valve handle screw

[NorthWoodsDiver]

is it a common practice for your tank to go in for VIP with the standard flathead type screw holding the valve handle on and getting it back with nylock nuts instead. I was talking to a dive shop and thats his standard practice and it sounds like a good idea so I was thinking of changing over all 14 of my tank valve handles too the nylock nuts instead of having to carry that special screw driver around or getting one of Tobin's neat little key chains. I have not put a thread gauge on their but they dont look like standard thread either, maybe metric or something. Thanks

 

[cummings66]

I've never heard of it and I'm not sure it's a great idea either. Why did the dive shop replace the metal screw with a plastic one? What's the great part?

We never discussed this in my VIS course I took so I'm at a loss as to why he'd do it.

 

[DA Aquamaster]

A nyloc nut is a metal nut with a nylon insert on the end that holds the threads and prevents it from coming unscrewed. They are very nice to have in applications where you want things to stay attached but cannot use a lock washer (as in this application where it is not torqued down tight against something), a castle nut or safety wire.

As long as the nut it is stainless I don't see the problem but it also has to be large enough to retain the spring and/or have a stainless steel washer under it and the nut or washer needs to be large enough in diameter to provide some support to the knob itself.

If all of the above criteria are met, it would be a big improvement over the stock knob retaining nuts that can screw themselves off, leaving you with a valve you cannot close without a wrench or pair of pliers.

One potential concern is that with the height of the nut and a washer on top of the spring, you may be in a situation where you do not have enough working range on the valve stem to let the valve open all the way. That could be bad, I'd make sure it still opens the same number of turns.