ASSIGNMENTOFINDUSTRIAL AUTOMATIONAND ROBOTICS

SUBMITTED TO:- SUBMITTED BY:-Er. Arshpreet Kaur Akshay MehraProduction Engg. Deptt. D4 PE G.N.DEC, Ludhiana 104063 100371234246

Q1. What are the different types of Pumps and Compressors? Explain?Ans. PUMPSApumpis a device that moves fluids (liquidsorgases), or sometimesslurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid:direct lift,displacement, andgravitypumps.Pumps operate by some mechanism (typicallyreciprocatingorrotary), and consumeenergy to performmechanical workby moving the fluid. Pumps operate via many energy sources, including manual operation, electricity,engines, orwind power, come in many sizes, from microscopic for use in medical applications to large industrial pumps.Mechanical pumps serve in a wide range of applications such aspumping water from wells, aquarium filtering,pond filteringandaeration, in thecar industryforwater-coolingandfuel injection, in theenergy industryforpumping oilandnatural gasor for operatingcooling towers. In themedical industry, pumps are used for biochemical processes in developing and manufacturing medicine, and as artificial replacements for body parts, in particular the artificial heartandpenile prosthesis.TYPES OF PUMPSMechanical pumps may besubmergedin the fluid they are pumping orexternalto the fluid. Pumps can be classified by their method of displacement intopositive displacement pumps,impulse pumps,velocity pumps,gravity pumps,steam pumpsandvalve less.Positive displacement pump:-A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation.

Positive displacement typesScrew pumpA positive displacement pump can be further classified according to the mechanism used to move the fluid: Rotary-typepositive displacement: internal gear, screw, shuttle block,flexible vane or sliding vane, circumferential piston,flexible impeller, helical twisted roots (e.g. the Wendelkolben pump) orliquid ringvacuum pumps Reciprocating-typepositive displacement:pistonordiaphragm pumps Linear-typepositive displacement:rope pumpsandchain pumps

Rotary positive displacement pumps

Rotary vane pumpPositive displacement rotary pumps move fluid using a rotating mechanism that creates a vacuum that captures and draws in the liquidAdvantages:Rotary pumps are very efficient because they naturally remove air from the lines, eliminating the need to bleed the air from the lines manually.Drawbacks:The nature of the pump demands very close clearances between the rotating pump and the outer edge, making it rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids cause erosion, which eventually causes enlarged clearances that liquid can pass through, which reduces efficiency.Rotary positive displacement pumps fall into three main types: Gear pumps- a simple type of rotary pump where the liquid is pushed between two gears Screw pumps- the shape of the internals of this pump usually two screws turning against each other pump the liquid Rotary vane pumps- similar toscroll compressors, these have a cylindrical rotor encased in a similarly shaped housing. As the rotor orbits, the vanes trap fluid between the rotor and the casing, drawing the fluid through the pump.Reciprocating positive displacement pumps

Simple hand pump

Hand-operated, reciprocating, positive displacement, water pump inKoice-ahanovce,Slovakia(walking beam pump)Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes (diaphragms), while valves restrict fluid motion to the desired direction.Pumps in this category range fromsimplex, with one cylinder, to in some casesquad(four) cylinders, or more. Many reciprocating-type pumps areduplex(two) ortriplex(three) cylinder. They can be eithersingle-actingwith suction during one direction of piston motion and discharge on the other, ordouble-actingwith suction and discharge in both directions. The pumps can be powered manually, by air or steam, or by a belt driven by an engine. This type of pump was used extensively in the 19th centuryin the early days of steam propulsionas boiler feed water pumps. Now reciprocating pumps typically pump highly viscous fluids like concrete and heavy oils, and serve in special applications that demand low flow rates against high resistance. Reciprocating hand pumps were widely used to pump water from wells. Commonbicycle pumpsand foot pumps forinflationuse reciprocating action.These positive displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation.Typical reciprocating pumps are: Plunger pumps- a reciprocating plunger pushes the fluid through one or two open valves, closed by suction on the way back. Diaphragm pumps- similar to plunger pumps, where the plunger pressurizes hydraulic oil which is used to flex a diaphragm in the pumping cylinder. Diaphragm valves are used to pump hazardous and toxic fluids. Pistondisplacement pumps- usually simple devices for pumping small amounts of liquid or gel manually. The common hand soap dispenser is such a pump. Radial piston pumpVarious positive displacement pumpsThe positive displacement principle applies in these pumps:Rotary lobe pump Progressive cavity pump Rotary gear pump Piston pump Diaphragm pump Screw pump Gear pump Hydraulic pump Vane pump Regenerative (peripheral) pump Peristaltic pump Rope pump Flexible impellerGear pump

