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Anti Surge Valve Passing


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#1 Aroora

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Posted 07 May 2020 - 09:20 AM

We have some issues on turbine HP valve (higher opening and steam flow) and also turbine speed is running higher than normal. All the possible causes are being investigated (Mechanical integrity of the valve, control oil circuit and valve linearity issues) 

There is suspicion that anti-surge valve of syn gas compressor is passing. Can any one please advise will this have any impact on compressor power, in turn more power demand from turbine



#2 Bobby Strain

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Posted 07 May 2020 - 04:35 PM

The symptoms you describe are consistent with a reduced turbine efficiency. This can be caused by salt deposits on the blades. You should first check the turbine efficiency.

 

Loss of turbine efficiency wouldn't explain the need for higher speed. In addition to leaking valves, some problem in the compressor would cause the conditions you observe for the turbine. So, you need to take data to properly analyze the problem. Efficiency checks are are easily done. You should compare your observed performance with the design. Hopefully you have performance curves for both the turbine and compressor.

 

Let us know what you find.

 

Bobby


Edited by Bobby Strain, 11 May 2020 - 06:51 PM.


#3 Aroora

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Posted 12 May 2020 - 10:56 AM

Bobby

Thanks for the response

To add further we have gas composition issues in the loop, because of increase in molecular weight on the NG feed and also other parameter referred as carbon number. 

Because of these changes, the differential pressure across the compressor increased over the last two months, I suspect this is causing more power demand  and in turn higher steam flow/speed

Regarding turbine blade deposits, the steam quality is good and turbine has been inspected thrice over the period on 10 years and no deposits are observed.  Moreover turbine wheel chamber pressure is consistent with the steam throughput and we supposed to see an increase in case of any deposits. Turbine power has increased by 2 to 3MW which I believe have direct correlation with gas composition and high Diff Pr. across the compressor

My concern is apart from the above gas issues, will the passing of ASV can add more load on the compressor. Based on the estimation around 2 to 3% of passing is suspected through ASV (total flow 620t/h)






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