Basic Parts Of Reciprocating Compressor
Reciprocating compressors play a significant role within the chemical, organic compound, gas, and general business processes. it’s the best well-known and most generally used compressors of the positive displacement kind.
Cylinders:
Cylinders of the mutual compressor square measure utilized in the method industries ar severable from the frame. they’re connected to the frame by the manner of AN intermediate half referred to as the gap piece. The cylinder can accommodate each suction and discharge valve plates.
Normally most of the cylinders utilized in the method square measure equipped with replaceable liners. the aim of the liner is to produce a renewable surface to the carrying portion of the cylinder.
his protects the value of substitution an entire cylinder once the bore has been worn or scored. within the larger, additional complicated compressors, this feature is commonplace or pronto accessible as Associate in Nursing choice.
On the smaller frames, notably the single-stage models, the smaller cylinder size is specified the replaceable liner isn’t economical and will not be accessible.
The cylinders ar equipped for cooling to cut back the temperature throughout the compression cycle. this can be typically by means that of a water jacket.
If water jacketing within the cylinder isn’t possible than fins ar provided within the cylinder for air cooling. The latter technique is proscribed to either tiny or special purpose machines.
The most common material utilized in-cylinder construction is cast iron for the larger, unaggressive cylinders and steel for the smaller, aggressive cylinders. In some cases, nodular or ductile iron is utilized in part of cast iron. For organic compound service, steel is most fascinating, though not universally accessible.
For capability management, clearance pocket enclosed within the cylinders. within the case of multi-stage compressors, the clearance pocket is employed within the 1st stage cylinder.
Piston:
The piston is the heart of the mutual compressor. The piston interprets the energy from the crankcase to the gas within the cylinder. so as to avoid the outpouring of compressed gas between the piston and cylinder, the piston is supplied with a group of slippy seals known as piston rings.
Usually, the rings square measure fabricated from a piece of fabric, that having self-lubricating property to cut back the slide friction force between the cylinder and therefore the piston. This to avoid the damage within the cylinder wall and conjointly increase potency by reducing the friction force.
Different types of rings square measure used for lubricated or non-lubricated service. within the case of non-lubricated service, the rings shall have sensible self-lubricated property. Usually, this sort of seal is formed from PEEK and different fluorocarbon compounds.
For lubricated service, metallic rings like cast iron or bronze moreover as non-metallic materials like stuffed nylon ar used. these days the compressor manufacturer’s most popular non-metallic materials thanks to less weight once compare with metallic rings.
In the case of horizontal cylinder piston, along with side piston rings, an extra ring is employed to cut back the avoid the damage between cylinder and piston it’s known as wear band or rider ring. The rider ring is one piece configuration, to accommodate the rider ring the piston is divided construction.
As per API, 618 one-piece rider rings ar needed. Rider band life is extended by rotating a piston 120° to 180° at every overhaul.
Normally the piston is formed from lesser weight materials like aluminum and aluminum alloys, this can be to cut back the reciprocating compressor shaking forces and Rod load. within the case, piston diameter larger piston diameter hollow pistons are wont to cut back the weight.
Piston Rod:
The connecting rod is rib to the piston and transmits the reciprocating motion from the crosshead to the piston. The connecting rod is often created of steel and should have a hardened and polished surface notably wherever it passes through the cylinder packing (double-acting cylinders).
Rod loading should be unbroken inside the bounds set by the compressor merchandiser as a result of overloading will cause excess run-out of the rod leading to premature packing wear. This, in turn, ends up in outpouring, reduced potency, and inflated maintenance expenses.
Distance Piece:
The distance piece could be a severable housing that connects the cylinder to the frame. the gap piece could also be open or closed and will have multiple compartments. it’s going to be furnished with as single, double, or further long.
The purpose of an extended distance piece is to isolate that {part of|a half of} the connecting rod getting into the crankcase and receiving lubrication from the part getting into the cylinder and contacting the gas.
This prevents stuff from getting into the cylinder and contaminating the gas, notably necessary in non-lubricated cylinders. It can even keep artificial stuff in a very cylinder.
der from being corrupted by the housing stuff.
Compartments within the distance piece collect and management packing outpouring once the gas is poisonous or inflammable. The outpouring is directed to a flare or buffer element is employed to prevent the poisonous gas from outpouring to the atmosphere.
As per API 618, the gap items ar classified as four varieties
- Type A
- Type B
- Type C
- Type D
Rod Packing:
Rod packing is needed to forestall the gas outpouring on the connecting rod wherever it passes through the crank finish cylinder closure.