Gear pumpThis is the simplest of rotary positive displacement pumps. It consists of two meshed gears that rotate in a closely fitted casing. The tooth spaces trap fluid and force it around the outer periphery. The fluid does not travel back on the meshed part, because the teeth mesh closely in the centre. Gear pumps see wide use in car engine oil pumps and in various hydraulic power packs.Screw pumpAScrew pumpis a more complicated type of rotary pump that uses two or three screws with opposing threade.g., one screw turns clockwise and the other counterclockwise. The screws are mounted on parallel shafts that have gears that mesh so the shafts turn together and everything stays in place. The screws turn on the shafts and drive fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal.Progressing cavity pump

Widely used for pumping difficult materials, such as sewage sludge contaminated with large particles, this pump consists of a helical rotor, about ten times as long as its width. This can be visualized as a central core of diameterxwith, typically, a curved spiral wound around of thickness halfx, though in reality it is manufactured in single casting. This shaft fits inside a heavy duty rubber sleeve, of wall thickness also typicallyx. As the shaft rotates, the rotor gradually forces fluid up the rubber sleeve. Such pumps can develop very high pressure at low volumes.

Roots-type pumps

Named after the Roots brothers who invented it, thislobe pumpdisplaces the liquid trapped between two long helical rotors, each fitted into the other when perpendicular at 90, rotating inside a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous flow with equal volume and no vortex. It can work at lowpulsationrates, and offers gentle performance that some applications require.Applications include: High capacityindustrial air compressors Roots superchargersoninternal combustion engines. A brand of civil defense siren, theFederal Signal Corporation'sThunderbolt.Peristaltic pump

360 Degree Peristaltic PumpAperistaltic pumpis a type of positive displacement pump. It contains fluid within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A number ofrollers,shoes, orwipersattached to arotorcompress the flexible tube. As the rotor turns, the part of the tube under compression closes (oroccludes), forcing the fluid through the tube. Additionally, when the tube opens to its natural state after the passing of the cam it draws (restitution) fluid flow into the pump. This process is calledperistalsisand is used in many biological systems such as thegastrointestinal tract.Plunger pumps

