Reciprocating Compressors 2

RECIPROCATING RECIPROCAT ING COMPRESSORS COMPRE SSORS

Drive methods

Small compressors, particularly the trunk type, in single and multistage arrangement are usually V-belt driven by driven by electric motors.

The single-acting crosshead type and the small, double-acting, single-stage compressors are also driven in a similar manner.

RECIPROCATING COMPRESSORS

Drive methods

Larger, multistage, trunk type compressors can be sized to operate at common motor speeds and therefore are direct coupled. The larger, crosshead, double-acting, multistage compressors present the most variations in drive arrangements. If it has an integral electric motor sharing a common shaft ith the compressor it is called an engine type.


Drive methods

These compressors can also be directly coupled to a separate electric motor in a more conventional manner. !ear units may be involved in the drive train here speed matching is re"uired. #eciprocating compressors are available ith a large variety of other drivers, hich include the piston engine, steam turbine or in rare cases, a gas turbine.


Drive methods

The arrangement lends itself to skid mounting, particularly the semi-portable units found in the oilfield. The unit is also popular as a $lease$ unit hich may be lifted onto a flat bed trailer and moved from one location to another as needed. The engine is either direct coupled or as ith smaller compressors, it may be belt connected.


Drive methods

% variation to the smaller, skid mounted, engine driven compressor is a larger, engine driven version in the form of the integral engine compressor . The compressor and the engine share a common frame and crankshaft. &hen the engine cylinders are vertical or in a V configuration and the compressor's cylinders are horizontal, the machine is called an angle engine compressor .


Drive methods


Drive methods

% more rare form of driver is the steam cylinder . (ost arrangements combine the steam driver and compressor on the same frame ith the steam cylinder opposite the compressor cylinder. )ach cylinder's connecting rod is connected to a common thro on the crankshaft. % flyheel is used to provide inertia.

( /d × . ) − ( /s × % )


Rod reversal Rod load

The piston rod is constantly sub*ected to varying compression and tension pressure. This pressure is referred to rod load. #od load is calculated as follos+ ompression load ( /d × % )

( /s × .) Tension load ( /d × . ) − ( /s × % )

+&here ./s  Inlet pressure ./d  0ischarge pressure . %  1uter end piston area .  2rame end piston area

−









&hen the compressor is under load, all clearances are taken up in one direction 3compression4 or the other 3tension4. This transition to compression or visa versa is essential for metal surfaces to be lubricated.





2or the crosshead movement, it should be noted that the movement of the crosshead pin in relation to con-rod throughout compressor cycle.







Reciprocating Compressors 2

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