If cooling packing is needed, the chamber could also be jacketed for liquid agents.
The packing rings square measure the center of rod packing assembly. the most packing rings varieties square measure
- Tangent RingRod
- Radial Ring or Pressure Breaker Ring
- Backup ring
Tangent Ring
The tangent ring is removed 3 segments in order that every cut lies on the aspect of the associate equiangular triangle.
Radial Ring or Pressure Breaker Ring
The radial ring or pressure breaker rings ar remove 3 segments in order that every cut lies on the aspect of a radial direction of the ring. The cuts of this ring ar wont to break down the pressure act on the ring. Usually, a radial ring is that the 1st packing ring face the cylinder pressure.
Backup Ring
This type of ring construction is comparable to radial ring. because the name indicates this sort of ring is employed to backup all the rings once using within the high-pressure application.
CrankShaft:
Larger compressors, ordinarily higher than one hundred fifty kW(200 hp), have cast steel crankshafts. for compressor but or adequate to 150kW machines ductile iron shaft.
Crankshafts ought to have removable balance weights to complete rotary unbalance additionally as reciprocal unbalance. The shaft ought to be dynamically balanced once higher than 800 rpm.
When force lubrication is employed, the shaft oil passages ought to be trained. The Figure shows a trained crankshaft. within the case of machines higher than 150kW,
Bearing:
The crosshead pin ought to have a standardized bush bearing.
Connecting Rod:
For reciprocal compressor of higher than one hundred fifty kW(200 hp), have cast steel rod ar used and for compressor but or adequate to 150kW machines ductile iron material is employed. Like Crankshafts, the rod ought to have a trained hole for oil passage.
The association rod is used to attach the shaft and also the crosshead. The rod converts the motion into reciprocal motion. The rod bolts and fruity shall be firmly locked with cotter pins or wire when assembly.
Cross Head:
All industrial reciprocal compressors ar equipped with Crosshead. The crosshead is employed to guide the piston within the cylinder bore. the subsequent ar the advantage of the crosshead
- The compressor will use a slim piston, thanks to the employment of slim piston larger valve space for larger potency.
- Permits an extended stroke and larger capability.
- Separates crankcase from the cylinder, permitting management of oil carryover into the cylinder.
- Gives larger stability to the piston, eliminating piston “slap” and reducing ring wear
- Permits a stronger piston style and better operative pressures.
Valve:
The reciprocal compressor cylinder valves ar of the spring-loaded, gas-actuated sort. reciprocal compressors typically use one in every of 3 forms of valve configurations:
- Ring-type valve
- Poppet sort valve
- Plate type valve
Poppet type Valve
The poppePoppet Valve(see Figure) consists of multiple, same-size ports and protection components. The advantage of the valve is that includes a high flow potency thanks to the high carry used and also the efficient form of the protection component.
The disadvantage is that the valve isn’t tolerant of uneven flow distribution. The valve is most typically utilized in medium pressure vary. these days these forms of valves ar utilized in hydrocarbon service owing to easy maintenance.
Poppet valves ar counseled up to fifteen Mpa differential pressure or thirty Mpa discharge pressure and 600rpm.
Plate Type Valve
The plate valves, as shown in Figure, ar almost like the concentric ring valve except that the rings ar joined into one component. The advantage is that the vaPlate type Valve includes a single component creating flow control somewhat easier. owing to the only component, the quantity of edges obtainable for impact is reduced.
The valve could also be automatically damped, as this style permits the employment of damping plates. it’s the disadvantage that owing to the pure mathematics used, the strain is higher thanks to the potential of upper-stress concentrations. These valves ar principally utilized in the industrial method compressor.
Plate valves ar counseled up to twenty Mpa differential or forty Mpa discharge pressure and 1800 rev
Ring-type Valve
As the name implieRing sort Valve the ring sort valve consisting of concentric ring valve uses one or additional comparatively slim rings organized concentrically regarding the middle line of the valve (see Fig ).
These valves have the advantage of a low-stress level thanks to the shortage of stress concentration points. The disadvantage is that it’s difficult to take care of uniform flow management with the independent rings.
Ring valves ar recommended up to thirty Mpa differential or 60 Mpa discharge pressure and 600 rpm.
Lubrication System:
Force sort lubrication is used for medium and serious duty compressor. the most part of the force sort lubrication is that the main pump, twin filter, fill oil cooler, pressure control valve, fill oil tank, and its associated accessories.
Splash type lubrication is used for a little compressor of 100kW. this sort of system lubricating oil by the splashing of crank-throw moving through the lubricator within the sump.
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