A plunger pump compared to apiston pumpPlunger pumpsare reciprocating positive displacement pumps.These consist of a cylinder with a reciprocating plunger. The suction and discharge valves are mounted in the head of the cylinder. In the suction stroke the plunger retracts and the suction valves open causing suction of fluid into the cylinder. In the forward stroke the plunger pushes the liquid out of the discharge valve. Efficiency and common problems: With only one cylinder in plunger pumps, the fluid flow varies between maximum flow when the plunger moves through the middle positions, and zero flow when the plunger is at the end positions. A lot of energy is wasted when the fluid is accelerated in the piping system. Vibration andwater hammermay be a serious problem. In general the problems are compensated for by using two or more cylinders not working in phase with each other.Triplex-style plunger pumpsTriplex plunger pumps use three plungers, which reduces the pulsation of single reciprocating plunger pumps. Adding a pulsation dampener on the pump outlet can further smooth thepump ripple, or ripple graph of a pump transducer. The dynamic relationship of the high-pressure fluid and plunger generally requires high-quality plunger seals. Plunger pumps with a larger number of plungers have the benefit of increased flow, or smoother flow without a pulsation dampener. The increase in moving parts and crankshaft load is one drawback.Car washes often use these triplex-style plunger pumps (perhaps without pulsation dampeners). In 1968, William Bruggeman significantly reduced the size of the triplex pump and increased the lifespan so that car washes could use equipment with smaller footprints. Durable high pressure seals, low pressure seals and oil seals, hardened crankshafts, hardened connecting rods, thick ceramic plungers and heavier duty ball and roller bearings improve reliability in triplex pumps. Triplex pumps now are in a myriad of markets across the world.Triplex pumps with shorter lifetimes are commonplace to the home user. A person who uses a home pressure washer for 10 hours a year may be satisfied with a pump that lasts 100 hours between rebuilds. Industrial-grade or continuous duty triplex pumps on the other end of the quality spectrum may run for as much as 2,080 hours a year.The oil and gas drilling industry uses massive semi trailer-transported triplex pumps calledmud pumpsto pumpdrilling mud, which cools the drill bit and carries the cuttings back to the surface.Drillers use triplex or even quintuplex pumps to inject water and solvents deep into shale in the extraction process calledfracking.The plunger pump can be hand-held or gigantic. Triplex pump brands include Cat Pumps in the U.S., Ram Pumps in the U.K., big box store plunger pump pressure washers Lowe's, Home Depot, Menard's, the quintuplex oilfield brand NLB (Europe), and others.Compressed-air-powered double-diaphragm pumpsOne modern application of positive displacement diaphragm pumps is compressed-air-powered double-diaphragmpumps. Run on compressed air these pumps are intrinsically safe by design, although all manufacturers offer ATEX certified models to comply with industry regulation. Commonly seen in all areas of industry from shipping to processing, Wilden Pumps, Graco, SandPiper or ARO are generally the larger of the brands. They are relatively inexpensive and can perform almost any duty, from pumping water out ofbunds, to pumping hydrochloric acid from secure storage (dependent on how the pump is manufactured elastomers/ body construction). Lift is normally limited to roughly 6m although heads can reach almost 200 Psi.

Rope pumpsDevised in China as chain pumps over 1000 years ago, these pumps can be made from very simple materials: A rope, a wheel and a PVC pipe are sufficient to make a simple rope pump. For this reason they have become extremely popular around the world since the 1980s. Rope pump efficiency has been studied by grass roots organizations and the techniques for making and running them have been continuously improved.Flexible impeller pump

The Pulser pumpImpulse PumpsImpulse pumps use pressure created by gas (usually air). In some impulse pumps the gas trapped in the liquid (usually water), is released and accumulated somewhere in the pump, creating a pressure that can push part of the liquid upwards.Impulse pumps include: Hydraulic rampumps- uses pressure built up internally from released gas in liquid flow. (see below) Pulser pumps- run with natural resources, by kinetic energy only. Airlift pumps- run on air inserted into pipe, pushing up the water, when bubbles move upward, or on pressure inside pipe pushing water up.Hydraulic ram pumps

Airlift pump vs. Geyser pumpAhydraulic ramis a water pump powered by hydropower.It takes in water at relatively low pressure and high flow-rate and outputs water at a higher hydraulic-head and lower flow-rate. The device uses thewater hammereffect to develop pressure that lifts a portion of the input water that powers the pump to a point higher than where the water started.The hydraulic ram is sometimes used in remote areas, where there is both a source of low-head hydropower, and a need for pumping water to a destination higher in elevation than the source. In this situation, the ram is often useful, since it requires no outside source of power other than the kinetic energy of flowing water.Velocity pumps

A centrifugal pump uses a spinning "impeller" with backward-swept armsRotodynamic pumps(or dynamic pumps) are a type of velocity pump in whichkinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe. This conversion of kinetic energy to pressure is explained by theFirst law of thermodynamics, or more specifically byBernoulli's principle.Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved.These types of pumps have a number of characteristics:1. Continuous energy2. Conversion of added energy to increase inkinetic energy(increase in velocity)3. Conversion of increased velocity (kinetic energy) to an increase in pressure headA practical difference between dynamic and positive displacement pumps is how they operate under closed valve conditions. Positive displacement pumps physically displace fluid, so closing a valve downstream of a positive displacement pump produces a continual pressure build up that can cause mechanical failure of pipeline or pump. Dynamic pumps differ in that they can be safely operated under closed valve conditions (for short periods of time).Centrifugal pump

