Steam Turbine Vacuum Issue

Find the leak or increase cooling flow(tubes may be clogged)

Thaink you very much for your reply.

I have also checked condenser tubes by method candle testing one tube found leak so pluged it but vacuum is still poor. and also checked every leakage in codenser area including all drain valves.The combined cycle installed in 1994 that time on maximum load i.e 04 HRSG vacuum in condenser .105bar and naw a days on maximum load vacuum in condenser .320bar.Basicly I am senior operator in combined cycle plant daily try to improve vacuum ' my oppinion that operation fault and may be maintanace fault because same line i.e Gland steam area' Main steam by pass which enter to condenser and condenser hot well area line are in Inssolted so may be leaked which cause poor vacuum.

Please comment.

Thainks

One way of finding the vacuum leak is to deflect or shut down forced draft blowers that may be in the areas that you suspect and pass a smoking wick (even a cigarette) around the glands, flanges, valve stems, etc.

It could take a lot of cigarettes, so try to devise something that will smolder at a steady state (safely) for some time, so you can move from area to area.

If it is condenser flow related (assuming you've checked the water side of the tubes for blockage), check for restrictions in the supply and discharge lines. A lot of plants have had problems with growth and zebra muscles in the lines restricting flow.

Is the Main Condenser Vacuum supported by a vacuum system (Steam Jet Ejector or Liquid Ring) ? If so, check for proper operation of this equipment.

One simple check for condenser condition is to trend the difference between the cooling water outlet from the condenser and the temperature corresponding to the vacuum at a given load. If this has increased since startup it would indicate a fouled condenser.

Other possibilities are that your ejectors are eroded or dirty, gland sealing steam system not properly commissioned or that you have a leak. Maybe try commissioning your startup ejectors and see if they improve the situation. I do not know your system but assume that you have spared ejectors so that you can inspect them on the run.

dear Mr.saubinmasood,

The reasons for Low Vaccuum in the Condenser are many.

FROM DESIGN ASPECT:

1.Under Sized Condenser OR More Steam Flow in to the Condenser

2.Assuming High Heat Transfer Co-Efficient and High LOG MEAN TEMP.

3.Consideration of Very Low Approach Temperature of Cooling Water.

4.Higher Temp. of Steam at Turbine Exit.

5.Under Sized Ejector to create and maintain Vaccuum.

6. Wrongly Assumed Wet-Bulb Temp. for Cooling Tower Design

7.Wrong MEKREL RATIO for Cooling Tower.

FROM OPERATIONAL ASPECT:

1.Less Water circulation in the Condenser.

2.Highly Fouled Tube on Account of Scaling

3.Poor Ejector Operation

4.Less Temp.Difference of Cooling Tower/ Higher temp. of cooling Water entering the Condenser.

5.High Wet_Bulb Temp.

6.Less cooling Tower Fan Speed/ Less Blade Angle.

7.Air Leakage in to the Condenser.

Pl. check and give a feed back, so that we can understand what went wrong.?

DHAYANANDHAN.S