Turbine Lub Oil System(A Chemical Approach )

☻Ranjan Pal (Empl No. 101277)☻Tushar Kumar Sinha (Empl No. 101275)☻Munish Thakur ( Empl No.101269)

Presentation Features

Need of Lubrication System in Turbine. Components of Lubrication System. Lub Oil Circuit. Working of Different Components of Lub System. Different Aspects and Problems of Lub Oil and their

Chemical Reasons.

Why Lub Oil System Needed..?

Problem1. Very high amount

friction is produced in rotating elements.

2. Because of above reason very high amount of heat is also produced

Remedy1. Wear and Tear, because of

friction, can be avoided.

2. Cooling can be done effectively.

Lubrication System Components

۩ Main Oil Tank (MOT)

۩ Auxiliary Oil Pump. (AOP)

۩ Emergency Oil Pump. (EOP)

۩ Jack Oil Pump. (JOP)

۩ Main Oil Pump (MOP)

۩ Oil Coolers.

۩ Oil Injectors.

۩ Centrifuge.

۩ Vapour Extractor.

MAIN OIL TANK

☻Rectangular tank.

☻Supports all the oil pumps.

☻Size specified 25/40.

☻Location is 8.5m.

☻Clean oil chamber and Dirty oil chamber.

☻Oil pumps located on clean oil side.

☻Oil return comes to dirty oil chamber.

☻Tapping is taken to centrifuge.

MAIN OIL PUMP (MOP)

☻ LOCATION: This pump is mounted in the front bearing pedestal. It is coupled with turbine rotor through a gear coupling.

☻ Oil suction from MOT Through two number of injectors connected in series.

☻Takes over when turbine speed > 2800 rpm.

☻Supplies oil for turbine bearing lubrication as well as for the turbine governing system. .

AUXILIARY OIL PUMPS (AOPS)

☻Two in number, AC motor driven

☻Vertical one stage rotory pump with radial impeller & spiral casing.

☻Supplies oil during turbo-set starting and stopping when the turbine is running at speed lower than 2800 rpm supplies oil to governing system as well as to the lubrication system.

☻It also serves as standby to main centrifugal oil pump.

☻Submerged pump body

EMERGENCY OIL PUMP (EOP)

☻This is a centrifugal pump, driven by D.C. electric motor.

☻Vertical

☻Centrifugal submerged

☻This automatically comes in when ever there is failure of A.C. supply at power station and or the lub oil pressure falls below a certain value. This pump can meet the lubrication system requirement under the conditions mentioned above.

JACKING OIL PUMPS (JOPS)

☻There are three JOPs out of which two are AC and one is DC powered.

☻To lift the rotor assembly during TG start up and shut down.

☻Suction from MOT.

☻Delivers a pressure of 120kg/cm2 for lifting of rotor.

OIL COOLERS

☻To cool the lubricating oil☻Consists of tube nest, inner & outer shell & water boxes☻The cooling medium for these coolers is circulating water. ☻The pressure of the cooling water is kept lower than that of

oil to avoid its mixing with oil in the event of tube rupture.

OIL TEMP. CONTROLLER ☻For maintaining the lub oil temp at rated value by

controlling the flow through the coolers.

VAPOUR EXTRACTION SYSTEM

☻Two Vapour Extractor fans.

☻Exhaust fans.

☻Maintains NEGATIVE pressure inside MOT.

☻Removes oil fumes from the MOT.

OIL FILTER

☻Basket type filter inside the oil tank

☻For thrust bearing-Duplex filter

☻For jacking oil-Duplex filter☻Filter changeover required after choking.

MAIN OIL CENTRIFUGE

☻Required for removing moisture and mechanical impurities from the turbine oil.

☻A portion of oil is continuously circulated through the centrifuge to remove the moisture from the oil.

April 11, 2023 PMI Revision 00 14

Emergency operations of Lub. Oil System:

In case of AC failure ( Black out )….

☻EOP will start ☻Extend the DG supply to the emergency MCC☻Start AOP ☻Start JOP.☻Rotate turbine with Barring gear.