Centrifugal pump

Open Type Centrifugal Pump ImpellerAcentrifugal pumpis a rotodynamic pump that uses a rotatingimpellerto increase the pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pump used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward or axially into a diffuser orvolutechamber, from where it exits into the downstream piping system. Centrifugal pumps are typically used for large discharge through smaller heads.Centrifugal pumps are most often associated with the radial-flow type. However, the term "centrifugal pump" can be used to describe all impeller type rotodynamic pumps including the radial, axial and mixed-flow variations.Radial-flow pumpsOften simply referred to as centrifugal pumps. The fluid enters along the axial plane, is accelerated by the impeller and exits at right angles to the shaft(radially). Radial-flow pumps operate at higher pressures and lower flow rates than axial and mixed-flow pumps.Axial-flow pumps

Axial pump (propeller in pipe)Axial-flow pumps differ from radial-flow in that the fluid enters and exits along the same direction parallel to the rotating shaft. The fluid is not accelerated but instead "lifted" by the action of the impeller. They may be likened to a propeller spinning in a length of tube. Axial-flow pumps operate at much lower pressures and higher flow rates than radial-flow pumps.Mixed-flow pumpsMixed-flow pumps function as a compromise between radial and axial-flow pumps. The fluid experiences both radial acceleration and lift and exits the impeller somewhere between 0 and 90 degrees from the axial direction. As a consequence mixed-flow pumps operate at higher pressures than axial-flow pumps while delivering higher discharges than radial-flow pumps. The exit angle of the flow dictates the pressure head-discharge characteristic in relation to radial and mixed-flow.Eductor-jet pumpThis uses a jet, often of steam, to create a low pressure. This low pressure sucks in fluid and propels it into a higher pressure region.Gravity pumpsGravity pumps include thesyphonandHeron's fountainand there also importantqanator foggarasystems that simply use downhill flow to take water from far-underground aquifers in high areas to consumers at lower elevations. Thehydraulic ramis also sometimes called a gravity pump.Steam pumpsSteam pumps have been for a long time mainly of historical interest. They include any type of pump powered by asteam engineand alsopistonless pumpssuch asThomas Savery's, thePulsometer steam pumpor theSteam injection pump.Recently there has been a resurgence of interest in low power solar steam pumps for use in smallholder irrigation in developing countries. Previously small steam engines have not been viable because of escalating inefficiencies as vapour engines decrease in size. However the use of modern engineering materials coupled with alternative engine configurations has meant that these types of system are now a cost effective opportunity.Valveless pumpsValveless pumpingassists in fluid transport in various biomedical and engineering systems. In a valve less pumping system, no valves are present to regulate the flow direction. The fluid pumping efficiency of a valve less system, however, is not necessarily lower than that having valves. In fact, many fluid-dynamical systems in nature and engineering more or less rely upon valve less pumping to transport the working fluids therein. For instance, blood circulation in the cardiovascular system is maintained to some extent even when the hearts valves fail. Meanwhile, the embryonic vertebrate heart begins pumping blood long before the development of discernable chambers and valves. Inmicro fluidics, valvelessimpedance pumpshave been fabricated, and are expected to be particularly suitable for handling sensitive biofluids.

COMPRESSORSA compressor is a device that takes in air at atmospheric pressure and delivers it at a pressure higher than atmospheric. Every compressed air system begins with a compressor, which is continuous source of air flow for all the downstream equipment and processes. The main parameters of any air compressor are capacity and its pressure; capacity does the work and pressure affects the rate at which work is done.TYPES OF AIR COMPRESSORSAir compressors are of two types:1. Positive Displacement Air Compressors2. Non-Positive Displacement Air CompressorsIn positive displacement type, a given quantity of air or gas is trapped in a compression chamber and the volume it occupies is mechanically reduced, causing a corresponding rise in pressure prior to discharge. At constant speed, the air flow remains essentially constant with variations in discharge pressure.Dynamic compressors impart velocity energy to continuously flowing air or gas by means of impellers rotating at very high speeds. The velocity energy is changed into pressure energy both by impellers and the discharge volutes or diffusers.POSITIVE DISPLACEMENT COMPRESSORSThese are classified as:1. Rotary Compressors2. Reciprocating CompressorsROTARY COMPRESSORSRotary Air Compressors are positive displacement compressors. They have rotors that give a continuous pulsation free discharge. They operate at high speeds. Their capital costs are low, are compact in size, have low weight and are easy to maintain. These units are basically oil cooled. They are classified as :1. Screw Compressor2. Lobe Compressor3. Vane Compressor

