STEAM TURBINE LUBE OIL SYSTEMBy Moinuddin

CONTENTSWHY LUB OIL SYSTEM IS NECESSARYCOMPONENTS OF LUB OIL SYSTEMFLOW DIAGRAM OF LUB OILSYSTEMFUNCTIONS OF INDIVIDUAL COMPONENTSOIL FLOW TO DIFFERENT BRANCHESPROTECTIONS

LUB OIL SYSTEMSteam turbine lube oil system is usually required to provide oil for trip-and-throttle valve, governor system, bearings.

Oil Characteristics

Physical & Chemical PropertiesTest MethodTurbine speed(3000 rpm 50Hz)CEI/ISO Viscocity class-32Kinematic ViscocitycSt at 40 deg CASTM D44528.8 35.2Flash PointASTM D92180 deg CViscosity Index-95 MinimumNeutalization ValueASTM D9740.20 MaxEmulsion TestASTM D140145 Minutes MaxPour PointASTM D97-5 deg C Max

Oil PropertiesViscosity: The Viscosity of an oil is the measure of its resistance to flow. The kinematic viscosity of an oil is the measure of its resistance to flow under force of gravity action.Flash Point: The flash point of an oil is the lowest temperature at which sufficient vapors are given off to form an inflammable mixture with air that will burn momentarily when a small flame is applied.Neutralization value: The neutralization value (total acid number) is the quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize all acidic constituents present in one gram of oil.

Oil PropertiesEmulsion test: This method describes a procedure for measuring the ability of oil and water to separate from each other. A 40 ml sample of oil and a 40 ml sample of distilled water are stirred for 5 minutes at 130 deg F in a graduated cylinder. The time required for the seperation of emulsion, thus formed is recorded.

Oil PropertiesOil Requirements: shalbe mineral oil of highest quality and uniformity. It shall conytain no grit, inorganic acid, alkali, water soap, asphalt, pitch, resinous substances, or any other substance which will interfere with the lubricating properties of the oil, or that will be detrimental to the oil or to the metals with which the oil will come in contact in service.Rust prevention: the oil shall be capable of preventing the formation of rust on steel parts bathed with oil, should small quantities of water enter the oil in the normal operation of steam turbine.

Oil PropertiesResistance to oxidation : for long service in steam turbine systems, the lubricating oil must have high resistance to oxidation to protect against the formation of sludge and in general to maintain all initial characteristics.Water seperating ability: highly refined oils will separate from water more readily than oils which have been contaminated in service or which have begun to form insoluble sludge.Resistance to foaming: high quality turbine oils should have good resistance to foaming.

General informationOil Tank Capacity: 9500 LtLube Oil Flow :850 Lt/minWorking Temp :50 deg COil Header Pressure:1.8 barOil viscocity :20.4CST @ 50 deg COil Type :ISO VG 32

MAIN & AUX OIL PUMPTwo in numbersSpecifications Capacity- 1200 Lt/minDischarge pr- 6 barDesign Pr 10 bar.Working temp: 15 70 deg CSpeed - 1450 rpmDrive - A.C. MotorMotor power-30 KW

EMERGENCY OIL PUMPProvided as back up protectionCuts in whenever there is AC failure or the pressure in the lubrication system falls less than 0.9 barSpecifications-Capacity-850 Lt/minDischarge pr-4 bar Speed-1750 rpmDrive-D.C MotorMotor power- 11kw

DUPLEX FILTERLubrication Oil Type : ISO VG 32Fluid Viscocity : 10.2 Cst @ 70 deg CSpecifications-Working Temp : 15 70/80 deg CWorking PR : 5/10 bar.Delivery : min/ max 800 / 930 Lt/minFiltration: 23 microns.Delta normal / max: 0.3 1.0/ 1.5 bar

FLOW CONTROL VALVEFluid : Oil ISO VG 32Sp Gravity at oper cond: 0.852 at 50 deg COper Viscosity cst : 27.8 Cst @ 50 deg CControl range : 1.5 to 2.5 bar.Setting value : 1.8 bar

LUBE OIL ACCUMULATORType : bladderNominal capacity : 100 LtDesign pressure : 15 barTest pressure : 22.5 barDesign temperature : 80 deg COil type : LUBE OIL ISO VG 32Viscocity : 10.2 cSt at 70 deg COperating temperature : -10 to +80 deg COperating pressure : 9 bar

THERMOSTATIC VLAVE Fluid : LUBE OIL ISO VG 46Sp gravity @ operating cond : 0.875 Kg/ cdmOperating viscosity : 27.8 @ 50 deg CFlow : 900 Lt/minTemperature : 46 deg CPressure @ normal flow : 4 kg/scm IN 3.62 kg/scm OUTSet point : 46 deg

SLC AOPCommand goes to switch ON AOPWhen :SLC AOP IS ON and MOP trips OR Oil pressure < 1.3ksc

SLC EOPEOP ON Command goes whenSLC EOP is on andLub oil pressure< 0.9 bar

MAIN OIL COOLERSPurpose is to cool the oil , Wateris inside the tube and oil flows inouter shellMaximum lubricating oil temperature at cooler outlet restricted to 47 degBearing metal temperature alarm- 90 deg shut down-120 degThreewaycontrolvalve-Electrically driven & has the function ofregulating lubricating oil temperature

CENTRIFUGEDraws oil from turbine oil tank mainly DOT, after removing any water & entrained solid matter oil is returned back to oiltankCentrifuge does two functions:Clarification-Sludge separation inwhich the machine is used for separating offparticles normally solidPurification-Liquid(oil) Liquid (water)separating two intermixed liquids which are insoluble in each other & have different sp gravities. Solids with spgr higherthanthoseofliquidcanbe separated of at the same time

MOT VAPOUR EXTRACTORMounted on top of main oil tankFunction is to produce slight negative pressure in main oil tank and in the bearing casing and thus draws off oil vapour Oil vapour before exhausting to atm is passed through oil catcher

MOT VAPOUR EXTRACTORService : extraction and splitting air / oil fumes.Fliid : oil saturated airCapacity : 300 mc/h at 25 deg COperation temperature : 40 deg C maxSuction pressure : 175 mbarFiltering elements : coalescent cartridgesMotor power : 2.2 kw

ProtectionsThe minimum oil temperature value to start the oil pumps equal to 15CThe minimum oil temperature value to put in service the turning gear equal to 20 CThe minimum oil temperature value to running the turbine equal to 35CCooling water to oil heaters should be closed until the discharge lubricating oil temperature at turbine bearings inlet, reaches a value of 43-49C

PROTECTIONSDuring the operation, the normal oil temperature range should be around the following values :Lube oil temperature at bearings inlet 5052C.The maximum allowed values should be 55C.Bearing oil discharge temperatures should not exceed 85C. Alarm at 80C and trip at 85C