The Pressure Tank is one means of feeding oil under pressure to bearings, gears, and pinions. It is also extensively used where non-pulsating flows are desired, or where automatic pressure control of pump operation is preferred.
The tank may be equipped as an option with a safety valve, three pressure switches set at different pressures, and a pressure gauge. In actual operation the pressure is reduced as the oil flows from the tank, but when it reaches approximately 48 psig (330 kPag), the service oil pump automatically cuts in and the oil level is raised until the air pressure is restored again to 54 psig (370 kPag). Its operation is entirely automatic and the pumps can be operated intermittently if desired. If, for any reason, the service pump should fail to cut in, the spare pump comes automatically into service when the pressure is further reduced. Should the spare pump fail to cut in, the third pressure switch sets in operation a large, continuous-ringing electric gong or Howler.