Reciprocating Compressors Presented By : Mohamed Maher Presented to : Dr.Mohamed Gamal Wasel
Index • • • • • Introduction What is a reciprocating compressor? How reciprocating compressors w orks? Components Controlling Discharge Pressure
Introduction
Definition • A Compressor is a device that compresses gas or air to increases pressure leadin g to reduction of volume. • Shown in a (Fig.1) Is a Typical Industrial Reciprocati ng compressor. Fig.1
Classification • Two Main Classification of compressors : Positive Displacement Continuous Flow Reciprocating Rotary Centrifugal Axial
Applications 1. 2. 3. 4. 5. 6. 7. Transport natural gas through pipelines. Storing purified g ases in small volumes. Compressing intake air in gas turbines. Pressurizing air craft cabins. Moving heat in refrigeration systems. Storing air in submarines. P roviding air for air brakes. Note : Pressure range from 35 psi to 65,000 psi ( In extreme cases)
How it works • Molecules of a certain gas move at high speed striking against the walls of the enclosed vessel producing pressure.(Shown In Fig.2) Figure 2. Confined gas before heating
How it works • Temperature affect molecules speed , when heat is added to a fixed volume of gas , molecules travel faster thus hitting the walls of the vessel with a greater fo rce .(Shown In Fig.3) Figure 3. Constant volume of gas will experience pressure increase when heated.
How it works • When a piston is fitted within the vessel , gas is squeezed into smaller space l eading in restriction of molecules travel thus increase pressure. • Piston movemen t also deliver energy to the molecules increasing it speed , along with heating this results in temperature rise & since molecules has been forced into a small area therefore velocity & pressure will increase.(Shown In Fig.4)
How it works Figure 4. Compression process reduce volume of gas and increase pressure
Limitations of a compressor • Compression of gases from low to high results in high temperature creating probl ems in compressor design. All compressors have a certain design limiting operati on condition , resulting in increase of compression process steps which is terme d” Multistaging” using one basic machine element designed to operate in series with other elements of the machine.
Limitations of a compressor • Limitations vary with the type of compressors , but the most important limitatio ns includes : 1. Discharge pressure. 2. Pressure rise or differential. 3. Compre ssion ratio. 4. Effect of clearance. 5. Desirability of saving power.
Methods of compression • There are 4 methods to compress gases , two for positive displacement & two for continuous flow. • Positive displacement 1. Trap consecutive quantities of gas in some type of enclosure , reduce volume & increase pressure then push the compressed gas out of the enclosure. 2. Trap c onsecutive quantities of gas , carry it without a volume change to discharge ope ning , compress the gas by backflow from the discharge system then push the comp ressed gas out of the enclosure.
Methods of compression • Continuous flow 1. Compress gas by mechanical action of rapidly rotating impellers or bladed rot ors that impart velocity & pressure to the flowing gas. 2. Entrain gas in high v elocity jet of the same or different gas ( usually steam) & convert high velocit y of the mixture into pressure in a diffuser.
Converting Energy • Compressors change mechanical energy into gas energy , according to the first la w of thermodynamics , which states that energy can’t be created or destroyed durin g a process, process change mechanical energy into gas energy , some of the ener gy is converted into non-usable forms such as heat losses. There are two ways to convert energy: • Positive displacement of gas into a smaller volume , flow is di rectly proportional to speed of the compressor & pressure ratio is determined by pressure system into which compressor is pumping.
