Plant Oil System PDF

PLANT OIL SYSTEM The purpose of the oil system is to lubricate the compressor bearings, to control the steam turbine stop/start and the hydraulic oil devices. The purpose of the common oil system is to control the oil temperature and pressure and to supply oil to the plant equipment. The oil tank...

PLANT OIL SYSTEM The purpose of the oil system is to lubricate the compressor bearings, to control the steam turbine stop/start and the hydraulic oil devices. The purpose of the common oil system is to control the oil temperature and pressure and to supply oil to the plant equipment. The oil tank if fitted with two electrical oil heaters to warm the oil for startup, which is thermostatically controlled and provided with a high temperature alarm. There are two level legs, one with sight glass and the other with a low-level alarm. On the tank there is a local temperature indicator. The two return lines into the tank join a common manifold and flow through an internal strainer. The tank itself has a sloping base away from the pump suction lines and the lowest point of the tank is piped up to the oil centrifuge for the separation of moisture and dirt from the oil. There are two electrically driven positive displacement pumps. Normally one pump on line and one pump on standby. The stand by pump will automatically kick in and start on control oil low pressure. The third oil pump is also a positive displacement pump and is driven by a KKK steam turbine. This pump is normally off line and can be used if there is a total power failure. Each pump delivery has a local pressure gauge and a pressure relief valve with a bypass line with isolation valves around each pressure relief valve. 103  LUBE OIL PUMPS The pressure in the common pump delivery manifold is maintained at 934 kPa by the control valve by returning some of the oil to the tank. The pressure of the control system is 850 kPa and starts as a 2″ take off from the 6″common delivery manifold. There is a 4″ take off from the delivery manifold via a pressure control valve, which reduces the pressure to 350 kPa. This is the lubrication oil supply line. The purpose of the lubrication oil is to lubricate the compressor bearings. Lubricating oil at 350 kPa first passes through one of the two oil coolers. These are shell and tube heat exchangers with cooling water on the tube side and oil on the shell side. There are local temperature indicators on the oil inlet and the oil outlet and a DCS temperature indicator with high and low alarms on the outlet only. Next in line are the lube oil filters, one on line and one normally on standby, there is a high differential pressure gauge, if the pressure drop is more than 30 kPa the filter should be changed over and the dirty filter should be cleaned. 104  LUBE CONTROL OIL OIL FILTERS FILTERS The oil coolers and the filters are fitted with vent valves connected to 1″ drain lines to the oil return manifold. Both lines are fitted with sight glasses. The purpose of the vent system is to vent all the air from the filters or coolers to prevent a pressure drop when the filters or cooler are changes over. LUBE OIL COOLERS AIR PURGE Filler Valve 105 After the filter there is a tapping point for the pressure controller, two local pressure indicators, a pressure switch with a low-low alarm connected to the compressor trip system. The lube oil supply then splits to be distributed to the 8 journal bearings on the compressor set, the steam turbine thrust bearings, the compressor gear coupling (2x3), the barring gear and the emergency oil tank. The flow to the journal bearings is fitted with restriction orifices followed by 7 pressure gauges. The flow to the couplings is unrestricted. The return oil from each bearing and coupling housing all come together into a 16″ common return line back to the oil tank. The emergency oil tank is situated outside, high on the south side of the building, provides sufficient oil for the bearings in the case of a complete steam and power failure. The tank is kept full by a small reverse flow through a hole in the non-return valve, which opens as the lube oil pressure falls. Oil overflows from the tank back to the main oil tank during normal operation. 106