Question about diffrent type of valves

[stas]

Hi everybody.
I know that fundemantaly (Most often found in scuba), there are two types of tank valves. The din types and the yoke types. However, there are many diffrent types. Some seem to be idexed by letters like j, k and otherwise. I'm also having some trouble distinguishing beetwen propriety termenology and structual termenology. For example, what does it mean when the word "thermal" is attached. Finaly, can all din valves be converted to yokes with an insert? If sombody can clue me in by either some comments or a thorough refference, I would be most thankful.
Thanks, Stas

 

[DA Aquamaster]

IN the beginning there were J valves and K valves. J valves had a reserve lever that released spring pressure that held the last 500 psi in the tank. So in the days before SPG's were considered mandatory you dove till the reg got hard to breathe and then pulled the reserve lever and ascended on your 500 psi reserve. You did that until the day when the reg got hard to breathe and you reached back and discovered the reserve lever had gotten snagged on something and pulled itself earlier in the dive, which of course meant you had no air left. Which provided ample motivation to buy an spg.

K valves had no reserve feature and are still the term normally used for a "yoke" valve.

Scubapro made both K and J valves with a stem gauge in them that gave you an indication of the state of the tank fill during a pre dive inspection. They also had a Depth Compensating Automatic Reserve (DCAR) valve that was basically a J valve that increased the reserve at deeper depths.

Yoke valves of either J or K type are also called "International" valves, especially outside the USA.

DIN valves come in two flavors, a 232 bar version and a 300 bar version.

The 232 bar version is often referrred to as a 200 bar DIN valve. What ever you call it, it has 5 threads and a dimple on the back to center a yoke screw. This allows an insert to be installed which then converts it for use with a yoke regulator. This type of valve is also called a "DIN/K valve" for obvious reasons.

The 300 bar DIN valve has 7 threads and the extra lenght prevents a 232 bar DIN equipped regulator form seating in the deeper valve. They also lack a dimple on the back to center a yoke screw and in any event are too long to fit inside a yoke anyway.

"Thermo" is a company that makes a lot of tank valves including K valves, 232 Bar DIN/K valves and 300 Bar DIN valves as well as doubles manifolds in 232 and 300 bar versions. They are well regarded with a potential complaint being that they open up quite fast which can be problematic when using them on a 100% O2 deco bottle.

Thermo valves are actually sold by several companies in rebranded form.

Sherwood is another very big valve manufacturer.

The standard scuba tank uses a 3/4" valve, however some high pressure tanks were made for Genesis with a proprietary 7/8" thread. They are basically a pain in butt.

There are still some older steel tanks floating around with 1/2" valves, and while the tanks last forever, the valves do not and no replacements are currently available. These were mostly a straight valve with the valve "knob" on top like an O2 tank although some were made in a more modern "K valve" style with the handle on the side. Virtually all 1/2" valves used a tapered thread and relied on teflon tape for the seal although there were a very small number of tanks that used a 1/2" o-ring sealed valve.

Scubapro made a rather odd valve for a short time with a lever that switched the air on or off via a ball valve rather than using a rotating knob. It had the potential to eliminate the problem of a valve being left part way on (resulting in inadequate air flow at depth) but it never caught on.

 

[stas]

Hey Aquamaster, thanks alot for your info.
I have a few folowup questions.
For 200 and 300 bar dins, how do I know if a reg will work on them. specificaly, as far as I have seen, the manufactuers either provide din or yoke regs (or both). They dont specify what kind of din. Is there an insert that could be used in a 300 bar din to convert it to a 200 bar din? Also, these numbers (200 and 300), do they mean max pressure in tank allowable for these valves? Finaly, the 3/4" you refer to, is that the diameter of the hole oi the tank? Is the thread density and pitch of the thread standard these days?
Thank you very much, stas

 

[stas]

Hi,
I forgot to ask these dumb question:
What and where is the burst disk and what is an H valve?

 

[H2Andy]

200 bar DIN valves (really 232) will accept an insert that will allow you to use
Yoke regs. 300 bar DIN valves will not.

