravity4 ,mr4 ,gordon ,s4 ,layton1 describing dischargers in his paper1 before the ,engineering ,group of the ,society of ,chemical ,industry 7,birmingham1 ,april1 #aibj71 stated-- 8,there are two types of dischargers in use3 ,the first consists of a large steel box divided into two compartments4 ,this box is arranged to oscillate about a horizontal axis1 so that each compartment alternately is brought under the lower opening of the receiver vessel4 8,the other type of discharger consists of a bucket wheel rotating continuously inside a closely fitting casing4 ,the material which is being conveyed falls into the pockets of the bucket wheel when these are on the top of their revolution1 and is passed out through an opening in the lower side of the casing4 8,it will be obvious that the working of both types is liable to be interrupted by the jamming of a foreign body 7such as a piece of wood or a bolt7 in the working parts2 in each case1 special mechanism for driving the discharger has been devised1 to avoid the interruption resulting from such blocking1 and to enable the discharger to keep on working continuously40 ,the rotary type of discharger is preferable to the tipping box type1 for the following reasons3 because the rotary discharger is more easily kept air-tight1 works without vibration1 and gives a practically continuous stream1 whereas the discharge from the tipping box occurs as large isolated masses of material4 ,it is impossible to give specific details concerning the discharger because1 in all cases1 the conditions under which the plant has to work affect the whole design4 ,for instance1 where the working is only intermittent1 e4g4 the removal of ashes from a boiler-house1 the discharger can be eliminated1 provided that the ash bunker is large enough to hold the quantity of ashes to be dealt with at each operation4 ,in such a case1 the ash container would be capable of being exhausted1 and the material entering as before would simply drop by gravity into the container and remain there until the pump was shut down2 it would then be allowed to gravitate into the truck or other conveyance for disposing of the ashes4 ,hand-holes for cleaning1 and easy access to the interior are essential in the design of a discharger1 especially if the material to be handled is liable to 8pack0 when entering at a high velocity4 ,pipe ,lines4 ,one of the most important points in the designing of a pneumatic conveying system is the correct lay-out of the pipe line4 ,illustration3 ,,fig4 #i4--,,sturtevant ,,patent ,,junction4 ,a fatal mistake often made in low pressure and exhausting systems is that the numerous branch pipes are added to or altered after the makers have left the original installation4 ,almost invariably1 branches thus added are made to approach the main trunk at too great an angle1 with the result that eddies and whirlpools are created within the pipe1 seriously reducing the output of the main trunk4 ,so essential is it that this junction should be correct and that the two streams should run as nearly parallel as possible1 that the ,sturtevant ,engineering ,co4 has patented a special junction 7,fig4 #i7 to bring together the two streams of air in the main and the branch pipe practically parallel1 as shown4 ,bends4 ,in connection with high pressure systems1 the following points are of great importance4 ,all vertical and horizontal straight lengths may be of a light section constructed in steel4 ,bends should be avoided whenever possible1 and those which are inevitable should be made in hard cast iron1 with every possible provision for easy replacement of wearing parts4 ,the wear takes place at the point of actual contact which1 in elbows1 is practically confined to one place only4 ,the material rushes to the end1 strikes the bend1 and--suddenly changing its direction of travel--whirls off down the next straight length4 ,the impact and the resulting wear on the pipe1 as well as the breaking of the material conveyed1 are naturally much greater in elbows than in easy bends1 but if the breaking of the material is not detrimental1 elbows should be employed1 as they are less costly and can be replaced more quickly and easily4 ,certain raw materials--such as salt1 soda1 lime and various chemicals--which have to be ground before use1 may be prepared to a considerable extent for this operation by the use of elbows4 ,on the other hand1 easy bends should be employed for material which it is desired to convey without damage1 e4g4 malt1 coal1 and granular substances1 which are finally required in granular form and not as powder4 ,the wear in bends is only on the external radius of the bend1 and then is inclined to be localized at certain points rather than distributed over the full sweep of the bend 7see ,fig4 #aj72 this being so1 it is often desirable so to construct the bends that the back is in segments which can be renewed easily 7see ,fig4 #aa74 ,alternatively1 the bend may be constructed on the 8lobster0 principle 7,fig4 #ab71 only the worn sections being replaced when overhauling4 ,it is not necessary always to take a bend at an angle of #ij1 and if the small short angle sections are interchangeable1 then almost any angle can be constructed by building up with the necessary number of sections4 ,illustration3 ,,fig4 #aj4--;,,course ,,taken ,,by ,,material ,,round ,,bend4 ,illustration3 ,,fig4 #aa4--,,segment-,,back ,,bend4 ,illustration3 ,,fig4 #ab4--,,lobster ,,bend4 ,with regard to the straight lengths of pipe1 it is necessary to ensure a smooth internal bore1 especially at the joints4 ,it is therefore desirable that the joints should be self-aligning as1 if this is not the case1 eddies will be formed which will cause the material to deviate from the centre of the pipe1 striking the side at one or more definite points where holes will eventually be worn through the pipe4 ,in vertical pipes the evidence of wear is negligible1 in fact the conveyed material presumably does not touch the pipe at all1 but travels up the centre of it as a core4 ,capacity of ,pipes4 ,the velocity of the air passing up the pipe should be from #dj to #ej ft4 per sec41 equivalent to about #ce miles per hour4 ,the conveying capacity of an efficient pipe line is approximately #ae per cent4 of the total capacity3 in other words1 if the total cross-sectional area of the pipe be taken as #ajj1 the effective cross-sectional area as regards conveying is #ae4 ,flexible ,connections4 ,the flexible connections attached to the permanent pipes may be ordinary tubing1 as made by the ,flexible ,metallic ,co4 ,phosphor bronze and other metals have been tried1 but the extra cost is not justified4 ,a loose screw collar connection makes possible easy fixing1 and permits the flexible connection to be removed easily to prevent damage when not in use4 ,rubber tubing1 reinforced with steel wires1 would be best where it is important that the material conveyed should not be damaged1 but the wear on such tubing is so rapid that the extra cost is not recovered by the saving in damage to ordinary materials4 ,the length of the flexible pipe should be such that the movement over the greatest area to be covered does not put too great a strain on the bending properties of the tubing4 ,on the other hand1 unnecessary increase in the length of the flexible pipe merely increases the cost of one of the shortest lived portions of the plant1 the 8scrap value0 of which is almost negligible4 ,illustration3 ,showing ,three ,positions of the ,valve4 ,,fig4 #ac4--,,king ,,full-,,way ,,junction ,,valve4 ,valves1 etc4 ,for use where branches are inserted in the main pipe line for convenience in either lifting over1 or discharging over1 a large area1 special appliances have been designed and these should be used1 as they do not create eddies or increase the pipe friction appreciably1 or reduce the carrying capacity of the pipe line4 ,the ,king patent full-way junction valve is an excellent example1 and is shown in ,fig4 #ac1 from which it will be seen that a full bore circuit can be completed in any of three directions4 ,this valve has no corners where the material can collect1 hence the pipes are sucked perfectly clean the moment the feed is shut off4 ,another convenient fitting of this description is the ,boby patent pipe switch4 ,this device is similar to a switch as used on a railway track1 and by its use three separate side positions may be connected with one part on the main transport line4 ,when the switch is thrown over so as to connect to any one particular branch1 all other branches are disconnected4 ,telescopic ,pipes4 ,when the unloading of ships is carried out by 8suction0 it is necessary to make provision for lengthening or shortening the vertical suction pipe1 or pipes 7see ,frontispiece71 because the ship will rise as relieved of its cargo1 and the suction nozzle will simultaneously move towards the bottom of the hold as the cargo is discharged4 ,a still greater difficulty is encountered in tidal rivers1 where the rise and fall may be many feet and must be allowed for continuously4 ,this is best done by the introduction of telescopic pipes in the vertical downright pipes4 ,these must be so constructed that while it is fairly easy to increase or decrease their length1 the pipes must remain air-tight at the joints and connections4 ,where the rise and fall is small the difference in level may be compensated by a ball and socket joint1 and a counter balance on the jib arm1 but this method has its limitations4 ,pipes for ,high ,pressure ,systems4 ,coming now to the 8small pipe10 high pressure systems as used for vacuum cleaning plants1 the pipe lines must be designed and installed carefully and on a liberal basis4 ,it is mistaken policy to attempt to economize by using a smaller main on branch pipes4 ,small diameter pipes cause excessive losses by friction1 and naturally are less efficient as regards power consumption4 ,the frictional losses in a system of this description vary directly as the length of the pipe1 and inversely as the fifth power of the diameter4 ,large pipes are therefore very desirable1 not only because of their greater carrying capacity--which is very desirable--but also because such things as matches1 hairpins1 etc41 are picked up every day by an installation as fitted in hotels1 