Specifications of Oil:

☻ Specific Gravity 0.852 @ 50 0C☻ Kinematic Viscosity 46 cSt☻Flash point 201 0C (Min)☻Pour Point - 6.6 0C (Max)☻Mechanical Impurities Nil

The recommended turbine oil Servo Prime-46 of IOC.

Reasons for Deterioration of Lub Oil

Increase or Decrease in Viscosity.Oxidation Stability.Foaming. Rust Inhibition. Emulsification AcidityContamination by dirt & metallic particles.

Main Problems in Lub Oil System

Oil Contamination. Oil Heating. Oil Leaking.

REASON FOR OIL CONTAMINATION

• Stage I• Starts from

Component manufacturers, air breathers or hydraulic systems during repair or overhaul in oil replenishing. Sometimes new oil has also contamination.

• Stage II• Contamination from

stage I cause wear in machine which catalyses the oxidation of oil. It makes oil sticky and with the mixing of metal particles it forms “SLUDGE”.

Consequences of Oil Contamination

Chocked Filters. Pump Cavitation. Aeration Sludge Formation

a. Because of sludge heat exchange will be insufficient.

b. Inefficient oil cooler capacity.

Reasons Of OIL HEATING

• Oil Side 10-15 % of electrical

energy gets converted to heat energy and finally taken up by oil.

Very high friction among rolling bodies produces high heat.

• Water Side Scale formation in

water cooling tubes. Inadequate size oil

coolers and cooling towers.

Inadequate oil flow through oil coolers.

OIL Leaking• Leaking of oil from different oil seals and

glands.

Reasons of OIL Leaking

• Oil leaking is also dependent on oil contamination.

• The formation of sludge due to contamination is acidic in nature. It reduces the life of oil seal.

• Sludge has electrochemical attraction to metal surfaces & deposits on oil carrying tubes, and decreasing their life.

Methods for Removing Contamination of OIL

• There are two very widely used methods…

1. Mechanical Filter method

2. Centrifugation of Oil.

Filter Method

• In this method the contaminated oil is passed through a filter made of porous material with high pressure.

• Dirt separate out due to difference in size of oil and dirt particles.

Centrifugation

• In this method the contaminated oil is rotated with a high speed.

• Dirt separate out because of different densities of oil and dirt particle

CONSTRAINTS of above Methods

• Mechanical filters can’t separate a dirt particle less than a size of 10 micron whereas harmful dirt particle’s size can be less than 2 micron.

Filter Method

CONSTRAINTS of above Methods Contd..

Can’t remove completely EMULSIFIED water. To centrifuge we must heat the oil which reduce

viscosity but it also depletes oxidative additives. Can’t remove dissolved gases. Can’t remove low MWt. Oxidising impurities. Have high energy consumption.

Centrifugation

Analysis we use to do• Flash point : This is the temperature at which oil gives out

vapour which will just ignite if comes into contact with a flame. For lubricating oil in steam turbine it is 201 degree C.

• Acidity : Oil acidity is measured by neutralizing the acidity

with an alkali (KOH) . New oil acidity range normally lies in 0.02 to 0.10 mg KOH/g oil.

Analysis we use to do…

• Viscosity:

Viscosity of a lubricating oil is measured in a U tube viscometer using thermostat.

• Moisture content :

Lube oil in good condition will contain 100 to 200 mg/kg. of water and will appear clear ,if it appear cloudy, then level of water contamination should be measured by boiling a known volume of the oil with a solvent in a flask known as stark apparatus.

Amount of water, ppm Appearance of oil

0 Bright and clear

100 Trace of translucent haze

200 Slight translucent haze

250 Translucent haze

500 Opaque haze

1000 Opaque haze with slight water drop out

Visual Check of Water in Turbine Oil

Regular examination of an oil can

indicate its rate of deterioration. Thus the sampling and analysis of lubricating oils

ensures that they are satisfactory for continued service. If an oil beings to

deteriorate, it can be either changed or reconditioned (sometime at site) at a time

suited to the operation of the plant, rather than waiting until deterioration makes

the oil change essential at an inconvenient time.

On the basis of above finding

CHANGING OF OIL is MORE FAVOURED