Dip Tubes

[hydronaut]

I had a few old USD valves with plastic dip tubes. I removed and chased the threads and am now trying to find replacements. These are the 15/16-18 threads.

I have a lathe and machining/thread cutting capability and was just planning on taking some brass rod and making some new ones? Is there any specific requirement for these to be plated as the whole inside of the valve is exposed brass. I have an electroless nickel plating kit and could easily plate them but am curious if an why this needs to be done. I was reading the Luxfer tank inspection guide and it said dip tubes should be brass etc. with suitable plaing such as nickel or chrome.

A.

[Herman]

That should be 5/16-18.....or you have really big dip tubes.
While cutting the threads on a lathe is possible it's a lot easier to buy a die and use that. The 5 or 6 bucks you spend on a die will be worth it in reduced headaches,time and possibly messed up material. Unless you have cut a lot of threads on a lathe, it's not the easiest thing to do, setup takes a good bit of time. As for it being plated, I don't see the need. The air you put in a tank should be dry to start with and if the interior of a steel tank does not rust, brass is not going to corrode.

[hydronaut]

Typo on my part, meant 5/16. Have dies and a holder for the tailstock so would be using that to cut them. Just using the lathe for drilling.

Figure if the brass tubes corrode so will the interior of the valve.

Thanks for the reply.

That should be 5/16-18.....or you have really big dip tubes.
While cutting the threads on a lathe is possible it's a lot easier to buy a die and use that. The 5 or 6 bucks you spend on a die will be worth it in reduced headaches,time and possibly messed up material. Unless you have cut a lot of threads on a lathe, it's not the easiest thing to do, setup takes a good bit of time. As for it being plated, I don't see the need. The air you put in a tank should be dry to start with and if the interior of a steel tank does not rust, brass is not going to corrode.

[Herman]

Why drill solid rod? Use brass or SS tubing instead. It's inexpensive and a lot easier not having to drill a couple of inches into a rod.

[luis]

This all sounds like a lot of fun, but you should be able to get the dip tubes from an Aqua Lung dealer.

If I recall correctly, there was a recall on the plastic tubes and you may still be able to get them for free (there may be a minimal charge now). If your LDS is not able to help, I would get in touch with Aqua Lung directly.

The plastic dip tubes are notorious for breaking off. They are a liability for Aqua Lung.

[Herman]

Why buy what you can make....you take all the fun out of it Luis.

[hydronaut]

I can make them quicker then it will take to drive to the nearest aqualug dealer. The reason I said brass rod is due to having a bunch of cutoffs lying around. I agree tubing would make more sense but figure what I have is free. Plus I am sure a shop would charge me 10 bucks a tube anyway.

I have stainless tubing but am not sure what type of reaction the dissimilar metals would create as the internal threads are exposed brass.

Why buy what you can make....you take all the fun out of it Luis.

[Herman]

www.onlinemetals.com is your friend.

I would not worry about dissimilar metals, again, you need moisture for it to be a problem. And considering the SS screws and other parts used in regs that do get wet, I have not seen any big problems.

[captain]

I agree with Herman, it's much easier and faster to cut small threads with a die than on a lathe. Also cut the thread before drilling so the force of cutting the thread doesn't distort or break the piece.

[jhonsmith]

Hello dear i want to say that the 5 or 6 bucks you spend on a die will be worth it in reduced headaches,time and possibly messed up material. Unless you have cut a lot of threads on a lathe, it's not the easiest thing to do, setup takes a good bit of time. As for it being plated, I don't see the need. The air you put in a tank should be dry to start with and if the interior of a steel tank does not rust, brass is not going to corrode....!!!!

[antique diver]

The plastic dip tubes were recalled by US Divers, and free metal replacements were sent to dealers. Seems like the replacements were plated brass.

The stated reason from USD at the time was that in the event of a filled cylinder being in a fire the plastic could melt, then extrude into and plug up the air passages. This could possibly prevent the relief discs from rupturing, thus leaving the heated cylinder more vulnerable to explosion due to uncontrolled overpressure.

I don't recall if it had actually happened in the field, but they felt it had enough potential risk to recall the plastic diptubes.