Gate Valve Leakage

[MoReSo]

A recycle pump was blocked in for a bonnet gasket repair on a warmup line when the outside suction valve bonnet gasket started leaking. A small fire ignited under the insulation blanket.

Valve was closed to block in the pump. Several hours after closing the valve, the valve leaked out of the bonnet and started a small fire. The valve continued to leak until the repair on the other valve was made and this valve was opened, unblocking the pump. After the valve was opened the leak stopped.

Anybody to tell why leakage happened from the bonnet gasket when the valve was closed.


MRSohrabi;
Material and Welding Eng.

 

[MintJulep]

Pressure.

 

[MoReSo]

May I ask to provide more info?
Do you mean that pressure drop is the cause?

MRSohrabi;
Material and Welding Eng.

 

[btrueblood]

When the valve was open and the pump running, the low inlet pressure of the pump likely dropped the bonnet pressure of the valve below atmopheric pressure (and the valve probably allowed aspiration of air into the pump inlet). When the valve was closed, the pressure rose to something greater than atmopheric at the valve bonnet and allowed the fluid to leak out.

 

[Compositepro]

If the valve is a rising stem type, then when the valve is closed the portion of the valve that was exposed to the environment is now in the seal area. The stem may be damaged, corroded, or dirty.

 

[bcd]

And when the valve is fully open, it may have a back seat on the stem which may isolate the packing from pressure.

 

[Ripz]

Inlet piping systems are usually designed for lower pressures that your discharge pressures. With the pump blocked in, the inlet valve was exposed to discharge pressures, which would be higher that the inlet valve was designed for.