SCREW COMPRESSORRotary Screw Compressors are positive displacement compressors. Compression is achieved via meshing of two helically cut rotor profiles. One rotor is cut as a male profile and other as a female profile. These two rotors spin in opposite direction. It can be single screw or twin screw.

Twin Screw CompressorLOBE COMPRESSORIn this type of compressor, the rotors do not touch and certain amount of slip exists. The slip increase as output pressure increases. The principle of operation is analogous to the rotary screw compressor, except that with lobe compressor mating lobes are not typically lubricated for air service.

VANE COMPRESSORRotary vane compressorsconsist of a rotor with a number of blades inserted in radial slots in the rotor. The rotor is mounted offset in a larger housing that is either circular or a more complex shape. As the rotor turns, blades slide in and out of the slots keeping contact with the outer wall of the housing.Thus, a series of decreasing volumes is created by the rotating blades. Rotary Vane compressors are, with piston compressors one of the oldest of compressor technologies. With suitable port connections, the devices may be either a compressor or a vacuum pump. They can be either stationary or portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines. Dry vane machines are used at relatively low pressures (e.g., 2 bar or 200kPa; 29psi) for bulk material movement while oil-injected machines have the necessary volumetric efficiency to achieve pressures up to about 13bar (1,300kPa; 190psi) in a single stage. A rotary vane compressor is well suited to electric motor drive and is significantly quieter in operation than the equivalent piston compressor. Rotary vane compressors can have mechanical efficiencies of about 90%.

RECIPROCATING COMPRESSORSReciprocating compressorsusepistonsdriven by a crankshaft. They can be either stationary or portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines.Small reciprocating compressors from 5 to 30horsepower(hp) are commonly seen in automotive applications and are typically for intermittent duty. Larger reciprocating compressors well over 1,000hp (750kW) are commonly found in large industrial and petroleum applications. Discharge pressures can range from low pressure to very high pressure (>18000 psi or 180 MPa). In certain applications, such as air compression, multi-stage double-acting compressors are said to be the most efficient compressors available, and are typically larger, and more costly than comparable rotary units.Another type of reciprocating compressor is the swash plate compressor, which uses pistons moved by a swash plate mounted on a shaft (seeaxial piston pump.Household, home workshop, and smaller job site compressors are typically reciprocating compressors 1hp or less with an attached receiver tank.

They are classified as:1. Piston Compressors2. Diaphragm CompressorsPISTON COMPRESSORSThey are of two types:SINGLE STAGE PISTON COMPRESSORSThe single stage reciprocating compressor has a piston that moves downward during the suction stroke, expanding the air which causes pressure in cylinder to drop. When pressure falls below, the inlet valve opens and allows air in until the pressure equalizes across the inlet valve. The piston bottoms out and begins a compression stroke. The upward movement of piston compresses the air and the pressure developed is enough to open the discharge valve and compressed air is discharged until piston completes the stroke.

TWO STAGE PISTON CYLINDER

DIAPHRAGM COMPRESSORAdiaphragm compressor(also known as amembrane compressor) is a variant of the conventional reciprocating compressor. The compression of gas occurs by the movement of a flexible membrane, instead of an intake element. The back and forth movement of the membrane is driven by a rod and a crankshaft mechanism. Only the membrane and the compressor box come in contact with the gas being compressed.The degree of flexing and the material constituting the diaphragm affects the maintenance life of the equipment. Generally stiff metal diaphragms may only displace a few cubic centimeters of volume because the metal cannot endure large degrees of flexing without cracking, but the stiffness of a metal diaphragm allows it to pump at high pressures. Rubber or silicone diaphragms are capable of enduring deep pumping strokes of very high flexion, but their low strength limits their use to low-pressure applications, and they need to be replaced as plastic embrittlement occurs.Diaphragm compressors are used for hydrogen and compressed natural gas (CNG) as well as in a number of other applications.

