Blow out plugs

[treasureman]

I have several USd valves most notably the J 60 series and the USD three piece tank manifold.

All need blow out plugs and burst discs. The LDS here wants approx 30 bucks each, and I find this very rude for a price.

There was someone who posted a while back they could get them for about 6 bucks each. If so, please let me know where, and if you happen to know the size, let me know as well. If anyone has spares they want to sell, or can buy some and send them, I will pay pal right away.

Merry Christmas

Felice navidad

Happy Kwanza

Happy Channukah to all

[Bob3]

My local shop wants to see all the blowouts & fusible OPVs replaced with discs.
I've got 1 ancient Navy manifold needing discs too ...
It may be a matter of being able to locate the right size rather than cost.
TRIDENT has burst disc assemblies & plugs for around 5 bucks, though that's in an older catalog. They're 38" & 1/2"

[time2dive]

I get most of mine from Sherwood. They fit most valves. The problem with the Trident kits is that they are pre-assembled and sometimes do not fit. Most older valves take the smaller 3/8" assemblies. The old valves had lead slugs in them that were the size of a 22 bullet. Sometimes they would slowly work their way out of the plug, he was shot in the leg by one a few years ago filling tanks.
I can probably get some burst disk kits.

Tim

[captain]

Just use a drill the same size as the lead plug and drill the plug out. Put the new blowout disc in with the old drilled out plug

[luis]

Hi Tom

IMHO, I would recommend against that for a couple of reasons.

First, the new plugs have three holes so that the air doesn’t shoot out in only one direction. The single orifice created a jet stream thrust that will cause the tank to spin out of control. It is a small hole so the force is not that strong, but the tank can pick up inertia. I have actually witness that and it is kind of funny until you realize there are other tanks and objects on its path.
The three orifices should balance each other.


The second reason (which is at least as important) is that the plug main function is as a cutter for the burst disc. It is supposed to have a calibrated orifice (matched to the thickness of the burst disc) with a square (sharp) edge. In theory, the two are supposed to be replaced as a matched pair to preserve the best calibration for the burst pressure.

In practice we always used to replace just the disc. We will never know if they will burst at the correct pressure, but I do recall a number of premature blow out of burst plugs.


In some valves it may be difficult to use a new plug with the hex head and the three holes, but at least (as a last resort) I would recommend using a new straight plug with a clean cutting edge.

[Nemrod]

Why not just stick a heavy disc in there functionally disabling the blow plug. We did that back in the 70s when I was an active cave diver. Blow out plugs--bad--bad---when a hundred feet of limestone lay between you and the sunshine.
Really, I never understood a blow out plug. If the tank is in good shape and has been hydroed then it is good. If it gets hot in a car trunk and it is filled to the correct pressure it is not going to blow up. Blow out plugs are not even used I don't think in some parts of the world. I fail to see the logic of them. Why introduce a weakness into your air supply that could fail at any moment. The cylinder is either good or it is not, if it is good then it does not need a blowout plug and if it is questonable then don't put air in it to start with--what good is a blow out plug unless you plan on heating full cylinders with a torch?

Nemrod

[boogerdave]

Burst discs are required by law (CGA Standards) And as someone who is filling the cylinders I would prefer to have a safety device. Mistakes are made sometimes and blowing a 10.00 burst disc is better than cylinder failure. Temps in a trunk can reach 150+ degrees. Cave-ers put double discs so they can overfill the cylinders to start with. I.E. 2400 low pressure steel pumped up to 3000-3200 psi A 120 turns into a 160 cf.

[Nemrod]

"Cave-ers put double discs so they can overfill the cylinders to start with. I.E. 2400 low pressure steel pumped up to 3000-3200 psi A 120 turns into a 160 cf."

Yep, that is what we did , put a heavy disc or stacked discs in the recess thus functionaly disabling them which comes back to my question, why have them if they are disabled and still don't understand beyond beuracratic "Homeland" type mumbo jumbo what exactly should they be there for? Tanks have a working pressure and a ultimate burst/failure pressure that is well beyond anything a properly filled tank would be exposed to. Unless your pumping them up to cave fills and setting then in your trunk in the Sonaran desert then I cannot see the good of a burst disc. Good thing there is not much diving in the Sonaran, having lived there I can attest to that but what the heck, the sea of Cortez and the coast of SoCal are close enough.

