Tank Valve

[aquaregia]

Okay, I'm down to my last piece to fix from the grab bag - a Luxfer AL80. It needs hydro and vis, which seems to be at a fairly reasonable price from my LDS. They recommend a valve rebuild and burst disk replacement at the same time though, which almost doubles the cost. Additionally, I'd rather do it myself if possible.

Are these necessary, and are they DIYable?

 

[elan]

nothing is necessary if it works the other question is if it's worth doing it from the point of mitigating different risks. If you know how to overhaul the valve and have all tools and materials necessary you can do it yourself. Another question is if you are going to do partial pressure fills in this tank or premix or air only. If you need to do partial pressure it has to be O2 clean and the shop has all rights to refuse filling your tank if it was cleaned and rebuilt by someone they do not trust including you.

 

[Camerone]

Hydro time is the appropriate time to do valve overhauls...it's basically the standard time, unless the valve has quit functioning for you in between hydro intervals, or the tank gets excessive use.

It's extremely straightforward and the parts for valves are readily available. A standard Thermo valve is only about $15 (retail) for parts to rebuild - seat, washers, etc, plus a couple of bucks for a new burst disc assembly (not part of the standard kit). A manifold takes three kits, if you've got the tanks twinned up.

That said, you need three tools beyond the basics that most normal guys have in their garage: a valve handle removal tool, a 1/4" precision torque wrench, and an ultrasonic cleaner.

The handle removal tool can either be purchased online, or made yourself from an old regular screwdriver and a bench grinder to put a notch in the center of the blade.

The torque wrench is required to replace the burst disc. You _have_ to get the torque right on it, or it won't function properly. Also, they're one-time install items, whereby if you remove it, you need to replace it. Modern valves use the disc-and-plug assembly as a single piece; the old valves used to have a copper washer you could just swap out, but they've essentially quit making them.

The ultrasonic cleaner's functionality should be self explanatory (and, if it's not instantly apparent how and for what you'd use it, someone else should be doing this work)

 

[rjack321]

Okay, I'm down to my last piece to fix from the grab bag - a Luxfer AL80. It needs hydro and vis, which seems to be at a fairly reasonable price from my LDS. They recommend a valve rebuild and burst disk replacement at the same time though, which almost doubles the cost. Additionally, I'd rather do it myself if possible.

Are these necessary, and are they DIYable?

If they are charging ~$22 or less for the valve rebuild you won't save money doing it yourself. There is the satisfaction of doing it yourself factor, but if they are offering for cheap I would let them do it. Hydro time is a typical rebuild interval.

You can find a torque wrench for the burst disk at harbor freight. Typical spec is ~8 ft-lbs in the burst disk and 35 ft-lbs on the crush washer sealed bonnet nuts. Do not overtorque the burst disk or it will break off. Do not undertorque a bonnet nut or it will leak.

 

[aquaregia]

Does anyone have a takeapart guide for the Sherwood 3000psi K-valve? It's looking more and more like I'm going to have the LDS do it -- I can't find the burst disc for under $10 shipped and they only want $15 for parts+labor.

 

[Camerone]

http://www.frogkick.dk/manuals/sherwood/Cylinder Valves.pdf

$15 for parts and labor? And they're replacing the guts (seat, burst disc)? While I'm all about DIY, just let them do it...seriously.

 

[fppf]

You MUST have a torque wrench for the burst disk, MUST! Torque of the disk will effect its burst pressure.

Unless you have all the tools already I would just let the shop do it.

 

[redacted]

Back to the question of is it necessary. Unless the valve is leaking or has some other problem, it is not necessary. If it proves to be necessary later on, then do it or have it done.

 

[fppf]

Burst disks should be changed at least every 5 years.
The copper will work harden over time and eventually fail at a normal working pressure.

If the valve needs to be O2 clean I would have it serviced. There can still be trace amounts of hydrocarbons that can build up over years so its good to clean valves out every few years. If the valve is used just on an air cylinder its up to you, but I would have it serviced.

 

[Camerone]

...not to mention the valve seat will eventually set and the valve will start leaking. It's not a matter of if, but when.

The best thing for you to do would be just drop this valve off at the shop, and ask them to save the old parts for you in a ziploc (my local shop does that as a matter of course for people, but some shops are lazy...) You can easily see what we're talking about from those used parts, and it'll give you an idea for the next rebuild, which you can DIY.

Back to the "is it necessary" bit... I think it is, particularly since you don't know the history of the part in question. One red flag for me that it's sitting on a tank out of both hydro and viz that you don't know how or when was last used.