anybody ever heard of this?

Jim Sarrasin

Was trying to open on an old 4" gate valve on a steam system which had been shut off in order to install a new unit.

Needless to say when I finally got the thing to move the stem broke and the valve had to be replaced, I figured that with the age of the valve these things would be likely to happen, but then I was told that I shouldn`t have tried to open the valve with steam pressure upstream of it.

If that`s the case then why have a valve in there at all since according to that logic there should be no steam pressure in the line in order to open or close the valve.

Am I missing something or is this some rule that I was never aware of?

By the way the system only runs at 12psi so we`re not talking high pressure here.

Thanks in advance. Jim S

[Deleted User]

you should be

able to utilize the valve at will. thats what its for. in the navy the bigger steam valves had bypasses around them, typically 1/2 or 3/4'' that were for bringing up the downstream temperature more than for pressure equalization, if i remember right....but those were 1275 psi boilers...

Jim Sarrasin

Thats what I`ve always thought valves were for but when you hear something like that you kind of shake your head and wonder.

Cosmo

Ship boiler ?

Did you say 1,270psi? Wow, that must be how they keep the pipe sizes small. Are they still using gate valves (beause they are rebuildable?) or have things switched over to ball valves? I love to go to see the inner workings of retired naval ships converted to museums. I spent many hours in the battle cruiser Massachusets just looking at the mechanicals.....

Cas

Earthfire

steam valves

opening steam valves with pressure on one side has been known to cause line explosions and kill people near the pipes. You have to know were the condensate is in the lines,control the rate of valve opening and be very aware of system piping design. In the immortal words once heard at a seminar "IT DEPENDS" P.S. 12 psi of steam is not something to ignore. It can do a lot of damage if you screwup.

Gary Fereday

lets see?

4"disc with 12 #'s per each square inch on it? Humm? 4x4=16 x .7854= 12.56 x 12=150 #'s Shoving that old disc into the old seat. a little corrosion welds up and walla noopen! I have seen it happen with cold water gate valves.
And never open a gate quickly. Saw 12" ductile iron come out of the ground by the length because the apprentice was told to open "the damn thing up now"! by the forman. The apprentice knew what would happen and was "slowly" opening the gate valve. anyway bigugh