DYNAMIC COMPRESSORSThese are much smaller in size as compared to positive displacement type and produce much less vibration. These include centrifugal and axial types.Centrifugal CompressorsCentrifugal compressorsuse a rotating disk orimpellerin a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas. A diffuser (divergent duct) section converts the velocity energy to pressure energy. They are primarily used for continuous, stationary service in industries such asoil refineries,chemicaland petrochemicalplants andnatural gas processingplants.Their application can be from 100 horsepower (75kW) to thousands of horsepower. With multiple staging, they can achieve extremely high output pressures greater than 10,000psi (69MPa).Many largesnowmakingoperations (likeski resorts) use this type of compressor. They are also used in internal combustion engines assuperchargersandturbochargers. Centrifugal compressors are used in smallgas turbineenginesor as the final compression stage of medium sized gas turbines.

AXIAL FLOW COMPRESSORAxial-flow compressorsare dynamic rotating compressors that use arrays of fan-like airfoilsto progressively compress the working fluid. They are used where there is a requirement for a high flow rate or a compact design.The arrays of airfoils are set in rows, usually as pairs: one rotating and one stationary. The rotating airfoils, also known as blades orrotors, accelerate the fluid. The stationary airfoils, also known asstatorsor vanes, decelerate and redirect the flow direction of the fluid, preparing it for the rotor blades of the next stage.Axial compressors are almost always multi-staged, with the cross-sectional area of the gas passage diminishing along the compressor to maintain an optimum axialMach number. Beyond about 5 stages or a 4:1 design pressure ratio,variable geometryis normally used to improve operation.Axial compressors can have high efficiencies; around 90%polytropicat their design conditions. However, they are relatively expensive, requiring a large number of components, tight tolerances and high quality materials. Axial-flow compressors can be found in medium to largegas turbineengines, in natural gas pumping stations, and within certain chemical plants.

Q2. Explain Hydraulic and Pneumatic Cylinders.Ans.Hydraulic cylinders are linear hydraulic motors that turn hydraulic power of a fluid into mechanical power. The hydraulic fluid utilized in the cylinder is oil, most commonly used in industrial applications. They consist of a plunger or piston inside a cylindrical housing. Piston seals prevent the internal leakage from high pressure side of hydraulic cylinder to the low side. Rod seals are used to prevent external leakage. They may be single or double acting. In single acting cylinder an internal spring is used to provide plunger return when hydraulic pressure is removed. In single action, less valving and plumbing is needed than in double acting. The more complex double acting cylinder is pressurized to move in both directions along the vertical or horizontal plane or any other plane needed. These cylinders provide higher speed operations and tighter control than single acting cylinders and are sensitive to system back pressures that can control due to long lengths.

PNEUMATIC CYLINDERSThese are the final component in a pneumatic or compressed air control or power system. Air or pneumatic cylinders are devices that convert compressed air power into mechanical energy. This mechanical energy produces linear or rotary motion. In this way, the air cylinder functions as the actuator in pneumatic system, so it is called as a pneumatic linear actuator. Main components of a pneumatic cylinder consist of steel or stainless steel piston, a piston rod, a cylinder barrel and end covers. Pneumatic cylinders can be used for pressure ranges between 5-20 bars. They are constructed from lighter materials such as aluminium and brass. Because gas is a compressible substance, the motion of a pneumatic cylinder is hard to control precisely. The basic theory of hydraulic and pneumatic cylinders is otherwise the same. Pneumatic cylinders are a proven way to provide quick, clean, reliable and inexpensive linear motion and a multitude of available designs, styles and options can suit most any conceivable application.