restaurants and theatres4 ,such material quickly clogs small pipes and causes endless trouble and delay4 ,the flexible hose should be as short as is consistent with ease of working1 because the frictional losses in this class of tubing are very great4 ,it would be preferable to increase the number of wall plugs1 rather than have to use very long lengths of flexible hose4 ,illustration3 ,,fig4 #ad4--,,suction ,,nozzles ,,for ,,high ,,pressure ,,systems4 ,suction ,nozzles4 ,probably more patents have been taken out on new suction nozzles than on any other portion of a pneumatic suction plant4 ,the chief desiderata for a nozzle on a high pressure system for wheat1 coal1 ashes1 etc41 are that it be of light construction to allow of easy manipulation by the operator1 and that it have some means of allowing a 8free air0 inlet1 making it impossible to choke the nozzle by burying the end4 ,it is an advantage to be able to regulate the free air inlet according to the conditions existing with different materials4 ,the same nozzle that will act best while dealing with a large bulk of material1 may be quite unsuitable when it becomes necessary to 8clean up0 in the corners of the hold or waggon4 ,fig4 #ad shows different types of nozzles for high pressure plants1 but as the efficiency and capacity of the plant can be affected seriously by the design of this portion of the apparatus1 it is highly advisable to allow the designer to have a free hand and to make use of the experience already gained4 ,illustration3 ,,fig4 #ae4--,,sturtevant ,,equipment ,,removing ,,wood ,,refuse ,,from ,,double ,,tenoning ,,machine4 ,nozzles designed for low pressure systems1 dealing with dust1 shavings1 etc41 have to be built to suit the machine to which they are attached1 and they therefore vary indefinitely in details of design and construction4 ,the same remarks apply to the nozzles for use on suction cleaning plants4 ,figs4 #ae and #af show how the suction nozzles are adapted to the machines4 ,illustration3 ,,fig4 #af4--,,sturtevant ,,equipment ,,removing ,,dust ,,from ,,sand-,,papering ,,machines4 ,it must be remembered that in low pressure systems handling shavings1 dust1 etc41 the problem is quite different from that in high pressure systems handling wheat1 etc4 ,in the case of removing dust or shavings from a machine1 the material is already in motion1 and only requires drawing forward and into the pipe system1 but in the case of conveyors for wheat1 coal1 etc41 and in the case of suction cleaners1 the material to be moved is heavy and stationary and has to be lifted and started in motion before it can be carried away4 ,this necessitates a much higher air velocity through the collecting nozzles4 ,idle ,nozzles should be ,closed4 ,it is perhaps advisable to draw attention at this point to the disadvantages of using more than one suction nozzle on one receiver at one and the same time4 ,the reader is asked to recall the fact that the material is not lifted by vacuum1 but that the production of a partial vacuum causes a stream of air to pass up the pipe at high velocity4 ,the material to be conveyed is entrained with the air1 and due to the frictional contact between the particles of air and the particles of material1 the latter is lifted and carried forward4 ,if the conveying plant is to be efficient and of reasonable capacity1 the pipes must be relatively large1 and in order that the desired partial vacuum may be maintained in them 7establishing a vigorous air current7 without the use of an unduly large pump1 it is important that air be admitted only through those nozzles which are actually in use4 ,also1 when more than one nozzle is in use at the same time1 it is necessary to keep each nozzle covered with material to such an extent that the same amount of air passes into each pipe4 ,unless this is done a large quantity of air will pass up one pipe1 and a small quantity up the other1 and the amount of material taken in at each nozzle will vary as the quantity of air varies4 ,to consider an extreme case1 suppose that the man operating at one of the pipes allows his nozzle to become exposed4 ,air will rush in at this nozzle to the full capacity of the pump1 with the result that little or no air will pass up the second pipe1 and consequently no material either4 ,thus1 if one man is sufficiently neglectful to leave his nozzle idle and open1 he renders practically useless the other nozzle or nozzles on the same main4 ,even with care this is bound to occur to a certain extent1 as is shown by the figures given by makers for the estimated power consumption1 viz41 about #a h4p4 per ton on single-nozzle plants1 and #a h4p4 on double-nozzle plants4 ,under these conditions it should be considered whether it is more advisable to install one large plant with two nozzles1 or two small plants1 each with only one nozzle4 ,the decision depends upon the extra cost of power for the double-nozzle plant compared with the higher capital charges on the two single-nozzle plants4 ,,chapter ,,iv ,,typical ,,installations ,,for ,,grain ,the pneumatic principle has been applied to the handling of grain in bulk to a much greater extent than to any other material4 ,as previously stated1 the original successful plant invented and designed by ,mr4 ,frederic ,duckham was for the handling of wheat for the ,millwall ,docks ,co41 and the success of this plant was such that it was imitated by engineers in this country and abroad with equally satisfactory results4 ,grain lends itself admirably to pneumatic transport because it is easy of flow1 regular in size1 and practically self-feeding4 ,also1 the removal of dust1 which is incidental to pneumatic conveying1 is a special advantage where grain is concerned4 ,figs4 #ag and #ah show clearly the advantages of pneumatic conveying in point of simplicity and labour saving4 ,typical ,quayside ,plant4 ,fig4 #ai shows a typical lay-out for a comparatively small plant handling #ej tons per hour4 ,the diagram is almost self explanatory4 ,a represents the special suction nozzle through which the grain enters the system1 together with the 8free air0 which acts as the conveying medium4 ,illustration3 ,,fig4 #ag4--;,,ancient4 ,illustration3 ,,fig4 #ah4--,,modern4 ,illustration3 ,,fig4 #ai4--,,typical ,,grain-,,handling ,,plant2 #ej ,,tons ,,per ,,hour4 ,b is a length of flexible pipe to enable the nozzle to sweep the width of the barge1 the length being dealt with by moving the boat to within the radius of the swivel arm ,e4 ,c is a permanent pipe carried on the jib arm which is mounted on a swivel joint2 ,b is another short flexible pipe to permit of the swivelling already mentioned4 ,f indicates the receiver into which the grain is deposited1 and ,g the special rotary valves1 for releasing the material from the system without interfering with the vacuum of the conveying line4 ,h illustrates the twin air filters which are provided with valves1 so that each of the filters can be isolated in turn from the rest of the plant for cleaning of the fabric tubes1 without interrupting the continuous working of the plant4 ,j indicates the connecting pipes between the receiver1 air filters1 and pump1 and it should be noted they are considerably larger than those on the suction end ,c1 this being necessary to allow for the expansion of the air under vacuum4 ,k is the reciprocating air pump1 driven electrically by the motor ,m through large helical gear wheels1 which act as flywheels and are helpful in equalizing the torque required by the pump4 ,l is the outlet pipe for the air as it is exhausted from and by the pump4 ,illustration3 ,,fig4 #bj4--;,,floating ,,pneumatic ,,transport ,,plant2 #bjj-bej ,,tons ,,per ,,hour4 ,illustration3 ,,fig4 #ba4--,,portable ,,pneumatic ,,plant ,,on ,,railway ,,truck4 ,this plant is simple1 but every possible modification can be added that circumstances make desirable2 such as discharging on to a belt conveyor1 for feeding the silos or other storage bins4 ,where grain is bought by bulk it would be necessary to check the weight1 and in this case an automatic weigher would be installed1 into which the material would be discharged from the receiver4 ,with a bag filter the collected dust can also be weighed1 the total weight being then obtained by addition4 ,typical ,floating ,plant4 ,the most popular development of the above type of plant is the floating plant1 designed for erection on a hulk1 or barge1 and intended to suck grain from an ocean-going steamer and discharge it into barges or lighters on the other side of the discharging plant1 as indicated in ,fig4 #bj4 ,the plant shown is one of many in actual operation and its construction may be followed by reference to the description of the plant shown in ,fig4 #ai1 the same index letters being used in each case4 ,one great advantage of floating plants is that the difference in height due to tides is of no consequence4 ,portable ,plants4 ,still another modification consists of a complete quay-side plant mounted like a travelling crane1 so that it can be moved longitudinally along steel rails on the quay-side4 ,this plant is particularly useful where large cargo ships have to be emptied and then allowed to remain at their berth until reloaded with another cargo4 ,illustration3 ,,fig4 #bb4--,,portable ,,railway ,,plant ,,in ,,operation4 ,complete plants have also been mounted on railway trucks1 the engine and pump in this case being on a second waggon 7see ,figs4 #ba1 #bb74 ,in such a case the plant has to be mounted very low1 and it is necessary to lift from the under-side of the truck to1 say1 a railway waggon1 by means of an adjustable belt or bucket elevator 7shown at the extreme left of ,fig4 #ba74 ,many other applications will suggest themselves to the reader1 and sufficient has been said to prove that for the handling of wheat the pneumatic system is distinctly flexible and convenient2 also1 it effects a great saving in labour1 which is an important consideration nowadays4 8,bushelling10 conveying1 and weighing by hand used to cost well over a shilling per ton1 which figure was reduced to just over #a;d4 per ton by pneumatic conveying2 these are pre-war costs in both instances1 but the relative saving effected by pneumatic conveying is certainly not less under present conditions4 ,all