Nemrod, the contraian

[YankDownUnder]

http://cgi.ebay.com/Lot-of-6-3000-PSI-B ... dZViewItem

Ebay link to your disc problems. These are what I use on J-60s

[luis]

Hi Nemrod

You are correct in that in some countries blow out plugs are or were not required. My Poseidon and Draeger tanks do not have blow out plugs (you can see pictures of them in my gallery).

I love those tanks and think that they are the best, but it scares me to store them in my house. When I lived in PR where the houses were made out of concrete and fire departments were very rare, it wasn’t too bad. But here our houses are wood and fires are not uncommon. I strongly regret that I didn’t have a sprinkler system installed when I built my house.

In any case the big deal is fire. And it is not something to be taken lightly.

Steel will weaken very quickly under the heat of a burning building. As a mater of fact you have to protect any structural steel from the heat of a fire to give the occupants a chance to escape. It is very strange, but even do that wood will burn, it is know to maintain it structural properties longer than steel when exposed to fire.

In reference to tanks, it is recommended that they be stored either full or near empty. The reason is that in a full tank; the air will heat up and blow the plug before the steel weakens. If they are half full the steel could weaken before enough air pressure is developed to blow the plug.

The old lead plugs were supposed to melt, but they didn’t work well.

Up here in Maine it seems that house fires are way to common (and I assume it may also be the case in many parts of the country with many types of heaters and fire places).


A totally secondary reason for the blow out plugs is in the case of a malfunction of the filling station relief valve, but this is totally secondary in my opinion.

[standingup]

With older 1800lbs and 2200lbs tanks being filled by sometimes young employees not realizing that all tanks are not a minium of 3000lbs blow plugs might be a good idea. JMHO

[Nemrod]

"With older 1800lbs and 2200lbs tanks being filled by sometimes young employees not realizing that all tanks are not a minium of 3000lbs blow plugs might be a good idea. JMHO"


Well, not speaking for the 1800 psi tanks and converted CO2 bottles but the "old" steel 72s of 2250 psi working pressure are the ones we filled to 3,000 psi over and over again and the only one of those remaining that I have that does not have a liner in it (the rest are back home becasue I cannot get them VIP) still passes hydro.

House fires are the reason the plugs are in the tanks, not filling station errors, yes, they protect emergency personal fighting fires etc. That is why they are there.

I write in big letters with a permenant marker the fill pressures of my tanks just below the valve so the blonde bimbos and nose ring generation don't confuse their limited Nintendo attention span. If they still overfill it to 10,000 psi and blow themseleves up then that is what the Darwin awards are for--correct? Oh well.

Nemrod

[standingup]

Nemrod-I have a question for you. I'm considering hanging a tag with instructions to fill with j valve in down position. Do you think a tag or just arrows by permanent marker on the tank would work the best. I'm finding get every so often I get short fills on my doubles.

[captain]

I see the point of the 3 holes in the newer plugs but I have many older valves that came without the lead plug and one straight hole. I had one blow once from corrosion while the tank was stored. It rattled around a bit. Usually after I put the disc in the valve I put a dab of silicone grease on top the disc then screw in the plug. The grease helps prevent corrosion.

[luis]

In the post above, I was only thinking of steel tanks (which is all I use), but aluminum tanks would be even worse. It doesn’t have to be much of a fire to compromise the structural integrity of an aluminum tank. Just radiation heating from a near by fire will probably ruin the heat treatment in an aluminum tank and cause to fail if the burst disk didn’t let go soon enough.

I recall two aluminum tanks in Florida many years ago that the owner had then painted with a bake on paint and both tanks ended up failing. If I recall it did kill at least one person.

An aluminum tank will tend to fragment in many more pieces than a steel tank.

A house fire with Scuba tanks inside is probably one of those nightmares firemen don’t want to think about.