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TeamDoug2015
Vintage Diver
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First Name: Doug
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The Useful Life of a Tank Valve? Age Limitations?

Fri Sep 10, 2021 9:25 am

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 under 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.

What is the consensus among the highly experienced VDH divers and technicians when it comes to vintage valves?

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Nemrod
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Re: The Useful Life of a Tank Valve? Age Limitations?

Mon Sep 13, 2021 10:02 am

If the valve looks "pristine" then I would use it in a heartbeat. You can inspect the threads with a loupe. If the chrome is in good shape and no evident and observable damage to the threads, the valve is probably good for another 50 years. Brass does not fatigue in the same way as does aluminum from cycling. Neither does steel as long as the cycles remain within the elastic limit. You might want to learn how to service the valve, if you do not already know, and inspect the internal parts before returning it to service.

James

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TeamDoug2015
Vintage Diver
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Joined: Mon Nov 02, 2015 10:25 pm
First Name: Doug
Location: Singapore

Re: The Useful Life of a Tank Valve? Age Limitations?

Mon Sep 13, 2021 8:52 pm

Nemrod, Thanks for your insight. My question was exactly that - about age, cycling, etc. I attended a course on tank inspection, valve maintenance, and am comfortable servicing valves. Somehow the course material never covered if there were any age-related issues regarding brass valves - probably because there aren't. I figured with the hundreds of years of collective experience in this forum, someone would know the answer. I appreciate it.

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luis
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Re: The Useful Life of a Tank Valve? Age Limitations?

Mon Sep 13, 2021 9:13 pm

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.
Luis

Buceador con escafandra autónoma clásica.

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