the previous remarks also apply to linseed and cotton seed in bulk1 maize1 oats1 and in fact all cereals4 ,such materials have to be accepted as and when the ships arrive irrespective of convenience1 and it is an important advantage of pneumatic conveying that the material can be lifted and discharged in the most convenient position2 also1 when the barge or ship has departed the same apparatus can be utilized to lift the material from its position in store to the cleaning or grinding plant4 ,,chapter ,v ,,pneumatic ,,coal-,,handling ,,plants ,the writer was directly interested in the erection and installing of one of the first plants installed in this country for the elevation and conveying of coal1 and a description of the various details may give a good idea of a complete plant1 handling coal on a commercial scale4 ,the conditions to be complied with are as follows3 #bj tons of 8slack0 per hour1 to be raised #ij ft4 above canal level or #hj ft4 above road level4 ,the coal is brought alongside the power-house by canal barges of #be tons capacity1 or by tipping steam waggons from the railway sidings1 a distance of one mile away4 ,in both cases the coal is required to be elevated into overhead bunkers of #fjj tons capacity placed vertically over the boilers4 ,illustration3 ,,fig4 #bc4--,,pneumatic ,,unloading ,,of ,,coal ,,at ,,messrs4 ,,boots1 ,,ltd4 7,,nottingham74 ,in the first case1 immediately the barge is alongside1 the flexible suction pipe is lowered into the barge 7,fig4 #bc71 and coal immediately begins to rise in the pipe and is discharged as required4 ,little or no handling of the coal is required after the suction nozzle has once reached the bottom of the barge2 all that it is necessary to do is to bring the barge gradually up to the nozzle1 the coal then 8avalanching0 down to the nozzle4 ,fig4 #bd shows the discharger placed on girders over the bunkers into which it discharges continuously4 ,the coal enters at ,a and the major portion of the fuel is discharged through the rotary valves ,b4 ,the coal discharger itself consists of a cast iron vessel with two ,king's patent rotating valves4 ,these are designed in the form of a slightly conical taper divided into four sections1 one portion of the circular valve being under vacuum1 and the other under ordinary atmospheric pressure4 ,the outlet of the valves is larger than the inlet to allow the coal which is in the valve to drop out easily4 ,over each valve is also provided a four-armed sweeper to prevent any damp coal from forming a cone inside4 ,the discharger is provided with two inlets with full-way bored valves1 so that the coal can be drawn either from the water side or from the land side at will4 ,after the coal has been deposited in the main discharger1 there is provided a supplementary discharger consisting of a vessel #f ft4 high by #cj ins4 diameter1 with two inlet pipes of #h ins4 diameter1 to provide a contra-flow1 so that any particles of coal dust in the air will meet one another in the #cj ins4 box at equal velocity and be deposited4 ,the small particles are delivered by a supplementary rotary discharge valve which is set to run very much slower than the main discharger valves4 ,illustration3 ,,fig4 #bd4--;,,discharger ,,for ,,coal ,,conveying ,,plant4 ,the main discharger valves are driven by worm gearing1 the latter having one right-hand thread and one left-hand thread1 so that the end thrust on the worms is neutralized4 ,ball bearings are provided and the small motor which drives all three valves is coupled up with an electrical device designed by the author4 ,this device ensures that if anything happens to the top discharge valves--so that the #c h4p4 motor driving them cuts out1 owing to an overload or other cause--then the main motor also is cut out by the opening of its circuit breaker4 ,this prevents any 8flooding0 of the pipes and dischargers4 ,it may be mentioned that the valves are so designed that a portion of the weight of each valve is carried by the vacuum1 so that the vertical wearing lift on the valves when at work is very slight4 ,the intake pipes for the coal are #e ins4 diameter1 and they are provided with heavy cast iron bends1 having extra thick metal on the outside radius to allow for the wearing effect of coal passing at the rate of #bj tons per hour4 ,the pipe into the barge is provided with a flexible steel pipe at the suction nozzle end1 for convenience of handling4 ,india-rubber piping has been tried1 but the extra cost does not justify its continued use4 ,the nozzle is made as light as possible for convenience of handling1 and is fitted with a special 8free air0 inlet for the regulation of the amount of air necessary to blend with the coal4 ,ash ,handling4 ,in addition to unloading coal1 the above plant is capable of dealing with hot ashes which are first crushed in a portable clinker breaker1 electrically driven1 which runs under all the ash hoppers of the boilers4 ,the ash when crushed gravitates into funnel-topped tee-pieces1 inserted in the main ash-conveying pipe1 whence it is immediately sucked up into an overhead ash hopper to await the convenience of the waggons which dispose of it on the 8tips40 ,flue ,cleaning4 ,a #c in4 suction pipe has been run round the boiler-house in such positions that flexible hose can be attached for flue cleaning purposes4 ,in this case the cleaners simply use an enlarged nozzle such as is supplied with a domestic equipment and the dust is removed from the flues1 economizer soot chambers1 etc41 into the ash hopper without trouble or dust4 ,the success of this plant is best indicated by the fact that1 at the moment of writing1 a duplicate plant is being erected4 ,owing to the growth of the business1 and its demand for power and steam1 the original plant has to be worked continuously on coal1 so that the ash and flue dust problem has become acute again4 ,portable ,floating ,plant4 ,a third plant ordered by the same firm is of considerable interest4 ,this is intended to be mounted in a barge so as to be portable4 ,owing to lack of space in close proximity to the power-house1 considerable difficulty is found in keeping adequate stocks of coal on the site except the #fjj tons in the overhead bunkers4 ,in order to secure continuity of working1 it is essential that as much fuel as possible be stored1 and for this purpose a coal pile has been made about half a mile away from the works1 adjoining the canal4 ,ashes can be disposed of on certain fields a few miles outside the city in swamps and pools caused by subsidences1 due to colliery workings4 ,the portable plant is therefore arranged to operate as follows3 the barge is self-propelled by a #cj h4p4 paraffin engine which can be coupled by clutches to either the propeller or a ,roots blower1 the latter being the exhauster for the portable suction plant4 ,the barge is loaded with ashes for disposal1 and then proceeds under its own power to the site where they are to be dumped4 ,the clutch is operated disconnecting the propeller and operating the blower4 ,the suction side of the blower is coupled up with the pipe line in the boat and the barge feeds the plant by means of the flexible hose3 the discharge pipe is raised over the towing path so as not to interfere with passing traffic1 and the ashes are blown out into the swamps previously mentioned4 ,it will readily be recognized how simple this unloading becomes compared with trying to dig out the ashes with either a spade or a fork4 ,the empty barge then returns to the coal pile and takes up a load of coal in a similar manner1 then proceeding to the power-house under its own power and being unloaded by the original fixed pneumatic installation in the ordinary way4 ,the coal arriving by road is tipped into a concrete hopper excavated below the ground level1 and so designed with sloping sides that it is self feeding into a suction pipe connected to the bottom of the hopper4 ,the same procedure occurs except that in this case the coal enters the main discharger at the top 7,e1 ,fig4 #bd74 ,it is interesting to note that the very fine dust collected from the air filter is eagerly sought after by the foundry trade1 and what would at first appear to be a waste product impossible to burn1 is actually a valuable by-product of the plant4 ,,chapter ,,vi ,,the ,,induction ,,conveyor ,numerous means have been devised to cause the necessary current of air to flow along the conveyor pipe1 but the ideal method is probably yet to seek4 ,probably the most satisfactory and economical system1 until recently1 was the positive pump exhausting a vacuum chamber2 the latter receiving the material1 and discharging it into the receptacle provided for that purpose4 ,the difficulties arising in practice1 however1 incited the inventive genius of engineers responsible for the operation of these plants1 and a number of attempts were made to induce an air current by other means4 ,ejector ,systems4 ,steam ejectors were fitted to the closed tank provided for the reception of the material1 thus converting the tank into a vacuum chamber1 and eliminating the discharger4 ,in other cases injectors1 also operated by steam1 were placed at intervals along the conveyor pipe1 usually at such convenient points as #ij bends1 and the slight vacuum created by the condensation of the steam and also by the velocity of the jet1 induced an air current which swept the material along with it into the receiver chamber4 ,although both these methods are in practical use1 their applications are strictly limited to materials which do not suffer by contact with heat and moisture2 the methods are therefore used principally for conveying ashes and soot from boiler furnaces and flues4 ,ashes formed by the combustion of coal contain large amounts of abrasive matter1 and it is very important that all this matter should be extracted from the air1 before entering the exhauster of the suction system4 ,the steam jet cuts out the exhauster entirely1 but absorbs an excessive amount of power in the form of steam4 ,it has the advantage1 however1 of quenching the ashes on their way to the settling tank4 ,for flue dust1 however1 the steam jet is unsuitable1 as the condensed vapour causes the material to cake in the pipes1 and the latter rapidly become choked1 involving considerable