Converting Energy • Dynamic action imparting velocity to gas , this velocity is then converted into pressure . Both flow rate & pressure ratio varies as a function of speed but onl y within a very limited range & only with properly designed control systems(Show n In Fig.5) Figure 5. Velocity energy converted to pressure energy
Converting Energy • Total energy in a flowing air system is constant. Entering an enlarged section, flow speed is reduced and some of the velocity turns into pressure energy. Thus static pressure is higher in the enlarged section
Types of compressors Figure 6. Types of compressors
Types of compressors • Positive displacement : units are those in which successive volumes of gas are c onfined within a closed space and elevated to a higher pressure. (Shown In Fig.7 ) Figure 7. Positive Displacement
Types of compressors • Rotary positive displacement compressors are machines in which compression and d isplacement result from the positive action of rotating elements. (Shown In Fig. 8) Figure 8. Rotary positive displacement
Types of compressors • Sliding vane compressors are rotary positive displacement machines in which axia l vanes slide radially in a rotor eccentrically mounted in a cylindrical casing. Gas trapped between vanes is compressed and displaced. (Shown In Fig.9) Figure 9. Sliding vane compressors
Types of compressors • Liquid piston compressors are rotary positive displacement machines in which wat er or other liquid is used as the piston to compress and displace the gas handle d. (Shown In Fig.10) Figure 10. Liquid piston compressors
Types of compressors • Two-impeller straight-lobe compressors are rotary positive displacement machines in which two straight mating lobed impellers trap gas and carry it from intake to discharge. There is no internal compression. (Shown In Fig.11) Figure 11. Two-impeller straight-lobe or rotary blower
Types of compressors • Helical or spiral lobe compressors are rotary positive displacement machines in which two intermeshing rotors, each with a helical form, compress and displace t he gas. (Shown In Fig.12) Figure 12. Helical or spiral lobe
Types of compressors • Dynamic compressors are rotary continuous-flow machines in which the rapidly rot ating element accelerates the gas as it passes through the element, converting t he velocity head into pressure. This Occurs partially in the rotating element an d partially in stationary diffusers or blades. (Shown In Fig.13)
Figure 13. Dynamic compressors
Types of compressors • Centrifugal compressors are dynamic machines in which one or more rotating impel lers, usually shrouded on the sides, accelerate the gas. Main gas flow is radial . (Fig.14)
Figure 14. Centrifugal compressor
Types of compressors • Axial compressors are dynamic machines in which gas acceleration is obtained by the action of the bladed rotor. Main gas flow is axial.(Shown In Fig.15) Figure 14. Axial compressors
Types of compressors • Mixed flow compressors are dynamic machines with an impeller form combining some characteristics of both the centrifugal and axial types.
Reciprocating Compressors
What is a reciprocating compressor ? • The reciprocating compressor is a positive displacement , intermittent-flow mach ine & it simply operates at fixed volume. Figure 17. Reciprocating Compressor
Reciprocating Compressor Types Single Acting Compressor • It is a compressor that has one discharge per revolutio n of crankshaft, it also compresses on one side of the piston. Double Acting Com pressor • It is a compressor that completes two discharge strokes per revolution o f crankshaft. it also compresses on both sides of the piston. Most heavy duty co mpressors are double acting.
Theory of reciprocating compressors • Reciprocating compressors operate by means of a piston in a cylinder as piston m oves forward in the cylinder it compresses air or gas into smaller space, result ing in pressure increase. Figure 18. Multistage, double-acting reciprocating compressor in Varrangement
Theory of reciprocating compressors • Rotary motion provided at compressor shaft is converted to linear motion by use of a crankshaft, crosshead, and a connecting rod between the two. One end of the connecting rod is secured by the crankpin to the crankshaft, and the other by c rosshead pin to the crosshead which, as the crankshaft turns, reciprocates in a linear motion.
Theory of reciprocating compressors • Intake and discharge valves are located in the top and bottom of the cylinder. T hese are basically check valves, permitting gas to flow in one direction only. T he movement of the piston to the top of the cylinder creates a partial vacuum in the lower end of the cylinder; the pressure differential between intake pressur e and this vacuum across the intake valve then causes the valves to open, allowi ng air to flow into the cylinder from the intake line.
Theory of reciprocating compressors • On the return stroke, when the pressure in the cylinder exceeds the pressure in the discharge line, the discharge valve opens, permitting air at that pressure t o be discharged from the cylinder into the discharge or system line.
Construction • Reciprocating Compressors can be divided into two main groups : 1. Gas end 2. Po wer end
Gas End • Parts of the reciprocating compressor that handle process gas.
Power End • Parts of reciprocating compressor that assist in transferring power and converti ng rotary motion into reciprocating motion.
Components • Reciprocating compressors house a large system of moving parts, most of these co mponent parts have been precision machined with very tight tolerances for proper compressor efficiency & operation. • A typical reciprocating compressor consists of:
Crank Case • Crank case supports the crankshaft. All bearing supports are bored under setup c ondition to ensure perfect alignment. The bottom of the crankcase serves as the oil reservoir. A main pump is placed on the shield mounted on the side opposite the coupling and is driven by compressor.
