Figure 11-13. - Typical water-cooled aftercooler.

Air Discharge Systems

Some discharge systems require special consideration for the placement of auxiliary equipment. All positive displacement compressors require a relief valve on their discharge side to protect the equipment and piping upstream of the first shutoff valve. Relief valves should be sized for at least 125 percent of the maximum unit flow capacity and should carry the American Society of Mechanical Engineers (ASME) stamp, listing the capacity and pressure setting of the valve.

Separators

Water and oil separators are required to separate and free excess water from the discharge air or gas. This is necessary to prevent corrosion, deposit buildup, and water or oil buildup in the piping or service. For example, water will cause rust in piping, wash away lubricants, and plug nozzles. Oil will contaminate many industrial processes and may present an explosion hazard. The need for water or oil separators will be determined by the end use of the compressed air.

A centrifugal separator is illustrated in figure 11-14. Air is directed into this unit in a manner that creates a swirling motion. Centrifugal force throws the moisture particles against the wall where they drain to the bottom.

Figure 11-14. - Centrifugal-type moisture separator.