delay and trouble in cleaning out4 ,the ejector system is used for this material1 the tank being of the closed type1 and the necessary vacuum being created by a steam ejector fixed in a branch at the side near the top1 the dust striking a baffle and falling by gravity to the bottom of the tank4 ,a special air-tight gate or valve is opened to empty the tank4 ,air ,induction4 ,the cardinal feature of the induction system is the ease with which materials may be handled which cannot be conveyed by the suction method4 ,sand1 sugar1 salt1 soda ash1 and many other substances of a granular nature1 which are very troublesome when conveyed by the suction method1 may be dealt with economically by the induction system and1 although the latter is only in its experimental stages at the moment of writing1 it is possible that it may displace all other systems in the near future4 ,the induction system differs from the suction system in that the air flow along the pipe is induced by a jet of air1 at very high velocity1 fixed at any convenient distance from the intake nozzle of the conveyor pipe1 and the material conveyed is discharged either from an open end into an open container1 or by some form of cyclone4 ,the closed discharger or container1 with its baffles and rotary valves or air locks1 is eliminated1 and the substance to be handled has a free and unrestricted flow throughout the length of the pipe4 ,advantages of the ,induction ,system4 ,the advantages of the induction conveyor may be summarized as follows3 7#a7 ,low first cost1 the power unit being the only expensive item4 7#b7 ,low maintenance cost1 there being no moving parts and little wear4 7#c7 ,low labour cost1 practically no attendance being required4 7#d7 ,flexibility and ease of handling4 7#e7 ,high efficiency of power unit and reliability of system4 7#f7 ,ability to handle materials which are easily damaged4 ,in the case of a suction plant handling grain or coal1 the intake end of the conveyor is fairly flexible1 and the nozzle may be operated over a fairly large radius1 say1 all over the floor of a vessel's hold4 ,the discharge end1 however1 is fixed1 unless a cumbersome and expensive gantry is provided to permit of the discharge apparatus being moved about4 ,even should the discharger be mounted on rails1 the area over which it can operate is limited by the rails on which it runs4 ,with a large plant1 this would mean that a number of dischargers would be required to lift from a ship into a warehouse or store1 from the latter into bunkers or silos1 or perhaps into trucks or waggons4 ,each discharger would require a separate exhauster and a separate intake1 and valuable space would be occupied by the plant and expense incurred for machinery which would not be in use for a considerable part of the time4 ,the induction system1 however1 is flexible at both intake and discharge ends of the pipe4 ,it is only necessary to lower the nozzle into the material to be removed1 and to place the delivery pipe over the receptacle for the material1 and to turn on the air jet4 ,the delivery may be handled easily while working1 and the material distributed where required2 or suitable valves and branches may be fixed1 and a number of discharge pipes used in turn to deliver into different bins or into various floors4 ,the source of power for the operation of the induction conveyor is the air compressor4 ,as every operating engineer is well aware1 all machinery is kept in better condition and runs more economically1 when it is housed in proper environment and receives skilled attention4 ,the compressor1 in this case1 need not be erected near the work1 but may be placed some distance away1 preferably in the power station1 as the pipe line connecting the conveyor with the machine will have a very small bore1 compared with the air pipe to the exhauster on a suction plant1 and will also be inexpensive to erect and maintain4 ,in the instance quoted above1 where a number of suction and delivery points are required1 only these small pipes need be run from a common main1 and turned on and off as needed1 the compressor running continuously at or near its most economical load4 ,construction of ,induction ,plant4 ,the induction conveyor may be said to be a compromise between the suction and blowing methods4 ,the air jet is fixed in the conveyor pipe at a suitable angle1 some distance above the intake nozzle1 and a stream of air at high velocity is passed along the pipe in the direction of the discharge4 ,this air jet is designed carefully for the duty it has to perform1 and its discharge entrains the free air in the pipe1 causing it to move in the required direction4 ,a partial vacuum is created in the conveyor pipe1 behind the jet1 and free air rushes in at the intake1 carrying the material along with it4 ,in order to effect the greatest economy in the operation of this plant1 it is important that the power unit should be carefully chosen1 and that the pipe system should be designed to give the full pressure at the jet4 ,with modern multiple-stage compressors of the rotary or reciprocating type1 working at about full load1 very high efficiencies can be obtained1 and the pressure pipe line should be arranged to avoid loss by friction as far as possible4 ,the receiver should be of sufficient capacity to absorb any pulsations1 and to throw down oil and moisture before the air enters the pipes4 ,a separator of good design should also be incorporated4 ,in designing the conveyor pipe line1 bends should be avoided when possible1 by erecting the lifting pipes at an angle with the horizontal4 ,it is not sufficiently well appreciated that bends and angles rapidly increase the frictional resistance to the flow of the conveying medium1 and mean loss of power2 in fact there is no doubt that the difference between success and failure in pneumatic conveying is largely a matter of design4 ,many substances which are otherwise quite suitable for handling in this manner are very fragile1 and any friction on pipe walls or contact with metal baffles at high velocity1 so reduces or pulverizes them that their value is reduced considerably4 ,in the case of ashes from boiler furnaces1 this effect is advantageous rather than otherwise1 but when dealing with coal it is necessary to arrange the system so that the minimum amount of damage is done to the material4 ,some coals1 such as ,derbyshire bituminous1 is not easily broken or abraded1 and can be lifted very satisfactorily by the usual suction method4 ,welsh coal1 on the other hand1 is very friable1 and if conveyed into the usual discharger1 will emerge in a finely divided state1 even though it may be fed to the intake in large pieces4 ,for handling such materials1 the induction method is most suitable1 as the discharge end may be arranged so that the material is not delivered at high velocity1 and does not strike any obstacle which would reduce it or break it up4 ,it is possible to elevate potatoes and even oranges by the induction process1 and it is quite within the bounds of probability that eggs may be delivered in this manner1 without more than the usual percentage of breakages4 ,in conveying many materials1 which are conveyed whilst hot1 it is better if they can be kept at practically the same temperature at the delivery as when they enter the pipe4 ,this is provided for by heating the air to a suitable temperature just before it enters the jet4 ,this is also an additional source of economy in operation4 ,as is well known1 air1 like all other gases1 increases in volume with the temperature1 and if the heat lost by the air cooling after compression be replaced at the jet1 considerably more power is obtained4 ,if the compressor is situated in such a position that most of the heat of compression is delivered at the jet1 there is little to be gained by reheating4 ,in most cases1 however1 the air has returned to normal temperature by the time it reaches the point where it is to be used1 and1 if a suitable air heater is installed at this point1 the volume may be increased greatly by a comparatively small expenditure4 ,a heater consisting of tubes through which the air passes1 these tubes surrounded by water under high steam pressures1 offers the most convenient and satisfactory method of heating the air4 ,the air pipes between the heater and conveyor pipe should be lagged in order to retain the heat4 ,the pressure of the air may be increased by #ej per cent4 by heating to the temperature of steam at #bjj lbs4 per sq4 in4 gauge pressure1 while the cost will be comparatively small4 ,theoretically1 a gain of about #dj per cent4 in economy should be obtained1 and the practical results should be reasonably close to this figure4 ,air ,receivers4 ,it is a decided advantage in practice to install an efficient separator between the ordinary receiver of the compressor and the pipe line1 as large quantities of moisture will travel over with the air1 and will be condensed directly they meet some cooler surface4 ,the ordinary receiver is supposed to fulfil this function1 but it does not do so because it is1 in effect1 an enlargement of the pipe line1 and1 being filled with hot air under pressure1 has no tendency to condense the moisture4 ,the latter does not begin to cool to any extent until it reaches the small diameter pipes1 with the consequence that these pipes contain quantities of oil and water which eventually reach the jet1 and are blown into the material handled4 ,where compressors of the rotary or turbine type are installed1 there will be only water in expansion1 but it is good practice to remove this1 even though the air be re-heated1 because the moisture will recondense in the conveyor pipe1 and tend to choke the latter when small grained substances are being conveyed4 ,types of ,compressors4 ,reference has already been made to the power unit1 and it is hardly within the scope of this work to describe in detail the various machines available4 ,as1 however1 the economy of air conveying depends in a large measure on the cost of power1 it is evident that the compressor should be of the most suitable type for the duty to be performed4 ,for small installations1 single-stage reciprocating machines1 driven directly by steam engines or by electric motors are1 no doubt1 the most suitable4 ,in