Crankshaft • Transmit circular motion of rods into reciprocating motion for the piston. Figure 19. The relationship of the pistons, rods, and crankshaft
Crankshaft • They are normally manufactured of cast iron or soft steel. The crankshaft can be cast (molten metal poured into a mold) into a general shape and machined into t he exact size and shape. In this case the shaft is made of cast iron.(Shown in F ig.20) Figure 20. Crankshaft being machined in a workshop
Crankshaft • This machining process is critical because the throw (the off-center part where the rod fastens) does not turn in a circle (in relationship to the center of the shaft) when placed in a lathe. These off-center shafts normally have two main-b earing surfaces in addition to the off-center rod-bearing surfaces: • One is on th e motor end of the shaft, and one is on the other end. The bearing on the motor end is normally the largest because it carries the greatest load.
Crankshaft • Some shafts are straight and have a cam-type arrangement called an eccentric. Th is allows the shaft to be manufactured straight and from steel. The shaft may no t be any more durable, but it is easier to machine. The eccentrics can be machin ed off-center to the shaft to accomplish the reciprocating action, notice in (Fi g.18) the rod has to be different for the eccentric shaft because the end of the rod has to fit over the large eccentric on the crankshaft..
Figure 21. This crankshaft obtains the off-center action with a straight shaft a nd an eccentric. The eccentric is much like a cam lobe. The rods on this shaft h ave large bottom throws and slide off the end of the shaft. This means that to r emove the rods, the shaft must be taken out of the compressor.
Crankshaft • All of these shafts must be lubricated. The smaller compressors using the splash system may have an oil pan to store oil and cause it to flow down the center of the shaft (Fig.22). It is then slung to the outside of the crankshaft surface w hen the compressor runs. Compressors with splash type lubrication systems must u sually rotate in only one direction to be properly lubricated. This causes the o il to move to the other parts, such as the rods on both ends.
Figure 22. A Typical Splash type lubrication system.
Crankshaft • Some of the shafts are drilled and lubricated with a pressure lubrication system . These compressors have an oil pump mounted on the end of the crankshaft that t urns with the crankshaft. (Fig.20) .There is no pressure lubrication when the co mpressor first starts. The compressor must be running up to speed before the lub rication system is fully effective.
Figure 23. A crankshaft drilled for the oil pump to force the oil up the shaft t o the rods, then up the rods to the wrist pins. Magnetic elements are sometimes placed along the passage to capture iron filings.
Connecting Rods • Connecting rods connect the crankshaft to the piston. These rods are normally ma de in two styles: the type to fit the crankshaft with off-center throws and the type to fit the eccentric crankshaft , Rods can be made of several different met als such as iron, brass, and aluminum. The rod design is important because it ta kes a lot of the load in the compressor. If the crankshaft is connected directly to the motor and the motor is running at 3450 rpm, the piston at the top of the rod is changing directions 6900 times per minute. The rod is the connection bet ween this piston and the crankshaft and is the link between this changing of dir ection. The rods with the large holes in the shaft end are for eccentric shafts. They cannot be taken off with the shaft in place. The shaft has to be removed t o take the piston out of the cylinder. (Fig.24)
Figure 24. Rods being removed
Connecting Rods • The rods with the smaller holes are for the off-center shafts, are split, and ha ve rod bolts, these rods can be separated at the crankshaft, and the rod and pis ton can be removed with the crankshaft in place. The rod is small on the piston end and fastens to the piston by a different method. The rod normally has a conn ector called a wrist pin that slips through the piston and the upper end of the rod. This almost always has a snap ring to keep the wrist pin from sliding again st the cylinder wall. (Fig.25)
Figure 25. The end of the rod that fits into the piston. The wrist pin holds the rod to the piston while allowing the pivot action that takes place at the top o f the stroke. The wrist pin is held secure in the piston with snap rings.
The Piston • The piston is the part of the cylinder assembly exposed to the high-pressure gas during compression. Pistons have high pressure gas on top and suction or low-pr essure gas on the bottom during the upstroke. They have to slide up and down in the cylinder in order to pump. They must have some method of preventing the high -pressure gas from slipping by to the crankcase. Piston rings like those used in automobile engines are used on the larger pistons. These rings are of two types : compression and oil. The smaller compressors use the oil on the cylinder walls as the seal. A crosssectional view of these rings can be seen in Fig.26.
