What's missing?

[paulwall]

I have a pair of older USD valves that came on Steel 72's circa 1970. They're standard, 3/4 valves and I have had new burst disks put in.

However, on the side of the valve opposite the knob there is a threaded hole that is open. I assume that this is where the reserve assembly was mounted, but am unsure. A 3/8" LP hose will fit in there nicely (but would immediately burst, I know). I'd like to plug them, but don't want a potential missile shot out when the tanks are pressurized.

Should I use a SS plug, a brass plug or a SS screw to fill this hole, or will they never be "safe"?

The valves are not on the tanks, currently, so Pics can be posted, if that helps.

 

[Luis H]

Those are regular 3/8" plugs. All the old plugs (HP or LP) were all 3/8".

That port was often used for a SPG (submersible pressure gauge). Some old regulators (in particular some double hose regulators) did not have HP ports for the SPG, therefore this was a way of adding an SPG.

All the old SPG were 3/8" in size. I have plenty of 3/8" HP hoses and you can still buy them.

Just put a plug and you will be fine. Any brass plug will be fine. It looks better with the original style hex head plug, but any plug should work fine.

 

[captain]

I will add that the port is only pressurized when the valve is open so you can remove and replace the plug with the tank full as long as the valve is closed.

 

[Nemrod]

As per Luis and Captain, during that earlier time all LP and HP hoses were the same thread, 3/8ths. If you screw a LP hose in there it will go kaboom. Install a standard threaded plug and O ring.

This port was used for a SPG primarily. Once upon a time the SPG was mounted to the tank valve, not the regulator as is common practive now. As Captain mentions, the port is not pressurized except when the valve is on.

As well, during the early cave diving period before there were isolation manifolds it was possible to interconnect tanks with K valves using a loop of stainless tubing custom fitted thus allowing for a homemade isolation manifold.

N

 

[paulwall]

Thanks, Guys!