the case of large plants1 using the air continuously in a number of air jets1 where the load factor is high1 it is certainly more important to install a two or three-stage compressor1 owing to the greater economy of working4 ,the larger capital expenditure will be compensated by the considerable saving of energy4 ,as compared with single-stage compression to #ajj lbs4 gauge pressure1 a saving of #bj per cent4 can be effected by three-stage working1 and with a constant load of from #ge per cent4 to #ajj per cent4 of full load1 a turbine or electrically driven rotary multiple-stage compressor is decidedly the best type to adopt4 ,in plants where exhaust steam can be used to advantage1 as in large generating stations1 a steam turbo-compressor1 multiple-stage1 exhausting to a feed water heater will show great economy1 and the operating costs of a large plant of this type are very low compared with any other form of conveyor4 ,this will be obvious when it is pointed out that maintenance costs on the conveyor are confined to renewals of bends and junctions in the pipe lines1 and of flexible hose4 ,there are no discharge valves or air locks to be kept vacuum tight1 no filter strainers or sleeves to renew1 and the power unit is not subjected to undue wear through extraneous matter entering the cylinders and scoring the walls or wearing the valves4 ,compared with other forms of mechanical conveying1 the pneumatic induction system is very low in maintenance costs1 while the serious charges incurred in employing human labour are reduced to a minimum4 ,,chapter ,,vii ,,steam ,,jet ,,conveyors ,a method of removing ashes from boiler furnaces which has been developed extensively in ,america is essentially a pneumatic system1 although steam is the conveying medium instead of moving air4 ,steam is used because the apparatus is always in use on boiler plants1 from which steam can be taken as conveying medium4 ,no air compressor or other special plant is required4 ,on the other hand1 the simple use of a connection from the steam main is a matter of very little importance1 and no check is ever made as to the amount of steam so used1 hence #ii per cent4 of the users consider that the steam jet costs practically nothing for 8power0 compared with a compressor which would have a certain sized motor connected1 and could not escape attention as an additional power consumer4 ,steam ,consumption4 ,investigation into the actual consumption of steam jets would often give very startling results1 especially after the plant had been in operation for some time and the nozzles had begun to cut and wear4 ,as proof of the waste of steam possible in such a plant1 it is interesting to note that ,mr4 ,david ,brownlie1 in a paper on ,automatic ,stokers1#a gave results of actual tests made on steam jets as used in certain classes of stokers in which steam jets are allowed to blow down the hollow furnace bars4 ,these tests showed that1 whereas the makers estimated the steam consumption of the jets to be about #b per cent4 of the boiler output1 the tests on #hj plants showed a consumption varying from #je per cent4 up to as much as #bad per cent4 of the total output of boiler4 ,as further evidence of the waste of steam that can occur due to neglect of the cutting effect on the nozzles1 one ,american firm has designed an ingenious warning or 8tell-tale40 ,a small hole is drilled almost1 but not quite1 through the nozzle4 ,while the nozzle retains its initial shape and size the apparatus acts normally1 but as soon as the small amount of metal covering the end of the hole has worn away1 the hole is exposed1 and a certain amount of steam passes through it to a steam whistle which blows continuously until a new nozzle has been inserted in place of the one which is now worn so much as to make it uneconomical in steam consumption4 ,provided that means are taken to prevent waste of steam due to worn nozzles1 the steam jet conveyor is very serviceable and1 being flexible and convenient1 it is very useful for the purpose for which it has been developed4 ,the following estimated steam consumptions are given for what they are worth2 they are of comparative value in relation with the power consumption on the 8suction0 scheme3 ,one firm claims1 in an actual proposal for a plant to be erected in this country1 a consumption of #cj lbs4 of steam per min4 to deal with #aej lbs4 of ashes per min41 or #d tons per hr4 ,this is approximately equivalent to #gb electrical h4p4 for dealing with #d tons of ashes per hr4 ,a second firm states that a steam jet plant dealing with #ab tons per hr4 will require #c1dff lbs4 of steam per hr4 at #acj lbs4 pressure3 this1 if passed into a modern steam driven generator1 would produce over #acj h4p4 hours4 ,these figures indicate how variable are the estimates of power required4 ,note4--,the 8suction0 schemes for wheat actually work out at slightly more than #a h4p4 per ton per hr4 in single-nozzle plants1 and #a h4p4 per ton per hr4 in twin nozzle plants4 ,lay-out of ,plant4 ,the plant is usually designed on the following lines3 ,immediately under the ash hoppers are funnel-shaped tee-pieces fitted to a cast iron pipe laid on the floor1 or preferably in a small trench just below the ground level4 ,these funnel inlets are usually covered with a cap when not in use1 a tight joint being established by the 8suction0 in the pipe line4 ,when used on ,lancashire boilers having no ash basement the ashes are raked from under the furnaces on to the floor1 and swept into the inlets mentioned 7see ,fig4 #be74 ,large pieces of clinker are broken by hand until they enter the intake pipe1 when they are immediately conveyed through the rest of the system4 ,illustration3 ,,fig4 #be4--;,,brady ,,steam ,,jet ,,ash ,,conveyor4 ,in all large boiler houses with a proper ash basement it is usual to have a travelling clinker breaker1 motor driven1 which can be moved on light rails under each ash hopper and over each intake4 ,the breaker receives all the ashes when released by the hopper valve1 crushes them to a suitable size and discharges them by gravity over the intake funnels1 whence they are transported to the ash tank or hopper4 ,the method of creating the moving air currents is by passing steam through specially designed nozzles which are placed at the extreme end of the intake pipe1 and force the air out of the pipe1 thus inducing a stream of air to enter at the intake openings1 and carry forward the ashes which have been fed into the pipe with the air4 ,when the underground pipe has to rise vertically to cross roads1 etc41 or to reach an overhead tank1 it is usually found necessary to insert 8booster0 jets to impart additional velocity to the ashes1 which are naturally retarded seriously in changing their direction at the bend or elbow4 ,should circumstances necessitate many bends being employed in the pipe line the number of 8booster0 jets has to be increased1 and the total cost of steam for operation is increased seriously4 ,the capacity of the conveyor depends upon the volume of air passed through the pipe in a given time1 and the ashes must not be slacked before handling1 but must be handled either straight from the furnaces or allowed to cool and then conveyed to the ash hopper4 ,an #h in4 pipe is the largest used1 and this will handle approximately #h tons of ash per hour4 ,any increase over this size of pipe necessitates a consumption of steam which makes the scheme impracticable4 ,the conveyor pipe may be run at any angle1 elevation or level1 and therefore is not handicapped by the rigid straight line1 point-to-point1 requirements of bucket elevators1 skips1 etc4 ,the abrasive action of ashes is well known1 and when they are travelling at the high speed necessary with this form of conveyor they cause considerable wear at the bends and elbows in the pipe line4 ,to overcome this a special mixture of iron has been obtained1 which is extremely hard and wear-resisting4 ,steel is quite unsuitable and ordinary cast iron is too soft for these conditions4 ,steam ,jets4 ,the ,james ,brady ,foundry ,co4 7,chicago1 ,u4,s4,a47 state1 in their ,bulletin on this subject1 that the special steam jet elbows are usually placed at the top and bottom of a vertical riser4 ,the jet of steam from the nozzle enters the elbow directly in front of1 and parallel to1 the face of a special wearing liner4 ,this prevents or reduces the wear on the liners1 as the jet protects the liners from the pounding action of the ash4 ,a renewable sectional liner is provided of specially hard metal at all points in which the material makes actual contact with the pipe or fittings4 ,these liners are interchangeable in all elbows1 and each individual liner can be turned end for end when affected by wear4 ,in cases where the length of horizontal run exceeds #abe ft4 it is necessary to supplement the primary nozzles by 8booster0 steam jets to maintain the velocity of the air current4 ,buffer ,boxes4 ,at the discharge end of the pipe line it is necessary to insert a baffle or buffer box to take the impact of the ashes1 and thus prevent wear on certain parts that are not designed to stand up to the destructive effects of the impact4 ,the function of the box is to bring the ashes to rest1 so that they may fall by gravity into the ash tank or on to the storage pile4 ,when delivering into a tank it is very essential to install a buffer box1 as otherwise the velocity with which the ashes enter the tank will pack them so tightly that they will not discharge automatically through the valve or gate4 ,the location of the ash hopper can be wherever most convenient for loading the vans1 railway trucks1 or barges1 etc41 but preference should be given to a site which makes possible a pipe run with a minimum number of bends4 ,one ,american firm of engineers1 the ,vacuum ,ash and ,soot ,conveyor ,co41 ,new ,york1 have done away with the numerous steam jets and the blowing effect produced thereby1 and rely entirely on suction by using a sealed ash tank and exhausting the container and pipe system by means of a single steam jet injector built into the roof of the ash tank1 and discharging its steam directly into the air4 ,by this means it is claimed that the following advantages are obtained3 7#a7 ,no sand-blast effect1 such as is inevitable