Vintage Double Hose

I'm overhauling this manifold/valve. The on/off knob says Scubapro.
Anyway, two questions.

1. Which way loosens the main retaining nut for the valve stem- Clockwise or Counterclockwise? I can't get it to turn either way and I'm getting feedback from less-than-knowledgeable friends on both directions.

2. Where can I get this kind of flush-mounted burst disk?

Thanks, Mark.

It should be right hand thread. It has been decades since I service one of those, but I don’t remember it being anything different than other typical manifolds.

From what I remember it looked like is was made by Sherwood Selpac (like many other valves at the time).

You really don’t want to use that type of burst disc even if you do find some NOS. You want to replace them with the modern style with the hex head and the three vent holes. If they let go, they are a lot safer.

Thank you, Luis.

Lefty-loosey did the trick. Now, about those flush burst discs. The thread size appears to be the same as the modern 3-hole ones and a newer, safer one would fit in the end of the manifold pictured. However, the other side of the manifold has the disc directly under the J-valve and the 3-hole head on the newer discs is too wide to fit. Is there a new-style disc with the head no wider than the threads? I agree the old style is much less safe. Mark.

Ok, looks like the 3/8 2250 discs in Bryan's store would work, just no room to get a socket wrench, or any other kind of wrench around it. I guess that's why the old style is set with a screwdriver. Mark.

By the way, its probably known to all but me, but the reason everything is so tight is because the seals are brass (copper?) rings everywhere.

ScubaLawyer wrote:Ok, looks like the 3/8 2250 discs in Bryan's store would work, just no room to get a socket wrench, or any other kind of wrench around it. I guess that's why the old style is set with a screwdriver. Mark.

? area where the disc is located looks flat and easy to get at

Bryan, no problem with the end pictured. I'll have to post another pic of the other end, below the area of the J-valve. Tight area, no room. Mark

Bryan wrote:

ScubaLawyer wrote:Ok, looks like the 3/8 2250 discs in Bryan's store would work, just no room to get a socket wrench, or any other kind of wrench around it. I guess that's why the old style is set with a screwdriver. Mark.

? area where the disc is located looks flat and easy to get at

Here is a pic showing the other burst disc port. I put a 3-hole head plug near it for size comparison. This particular plug won't even screw in part way without hitting the manifold just behind the J-valve. It looks like with the plugs/discs you have the head is much smaller, but still not enough room for a torque wrench. Mark.

The requirements is to have a burst disc. I don’t know of any reason, technical or from a code perspective, that requires you to have two functional burst disc. This is not an isolation valve, therefore both cylinders are always protected by the one burst disc.

I would not totally disable this burst disc, but maybe put a disc for a slightly higher pressure cylinder than the requirement. That way it this disc, with the single hole screw, will be less likely to ever let go. The protection (in case of fire, etc) will actually come from the burst disc in the other side.

If someone knows of any problems with this approach please let me know. I have read the codes that talks about the pressure relief device and as long as the two cylinders are always tied together (no isolation manifold) you should be OK with one good burst disc.

I was thinking the same thing Luis.One plug should do the trick as far as safety goes unless I am missing something.

I'm not an engineer but this single-plug approach sounds like it would do the trick. Anyone else have any input pro or con? Mark.

ScubaLawyer wrote:I'm not an engineer but this single-plug approach sounds like it would do the trick. Anyone else have any input pro or con? Mark.

The cylinders are not isolated from one another, so I would stack two copper discs in the J-Valve side for protection against blowing, and the other valve body should get the appropriate single disc, which will protect both cylinders.

BTW, the sharp corners on the new style hex-cap containment plugs have a habit of barking my knuckles when handling the cylinders. I file the sharp edges and points slightly down to a more skin-friendly shape. The light corrosion that might occur doesn't bother me as much as the lost skin.

Thank you all for your sage advice. I truly appreciate the info. Mark.

antique diver wrote:

ScubaLawyer wrote:I'm not an engineer but this single-plug approach sounds like it would do the trick. Anyone else have any input pro or con? Mark.

The cylinders are not isolated from one another, so I would stack two copper discs in the J-Valve side for protection against blowing, and the other valve body should get the appropriate single disc, which will protect both cylinders.

BTW, the sharp corners on the new style hex-cap containment plugs have a habit of barking my knuckles when handling the cylinders. I file the sharp edges and points slightly down to a more skin-friendly shape. The light corrosion that might occur doesn't bother me as much as the lost skin.

Mark, after looking at the photo some more I am beginning to doubt my first thought that the cylinders are open to each other when the valve is closed. I think you should test that to see if you can blow air through one dip tube with the valve closed and the j-valve down, and see if it passes out the other.

Please check that out and let us know!

antique diver wrote:

antique diver wrote:

ScubaLawyer wrote:I'm not an engineer but this single-plug approach sounds like it would do the trick. Anyone else have any input pro or con? Mark.

The cylinders are not isolated from one another, so I would stack two copper discs in the J-Valve side for protection against blowing, and the other valve body should get the appropriate single disc, which will protect both cylinders.

BTW, the sharp corners on the new style hex-cap containment plugs have a habit of barking my knuckles when handling the cylinders. I file the sharp edges and points slightly down to a more skin-friendly shape. The light corrosion that might occur doesn't bother me as much as the lost skin.

Mark, after looking at the photo some more I am beginning to doubt my first thought that the cylinders are open to each other when the valve is closed. I think you should test that to see if you can blow air through one dip tube with the valve closed and the j-valve down, and see if it passes out the other.

Please check that out and let us know!

Ok, I closed the valve nice and tight, dropped the J-valve down and blew into a dip tube. Air flowed through and out the other dip tube. All is good save for my wife walked into the garage as this scientific experiment was being carried out. She muttered something about "lucky valve" and wanted to know if I loved my dive gear more than her. I'm very glad she has a sense of humor. Mark.

That's funny. Maybe you should lock the garage door before performing questionable acts on your gear.