8" Gate valve removal? 2

[Hamza1988]

Hi, if we are to remove an 8" gate valve or any other size gate valve from a pipeline, does the valve have to be in an open or closed position while removing? Logically it shouldn't make any difference but I've overheard from someone that it has to be in an open position since at closed position the valve body slightly expands therefore it would be difficult to remove.

Thanks

 

[pennpiper]

Aaaaaa,
"Beauregard Gustafson" strikes again!

Sometimes its possible to do all the right things and still get bad results

 

[LittleInch]

Good isn't google great. I had to go look that phrase up...pipingdesigners.com/contents/blog/130-blog-1l-who-is-beauregard-gustafson.

Hamza, stick to logic and you won't go wrong. This is a case in point. Whoever the someone is, make sure you don't bother overhearing them again....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Hamza1988]

Haha, I'll be honest...I looked it up as well. Thankyou guys. I am not disappointed as I have learnt something new today.

 

[PeterIgg]

The only comment I would have is that with the valve partially open the potential for trapped pressure within the valve is minimized. Don't believe the distortion comment at all, in fact I suggest that a valve which did distort would by default have failed test.

 

[wagga]

The only time I had to replaced a valve with the valve open was a water line.
It had a about 20 meters of head (residual). Too much pressure on one side, though it can be operated. But not easy to pull out the valve.

Didn't want to drain the whole header as well (would take about 1 hr from estimate). So had the valve opened to "equalize", unbolted and pulled out the valve, and in went the new valve (opened), bolted and closed. It was a bit wet, but did get done quick.

 

[Ehzin]

I personally haven't witnessed the phenomenon firsthand but the reasoning of the valve "locking" due to the valve being set in a certain position and closing is based on an extremely basic understanding of thermal expansion/contraction. The proposal is that if a valve is closed and subsequently brought down to ambient temperature the valve body will contract more than and seat against the valve stem disc leading to a VERY SIGNIFICANT load on the seat/disc (Please mind the CAPS). I've never seen a model but the shape of the valve body in this scenario would lead me to believe that the linear expansion in the y direction of the stem would be less than the contraction of the valve body in the y direction. My only comment is that the scenario isn't that far fetched and I would enjoy a rebuttal but more a discussion.

Thanks,
Ehzin