Leaky valve problem

I have a gate valve with a small leak I need to fix. The valve is
stainless and in good condition but has a very small leak when closed
tightly. It's a 3" valve with a non-standard flange so replacement is
out of the question. The valve will be seldom operated and I could live
with a fix that sealed the valve tight and allowed the valve to be
opened ONCE (for a fire hose connection).
The big complication is that the valve is welded together and cannot be
taken apart.
I was thinking of putting a thin sheet of plastic on the gate, but if it
washed off when opened it might jam something. Maybe just a thin bead
of silicone on the upstream side? It's a water gravity system with only
5' of water head so pressure is extremely low.
Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
Reply to
nick hull
Loading thread data ...
If you have the valve out of the system, and apparently you do, open the gate fully and check the seat under the gate for corrosion or dirt that keeps the gate from going completely closed. That may eliminate the problem. If that's not it perhaps placing a thin bead of silicone under the gate and allowing it to cure before closing the gate will solve the problem.
Jim
Reply to
Jim Chandler
I don't have lots of experience, but every gate valve I have seen (5 or 6 of them) leaked some when closed. I think that the silicone sound like a good idea, but I would think that the downstream side would be better since any (even your low) water pressure would force the gate into the silicone rather than away from it.
Carl Boyd
Reply to
Carl
Jim Chandler wrote:
Rather than RTV silicone (caulk), I'd suggest either silicone grease (I prefer the high-vacuum type - it's pure and pretty stiff - some of the automotive variety I've met is thinner) or beeswax (buy a toilet seal ring) on the sealing surface.
Reply to
Ecnerwal
Can you machine a small o-ring groove in the down stream face of the valve disk an glue in a small o-ring? This would be a permanent fix.
Wolfgang
Reply to
wfhabicher
After removing the gate assembly, you will probably see crud trapped in the valve seat. Remove crud and clean innards, lubricate with silicone grease and reassemble.
...Would be my advice.
--Winston
Reply to
Winston
You could put a cap on the output pipe. With a couple of nice handles for easy & fast removal. Bob
Reply to
Bob Engelhardt
In article , snipped-for-privacy@hotmail.com wrote:
No, I cannot remove the valve disk. The valve body is welded and I cannot access the top half of the disk in any way.
Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
Reply to
nick hull
I cannot see or feel any crud. I can feel most of the seat, except the top where the disk is in the way even when fully open.
Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
Reply to
nick hull
I was the Engineering Officer on two Coast Guard Cutters, Auxiliary Chief on one, Main Prop Chief on another, and general engineer on my first. When a cutter is in drydock the skin valves and other important valves are routinely removed and tested (the inlet side of the valve is filled with water and a blank flange with an water fitting attached is bolted to the valve flange. A predetermined amount of pressure is added through the fitting (150% of the working pressure? I don't recall exactly)). A specified amount of leakage is allowed depending on the size and type of the valve, and the normal operating pressure of the system. The quantity allowed is in Chapter 505 of the Naval Ships Technical Manual (NSTM) titled Piping Systems. Small valves did not allow any leakage, whereas larger valves were allowed XX drops per minute. Some valves (again depending on the type) weren't allowed any leakge (ball valves?). I tried to find a copy of this chapter (505) of the NSTM online without any luck ,to give as a link. I'm sure there are specifications elsewhere in the civilian world.
I did find two chapters that may be of interest to this group (at
formatting link
.); Chapter 075 - Fasteners and Chapter 613 - Wire and Fiber Rope Rigging. One chapter I couldn't find was Chapter 078 - Seals that is VERY good reading. I wish now I had kept copies of some of these manuals when I retired as they are is very good and can be very pertinent to our hobby/job.
Dave Young
nick hull wrote:
Reply to
Dave Young

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.