Turbine Operations: Actions Under Various Conditions

Questions and Answers

What is the purpose of the additional 50 NB drain provided at the PRDS floor?

To drain excess steam during a trip (correct)

To maintain required seal steam temperature

To prevent water entry if seal steam temperature is less than 250° C

To supply auxiliary seal steam during normal operation

Why does the seal steam supply control valve close on interlock?

If seal steam temperature is less than 250° C

If seal steam temperature is less than 280° C and HP shaft temperature is more than 300° C (correct)

If HP shaft temperature is less than 300° C

If seal steam temperature is more than 280° C

How often should the steam traps on drains of Aux.PRDS/HT Header/Station HT header/Aux.seal steam line be serviced?

Every 2 years

Every 6 months

Every 5 years

Annually (correct)

What is the purpose of the continuous draining through the warm up orifice in the Auxiliary Seal steam supply line?

To maintain required seal steam temperature Signup and view all the answers

What should be done if the DP across the jacking oil filter is more than 5-10 KSC even after cleaning?

Replace the filter element Signup and view all the answers

What is the minimum temperature of the piping near the orifice in the Turbine seal steam header?

100° C Signup and view all the answers

Why should the orifice size be increased by at least 25 % in the Auxiliary Seal steam supply line?

If the continuous draining is not effective Signup and view all the answers

What should be done after restarting the unit?

Clean the jacking oil pump discharge filter Signup and view all the answers

What action should be taken to ensure the auxiliary seal steam temperature is maintained when the machine is on load?

Operate the motorized drain valve intermittently at 285° C/300° C. Signup and view all the answers

During a grid failure, which action is appropriate regarding seal steam supply?

Vacuum killing is implemented when no other unit is available for seal steam supply. Signup and view all the answers

What should be ensured if the direct source of auxiliary seal steam from CRH is closed?

Charge auxiliary seal steam through the unit HT aux. steam header. Signup and view all the answers

What is a critical observation during shutdown when the turbine is on barring gear?

Monitor for turbine speed slowdown. Signup and view all the answers

What should be the rated pressure for auxiliary seal steam when charged through the unit HT aux. steam header?

16 kg/cm2 (g) Signup and view all the answers

During initial start-up when the aux. steam system is unavailable, which alternative is mentioned?

Charge aux. PRDS from the main steam. Signup and view all the answers

What happens at higher main steam pressures and temperatures concerning seal steam parameters?

It becomes difficult to maintain the required aux. PRDS and seal steam parameters. Signup and view all the answers

What should be done during post-barring stalling?

Perform an inspection for any mechanical faults. Signup and view all the answers

Study Notes

Actions Needed Under Various Operating Conditions

Actions required when machine is on load, coasting down, during grid failure/total AC failure, during shutdown, and during startup
Vacuum killing required in cases where no other unit is available for seal steam supply or when seal steam supply is available from another unit
Shutdown of unit required when turbine speed slowdown is observed during barring gear operation or when turbine rotor comes to a standstill

When Machine is on Load

Ensure condensate-free auxiliary seal steam with temperature above 290°C
Maintain auxiliary seal steam temperature using motorized drain valve MAW-10-A0 41, opening/closing at 285°C/300°C
If direct source of auxiliary seal steam from CRH is closed/not provided, use Unit HT Aux.steam header and maintain rated pressure (16 kg/cm²) and temperature (320°C)

Initial Start-up and Seal Steam Parameter Maintenance

During initial start-up, if Aux steam system is not available from other units, use Main steam to charge Aux PRDS and maintain required seal steam parameters
However, at higher MS steam pressure and temperature, it's difficult to maintain required Aux PRDS and seal steam parameters
In such cases, CRH Source is to be lined up for HT header and auxiliary seal steam supply (or direct source of seal steam from CRH)

Additional Precautions

Ensure seal steam supply control valve closes on interlock if seal steam temperature < 250°C or HP shaft temperature > 300°C and seal steam temperature < 280°C
Ensure all steam traps on drains of Aux.PRDS/HT Header/Station HT header/ Aux.seal steam line are functional and serviced annually
Check steam traps jointly with TMD & Operation and create a joint protocol
Ensure continuous draining through warm-up orifice provided in Auxiliary Seal steam supply line, upstream of seal steam control valve
Ensure orifice size is increased by at least 25% if continuous draining is not effective

Turbine Seal Steam Header

Ensure continuous warm-up flow through given orifice (Parallel to MAL-81) in Turbine seal steam header
Use Non-contact thermometer to ensure temperature of piping near orifice is at least 100°C+
Investigate and correct reasons for low temperature/flow through this line (e.g. line/orifice choked)

After Restart of Unit

Ensure Jacking oil pump discharge filter has been cleaned
Ensure DP across jacking oil filter is not more than 5-10 KSC; replace filter element if necessary

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Description

This quiz covers the necessary actions to take when operating a turbine under different conditions, including during load, coasting down, grid failure, and shutdown.