We are in the middle of a construction project and the construction company's engineer refuses to listen to our safety concerns about a 48 inch butterfly valve. The line on one side of the closed valve is full of sludge. The line for the other side of the valve has not yet been constructed. This side opens to a lower level full of expensive pumps and blowers. We asked that the construction company bolt a bar or something on the open side to prevent the valve from opening and flooding the basement and/or injuring one of our employees. The construction company's engineer scoffed at the idea the valve could fail or leak and will not have his people put a restraint in place. My question is are we out of line to ask for this safety step? Does anyone have experience with a valve such as this failing? Thanks for your advice.
Eng-Tips is the largest forum for Engineering Professionals on the Internet.
Members share and learn making Eng-Tips Forums the best source of engineering information on the Internet!
-
Congratulations JStephen on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
butterfly valve safety question
- Thread starter mikeab
- Start date
While I have never heard of a butterfly valve opening on its own and I don't profess to be a safety expert, it would however make sense to me if it is possible in some secure fashion to at least "lockout" the operating mechanism of the valve for the safety reasons you describe so it couldn't be opened (at l3ast easily) when it should not be (by anyone inadvertently, or by a prankster or terrorist on purpose??)
I haven't seen a valve that large that didn't have a geared actuator, which would prevent it from opening by itself. To prevent unauthorized use, remove the handwheel from a manual operator, or lock out the circuit breaker for a motor operator.
As for the seal failing, a blind flange would prevent leakage, at least until it is removed to extend the pipe. How much pressure is on the valve and what is it rated for?
Since there is sludge on the upstream side, I'd worry more about being able to open the valve when the time comes.
As for the seal failing, a blind flange would prevent leakage, at least until it is removed to extend the pipe. How much pressure is on the valve and what is it rated for?
Since there is sludge on the upstream side, I'd worry more about being able to open the valve when the time comes.
- Thread starter
- #5
I should have mentioned we are trying to avoid buying a blind flange - its a big valve, so a blind flange would be pretty expensive for a government job.
Maury, the sludge is return activated sludge in a constantly mixed return box - not thick enough to settle out against the valve and prevent opening when the time comes. I do feel better no one thinks the valve or actuator will fail. We did remove the handwheel yesterday. We were thinking to be safe, we could fabricate a bar with pins against the plate that would bolt to existing bolt holes.
The valve is rated to 150 psig - The pressure on it will vary depending how many pumps are on line. We could have as many as four pumps on pumping up to 5 MGD each, but we are only using one in that line at 4 MGD for the time being. Obviously the flow is going through a common temporary line until the summer when work has been completed on the dry side of the valve.
Maury, the sludge is return activated sludge in a constantly mixed return box - not thick enough to settle out against the valve and prevent opening when the time comes. I do feel better no one thinks the valve or actuator will fail. We did remove the handwheel yesterday. We were thinking to be safe, we could fabricate a bar with pins against the plate that would bolt to existing bolt holes.
The valve is rated to 150 psig - The pressure on it will vary depending how many pumps are on line. We could have as many as four pumps on pumping up to 5 MGD each, but we are only using one in that line at 4 MGD for the time being. Obviously the flow is going through a common temporary line until the summer when work has been completed on the dry side of the valve.
If the pressure upstream of the butterfly valve is not very high, the likelyhood of the butterfly letting go is small.
If the concern is inadvertent opening, then the above suggeston of using the lockout procedure, chaining, removal of handwheel, etc. are all good suggestions.
A blind flange will of course work also. But in this case, I think I am thinking like your construction contractor - it may be a bit overkill.
Even if the valve lets go, the amount of leakage is not so much a safety issue as it is a messy issue.
However, if you feel there is a safety risk, you need to follow your believe and get it blinded off.
If the concern is inadvertent opening, then the above suggeston of using the lockout procedure, chaining, removal of handwheel, etc. are all good suggestions.
A blind flange will of course work also. But in this case, I think I am thinking like your construction contractor - it may be a bit overkill.
Even if the valve lets go, the amount of leakage is not so much a safety issue as it is a messy issue.
However, if you feel there is a safety risk, you need to follow your believe and get it blinded off.
If the problem is mess, then a 3/4 inch plate with 8-10 bolt holes would stop the mess (it would hold about 20 psig with a deflection less than 0.4 inches if all the bolt holes in the flange were cut, studs installed, and bolts tightened). If the problem is safety (i.e. a flooding hazard or an abrupt energy release) then a single butterfly valve wouldn't be legal protection for workers.
David Simpson, PE
MuleShoe Engineering
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
David Simpson, PE
MuleShoe Engineering
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
Why don't you just rent a flange and then everyone will be happy.
I appreciate your concern as over the years I've seen things that weren't supposed to happen, happen.
I appreciate your concern as over the years I've seen things that weren't supposed to happen, happen.
- Status
Similar threads
- Question
- Locked
- Question