Hello I&C experts,
I need your advice how to solve the problem that repeats itself now two times.

In a power plant there is a feedwater pump that supply water to the boiler. Pressure of the feedwater is about max 150bar. A pressure is measured immediately after control valve. During startups this valve is manipulated by the operator. It seems that because of the sudden valve's opening pressure transmitter is damaged. Pressure transmitter that is used is SITRANS P with Max. perm. test pressure 250 bar, and nominal range 0 to 160 bar. But so far it happens twice that this transmitter starts working after plant is started. There is an idea to extend impulse pipe or even to make it like letter U in order to prevent sudden pressure changes. The pressure transmitter becomes faulty when control valve is open for the first time (on one side is 145 bar, on other 1 bar).

What could we do in order to "cushion" or soften this pressure change?
Thank you in advance for any suggestions.

 

>(on one side is 145 bar, on other 1 bar)

This is a differential pressure transmitter (DP) transmitter?

 

Hello I&C experts,
I need your advice how to solve the problem that repeats itself now two times.

In a power plant there is a feedwater pump that supply water to the boiler. Pressure of the feedwater is about max 150bar. A pressure is measured immediately after control valve. During startups this valve is manipulated by the operator. It seems that because of the sudden valve's opening pressure transmitter is damaged. Pressure transmitter that is used is SITRANS P with Max. perm. test pressure 250 bar, and nominal range 0 to 160 bar. But so far it happens twice that this transmitter starts working after plant is started. There is an idea to extend impulse pipe or even to make it like letter U in order to prevent sudden pressure changes. The pressure transmitter becomes faulty when control valve is open for the first time (on one side is 145 bar, on other 1 bar).

What could we do in order to "cushion" or soften this pressure change?
Thank you in advance for any suggestions.

I'm not sure about what is the fault that you are talking about is happening to your transmitter...Is there a pressure spike or is it one side is 145 bar, while on the other side it is 1 bar...????
But the one side 145barg while on the other 1 barg, this is a phenomenon that occurs during cold startup of boilers when feed water is fed to a boiler drum which is at atmospheric pressure. All pumps work on back pressure and if there is no back pressure the water is pushed at the drum pressure, in your case 1barg(the pressure of the drum). In many plants there is a different control valve(much smaller in size than the actual feed water control valve) which is used for filling purpose during cold startup because during cold startup there is a huge amount of pressure drop across the feedwater valve which will lead to the control valve's plug and seat erosion faster if the pressure of the fluid inside the pipe drops below the vapour pressure.This is done just to increase the life of the larger and costlier feedwater control valve. Also the control valve's discharge pressure will always be equal to the drum pressure...and the modification of the impulse line that you are talking about to make a 'U' should be done too as you dont want high pressure and temperature fluid to directly affect the impulse piping and the transmitter.

 

Mikas... try Siphon tube.