Boiler Feed Pump Speed Control Scoop Problem/Abnormality

Check the feedback sensors or perhaps PID controller, probably it might be caused by abnormal PID operation or delayed feed back sensing. Calibrate regularly controllers and feedback sensors.

Sensor as well as PID controllers are working normal. No abnormality observed. Scoop variation is actual. That throttles IP FCV.

No sir we checked thoroughly that process is working as per logic in manual as well as DCS. But why after a year this kind of abnormality is observed. 100 % opening of scoop is not defined anywhere. And full opening of scoop is also not required.

You can see the process flow in the pic

only one 100 % line in service at a time in 3 element control mode. As described in problem feed flow is same. Set Point is also same. SCOOP and PUMP speed is different. It is showing that it is absolutely working as per logic but 100 % scoop is not proper.

Is it alright if ask you questions? This is a part of the solution, i believe.

what made you think 100% scoop is not proper? Does the manual tells you 100% scoop is not proper?

The scoop has nothing to do with the controls. It's included in the display actually as a sort of diagnostics. It's just fine no need to worry, its working very well.

However it is evident given the previous & the recent data, that your systems suffer some sort of scaling (restrictions to flow down streams). Look at the power output - from 391 to 380MW, DP increases & IP increases.

The pressure increase is what caused the scoop to go 74 to 100%.

Well, its not an instrumentation problem, I believe. The root cause is scaling or fouling material accumulation on heat exchanger.

Consult subcontractor or specialist on the field of descaling services and schedule shutdown for maintenance 11MW/time losses is a big money.

yes sir...

thank you very much for the solution. It is one of the possibility we have to inform the specialist...

u can ask me any question.

my aim is to get the solution.

100 % scoop is not proper means at the given parameters the scoop position should not be 100 % as previous it was only 54 %.

Is there any other possibilities except instrument fault and scaling ?

if we are using the DM water for all kind of application then how scaling is possible ?

at 86 % of speed pump is achieving its rated RPM : 2900. and discharge pressure is 187 bar in normal condition year before. And same condition is at present also.

We also checked in the logic that Scoop is varying due IP feed control valve only. There is a criteria in logic (IP FCV > 60%). We also verified the DP across FCV and it is normal.

We have different discharge lines for HP(Last stage) and IP(Intermediate stage) from the Feed Pump.

after 86 % opening of scoop we observed that from 87 % to 100 % there is no pressure rising or Pump Speed Rising.

Nothing more, I could add up man, but, can I have my last questions?

1) "What's the purpose of the scoop to the whole system-why is it there"

2) Does it mean that water when Demineralized is free of all impurities that form the scales?

1) "What's the purpose of the scoop to the whole system-why is it there"

YOU MUST BE KIDDING BY ASKING ME THIS QUESTION ?

ANYWAY SCOOP IS NOTHING BUT FOR THE SPEED CONTROL OF THE PUMP. IN HYDRAULIC COUPLING ACCORDING TO LOAD DEMAND FLOW DEMAND IS VARYING THAT'S WHY SCOOP IS VARYING. AS SCOOP VARIES FLOW AND AS WELL AS DISCHARGE PRESSURE IS ALSO INCREASE/DECREASE BY VARYING IN PUMP SPEED. I HAVE SOME ANIMATION FOR THAT. I CAN SEND IT TO YOU IF YOU WISH. OR YOU WILL FIND ON ANY POWER PLANT RELATED WEB SITE.

2)Does it mean that water when Demineralized is free of all impurities that form the scales?

I DON'T KNOW MORE ABOUT THAT. BUT I THINK SO THAT DEMINERALIZED WATER WILL NOT AFFECT THAT MUCH THAT IT CAN RISTRICT FLOW WHICH CAN VARY SPEED OF PUMP FROM 2730 TO 2899 IN JUST A ONE YEAR OF OPERATION LIFE OF THE WHOLE SYSTEM.

ANYWAY THANKS FOR YOUR REPLY. YOUR ANSWERS HELP ME A LOT TO GAIN MY KNOWLEDGE. THANKS BUDDY.

I am not kidding. In a way I want people learn and correct themselves other than me teaching them. The best way of learning is by learning it yourself. This is where learning becomes irreversible-> once you learn, you know. No bigger gift you give to yourself, other than you learn.

Cheers!