Elements of Lubrication system of a gas turbine are given below:
1. Oil tank,
2. Oil pump,
3. Filter and strainer,
4. Relief valve,
5. Oil cooler,
6. Oil and pipe line,
7. Magnetic drain plug,
8. By-pass, valve, and
9. Warning devices.
1. To replace the oil which may be lost during the normal duration of run, sufficient oil is stored in an external tank .
2. The oil from tank is drained by a gear or rotor type lubrication pump.
3. A relief valve is fitted to return the excess oil to the pump inlet than that required for lubrication.
4. The oil flows through a 10 to 40 micron filtration capacity paper or metal screen filter. If clogged filter used, pressure of oil drop across the filter increases which causes a bypass valve to open and unfiltered oil to reach the bearings.
5. In the filtered oil line, safety and indicating devices such as oil temperature indicator bulb, oil over temperature switch, low oil pressure switch are installed to avoid such malfunctions.
6. Filtered oil flows to the bearings and gear case of turbine and after cooling and lubricating the oil washed components, it is returned to the oil tank by a scavenge pump through a cooler.
7. Scavenge pumps have a greater displacement than the quantity of oil flowing into the cavity from which they are pumping.
8. This introduces a negative pressure, which draws air into the sump through any leakage paths, precluding leakage of oil.
9. The oil and air mixture returned through the cooler to the tank must be separated and for this it is recirculated in a separator and the air is permitted to escape.
10. To burn off any remaining oil vapor, separator vent is usually connected to the tail pipe.
11. This vent must be checked for obstruction regularly; if not then air may build high pressure in the tank and result in failure of it.
12. The separator causes the air-oil mixture to follow a devious path, the oil will tire to turning the corners and will find its way out through
the vent into the tank, and the air will find its way out through the vent into the exhaust system.
13. A drain plug of magnetic type is used in the oil line before oil pump, which tends to collect any metal particles circulating in the oil system.