Pump Suction Pressure Frequently Increase and Decrease


Thread Starter


In our Boiler Feed water Pump all the time pump suction pressure increase and decrease trend. Why this is happening and how we can overcome the problem. please help me.
Not enough Information
Is the pump fed from a tank, is the level changing?
From a condenser where the pressure is changing?
Some restriction in the pump intake?
Change in flow due to varying boiler demand?

I'm really the last person to answer a boiler question but I do have some understanding of pumps, the suction pressure shouldn't be caused by the pump.

Mahabubur Rashid Khan

The pump is taking suction from LP drum. In full load condition suction pressure not vary too much. only vary during in partial load.

Last two years pump and boiler not in operation due to problem in steam turbine. After again put back in service problem starts. It is mentioned in here two hrsg in here and both we are facing same problem.


Sounds to me you should start ruling out first.

Is it the pump or the process? Monitor variables of the pump like amperage or frequency. If it remains constant you got most likely something in the process.

Is it downstream or upstream? U not talk about outlet pressure. So presumably that's just fine?

Then start looking upstream. Talking about both HRSG one would suggest you got something going on from the point where both systems intertwine.

Work analytical and rule out possibilities. Hard to troubleshoot up till a cause without being on site.
> The pump is taking suction from LP drum.

if this LP drum is also the dearator, where make up water is brought in, you can have drastic level changes depending on water temperature.

You need to stabilize the drum pressure and temperature with steam.
>Last two years pump and boiler not in operation due to
>problem in steam turbine. After again put back in service
>problem starts.

Thats the reason I guess. For two long years, the HRSGs must not have been preserved appropriately resulting into corrosion. Once you fill the boilers again and circulation resumes, the rust keeps accumulating at the BFP Suction strainer causing choked suction and wide fluctuations in suction (and henceforth discharge pressure as well). The same thing usually occurs when one tries to commission pump for the first time after erection specially after hasty steam blowing.

So look for Differential Pressure across suction strainer of BFPs. Most probably 5-10 cleanings of the strainer should be sufficient to restore normalcy.

Can also look for insufficient de-aeration or dissolved O2 test results, although it appears less likely in your case.

Please do post feedback even if the problem has already been solved.

I think the problem is in the discharge of the pump not suction
so if there is a control valve in the boiler side for controlling the flow or temperature so this will make oscillating in the pressure line if the control valve tuning is not right

if you have a P&ID diagram that will help us analyzing this issue
and also the trend of discharge pressure.