Figure 26. The piston rings for a refrigeration compressor resemble the rings us ed on automobile pistons
Cylinder & Liner • Piston reciprocates inside a cylinder. To provide for reduced reconditioning cos t, the cylinder may be fitted with a liner or sleeve. A cylinder or liner usuall y wears at the points where the piston rings rub against it. Because of the weig ht of the piston, wear is usually greater at the bottom of a horizontal cylinder . A cylinder liner is usually counter bored near the ends of the outer ring trav el.
Refrigerant cylinder valves • The valves in the top of the compressor determine the direction in which the gas entering the compressor will flow. A cutaway of a compressor cylinder is shown in Fig.27.These valves are made of very hard steel. The two styles that make up the majority of the valves on the market are the ring valve and the flapper (ree d) valve. They serve both the suction and the discharge ports of the compressor.
• • • Counter seat Rings Main Components of valves o limits the lift and contains the springs o withstands the differential pressure, ensuring gas seal o acts on the rings, c ausing valve closing o determines the valve lift. o fasten all the components to gether Spring • • Shim Stud bolt, nut & pin
Figure 27. This cutaway of a compressor shows a typical cylinder.
Refrigerant cylinder valves • The ring valve is made in a circle with springs under it. If ring valves are use d for the suction and the discharge, the larger one will be the suction valve, F ig.28. Flapper valves have been made in many different shapes. Each manufacturer has its own design.Fig.29. •
Figure 28. (A) Ring valves. (B)– (D) They normally have a set of small springs to close them.
Figure 29. Reed or flapper valves held down on one end. This provides enough spr ing action to close the valve when reverse flow occurs.
The Valve Plate • The valve plate holds the suction and discharge flapper valves. It is located be tween the head of the compressor and the top of the cylinder wall, Fig.30. Many different methods have been used to hold the valves in place without taking up a ny more space than necessary. The bottom of the plate actually protrudes into th e cylinder. Any volume of gas that cannot be pumped out of the cylinder because of the valve design will re-expand on the down stroke of the piston. This makes the compressor less efficient.
Figure 30. Valve plates typical of those used to hold the valves. They can be re placed or rebuilt if not badly damaged. There is a gasket on both sides.
Poppet Valve • These are separate, round poppets to seat against holes in the valve seats. Popp ets are made of low friction material (e.g. Bakelite), they provide a low-pressu re drop and are often used when ratios of compression are low and also for high flow rates.
Channel Valve • These valves use channel shaped plates instead of flat plates. Above each channe l is a bowed, steel tension spring. Spring pushes from the stop plate and channe ls cover the slots in the valve seat.
The Head of the compressor • The component that holds the top of the cylinder and its assembly together is th e head. It sets on top of the cylinder and contains the high-pressure gas from t he cylinder until it moves into the discharge line. It often contains the suctio n chamber, separated from the discharge chamber by a partition and gaskets. Thes e heads have many different design configurations and need to accomplish two thi ngs. They hold the pressure in and hold the valve plate on the cylinder. They ar e made of steel in some welded hermetic compressors and of cast iron in a servic eable hermetic type. The cast iron heads may be in the moving airstream and have fins on them to help dissipate the heat from the top of the cylinder, Fig.31.
Figure 31. Typical compressor heads. (A) A suction cooled compressor. (B) Air-co oled compressors that have air-cooled motors must be located in a moving airstre am, or overheating will occur.
Mufflers • Mufflers are used in to muffle compressor pulsation noise. Audible suction and d ischarge pulsations can be transmitted into the piping if they are not muffled. Fig.32. Figure 32. A compressor muffler.
The Compressor Housing • The housing holds the compressor and sometimes the motor. It is made of stamped steel for the welded hermetic and of cast iron for the serviceable hermetic. The welded hermetic compressor is designed so the compressor shell is under low-sid e pressure and will often have a working pressure of 150 psig.
The Compressor Housing • The compressor is mounted inside the shell, and the discharge line is normally p iped to the outside of the shell. A cutaway of a hermetic compressor inside a we lded shell and the method used to weld the shell together are shown in Fig. 27.
The Compressor Housing • Two methods are used to mount the compressor inside the shell: rigid mount and s pring mount. Rigidmounted compressors were used for many years. The compressor s hell was mounted on external springs that had to be bolted tightly for shipment. The springs were supposed to be loosened when installed,Fig.29.
