Figure 8-15-Oil separator element.

Maintenance for the air receiver is not complicated and is limited to visual inspection of flanges and threaded fittings. The demister (fig. 8-15), or oil separator, should be removed and replaced according to the manufacturer's recommendations for the unit you are working on.

INTERCOOLERS

As the air compressor compresses air, heat is generated which causes the air to expand requiring an increase of horsepower for further air compression. If you remove the heat generated by compressing air, the total horsepower required for additional air compression is reduced up to 15 percent. In multistage reciprocating compressors, heat is removed by the use of intercoolers (fig. 8-16) or heat exchangers placed between each stage of compression.

NOTE

In the rotary and screw types of air compressors, oil is injected into the compressor at the first stage-cooling the air. Thus, the intercooler is not required.

Some intercoolers have a condensation drain that should be serviced daily (at a minimum), and some have a safety relief. If the safety relief valve is opening due to overpressure, it is an indication of possible leakage in the high-pressure suction valves. You should keep the intercooler clean.

AFTERCOOLERS

Water or moisture is not desirable in the transmission lines of an air compression system. Water carried through the lines washes away lubricating oil from the tools the compressed air is running. This causes the tools to operate sluggishly and increases the need for maintenance. The effect is compounded in high-speed tools, where the wearing surfaces are limited in size and excessive wear reduces efficiency by creating air leakage. Further problems result from the decrease of temperature caused by the sudden expansion of air at the ted. This low temperature creates condensation which freezes around ports and valves and impairs efficiency. These conditions can be minimized by removing the moisture from the air directly after compression, before the air enters the distribution systems. Through the use of an aftercooler or air radiator, heat is transfered from

Figure 8-16.-Example of an intercooler on a two-stage reciprocating air compressor.