DIY K-valve repair?

[Diving Dutch]

Bought 2 used Al 80s a couple of years ago, and all has been going great. Now I have valve leaks on both bottles: a small stream of air escaping from the knob-end of the valve (on both). Is there some way I can repair this myself, or am I SOL, and need to just buy new valves?
Also, I find it odd that they both go at the same (a matter of a few days) time. Coinsidence? A bigger problem?

 

[rjack321]

Probably the stem oring. Although, depending on the brand you may also need to replace a crush washer. Do you know their brand?

 

[Gilldiver]

What you need to replace in a K valve rebuild are:

1) valve seat
2) copper crush washer also called a copper gasket
3) small vale stem o-ring
4) blow out disk (some valves use a combined plug & disk.
5) yoke and DIN o-rings as required
6) tank to valve o-ring

I get all my o-rings from a hydraulic supply house near by. A pack of 50 cost me about $2 for each size. You can try or McMaster Carr or Grangers for them also, get a sizing chart to figure out what size you need. Most older valves in the US will use english size, newer tend to be metric. I try to get viton o-rings if you will be using >21% O2 mixes.

The crush washers, blow out plugs, and valve seats are a bit tougher. Usualy it is quickest to get them from a dive shop or mail order them. Try TDL I know they have the washers.

I usualy take the valve apart and let it soak overnight in 50% white vinager to remove all salt and corrosion build up.

Then a soak and scrub in hot 50% simple green. Use a small tooth brush and pipe cleaners as required to get all threads and openings clean. Then a good rinse in fresh flowing water.

On reassembly I put a spot of O2 grease on the valve seat threads and lube all O-rings.

Acctual labor time is about 30 -40 minutes for one valve, but it takes very little additional time to do 4 valves then to do just one.

By the way, this procedure just O2 cleaned the valve.

I rebuild my valves/manifolds every time the tank goes into Hydro or as required.

What I really do is collect 3 or 4 valves and clean them up (if you go with double tanks you should have a few extra K's around), put them into ziplock bags and then on the shelf. When I need a clean valve I just pull one out and screw it on.

Then about ever two/three years in Feburary I go through the process all over again.

Pete

 

[Diving Dutch]

The 2 valves are made by US Divers.

Thanks for suggestions on the rebuild. I think that's a good idea about keeping an extra valve or 2 around. I dive single 80s, but it's always a bummer when a piece of equipment is taken out of service.

 

[pescador775]

Dutch, you didn't say whether the leaks are occurring with valve on or "off". I presume the valve is on, the usual complaint for this problem. Drain air from the tank. Valve repair requires disassembly. For that, you will need a tool which fits the nut in the center of the knob. This tool looks like a wide screwdriver with slot in the center of the blade. Behind the nut is a spring, knob and washer. Remove these parts along with the nut. Now, you will see that the threaded stem is held in place by a large nut called a bonnet. Use a box end wrench to remove the bonnet. Make sure the valve is well secured in a vise with brass or aluminum jaws. The stem will likely come out with the bonnet. Set aside and observe how the stem forms a seal inside the bonnet. This assembly is also called a "gland". There will be an O ring or teflon washer, rarely both. However, old USD valves used a teflon washer. Inside the valve, there is a valve holder. Unscrew for inspection and set aside all parts for cleaning and lube (christolube). Observe that in the bottom of the cavity is a copper washer. If this washer is hard to remove, try dislodging it with a sharp tool being careful of the valve body. If the washer appears otherwise usable it is permissable to leave it in place unless the valve is to be oxygen cleaned. Repair of a valve is limited to repair or replacement of the defective part or parts, nothing more. Overhaul is an attempt to put the defective valve in new condition. Repair will involve replacement of the washer and teflon seal or O ring. These parts cost about a dollar. Washers of the correct size can probably be found at PEP Boys or similar place. They are the same size as washers used to overhaul Volvo carburetors and other such stuff.

 

[Diving Dutch]

I noticed the leak before a dive when the regulator was charged, and the leak continued when I turned off the air. However, I didn't think to depressurize the regulator and check it again.
Anyway, pescador775, I did manage to disassemble the valve to the point of removing the nut, the knob, the spring and couple of washers. However, it didn't look like I could proceed any further. The stem was not held in place by a bonnet; it continued into a metal casing, if that makes any sense. Was I high? Maybe a picture is warrented. Maybe I should go look again, but I thought it a little strange that I couldn't have access to the valve through the knob assembly.

 

[pescador775]

Yes, that is a really old valve design from the 70's.. Let me check and see if I have one to examine.

Edit: OK, I was thinking of the J mechanism. The USD valve stem should pull out but the bonnet must be removed. It is there, you must be staring right at it. The stem is sealed with a backup ring, O ring and washer. After the stem is pulled, unscrew the valve holder for inspection. Replace the O rings on both valves as cold weather can cause old rings to stiffen and fail, and put everything back together. The bonnet takes a box end hex wrench normally. It has right hand thread (50216)normally but USD also supplied valve bonnets with left hand.(50233) Either way, it should just unscrew. That should work OK for the K side. If there is a J leave it alone if not leaking. Sometimes, a box is difficult to fit on the J bonnet making a PITA.

 

[Diving Dutch]

Viola! Just like you wrote. Guess I was high, or something.

Thanks for everyone's input.

 

[pescador775]

No, not "Viola", just call me Pesky, heh heh. Are you in Dutch Harbor? Must be cold as a witch's tit. I spent some time in Adak when the NAS was active. Lots of sea otters and eagles. Eagles ruled the dumpsters and light poles. Seagulls beware. Strong currents in those waters.

 

[Diving Dutch]

Yes, I'm in Dutch Harbor. The ambient temperature isn't too bad, but the wind... Of course, you should know about "the wind" if you were stationed in Adak.
Did you dive in Adak? I'd love to get out along the chain and do some diving other than Unalaska. A small group of us have been trying to organize a trip to Kiska. Now that would be some great diving....maybe find a Zero or two.