when blowing at high velocity4 7#b7 ,no steam enters the ash tank and consequently there are no condensation troubles4 7#c7 ,much less dust is blown into the atmosphere as the steam is never in contact with the dust4 7#d7 ,conveyor pipes are cleaner since no steam enters them1 as in 8blowing10 and there is therefore no condensation1 caking and corrosion4 ,,footnotes3 #a ,inst4 ,mechanical ,engineers ,journal1 ,march1 #aibj1 p4 #bia4 ,,chapter ,,viii ,,miscellaneous ,,applications ,,of ,,pneumatic ,,conveying ,pneumatic ,despatch ,tubes4 ,the ordinary pneumatic conveyor picks up material at one point and unloads it at another and continues this course consistently1 whereas the 8pneumatic despatch tube0 is a conveyor of small articles enclosed in a special cartridge which is built to fit the tube and which travels to and fro as required1 carrying a variety of articles1 or if necessary1 the same articles1 backwards and forwards between the same two stations or a series of fixed stations4 ,the despatch tube thus constitutes an effective 8mechanical messenger40 ,one or more tubes are run between the points to be connected1 with a despatch and receiving terminal at each end1 or if necessary1 a single line to operate in both directions can be designed4 ,the tubes vary from #a ins4 to #d ins4 diameter1 and they are also made of oval sections up to #d ins4 #g ins42 rectangular tubes have been installed in special installations1 chiefly in telephone exchanges for convenience in dealing with certain cards there employed4 ,tubes4 ,the tubes are of lead and are usually encased for protection against mechanical damage1 and the erection is carried out with great care so as to preserve the smooth interior4 ,joints occur at intervals of #bh ft4 or less1 and are 8wiped0 with an ordinary plumber's joint over an internal mandril which is heated previous to insertion in the tube4 ,air-tight joints and smooth interiors are absolutely essential to a successful installation4 ,carriers4 ,the carriers or cartridges in which the material to be transmitted is placed are made of gutta-percha covered at the ends with felt4 ,one end of the container is closed and the other end is left open1 but a 8skirt0 of felt surrounds the open end1 and1 as this is the 8trailing0 end and the air pressure is behind it1 the air forces open the 8skirt10 making a tight fit and preventing leakage of air past the carrier4 ,the nose of the carrier is usually fitted with a felt 8buffer0 which also assists in making an air-tight fit4 ,a carrier for a #b in4 tube is #f ins4 long and weighs empty about #c ozs4 ,fig4 #bf shows a large carrier4 ,methods of ,working4 ,pneumatic tubes are worked either by air above atmospheric pressure or by reducing the pressure below atmospheric4 ,in the pressure system the usual pressure is about #aj lbs4 per sq4 in4 above atmospheric pressure1 whilst in the suction system the vacuum employed is equivalent to about #f lbs4 per sq4 in4 ,illustration3 ,,fig4 #bf4--,,typical ,,lamson ,,intercommunication ,,carrier4 ,also1 the method of working may be either 8continuous0 or 8intermittent02 in the first system the air1 either above or below atmospheric pressure1 is circulating continuously and the cartridge or carrier is inserted into a stream of air already in circulation1 whilst in the 8intermittent0 system the power1 either pressure or suction1 is admitted to the conveyor tube only after the carrier has been inserted1 and it is again cut off when the carrier reaches the end of its journey4 ,to a great extent the success of a pneumatic tube system is the speed at which it can transmit the message sent by this means4 ,in the 8continuous0 system1 working above atmospheric pressure1 the speed is not so great as in the 8intermittent0 scheme1 because the pressure in the tube is the same in front of and behind the carrier1 which has to displace the air in front of it4 ,in the 8intermittent0 system the pressure is turned on after the carrier is in place1 and the advancing carrier has only to move the air at atmospheric pressure4 ,on the other hand1 if suction is employed1 the 8intermittent0 system is slower than the 8continuous0 system because the air has to be exhausted to a certain point before the carrier begins to travel4 ,it is true that it will begin to move as soon as the difference in pressure amounts to a few ounces1 but there is a distinct 8time lag0 compared with inserting the cartridge into a tube continuously exhausted when it starts off at practically full pressure and speed immediately4 ,the difference in time is stated by ,kemp to be #c per cent4 longer with 8continuous0 pressure1 compared with 8intermittent0 pressure at #f lbs4 per sq4 in42 the difference increasing to #f per cent4 when the pressure is raised to #ad lbs4 per sq4 in4 ,the average working speed of these tubes is from #be to #cj miles per hour4 ,power ,required for ,operation4 ,it is difficult to determine the actual amount of power necessary to carry a cartridge through a tube4 ,kemp's ,engineer's ,year ,book states that1 working at the standard pressure of #aj lbs4 per sq4 in41 the power required is theoretically #cce h4p4 for a #b in4 tube1 #a mile long1 but actual experience suggests that at least #ej per cent4 should be added to allow for losses from various causes1 making the actual power1 say1 #e h4p4 per #b in4 tube per mile4 ,pressure receivers or tanks are inserted between the pump and the travelling tube to compensate for the impulses due to the irregularity of the pumps and also to act as reservoirs furnishing additional power during periods of abnormal working4 ,the vacuum system takes less power 7for a definite time of transmission7 than is required by the pressure method of working1 but local conditions always influence results considerably1 and it is inadvisable to give any definite figure as to the power required1 without actual knowledge of the system and conditions involved4 ,the air compressors are usually driven electrically1 but they can1 of course1 be operated by any other prime mover such as oil1 gas1 or steam engines4 ,it is economical to combine the pressure and suction systems by arranging the air compressor to draw air from the vacuum receiver into the compressor cylinders whence it is returned to the pressure line4 ,automatic valves keep the pressures in the pressure and vacuum sides of the system within pre-determined limits4 8,make up0 air is admitted by the automatic opening of an atmospheric valve when the pressure side of the system is low and the vacuum side high1 so that the pump is deprived of sufficient air to operate the system efficiently4 ,should the conditions become reversed1 that is1 a low vacuum and a high pressure1 then the pump is working against a high back pressure1 and this is reduced by the opening of an atmospheric relief valve which remains open until the vacuum is restored to normal pressure4 ,this system is preferable to and more economical than the use of two separate pumping and exhausting machines4 ,elaborate and valuable tables of horse-power required by compressors and of 8transit times0 for distances up to #d1ejj yds4 with #a in41 #b in41 and #c in4 tubes are given in ,kemp's ,engineer's ,year ,book4 ,the ,lamson ,tube ,co41 ,ltd41 have brought what was originally invented as a means of conveying persons to a practical business accessory1 capable of saving a great amount of time by despatching sketches1 papers1 small articles1 money1 etc41 here1 there1 and everywhere at the rate of #cj miles an hour4 ,the utility of these plants has long been recognised by banking establishments1 the ,general ,post ,office1 large stores1 factories1 newspaper publishing offices1 etc4 7see ,figs4 #bg and #bh74 ,in addition to the conveyance of messages and papers1 they are frequently installed to convey money and bills from the numerous departments of a large store to the cashiers1 thus saving time and effecting economy in labour and floor space4 ,one cashier can attend to from #aj to #ae stations1 or in small establishments all the stations can be centralized around the book-keeper4 ,the installation of a power-driven plant is not essential1 providing that the service required is not too great4 ,a foot power pneumatic service is available and it is in use in many business establishments4 ,in this system the methods of transportation are similar to those in a power plant1 but the tubes are brought to a special cabinet #ae ins4 square by #b ft4 #f ins4 high1 in which is mounted a foot-operated pump of patented design without bellows or cords4 ,the pump is operated as and when the service is required1 and there is no loss of any description when the apparatus is not in use4 ,pneumatic ,tubes for ,heavy ,articles4 ,it is interesting to recall1 especially in view of the proposed use of pneumatically-propelled parcel-conveying trains by the ,g4,p4,o4 in ,london1 the proposal made by ,mr4 ,medhurst1 in #ahaj1 when it was suggested that a carriage somewhat similar to the modern railway carriage should be moved through a tunnel by pneumatic means4 ,so long ago as #affg1 ,denin ,papin read before the ,royal ,society a paper entitled 8,a ,double ,pneumatic ,pump10 and definite mention of despatch tubes was made in this paper4 ,illustration3 ,,fig4 #bg4--,,tube ,,central ,,in ,,wholesale ,,drug ,,house1 ,,distributing ,,orders ,,to ,,all ,,departments4 ,illustration3 ,,fig4 #bh4--,,lamson ,,distributing ,,station ,,in ,,well-,,known ,,publishing ,,house4 ,in #ahdj a pneumatic railway was actually built and worked between ,london and ,croydon1 and in view of its success was followed by others between ,dalkey and ,kingstown and between ,exeter and ,plymouth4 ,from this it will be seen that transportation by pneumatic means is not modern in its application1 and was originally intended for very large tubes and weights1 but modern development has been toward small tubes and light weights4 ,the ,vacuum ,cleaner4 ,the pneumatic transporting of material in the form of dust has been brought to a very high state of perfection during recent years and an enormous number of plants is now in use1 ranging from the hand-propelled machine to very large stationary equipments4 ,certain hand-propelled machines have been constructed in such a way that the fan is directly