Broken on/off knob

[Genesis]

is managing to bleed down the tank without being able to open the valve the usual way.

If you're not comfortable with doing this, get a shop involved. There is a LOT of energy in a charged scuba tank - more than enough to make missles out of things like burst discs and valve parts (or whole valves and the tank itself!) if you're imprudent.

 

[Uncle Pug]

swimndive once bubbled...
Sounds like you may only have sheared a valve stem. If your shop will sell you a new stem, then yes you can fix it your self. You won't need to bleed the tank to do this and YOU WILL NOT NEED A NEW VALVE. Any one who tells you otherwise is misinformed or trying to rip you off.

swimndive you may be right... but you could be wrong as well.

I was going to explain to july how to fix the broken valve stem... but decided that it would be more prudent to have him take it to an LDS that could assess the damage before attempting to replace the valve stem.

I am not trying rip him off nor am I generally misinformed... I just don't have enough information about july's mechanical abilities and the condition of the valve to recommend that he deal with it himself.

 

[OkieDiver]

I was going to explain to july how to fix the broken valve stem... but decided that it would be more prudent to have him take it to an LDS that could assess the damage before attempting to replace the valve stem.

OR

send it to LP or Diveinn or Simplyscuba.... etc. for service

 

[Wreck/Tec]

Guys, Pug is correct. The only thing worse than changing parts is not knowing what your doing. This will look very inexpensive if you get hurt. This isn't rocket science, however, it does require somewhat special tools, a knowledge of design, and specific order and composition of parts, IE O2 "Viton" rings. I hate paying for foolish mistakes as well. This may be money in the bank though. If your curious, they may let you watch, all be it unlikely. Chalk it up as a lesson learned.......
Wreck/Tec

 

[pescador775]

Fred, how would you do a valve repair at sea? If the stem can't be gripped from the outside, then the only way I can see is to stand to the side and back off the packing nut (gland) a bit. If the valve seat turns with it and bleeds air, the problem can be solved, eg, if there is no damage to the nut or main casting. However, if turning the nut does not back out the valve seat the nut would have to be removed? Then, a small pair of vise grips would be needed to grip the broken stem and rotate and tiny bit? Sounds like fun.

 

[FredT]

If the tank is full and off, simply remove the knob and packing nut, replace the stem and seals, then reassemble.

IF the valve is open with a reg installed and the valve cannot be turned "off" the problem is simply one of removing a lp hose, or holding down a purge valve and allowing the tank to empty. Then the repair proceeds normally with a full teardown.

A "normal" at sea repair is one where the full tank is dropped on deck, and the stem simply bends. The valve is still tight since the seat and stem are not hard connected. Many valves will allow the handle to be removed, then reversed and used to hold the stem to keep it from rotating while the packing nut is removed. The valve packing chamber is under atmospheric pressure with this repair, and the seat is still firmly in place against the valve body. With the stem and packing seals replaced the valve can be reassembled and used immediately without loss of the air in the tank during the repair. THE SEAT PLUG IS NEVER TO BE DISTURBED WITH THE PACKING NUT REMOVED AND PRESSURE IN THE TANK! If it is disturbed the proper method would be to go ahead and let it drain, or the more risky method is to tighten the plug again with a new stem if it is only a slow leaker. You'll risk continued possession of your hand if you try to tighten it though.

It IS easy to shoot yourself in the foot with this repair technique if you don't know EXACTLY what you are doing and EXACTLY how the valve internals are arranged! In this I agree with Pug that a novice field repair is not a wise choice. It's better to have fixed a couple hundred valves on the bench before attempting this one.

BTW if it's ABSOLUTELY necessary that a tank with a non-functional reg and stuck open valve MUST be drained simply backing off the burst disk plug a half turn will usually create enough of a slow leak to drain the tank overnight. Again it's easy to shoot yourself in the foot with this repair technique too. Too many turns and that plug becomes a very effective missile.

In dealing with any pressurized tank valve repair it's best to assume you are working on a live 500# bomb with an impact shocked fuse. Bad things can happen fast both places if you slip up and tweak the wrong thing.

FT

 

[pescador775]

Thanks, forgot that the stem and seat are a tongue and groove fitting.