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Post by teamdoug2015 on Sept 10, 2021 23:15:32 GMT -8
We hydro and VIP tanks to scrutinize the metal integrity and threads to avoid unpleasant outcomes when put under pressure.
But what are the issues with tank valves? We can easily inspect the threads, change the seats, burst disk assemblies, and 0-rings - but is there a limitation on the J-valve’s or K-valve’s useful life from an integrity perspective?
Does brass get brittle with pressure cycles?
Does the chrome hide cracks in the threads that should be of concern?
I have seen plenty of pristine J-Valves that were manufactured 30 years or more ago. Is there any reason not to use them after they've be overhauled?
What is the consensus among the highly experienced vintage divers and technicians when it comes to vintage valves?
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Post by snark3 on Sept 11, 2021 0:04:31 GMT -8
I bought 2 tanks new in 1974, neither valve has been serviced and I've never had a problem with either. I have older valves, some still have the lead safety plugs. I don't know if they've been serviced or not but they still work.
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Post by scubalawyer on Sept 11, 2021 4:53:03 GMT -8
I've overhauled many a K-Valve, J-Valve and their dual manifold counterparts (and still actively use them) from the 1950's and 1960's. They are all going strong without issue. I'll replace the burst disc every few years but that's just me. The only consistent problem I've encountered are with Voit J-Valves. I've found several with disintegrating reserve seats. Not sure what material they used but they-a-no-workie.  |
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Post by snark3 on Sept 11, 2021 6:48:19 GMT -8
I've overhauled many a K-Valve, J-Valve and their dual manifold counterparts (and still actively use them) from the 1950's and 1960's. They are all going strong without issue. I'll replace the burst disc every few years but that's just me. The only consistent problem I've encountered are with Voit J-Valves. I've found several with disintegrating reserve seats. Not sure what material they used but they-a-no-workie. Mark- The Scuba Museum has a plug to replace the "J" section of the Voit valve. Obviously it's not a "J" any longer but the valve is still usable. |
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Post by nikeajax on Sept 11, 2021 7:34:54 GMT -8
Hmmmm? Someone like Luis will have to answer this one, but, it is my thought that because they don't have the same surface area to expand and contract, they aren't subject to the same type of metal-fatigue that tanks are.
JB
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Post by cnotthoff on Sept 11, 2021 8:38:57 GMT -8
Hmmmm? Someone like Luis will have to answer this one, but, it is my thought that because they don't have the same surface area to expand and contract, they aren't subject to the same type of metal-fatigue that tanks are. JB Gotta agree with you there. I've seen high pressure cylinders (for welding and other uses) from the 30's with brass valves that are still going. A scuba tank came in recently with a valve bent at about 10°. It was working just fine. Those things are tough. I still replaced the damaged valve before it passed visual. Good Dives, Charlie |
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Post by SeaRat on Sept 11, 2021 16:47:57 GMT -8
I've overhauled many a K-Valve, J-Valve and their dual manifold counterparts (and still actively use them) from the 1950's and 1960's. They are all going strong without issue. I'll replace the burst disc every few years but that's just me. The only consistent problem I've encountered are with Voit J-Valves. I've found several with disintegrating reserve seats. Not sure what material they used but they-a-no-workie. Mark- The Scuba Museum has a plug to replace the "J" section of the Voit valve. Obviously it's not a "J" any longer but the valve is still usable. AMF Voit made two different versions of this valve. I have both, and have photos of the seats. There is a black version of this valve, made apparently out of aluminum, which appears to me to be a version for an anti-magnetic system for the U.S. Navy:  IMG_1043 by John Ratliff, on Flickr The J-valve material for the anti-magnetic version appears to be made of a different plastic than the AMF Voit brass version:  IMG_1044 by John Ratliff, on Flickr The J-valve version will still work with the plastic missing, but not well. Simply be aware of it, and after it has been cleaned it can be used simply as a K-valve with the J-reserve mechanism in the down position. Or, it can be plugged as mentioned above. John |
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Post by luis on Sept 13, 2021 17:18:33 GMT -8
The valves (and regulators) have very thick walls as compared to the small inside diameter gas passages. The stresses due to gas pressure in both valves and regulators tend to be very low. Fatigue live of the pressure body (valves or regulators) should not be an issue and I have never seen a design that I would be concerned, from this aspect.
The higher stresses on both valves and regulators comes from handling and from impact against other objects. Also sometimes from people putting wrenches in the wrong places or using the wrong wrench.
The other damage to valves comes from corrosion and wear of the chrome surface and sometimes the threads.
The wear issue is particularly bad in some vintage DIN valves (OK they were not call DIN in the old days). This is not as much of an issue in the US since that type of connection is relatively new around here. I have some Threaded European valves (DIN) that the connecting threads are shot. I have had them since the 70's, but some were manufactured in the late 50's.
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