operated by gearing from the running wheels1 and after a few moments a very considerable speed is attained and the suction of the fan is used for lifting the dust from the surface over which the apparatus is travelling4 ,numerous designs of more powerful machines actuated by hand bellows have been placed on the market and these possess the advantage that they are independent of the use of power2 but it is not altogether easy to operate a machine by one hand and to manipulate the nozzle with the other4 ,electrically driven machines of almost numberless designs are available4 ,these usually employ a high speed fan of the single-stage type1 but a piston pump is embodied in some designs4 ,in the removal of dust the same principle applies as in the conveying of heavier materials1 i4e4 it is not so imperative to obtain a high vacuum as it is to have a large volume of air moving at high velocity1 hence the multi-stage turbine machine has distinct advantages as regards weight of material moved and economy of power4 ,the multi-stage exhauster consists of turbine wheels mounted on a single shaft1 the air being drawn into the first wheel1 from this to the second wheel and so on right through the machine1 each wheel increasing the suction on the intake end according to the total number of wheels or stages4 ,this style of machine is procurable in either the stationary or portable type1 and in both it is made in various sizes1 the portable machines ranging from #a_/ab h4p4 up to h4p4 for domestic purposes1 and from #a to #c h4p4 on trucks for cleaning electrical machinery1 railway carriages1 etc4 ,figs4 #bi and #cj illustrate typical stationary and portable plants respectively4 ,illustration3 ,,fig4 #bi4--,,stationary ,,turbo-,,exhauster ,,with ,,dust ,,separator4 ,illustration3 ,,fig4 #cj4--,,portable ,,turbo-,,exhauster ,,driven ,,by #a ,h4,p4 ,d4,c4 ,,motor4 ,it is not generally recognized what enormous amounts of dust and dirt may be extracted by these machines4 ,from one ,london hotel a h4p4 cleaner removed #aff lbs4 of dust from the carpets of the public rooms only4 ,on a cleaning test in a first class dining car on one of the ,english railways #be lbs4 of dust was removed from #ch sq4 yds4 of carpet4 ,a rug in front of a lift in a ,london stores yielded #ia lbs4 #a oz4 of dirt to a small machine4 ,the stationary plants are usually installed in the basements of large office buildings1 theatres1 hotels1 clubs1 etc41 and the whole building is piped suitably1 wall plugs or connectors being fitted to which the staff make connection by flexible hose as and when required4 ,the free end of the flexible hose is fitted with one or other of a series of special nozzles1 the latter being adapted to the varying requirements of everything in the room from floor to ceiling4 ,with the portable hand sets or even with the larger truck type1 the design is complete as a working unit2 the equipment is used as manufactured and there is little or no chance for the user to endanger the working efficiency of the plant4 ,in permanent plants1 however1 as installed in hotels1 etc41 it is necessary that all points previously mentioned regarding pipe lines1 valves1 junctions1 bends1 etc41 should be considered and acted upon4 ,the pipe lines should be too large rather than restricted in any way1 the suction flexible should be kept as short as possible1 and if necessary extra connections should be allowed rather than require flexibles too long for use without 8kinking40 ,illustration3 ,,fig4 #ca4--,,suction ,,cleaning ,,for ,,railway ,,carriage ,,cushions4 ,illustration3 ,,fig4 #cb4--,,sturtevant ,,equipment ,,for ,,office ,,cleaning4 ,fig4 #ca illustrates a stationary suction cleaning plant applied to cleaning railway carriage cushions1 and ,fig4 #cb shows a similar installation in use in an office building4 ,cleaning by ,air ,blast4 ,by transferring the hose from the suction side to the discharge1 a suction cleaner may be used to blow dust from machinery of all kinds and from places that are high up and cannot be cleaned economically by suction4 ,for cleaning electric generators and motors by blast1 these machines have many advantages1 and on account of the large volume of air handled they are much to be preferred to the small-volume high pressure jet of the ordinary air compressor often used for this purpose4 ,with the portable turbo-blower there is no danger of damage to the insulation through high pressure1 or through the carrying of moisture and oil into the windings with the air jet4 ,pumping by ,compressed ,air4 ,although1 generally speaking1 the raising of water by compressed air is not an economical method1 it is frequently adopted in mining and tunnelling where the use of steam or electricity is objectionable4 ,in these cases1 cost of operation is a minor factor1 and it may be interesting to give a few particulars of this form of pneumatic conveying4 ,the simplest form of compressed air pump consists of a closed chamber or tank immersed in the water1 to be raised or fixed at such a level that the water will flow into the tank4 ,an air pipe is connected to the top of the chamber1 and the rising main is carried inside the tank to the bottom4 ,on opening the air valve1 pressure is exerted on the surface of the water in the tank1 and the water is expelled through the lift pipe or rising main4 ,on closing the air valve1 water again fills up the tank1 and the process is repeated4 ,a decided improvement on this pump is the return air pump1 which consists of two closed chambers connected through valves with the rising main4 ,the compressed air pipe passes through a two-way valve1 either into one tank or the other1 this valve being positively operated4 ,the method of working is similar to that of the single acting pump1 considering each chamber separately1 but one tank is filling while the other is being emptied4 ,the air expelled from the filling tank1 instead of being discharged to atmosphere1 and part of its expansive power lost1 is carried back through the pipe1 which would be the air intake pipe when discharging1 through a port in the two-way valve1 and into the compressor intake pipe4 ,the air leaving the filling tank is naturally above atmospheric pressure1 and assists the piston on entering the compressor1 thus reducing the power absorbed in driving the latter4 ,air-lift ,pumping4 ,the air-lift pump is a common means of conveying by pneumatic means and should not be confused with the above methods of raising water by compressed air4 ,in the air-lift method of pumping air under pressure is admitted at the foot of a pipe already submerged in the well4 ,the air does not merely bubble through the water1 as might be supposed1 but passes up the pipe as a mixture of air and water4 ,the introduction of the air into the rising column of water makes the latter as a whole less dense than the water around the tube1 and therefore we have a difference in head between the internal and external columns of water which will carry the internal column considerably higher than the external column4 ,as the lifting force depends upon the 8head0 of water outside the rising main1 it follows that the maximum height to which the water can be raised depends upon the depth to which the air pipe and rising main are submerged below the standing level of the water in the bore-hole4 ,in other words1 the greater the lift1 the greater the depth to which the air pipe must be carried before releasing the air into the rising main4 ,experience shows that the water pipe should be submerged #ah ins4 for every #a ft4 lift above the water level in the bore-hole1 and allowance must be made for the 8depression0 of the water level in the bore-hole1 which will probably take place when pumping is in progress4 ,this depression will vary according to the water bearing capacity of the strata1 in which the hole has been bored1 hence it is necessary to go carefully into the conditions before boring the hole4 ,if available1 data should be studied concerning the standing water level1 and the pumping depression in other bore-holes in the immediate neighbourhood4 ,also tests should be made before the boring machinery is removed because1 although the initial depth of bore-hole may be satisfactory on the basis of standing level calculations1 it may be found that when pumping the depression is so great that the bore-hole has to be carried to a greater depth4 ,the air is supplied at a pressure suitable for the conditions1 and can be carried down a separate tube and connected to the rising main at the correct depth 7,fig4 #cc71 or1 as is often done1 one pipe may be lowered and the rising main supported centrally inside the casing tube1 the annular space between the two being used as the air pipe 7see ,fig4 #cd74 ,the amount of free air required is from #jf to #aj cu4 ft4 per gallon of water raised per min41 provided that all the details have been studied carefully and the design of the plant worked out accordingly4 ,if the air pipe is too small the air will bubble slowly through the water1 while if it is too large it will blow out with great force1 spraying and losing the water3 the ratio between the cross-sectional area of the air and water pipes is about #a to #d4 ,advantages of air-lift pumping are that a greater amount of water can be obtained from a hole of given size than by ordinary pumping2 and that one compressing plant can deal with several wells instead of needing a separate pump to each well4 ,,air-,,lift ,,pumping ,illustration3 ,,fig4 #cc4--;,,air ,,pipe ,,outside ,,riser4 ,illustration3 ,,fig4 #cd4--;,,air ,,between ,,casing ,,and ,,riser4 ,the disadvantages are1 that the mechanical efficiency is low2 that a considerable amount of air is entrained in the water1 and aerated water is very unsuitable for boiler feed purposes2 and that means must be provided to allow air to escape by passing the discharge from the pump over a weir or similar contrivance4 ,it is necessary to have some reliable form of oil trap between the compressor and the well to prevent contamination of the water by oil carried over by the air from the cylinders of the compressor2 this is difficult1 because the oil is not only 8atomized0 but is actually vaporized while in the compressor cylinders and as a gas it is difficult to reclaim4 ,the air