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WRITE UP ON TURBINE LUBE OIL SYSTEM Ref: Lube oil P&I Diagram HY-DG-1-31701-16962 OWNER: TATA STEEL LTD, JAMSHEDPUR CONSULTANT: TATA CONSULTING ENGINEERS LIMITED, MUMBAI PROJECT: 40MW CDQ WASTE HEAT RECOVERY CO-GENERATION POWER PLANT
GENERAL A sufficient and continuous supply of oil is essential for the safe and reliable running of a turbine and its driven equipment. The oil supply system should ensure the operational safety of bearings. The system is of the closed circuit type i.e., a definite amount of oil quantity is continuously recirculated. The Oil Supply System includes the following equipment: Main Oil Tank (MOT-3012-876), housing the oil volume required for lubricating oil, Lube oil pumps, MOP (MOP-3012-876) driven by AC motor, AOP (AOP-3012-877) driven by AC motor for pumping oil that required for lubricating oil systems, Emergency oil pumps (EOP-3012-878) driven by DC motor supplies oil to the turbine bearings after turbine trip during coasting down of the turbine, when all sources of oil fail, Twin oil coolers (HE-3012-876 & HE-3012-877), in which the heat absorbed in turbine oil system is dissipated, Duplex type oil filters (FLT-3012-876 & FLT-3012-877) to supply clean oil to the bearings, Adjustable orifices (AFO-3403 to AFO-3407), which permit adjustment in the oil quantity, required for the respective bearings. Oil vapor extraction fans (EAF-3012-876 & EAF-3012-877) to remove oil vapors settled over the oil surface in oil tank.
MAIN OIL TANK (MOT-3012-876): The Oil tank is located on the mezzanine floor. Normal capacity of the tank is 5000 Liters. Bharat Heavy Electricals Limited
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The Oil tank serves for storing the oil volume required for lubricating systems. It allows the impurities to be settled at the bottom of the tank along with the oil sludge. Baffle plates are provided to give a longer time in the tank so that the entrapped air is effectively released. The level in the tank is indicated by level transmitters (LT-3012-3501A&B) and level gauge (LG-3012-3502). Oil vapours accumulated in the oil tank are evacuated by the oil vapour extraction fans (EAF-3012-876 & EAF-3012-877) mounted on the oil tank top plate. The exhaust is led to safe location outside TG hall. The oil tank is supplied with connection for oil centrifuging. The oil centrifuge inlet connection provided in the oil tank is of loop configuration in order to prevent emptying of the oil tank in case of leakage in the oil purification circuit. The top of the loop is in line with minimum oil level in the oil tank. If the oil level in the tank falls below the minimum level, flow to centrifuge circuit is interrupted as air enters into the loop through the hole provided at top of the loop. Level transmitters (LT-3012-3501A&B) is provided to give signal to control room where from indication and turbine trip are generated and alarm annunciated in control room. Due to vaporization, there will be loss of oil in the circuit over a period of running of the set which results dip in the oil level. Whenever this happens, oil is to be replenished by adding clarified oil. LUBE OIL PUMP (MOP-3012-876 & AOP-3012-877): The Lube oil pump is a horizontal centrifugal pump driven by AC motor. The pump delivers the total oil required for lubricating oil systems. Isolation valves are provided in suction and discharge. If the pump discharge pressure falls below 6.5 Kg/cm2 (g) or Lube oil header pressure falls below (1.5 kg/cm2g), the standby pump (AOP) will be started through pressure transmitters at respective locations (PT-30123504A & B and PT-3012-3509A, B). If the standby pump also fails, the turbine will be tripped through a pressure signal generated from pressure transmitters (PT-3012-3510A,B,C) in 2/3 voting logic. The set value for turbine trip is 1.0 Kg/cm2(g) on Lube oil header. EMERGENCY OIL PUMP (EOP-3012-878): A certain time period is required by the unit to stop completely after the trip owing to the high inertia of the rotating masses. Therefore sufficient oil quantity should be supplied to the bearings until the unit comes to standstill. During
Bharat Heavy Electricals Limited
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coasting down of turbine, when lube oil pump is not available, lubricating oil is provided by Emergency oil pump. This pump is driven by a DC motor. The EOP will cut in automatically by lube oil pressure transmitter (PT-30123509A & B) set at 0.8 Kg/cm2(g). In order to ensure positive supply of oil to the bearings, this pump is connected directly to the lube oil header without going through cooler and filters. To take care of abnormal condition of power supply failure in turbine control system, a pressure switch (PSLL-3012-3512) is directly connected to DCSC to start the EOP automatically OVERHEAD OIL TANK (EOT-3012-878): When Emergency oil pump also fails, as a last resort to protect bearings, an overhead oil tank is envisaged. The tank is kept at a higher elevation w.r.t. center line of turbine to provide lubricating oil by virtue of gravity. The tank is filled using lube oil pump during initial startup. While filling the overhead oil tank, level in the main oil tank shall be monitored. The oil filling completion is indicated by overflowing of oil through flow glass (GJ-3409-80). Once the tank is full, the inlet valve (GV-3467-80) is closed and a small amount of oil is allowed to continuously over flow through the tank through orifice (ROP-3455). Machine start permissive is taken through a level transmitters (LT-3012-3503A&B).
OIL COOLER (HE-3012-876 & HE-3012-877): The heat absorbed in the bearings is dissipated in the oil cooler which is of shell and tube design. The system consists of two oil coolers each of 100% capacity. A change over device (double 3 way transflow valve arrangement) is provided for switching over to stand by oil cooler manually. The changeover device is so designed that under all circumstances oil is led to either of the coolers. A small amount of cooled oil goes to the standby cooler through a valve provided across transflow valve (GL-3495-8) and after filling ,overflows to oil tank through crack open valve (GV-486-25), orifice and sight flow glass. This will facilitate standby cooler to come into service immediately when required. A temperature control valve (TCV-3012-3505) is provided as a bypass to Lube oil cooler. This is basically to take care of varying cooling water temperatures during different seasons. Oil cooler outlet temperature high alarm is provided through temperature elements (TE-3012-3505 A&B) and is set at 500C. This will prompt the operator to switchover to standby cooler and take the running cooler for maintenance. OIL FILTERS (FLT-3012-876 & FLT-3012-877): The duplex type of Oil filter with disposable cartridge type with filtration of 10 microns (nom.) is provided. A change over device is fitted for Bharat Heavy Electricals Limited
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switching over to standby filter in case of choking of the working filter. The changeover device is so designed that under all circumstances oil is led to either of the filters. A small amount of filtered oil goes to the standby cooler through a valve (GL-3496-8) provided across trans flow valve and after filling, overflows to oil tank through crack open valve(GV-3488-20), orifice and sight flow glass (GJ-3407-25). This will facilitate standby filter to come into service immediately when required. A differential pressure transmitter (DPT-312-3505) set at 1.5 Kg/cm2 is provided to annunciate high differential pressure across the filter warning the maintenance and replacement of Filter Cartridge.
Bharat Heavy Electricals Limited
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Oct Wed 5 15:38 2016
This Drawing is printed from Engineering Digital Archive System (EDAS). Therefore signatures are not essentially required.