200 bar valves will accept both 200 and 300 fittings. 300 bar valves will only
accept 300 bars

the numbers are sort of a misnomer. 200-bar valves (really 232 bar) can
handle pressure up to 300 bars. 300 bar valves can handle pressure up
to 450 bar.

a burst disk is built into a valve, and will "burst" at a pre-arranged pressure
to avoid a build up of pressure that could cause structural damage to the tank.

an H valve is a valve that allows two first stages to be connected to a tank.

 

[DA Aquamaster]

There are also "Y" valves or "slingshot" valves, which were the older non-modular equivalent of an "H" valve allowing two first stages to be used on one tank.

The term "modular" refers to an ability to mix and match valve componets. For example you can use a left and right modular valve in conjunction with an cross bar or isolator to create a manifold or you can use an attachment as indicated above to create an "H" valve.

I don't agree with Andy on his assessment that 232 bar valves can be used to 300 bar or that 300 bar valves can be used to 450 bar.

My understanding is that 232 bar valves can be used to 232 bar (about 3450 psi) while 300 bar valves can be used to 300 bar (about 4350 psi). That is based on the service pressure standards associated with regulators designed for use on 232 and 300 bar valves. In keeping with that tanks with service pressures of 3500 psi or more will have 300 bar valves on them to prevent regulators with lower service pressures from being attached to them.

By law (in the US) burst discs have to burst and release the gas from the tank in controlled manner in a range from 10% below the the hydro test pressure to the hydro test pressure of the tank. This test pressure is normally 5/3rds the service pressure for non-exempt tanks. In practice, burst discs start getting weaker with use almost immediately and they will eventually burst at the normal service pressure, usually while the tank is being filled, so it is a good idea to replace them at least every 5 years. This will greatly reduce the possibility of them bursting in the middle of a dive.

Burst discs are copper discs that are placed in the body of the valve under a retainer that looks like a small bolt with holes in the head. The retainer is hollow inside to allows escaping gas to through and exit through the holes on the sides of the head. Really old burst assemblies used a lead slug that actually shot out of the assembly. This could be bad news to anyone in it's way and if you see one of these, retire it before filling the tank again.

232 bar connections on first stages are pretty rare today as most are equipped for 300 bar service and come with 300 bar DIN connections.

If the DIN connection on your regulator has 7 full threads on it, it is a 300 bar DIN connection. If it has only 5 full threads on it, it is a 232 bar connection.

3/4" tank valve threads are standard, but I am not sure off hand of the pitch or angle of the threads.

 

[H2Andy]

i must admit i got my info from DIveRite, and it may be wrong:

Outlet/Connector #13 is from DIN 477 part 1 - for cylinders with test pressure ratings up to 300 bar and is commonly referred to in the SCUBA industry by the slang term "200 bar", probably because most cylinders with 300 bar test pressures have working pressures in the 200 bar range. Outlet/Connector #56 is from DIN 477 part 5 - for cylinders with test pressure ratings up to 450 bar and is commonly referred to in the SCUBA industry by the slang term "300 bar".

http://www.diveriteexpress.com/library/valves.shtml

 

[Leadking]

Thermo valves are actually sold by several companies in rebranded form.

I am unaware of Thermo offering any "re-branded" merchandise. In the U.S. there are now two authorized distributors, Sea Pearls and XS Scuba.

Lee
www.seapearls.com

 

[Walter]

Really old burst assemblies used a lead slug that actually shot out of the assembly. This could be bad news to anyone in it's way and if you see one of these, retire it before filling the tank again.

A couple of years ago, I bought a tank with one of these burst assemblies. It's not just an interesting bit of trivia, they are still out there.

 

[oxyhacker]

You cannot use an insert in a 300 bar valve - its too deep (usually) to fit in the yoke and there's no dimple to hold the yoke screw. This is intentional.

I think the comment about using 232 bar valves to 300 bar may have to do with the fact that there is no significant difference in strength or construction between the two configurations - the extra threads are there not to make the 300 bar able to handle the higher pressure, but just to prevent using a 200 bar regulator on a 300 bar valve. So there's no physical reason why one can't use a 200 bar combo valve or manifold in the DIN mode at higher pressures, as long as suitable burst disks are installed.