must be kept as low in temperature as possible1 and it is usually passed through a cooler before being delivered down the well4 ,at times1 air-lifts are installed for conveying other liquids to a height1 and when these can be treated at a high temperature it is advisable1 as the efficiency is then much improved4 ,even under these conditions it is advisable to cool the air to the lowest feasible temperature1 before using it as a lifting medium4 ,when starting up1 the column of water in the rising main has to be moved as a solid column1 and consequently a higher pressure of air is required at starting than when the column has been set in motion1 as the water and air then pass up in alternative 8pellets40 ,in chemical works and allied industries this pneumatic method is frequently used for pumping acids1 and other corrosive liquids from one place to another4 ,compressed air is a very handy medium for this class of work as ordinary mechanical methods are ruled out1 due to the impossibility of introducing corrosive liquids into the pumps and syphons unless great expense is incurred by the use of acid-proof materials4 ,the air-lift is also very advantageous for pumping water which contains a large amount of sand or similar gritty material which would cut and score the walls of an ordinary piston pump4 ,air-lift pumping is frequently used1 therefore1 on new bore-holes until the sand1 etc41 has been eliminated1 after which the final pump can be installed without fear of damage4 ,the question of submergence will frequently make it impossible to use air-lift without boring many feet deeper than would otherwise be necessary1 but when the water bearing strata is low this form of pumping is frequently very convenient4 ,miscellaneous ,applications of ,pneumatic ,conveying4 ,several other interesting applications of pneumatic conveying may be enumerated but1 being somewhat outside the primary scope of this book1 they will not be discussed in detail4 ,the main object of the author is to raise interest in the handling of solid materials in a manner practically unknown to the general reader4 ,the housing problem has developed the pneumatic handling of cement in a liquid form1 and houses are now being built of reinforced cement in the following manner4 ,an expanded steel frame is supported between concrete or brick piers1 and on wood sheeting where necessary1 and liquid cement is blown on to the metal in the form of a liquid spray3 the first coat dries quickly and leaves a certain amount of cement covering the framework4 ,then follows another coat1 and again another and so on1 until the whole of the framework has been covered to an appreciable thickness4 ,the result is a thin wall or slab of cement reinforced with the steel and of great combined strength4 ,slightly domed roofs constructed in this manner have proved very strong and durable4 ,the ,aerograph is an instrument working on the same principle for the application of paint1 and it is used a great deal in the art world1 in the manufacture of ,christmas cards1 in panel painting1 and in interior decoration generally4 ,excellent 8tones0 and shades are obtained by the simple method of varying the thickness of the colour or the number of coats applied4 ,it is usual to convey the surplus colour and fumes away from the operator by means of a stream of air through a special hood placed at the back of the work1 thus maintaining clean pure air for the operator4 ,a similar machine of more crude design is used for whitewashing walls of stables1 cattle pens1 etc4 ,all these plants comprise an air compressor1 either power or hand operated1 from which the air is led to a special injector which draws up through a second pipe a certain amount of the material to be sprayed4 ,the paint or other material is then atomized and impelled with considerable force on to the surface to be covered4 ,the sand blast is another application of pneumatic conveying in which the medium conveyed is sand1 which has well-known cutting and erosive effects when it impinges on a surface at high velocity4 ,this plant is used for decorating glassware1 obscuring sheet glass1 and also for cleaning stone buildings by the actual removal of the face of the previously discoloured stone4 ,the pneumatic conveyance of energy is exemplified by rock drills1 riveting machines1 coal-cutters and innumerable other portable tools4 ,energy is expended in compressing air which is transmitted through pipes and made to yield its stored energy by driving the air motors of the tools or other apparatus in question4 ,conclusion4 ,enough has been said to show that pneumatic conveying has made great progress1 and that the possibilities of this method of dealing with the moving of solid materials are much greater than has been generally recognized4 ,almost anything that will enter a pipe up to about #i ins4 diameter can be conveyed in this way1 either by 8blowing0 or 8suction0 or by the 8induction0 method4 ,weight and size is an advantage rather than otherwise1 and bricks can be dealt with more successfully than flour4 ,the writer's experience1 in the results of actual working with pneumatic conveying1 indicates that no problem should be considered too difficult to be tackled by this method1 and that even the most unlikely materials can be conveyed successfully by pneumatic means4 ,,bibliography ,readers wishing to amplify their knowledge of pneumatic conveying may find useful the following references-- 8,pneumatic ,dispatch10 by ,h4 ,r4 ,kemp1 ,m4,i4,c4,e41 ,m4,i4,e4,e41 ,m4,r4,m4 ,paper before the ,inst4 of ,post ,office ,engineers4 ,october1 #aiji4 8,power ,plant for ,pneumatic ,tubes in the ,post ,office10 by ,a4 ,b4 ,eason1 ,m4,a41 ,a4,m4,i4,e4,e4 ,paper before the ,inst4 of ,post ,office ,engineers4 #ahth ,october1 #aiac4 8,portable ,plant40 ,editorial article in ,cassier's ,engineering ,monthly1 ,june1 #aiai4 8,pneumatic ,handling ,machinery40 ,engineering and ,industrial ,management1 #eth ,june1 #aiai4 8,history of ,conveying10 by ,g4 ,f4 ,zimmer1 ,a4,m4,i4,c4,e4 ,engineering and ,industrial ,management1 ,july to ,sept41 #aibj4 8,boots as ,power ,users10 by ,e4 ,g4 ,phillips1 ,m4,i4,e4,e41 ,a4,m4,i4,mech4,e41 describing the coal handling plant used by ,messrs4 ,boots ,pure ,drug ,co41 ,ltd41 ,nottingham4 ,power ,user1 ,march1 #aibj4 8,pneumatic ,handling ,installation for ,calcium ,sulphide10 by ,g4 ,f4 ,zimmer1 ,a4,m4,i4,c4,e4 ,chemical ,age1 #ajth ,april1 #aibj4 8,pneumatic ,conveying of ,granular ,substances1 including ,chemicals10 by ,g4 ,s4 ,layton4 ,paper before the ,society of ,chemical ,industry1 ,third ,conference 7,birmingham71 #bcrd ,april1 #aibj4 8,pneumatic ,conveying of ,coal and ,similar ,substances10 by ,j4 ,h4 ,king1 ,m4,i4,mech4,e4 ,paper before the ,society of ,chemical ,industry1 ,third ,conference 7,birmingham71 #bcrd ,april1 #aibj4 ,instructive catalogues on this and allied subjects are issued by the following firms 7amongst others73 ,messrs4 ,ashwell ,nesbit1 ,ltd41 ,leicester2 ,r4 ,boby1 ,ltd41 ,bury ,st4 ,edmunds2 ,h4 ,j4 ,king ,co41 ,nailsworth1 ,gloucester2 ,the ,lamson ,store ,pneumatic ,co41 ,ltd41 ,london2 and ,the ,sturtevant ,engineering ,co41 ,ltd41 ,london4 ,,index ,advantages of system1 #e ,aerograph1 #aja ,air compressors1 #fg1 #gj1 #ga ---- filters1 #aj1 #ba-bg ---- induction1 #fc ---- lift1 advantages1 #ig ---- ----1 air required1 #ig ---- ---- 8depression10 #if ---- ---- pumping1 #ie-ajj ---- ---- submergence1 #if1 #ajj ---- receivers1 #fi ---- reheating1 #fh1 #fi ---- velocity1 #cf 8,aquadag10 #bj ,ash handling1 #eh1 #gd-gg ,bag filters1 #bb-bd ,bends and elbows1 #cd1 #ce1 #fg ,bibliography1 #aje 8,blowing0 system1 #d ,breaking of materials1 #cd1 #ce1 #fg ,buffer boxes1 #gh ,capacity of pipe lines1 #cf ,cement handling plants1 #aja ,cleaning with air blast1 #id ,coal-handling plants1 #ed-eh1 #fj1 #fa ,comparative costs1 #ec ,conveying above atmospheric pressure1 #f ---- below atmospheric pressure1 #f ---- above and below atmospheric pressure1 #f1 #fd-ff ,cyclone separators1 #ba ,design1 factors influencing1 #h ,despatch tubes1 #hj1 #ha ,dischargers design1 #aj1 #bh-cb1 #ef1 #eg ---- difficulties1 #i ---- valves1 #bh1 #ca1 #cb1 #ef1 #eh ,exhausters1 #aj1 #ad ,factors influencing design1 #h ,flexibility1 #e ,flexible suction pipes1 #cf ,floating plants1 #c1 #df1 #ea1 #ei-fa ,flue cleaning1 #ei ,foot power pumps1 #hf ,fundamental principles1 #c ,grain-handling1 #de1 #dg ,heavy commercial systems1 #g ,high pressure systems1 #f1 #ci ,historical1 #a1 #b 8,induction0 system1 #d1 #f1 #fb-ff 8,intermittent0 tube system1 #ha1 #hc ,junctions in pipe lines1 #cc ,king's exhauster1 #aj-ad ---- three-way valve1 #cg 8,kinking0 to be avoided1 #ib ,large pipe systems1 #g ,lime washing1 #aja ,low pressure systems1 #f ,lubrication1 #bj ,materials1 breaking of1 #cd1 #ce1 #fg ,mollers' air filter1 #bd ,nash hydro-turbine1 #ah1 #ai ,nozzles 7suction71 #aj1 #dj-dc ,oil contamination1 #aa ,pipe lines1 #aj1 #cc1 #cf1 #ci ---- ----1 capacity of1 #cf ,pneumatic tube carriers1 #ha1 #hb ---- ----1 8continuous10 #ha1 #hc ---- ---- foot power1 #hf ---- ----1 8intermittent10 #ha1 #hc ---- ----1 power required1 #hd1 #he ---- ---- pressure system1 #ha1 #he ---- ---- vacuum system1 #hd ,portable quay-side plant1 #e ---- railway plant1 #di-ea ---- vacuum cleaners1 #ib ,power required1 #dd ,pressure systems1 #d1 #f ,pumping by compressed air1 #id1 #ie ,quayside plants1 #ea ,reheating compressed air1 #fh1 #fi ,rotary blowers1 #ad1 #ae ,sand-blasting1 #ajb ,stationary plants1 vacuum1 #ib ,steam consumption1 #gb-gd ---- jet conveyors1 #gb1 #gd1 #gf ---- jets1 #gg ---- jets1 economy of1 #gb1 #gc ,sturtevant blowers1 #af1 #ag 8,suction0 nozzles1 #aj1 #dj-dc ---- systems1 #d-g ,systems1 advantages of1 #e ,telescopic pipes1 #ch ,turbo-blowers1 #aa ,vacuum cleaners1 #hi ---- ----1 tests1 #ib ---- required1 #c ,valves in pipe line1 #cg ,velocity of air in pipes1 #cf ,water pumping1 #ie-ajj ,waterside plants1 #de1 #dg1 #dh1 #ei ,wear of pipes and bends1 #cd1 #ce ,wet air filters1 #be-bg ,printed by ,sir ,isaac ,pitman ,sons1 ,ltd41 ,bath1 ,england ,transcriber's ,notes pg #ei ,changed3 await the convenience of the wagons to3 await the convenience of the waggons pg #fi ,changed3 practice to instal an efficient separator to3 practice to install an efficient separator