Reciprocating compressors maintenance

Another important feature regarding reciprocating compressor maintenance is shown in Exhibit 4-35- A clear area must be provided in line with each compressor cylinder to permit cylinder removal during the maintenance cycle. The area between two machines must be common for both cylinders. 

Gas turbine driven centrifugal compressors are very efficient under the right operating conditions but require careful selection and demand higher levels of maintenance than reciprocating compressors. Compression facilities are generally the most expensive item in an upstream gas process facility. 

The basis for evaluation of piston speed varies throughout industry. This indicates that the subject is spiced with as much emotion as technical basics. An attempt to sort out the fundamentals will be made. First, because there are so many configurations and forms of the reciprocating compressor, it would appear logical that there is no one piston speed limit that will apply across the board to all machines. The manufacturer is at odds with the user because he would like to keep the speed up to keep the size of the compressor down, while the user would like to keep the speed down for reliability purposes. As is true for so many other cases, the referee is the economics. An obvious reason to limit the speed is maintenance... 

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. 

While not necessarily improving the reciprocating compressor s indi vidual reliability, using spared units does improve the overall plant reliability. With proper monitoring, the compressors may be removed from service in a timely manner for maintenance. If the program is properly administered, unplanned shutdowns can be avoided and a higher plant reliability achieved. 

Reciprocating compressors are also favored over centrifugal machines for temporary installations such as gas and field-well head service. Also, when low initial capital investment is favored over longterm maintenance costs, reciprocating compressors are used. 

Using this easy technique, we can guide the maintenance effort as to which reciprocating compressor valves must be overhauled, and which valves are working correctly. 

Because reciprocating compressors are driven by electric motors, they are more efficient than centrifi al compressors. Typical effidencies are reported to be 87% for reciprocating connpressors as compared with 70% for the centrifi al type. However, reciprocating compressors are more expenave, espedally for large plants. Their maintenance costs are also higl. ... 

Purchaser should note that a good strainer to remove all dust/liquid entrainment from the suction side should be provided for the reciprocating compressor since the clearances are very small. In case non-lubricated type compressor is required, more than one unit should be procured because these machines have more maintenance problems. 

Maintenance of reciprocating compressors for open and enclo.sed installation is shown in Exhibit 4-34. Although it is common to use permanent handling facilities (e.g., traveling crane.s) for enclo.sed installations, another option is available. If the. structural engineers provide removable panels in the roof, mobile equipment may be u.sed to facilitate component removal. 

Poor maintenance of lubrication-system components, such as filters and strainers, typically causes premature failure. Such maintenance is crucial to reciprocating compressors because they rely on the lubrication system to provide a uniform oil film between closely fitting parts (e.g., piston rings and the cylinder wall). Partial or complete failure of the lube system results in catastrophic failure of the compressor. 

Maintenance In general, maintenance cost of reciprocating compressor is higher than that of centrifugal and rotary compressor. 

Presently, many large, but older, refrigerators and liquefiers use reciprocating compressors. Although efficient, reciprocating compressors tend to be large, noisy, prone to high maintenance requirements, and often exhibit... 

Reciprocating compressors can handle wide ranges of volumes and pressures. Balanced-opposed reciprocating compressors operate up to 11,200 kW (15,000 brake horsepower) in units that utilize two to ten compressor cylinders and can handle such pressure ranges because they operate at maximum efficiency under all load conditions. For applications where horsepower requirements are below 400 kW, induction motors are used because such units usually permit starting under load conditions, have simpler design, and have low maintenance requirements. 

Bloch, H.P., and J. J. Hoefner. 1996. Reciprocating Compressors Operating and Maintenance. Houston Gulf Publishing. 

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