Figure 33. A compressor ce to remove the motor. lp eliminate vibration. rough the springs. This
motor pressed into its steel shell. It requires experien The compressor has springs under the mounting feet to he This compressor is shipped with a bolt tightened down th bolt must be loosened by the installing contractor.
The Compressor Housing • Occasionally they were not, and the compressor vibrated because, without the spr ings, it was mounted rigidly to the condenser Casing. External springs can also rust, especially where there is a lot of salt in the air. The internal spring-mo unted compressors actually suspend the compressor from springs inside the shell. These Compressors have methods of keeping the compressor from moving too much d uring shipment. Sometimes a compressor will come loose from one or two of the in ternal springs. When this happens, the compressor will normally run and pump jus t like it is supposed to but will make a noise on start-up or shutdown or both. If the compressor comes off the springs and they are internal, there is nothing that can be done to repair it in the field, Fig.34. •
Figure 34. A compressor mounted inside the welded hermetic shell on springs. The springs have guides that only allow them to move a certain amount during shipme nt.
Compressor Motor in a refrigerant atmosphere • The compressor motor operating inside the refrigerant atmosphere must have speci al consideration. Motors for hermetic compressors differ from standard electric motors. The materials used in a hermetic motor are not the same materials that w ould be used in a fan or pump motor that would run in air. Hermetic motors must be manufactured of materials compatible with the system refrigerants. For instan ce, rubber cannot be used because the refrigerant would dissolve it. The motors are assembled in a very clean atmosphere and kept dry. When a hermetic motor mal functions, it cannot be repaired in the field.
Motor Electrical Terminals • There must be some conductor to carry the power from the external power supply t o the internal motor. The power to operate the compressor must be carried throug h the compressor housing without the refrigerant leaking. The connection also ha s to insulate the electric current from the compressor shell. These terminals ar e sometimes fused glass with a terminal stud through the middle on the smaller c ompressors. When large terminals are required, the terminals are sometimes place d in a fiber block with an O ring–type seal, Fig.35.
Figure 35. Motor terminals. The power to operate the compressor is carried throu gh the compressor shell but must be insulated from the shell. This is a fiber bl ock used as the insulator. O rings keep the refrigerant in.
Motor Electrical Terminals • Care must be taken with these terminals (due to loose electrical connections) to prevent overheating. Should the terminal overheat, a leak could occur. If the t erminal block is a fused-glass type, it would be hard to repair. The fused-glass type will stand more heat, but there is a limit to how much heat it can take. L ess heat can be tolerated with the O ring and fiber type of terminal board. When the O ring and fiber board are damaged, they can be replaced with new parts. Ho wever, refrigerant loss can result before the problem is discovered.
Internal Motor Protection devices • They protect the motor from overheating. These devices are embedded in or near t he windings and are wired in two different ways. One style breaks the line circu it inside the compressor. Because it is internal and carries the line current, i t is limited to smaller compressors. It has to be enclosed to prevent the electr ical arc from affecting the refrigerant, Fig.36. If a contact in this line type remains open, the compressor cannot be restarted. The compressor would have to b e replaced.Fig.37 illustrates a three-phase internal thermal overload. All three of the overload contacts will open at the same time if a motor overheating prob lem occurs. This prevents single phasing of the three-phase motor. This overload device is located in the compressor’s shell, usually in the motor barrel compartm ent over the motor windings.Fig.38 is a photo of a three-phase overload protecto r taken out of a working three-phase motor.Fig.38.
Figure 36. An internal compressor overload protection device that breaks the lin e circuit. Because this set of electrical contacts is inside the refrigerant atm osphere, they are contained inside a hermetic container of their own. If the ele ctrical arc were allowed inside the refrigerant atmosphere, the refrigerant woul d deteriorate in the vicinity of the arc.
Figure 37. A three-phase wye wound motor with internal thermal overload protecti on. All three internal overload contacts will open at the same time to prevent s ingle phasing of the three-phase motor.
Figure 38. A three-phase internal overload protector.
Internal Motor Protection devices • Shown Is a wiring diagram of a typical electronic motor protection package showi ng the motor contactor and electronic protection module. Another type of motor o verload protection device breaks the control circuit. This is wired from the out side of the compressor to the control circuit
Figure 40. The wiring diagram of a typical electronic three-phase motor protecti on package.
