Compressors reciprocating piston type

Fig. 5. Compressor types used in refrigerator/free2ers (a) typical arrangement (b) reciprocating piston mechanisms connecting rod and Scotch yoke and...

Figure 3-71. Single-acting (trunk-type) reciprocating piston compressor [23].

Because of the reciprocating pistons and unbalanced rotating parts, the unit tends to shake. Therefore, it is necessary to provide a mounting that stabilizes the installation. The extent of this requirement depends on the type and size of the compressor. 

In oxidizing, oil becomes thicker and it deposits carbon and gummy, resinous substances. These accumulate in the piston-ring grooves of reciprocating compressors and in the slots of vane-type units, and as a result, they restrict free movement of components and allow air leakage to develop. The deposits also settle in and around the valves of piston-type compressors, and prevent proper sealing. 

After a lively development in the past two decades during which positive-displacement screw-type and radial-turbo-compressors have replaced piston-type compressors in certain areas. The trend is now towards reciprocating compressors, again owing to their lower power consumption for many applications. 

Several steps can be taken to maximize the run time for the reciprocating compressor. Since wear is a function of rubbing speed, the piston speed can be kept to a minimum. Chapter 3 made recommendations for piston speed. Reliability problems due to valves are reputed to account tor 40% of the maintenance cost of the compressor. Valves are the single largest cause for unplanned shutdowns. Basically, valve life can he increased by keeping the speed of the compressor as low as practical. At 360 rpm, the valves are operated six times a second. At 1,200 rpm, ihc valves operate 20 times a second or 1,728,000 times in a day. It is not difficult to understand why the valves are considered critical. To keep the reliability in mind, valve type, material selection and application considerations such as volume ratio, gas corrosiveness, and gas cleanliness need attention by the experts. One final note is that while lubrication is an asset to the rubbing parts, it is not necessarily good for valve reliability. 

Reciprocating compressors are positive-displacement types having one or more cylinders. Each cylinder is fitted with a piston driven by a crankshaft through a connecting rod. As the name implies, compressors within... 

For natural gas service, five types of compressors are typically used, that is, diaphragm, piston, rotary, screw, and turbo compressors. The characteristics of each type of compressors are a function of throughput and pressure, as shown in Figure 10.22 [6]. Currently, piston (or reciprocating) and rotary compressors are used to compress hydrogen that are similar to those used for natural gas, with modifications of design and materials. 

D. Diaphragm Compressors. Diaphragm compressors effectively have a reciprocating action, but they differ mechanically from the reciprocating type described above. A diaphragm that usually moves vertically replaces the piston. It draws gas into a chamber... 

Reciprocating compressors which are of the positive displacement type using pistons are available for higher pressures. Multistage machines are also available for pressures up to lOOOOkPa or more. 

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