Boiler Feed Pump Problem 1

[Whyknot]

I have a customer who experianced the following which is something he does not want to repeat. Does anyone have an idea what caused this?

The Pump is a 3GT I-R Boiler Feed Pump, Steam Turbine Driven, 240-257 deg F water from DA tank
Pump was shut down and not turning but hot or at least warm
Discharge valve downstream of pump was closed first. This valve was some distance away from pump (20-30’?)
Pump has discharge check valve
Bypass Line to DA Tank from Pump discharge was open
Suction Isolation Valve (Gate valve) was manually closed – takes maybe 30 seconds
There is an expansion joint on suction side next to the pump
A loud explosion/noise was heard by the person closing the suction valve immediately when the suction line valve was closed and there was violent movement of the suction line to such an extent that the hold down anchors for the suction line pipe support (next to the pump) were ripped from the floor. The expansion joint was extended to its maximum.

Operator was visibly shaken and doesn’t want to go through this again


If you have any ideas please let me know. I have asked the customer to check on a couple of theories I have but I want tell you what they are as I don’t want to color your thinking.

 

[Whyknot]

Sorry guys - Had a bit of vacation. Thanks for the suggestions I will try and find out the answers to your questions and post them.

 

[WhatIfTrue]

I have experienced the same thing, except one difference. The suction valve was in the open position. The sequence of events were however the same. The pump was shut down, and in a short time (maybe less then a minute)the suction valve failed and cracked all along its base.

A plausable explanation is that there was a leakage from the discharge valve and also check valve into the pump. This condensate leakage, when finding itself at a lower pressure, flashed initiating a surge or waterhammer. The only flaw in this is that the suction valve was open, therefore any waterhammer if any could not have any effect on the valve, because it would not offer any resistance.

Therefore, what could have happened is that first there was condensate flashing and after some time it cooled down and collapsed again (Condensation-Induced Water Hammer), which did all the damage.