Internal Motor Protection devices • Shown a three-phase motor with internal thermistor protection. Thermistors are r esistors that vary their resistance according to their temperature. If a motor o verheating problem occurs, the thermistors will sense the heat, change resistanc e, and relay this change in resistance to a solid-state motor protection module. The thermistor circuit is usually a 24-V control circuit. The motor protection module controls the coil of the contactor or motor starter and can turn the moto r off when necessary for a cool-down period.Fig.38.
Figure 39. A three-phase wye wound motor with internal thermistor protection lin ked to solid-state electronic motor protection module. The motor sensors are the rmistors.
The serviceable Hermetic Compressor • The serviceable hermetic normally has a cast-iron shell and is considered a lowside device, Fig.41. Because of the piping arrangement in the head, the discharg e gas is contained either under the head or out the discharge line. The motor is rigidly mounted to the shell, and the compressor must be externally mounted on springs or other flexible mounts to prevent vibration. The serviceable hermetic is used exclusively in larger compressor sizes because it can be rebuilt.
Figure 41. Serviceable hermetic compressors. (A) Courtesy Trane Company. (B)
Open-Drive Compressor • Open-drive compressors are manufactured with the motor external to the compresso r shell. The shaft protrudes through the casing to the outside where either a pu lley or a coupling is attached. This compressor is normally heavy duty in nature . It must be mounted tightly to a foundation. The motor is either mounted end to end with the compressor shaft or beside the compressor and belts used to turn t he compressor.
The Seal Shaft • The pressure inside the compressor crankcase can be either in a vacuum (below at mosphere) or a positive pressure. If the unit were an extra-low-temperature unit using R-12 as the refrigerant, the crankcase pressure could easily be in a vacu um. If the shaft seal were to leak, the atmosphere would enter the crankcase. Wh en the compressor is setting still, it could have a high positive pressure on it . the crankcase pressure may go over 200 psig. The crankcase shaft seal must be able to hold refrigerant inside the compressor under all of these conditions and while the shaft is turning at high speed, Fig.42. •
Figure 42. The shaft seal is responsible for keeping the refrigerant inside the crankcase and allowing the shaft to turn at high speed. This seal must be instal led correctly. If the seal is installed on a belt-drive compressor, the belt ten sion is important. If it is installed on a direct-drive compressor, the shaft al ignment is important.
The Seal Shaft • The shaft seal has a rubbing surface to keep the refrigerant and the atmosphere separated. This surface is normally a carbon or ceramic material rubbing against a steel surface. If assembled correctly, these two surfaces can rub together fo r years and not wear out.
How to control Pressure • Pressure regulation is done by the use of free air loading. The purpose of this control is to unload the air compressor when more air is compressed than being c onsumed, thus reducing power require & providing maximum economy during the unlo ading period. • this control was done manual by unloaders such as “m” or “w” type , but no w it can be done by PLC . • when pressure in the discharge line reaches a point wh ere the unloader is set to operate the plate valve is forced away from it s seat on the unloader body . when this happened air from the discharge line passes to the unloader and then to the unloading suction valve covers that is holding the valves open. Then the compressor operate against the atmospheric pressure only.
Thank You
References Books: Reciprocating compressors: Operation & Maintenance by Heinz p.bloch & joh n j.hoefner Refrigeration and Air Conditioning Technology, Sixth Edition by Will iam C. Whitman, William M. Johnson, John A. Tomczyk, and Eugene Silberstein Comp ressor handbook by paul c.hanlon Compressors & compressed air systems A practica l guide to compressor technology by HEINZ P. BLOCH Manuals: Mycom wseries , new, premium industrial reciprocating compressors
References Websites: http://www.machinerylubrication.com/Read/775/reciprocareci-compressor http://www.sereneenergy.org/a/reciprocating-compressors-constructiondetails/ htt p://www.airbestpractices.com/ http://www.scribd.com/doc/52572544/Article-on-reci procating-compressor http://www.scribd.com/doc/64630370/Advanced-Technologies-in Reciprocating-Compressors http://www.scribd.com/doc/66667324/Foundation-Design-f orReciprocating-Compressors-Arya http://www.scribd.com/doc/80395496/Hermetic-Rec iprocating-Compressors http://www.airbestpractices.com/technology/compressorcont rols/compressed-air-controls http://prasannasutrave.hubpages.com/hub/How-To-Cont rol-Discharge-AirPressure-In-Compressor www.jennyproductsinc.com/manuals/JennyCo mpressorManual.pdf
