Document JKMaJpoVV69vQzXE7arGd15X

en pipe air tools properly I-Effect of Initial or Intake Temperature on Delivery of Air Compressors Itesad on o nominal Intake femparofstr# of 60ft faJlJaf (enptnrtvti, Xafotlv* t f, obr delivery -10 -10 0 440 4JO 400 1.11 I.1JJ Ml 10 470 to 4o 10 490 1.104 t.o*i 1.061 31 491 40 500 SO 510 00 530 I.0JS 1.040 1.010 1.00 fnftfaf famperotsrra. Relative 9 f, obi delivery 70 530 0 540 90 no .980 .961 .944 100 560 i to S70 1)0 510 130 590 140 600 150 610 160 630 .936 .913 .896 .880 .866 .153 .838 System Layout Firtt step: Study your plant to see If It would be better served by one lorge cornpmior in a central location, or by several smaller ones in areas> needing air. This Impor tant decision affects system costs from start to finish. Control system, above left, has one or more large com pressors In a more or less central location. Supply piping, often in the form of a loop, runs to areas needing air. Advantages claimed for central systems include: low In vestment cost per unit of capacity, low unit power cost, chance to use synchronous motors to correct power factor, good pressure regulation, minimum wiring for motor drive. Unit system, above right, has compressors spotted in areas using air. In the usuol plant, each compressor serves the area In which it is located, with only emergency connec tions between the different areas. Advantages cited for unit systems include: low initial' Investment, less pressure loss in piping, reduced engineering and planning, simpler installation, greater fleaibUity, easier financing of plant expansion, simplified purchasing. All these ore fully discussed in Powut, Jan 1953, pp 75-77. Study Needed. There are no simple rules to use In choos ing e system. Bach plant must be analysed separately and the decision based on the results. Por many years central systems have been popular in large industrial plants, and have given excellent service. Unit systems, while used In both large and small plonts, are newer and are not yet os extensively sppHed in large plants. Compressed-Air Piping Regardless of compressor or distribution system chosen, piping is of major importance In every setup. Because pip ing conveys air from high-pressure source (compressor) to point of use (tool), U can be a definite help or hindrance in plant operation. Good piping design limits pressure drop between compres sor and tool because low pressure at the tool cuts produc tion. We haven't space for a complete rundown on all angles of piping design but here are some helpful pointers: intake, Dlsehorgo. Hove intake pipe at least as Urge t> compressor intake opening. For every 10 ft of run from compressor, moke line diameter one inch greater. Keep sir velocity in Intake below 1500 fpm. This cuts friction loss. Make discharge line at least os large as compressor out let opening; use as few bends as possible. Be sure run Is short and direct. Fit valved drain to lowest point of dis charge line end in any pockets formed by piping. Support Intake and discharge piping so vibration sad strain don't reach compressor cylinder, aftercooler or re ceiver. Use gate-type shutoff valves in air lines to keep friction loss low. Distribution Piping. Line from receiver to point of use is generally sited so pressure loss is reasonable --below 5 psi. Provide outlets on each heoder or main for connection of hoses to air-operated tools or devices. Fit outlet to top of pipe so moisture won't drain from main into hose, u several tools connect to one outlet, be sure it is big enough to prevent excessive pressure lots. Sketch, abort, shows typicol main with connections for several tools. Always remember: Low air pressure at tools can causa lar greater tost In plant income than a tew pointe in com pressor efficiency. Next to low pressure, moisture and aolkw ore the wont enemies of good air-tool operation. Moke fuU use of separators, strainers, traps, drop legs. Intake location is of prime importance because high tem- perotures reduce compressor output, as Table I shows- See that Intake Is as far as possible from heat, dirt and ture sources and not too close to building walls and win* dows. Put Intake on north side of building, if possible. Roceivor* that are sited liberally reduce compressor loo ed periods and Insure more thorough cooling of air before it reaches toots. Use ASMS standard receivers and flttioS1 egept where local codes differ.* It is e good plan to install atra.receivers near points of heavy usage to insure odepate volume end pressure, and smooth out flow in supply atlas tnd branches. Sofstr davicoi are needed to protect personnel ond equipMl from excessive pressure end other conditions that lead 0 trouble. Table 111 lists typicol devices used in large dusts: many would not be justified in smell installations, fan the simplest system, however, is always fitted with a future-relief device of some sort on the discharge side. Compressor Cooling Oood cooling is essential to good operation. Though airM compressors may run satisfactorily in warm orcas, aike every effort to put them in cool spots. Copacity will kfreater and there'll be fewer operating problems. -tellable strainers in main water-supply line to waternled compressors protect against solids. Run piping so won't Interfere with maintenance work on cylinders ond Put drain valves at all low points so entire system *7 be drained during shutdown in freexlng weather. Fit each cylinder and intercooler with its own regulating 'she, even though an automatic vnlve starts and stops Wn flow to compressor. Put such valves on inlet side, silk outlet free to flow into an open funnel or sight glass. Csallng water should enter cylinder or intercooler et T*0* leave from top. This keeps jsekets full and helps 'ttt any air, A check volve between cylinder and interder above it keeps wster from draining back into cytlnder unit is shut down. fcttremely cold water may cause condensation on cylinder **|h. Thu destroys lubricant, increose* wear. To avoid ?* P*** cooling water through intercooler first, then to and high-pressure cylinders in turn, jftble II shows recommended water quantities. With ttmpcrature of air leaving intercooler or oftercooler ^ be within 20 and IS P, respectively, of the temperature ter entering the cooler (for ordinary plant toads). e enough plugged fittings In water lines to cylinders j to permit cleaning jackets and tubes with an boie or with a caustic-sodo solution. II-Cooling Water Recommended (or Inter coolers, Cylinder Jackets, Aftercoolers Cam per 100 rfm octvaf froo ofr Intercooler sapotale ......................................................... 1.5 to 2.8 Intercooler end lockets in series.................................. l.Stol.S Aftmcoelnri, 0-100 pit, I-itoos................................................. 1.35 80-100 pit, liftflle-tlaas........................................1.1 Two-stag* Jockaii atonn (belli) ............................ 0.1 Sloglo-itogo fackoti, 40 pi! ......................................................................... 0.6 60 p.l ......................................................................... 0.1 10 ptt .........................................................................1.1 100 p.l ........................................................................ u Ill-Typical Compressor Safety Devices Mam* K*1I*< volvai Ovanpaed shutdown Oil-follvra shutdown Jockal-wotar valve Orar-presiura shutdown Cecaulva. * lamparoiura shsrtdown Molrt-booring protection Msritiiloga lamparoiura protrdten Reaction Or compressor discharge tide roll*** (*sti** pressure. Don't us* o*y shut11 voWas Wim (Mpsiip and Iks* solely rot?* Trips mi drlit whan compressor <a*dt pradaiamlnad sofa tpaad for large compressors tilled wilts pratsura lubrlcollon, this device pretacts baorirsgi by stopping unit whan oil pratsur* foils for any reason Shots down compressor ff water pressore lolls. It is eparolad by oilhar pratsura or lansporatwra Slops compressor whan ditchorg* prat* tssra goat obo*a pra-tal sofa votaa for I soloted compressors this glras protaction ogolncl high diichorga temporetor* by ositonsoticolly stoppieg sintl Thermal shutdown devices step comprattor II bagring tamparotwra goes too Mgh tacordlag tkarmemalars for *och sioga ora good for this, give conllnaavs raoding *f aoch stoge's oullel lamparotMt* tot HANDBOOK ON COMftESSID All 1859 HAN06OOK, OM COUftfSSED All 10)