Steam Turbine Start up

• GT load 50MW for Cold Start up Conditions• GT load 65 MW for warm/hot start up• ST on Turning Gear minimum 6 hrs• One CEP in service• One CW pump in service

ST Turning Gear Operation

• F.G of Lube oil ON, Lube oil pump in service.• Turning Gear Functional Group ON.• Turbine Lifting oil and Jacking oil Pumps in

service• T/G Engaging sequence• Engaging Solenoid valve will be ON• Creep Solenoid valve will be ON for few seconds• Turning Solenoid valve will be ON

• Set HP Main Steam Pressure 40 bar• Set LP Main Steam Pressure 3.9 bar• Check and Confirm HP/LP Super heaters drain valves on

Auto• Check and Confirm HP/LP Super heaters vent valves on

Auto• Check ST Rotor temperature and set Main Steam

Temperature accordingly• For Cold/Hot/Warm start up rotor temperatures are

mentioned below• Cold Start up: Turbine Rotor metal Temperature <150 0C• Warm Start up: Turbine Rotor metal Temperature >150

0C-- <350 0C• Hot Start up: Turbine Rotor metal Temperature >350 0C

STEAM INJECTION SYSTEM

• The Steam injection into the HP outer casing is aimed at improving the heating of the outer casing during the startup phases, when there is no steam flow or a very small amount of steam flow heating the outer casing inner wall in correspondence of the first inner casing. Therefore the steam injection is aimed at improving the expansion of the outer casing and at limiting the differential expansion (long rotor conditions) during the startup.

• It is achieved through two nozzles mounted on the lower outer casing; also an additional drain is mounted on the lowest part of the lower HP casing.

• The heating steam is get from the drain line pipe downstream the Stop valve and is supplied to the nozzles through a globe valve pneumatically operated with ON/OFF operation.

• The steam injection will be switched ON, with the unit reset, before rolling and be maintained on up to synchronization or 15% load: Initially operation of the steam injection will be by the operator; later, when properly tuned, it will be according to logic.

• Steam injection valve opens when rotor metal temperature is <150 0C

• Steam injection valve closed when rotor metal temperature is >250 0C

Auxiliary Steam Header Charging

• At pressure 12~15 bar start charging Auxiliary Steam Header.

• Steam traps bypass valves should be open to release water and prevent water hammer.

• Start heating and pressurizing of Auxiliary header.

Vacuum Pulling

• Establish water seal at Steam Turbine Glands sealing Steam Condenser through U-siphon

• Seal the vacuum breaker valve, ensure its water over flow• Start one Glands sealing steam condenser vapor

extracting fan.• Start heating and pressurizing the Sealing steam (Open

traps bypass valves to remove the condensate from line)• Set Glands sealing steam temperature 150~200 0C • Sealing Steam pressure Gradually 30~70 m.bar• When LP side sealing steam temperature reaches to 130

0C- Put Start up Ejector in service• When vacuum reaches to 500 m.barA put Main Ejector in

service

Observing the parameters

• During vacuum pulling observe all parameters of vibration, Thrust position, Differential expansion and ST upper and lower casing temperature difference, bearing temperatures etc.

• Initially differential expansion goes to positive side and then reduces

HP/LP By pass system release

Conditions– Main Steam pressure 40 bar– Vacuum <500 m.barA

NOTE: Maintain HP drum pressure 20~22 bar, until HP/LP bypass valve release is obtained, to prevent HRSG TRIP If Pressure is >25 bar and vacuum is >550 m.barA and bypass valve not available, HRSG will trip

Preparation for ST rolling

• Put CW pump 02 in service• Gradually open HP by pass valve up-to 100% (HP Steam Pressure

40 bar , Temp. 350 0C)• Gradually open LP control valve 15~20% (LP Steam Press. 3.9 bar ,

Temp. 1750C)• Start Control Oil pump F.G ON• Check all parameters Vibration, Thrust, Differential Expansion etc.• Thrust position <0.5mm• Upper and lower casing Temp. > 150 0C• Set Speed 3000 rpm• Set Acceleration value 5% in cold start up and 10% in hot start up.• RESET the Machine• Start rolling• Watch all parameters very carefully

Steam Turbine Start up and loading

• At the speed of 2850 rpm Close Excitation breaker.

• AT the speed of 3000 rpm synchronize STG from vertical panel

• AOP, T/G and lifting oil pumps will cut off and Main Oil pump will come in service

• LP exhaust hood spray closed at ST load 8MW• Turbine drains closed at ST load >15MW• Extraction steam to dearator in service at ST

load 53 MW

Three ways to load ST