Chapter 17. -COMPRESSED AIR PLANTS 



VALVE PLATE VALVE PLATE ^ GUIDE 



Figure 17-5.— Diagram of a thin plate air compressor valve. 



STOP PLATE 



47.154X 



a filter, to an oil cooler. From the cooler, the 

 oil is distributed to the top of each main bearing, 

 to spray nozzles for reduction gears, and to out- 

 board bearings. The crankshaft is drilled so that 

 oil fed to the main bearings is picked up at the 

 main bearing journals and carried to the crank 

 pin journals. The connecting rods contain pas- 

 sages which conduct lubricating oil from the 

 crank pin bearings up to the wrist pin bushings. 

 As oil leaks out from the various bearings, it 

 drips back to the reservoir in the base of 

 the compressor and is recirculated. Oil from the 

 outboard bearings is carried back to the base by 

 the drain lines. 



The discharge pressure of lubricating oil 

 pumps varies, depending upon the pump design. A 

 relief valve fitted to each pump functions when the 

 discharge pressure exceeds the pressure for 

 the valve is set. When the relief valve opens, ex- 

 cess oil is returned to the reservoir. 



COOLING SYSTEM.— Most compressors are 

 cooled by sea water supplied from the ship's fire 



and flushing system. The cooling water is usually 

 available to each unit through at least two 

 sources. Compressors located outside the larger 

 machinery spaces are generally equipped with an 

 attached circulating water pump as a standby 

 source of cooling water. Some small low pres- 

 sure compressors are air cooled by a fan 

 mounted on or driven by a compressor shaft. 

 The path of water in the cooling water system 

 for a four- stage compressor is shown in figure 

 17-9. The flow paths are not identical in all 

 cooling water systems, but in all systems it is 

 important that the coldest water be available for 

 circulation through the oil cooler. Valves are 

 usually provided so that the flow of water to the 

 cooler can becontroUedindependentlyof the rest 

 of the system. Thus the oil temperature can be 

 controlled without affecting other parts of the 

 compressor. Cooling water is then supplied to the 

 intercoolers and the aftercooler and then to the 

 cylinder jackets and heads. A high pressure air 

 compressor may require from 6 to 25 gallons of 

 cooling water per minute, while a medium 



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