1/2" Valve Condemned?

[duckbill]

Thanks for all the helpful responses. They are confirming my suspicion so far.

As for the threads, he was specifically talking about the valve threads. I know that the brass tapered threads of the valve will swage down further at each tightening, but I don't know how much the steel threads of the cylinder are really affected. Anyhow, thanks for the specific CGA quotes. I'll save them for future reference. The DOT regs can be looked up (with difficulty), but the CGA seems to keep their codes under lock-and-key unless you send them a pretty good sum. I appreciate your sharing them.

Even if he is mistaking three threads exposed for three threads engaged, three threads engaged seems like too few.

When I asked if he could cite the reference for this regulation, he said, I'd prefer if you could look it up....I'm really busy...etc. I know he is busy and that it is pointless to argue with him. Unless I can prove to him that this supposed regulation DOESN'T exist, how could he be convinced? It just makes more sense for him to prove to me that it DOES exist. It's easier to SEE something in print than it is to see something that ISN'T in print! Oh, well. Nothing requires him to satisfy his customers, I guess.

 

[pescador775]

Duckbill, that is strange story. Thanks for sharing and don't worry about the valve so long as the shop monkey didn't drill a hole in it or something of the kind. Vintage divers really need access to personal or group owned compressors. Even so, it is sometimes difficult to opt out of the circle of capricious inspectors and sales pitches. Three threads is the maximum, not the minimum.

 

[pescador775]

Bump. Maybe I should explain further. The minimum safe engagement is 7 threads. Ten threads minus three threads equals seven.

 

[northcoastdiver]

Go to a different shop - that dude is smokin crack! If you need an extra half inch valve I've got a couple floating around here somewhere.

 

[akdeepdiver]

This seems pretty fishy to me. I am a diver, PSI inspector, and a Hydrostatic retester and run a hydro shop. I will look through the regs again, but I have never heard this. Demand from the shop person to show you the reg. If he cant, or wont, I am suspecting he is 1. trying to sell you a new tank, 2. To lazy to do the work, or 3. Both. If he truly knows the regs, he should be able to turn right to it. On the off chance, he is correct though, please post online where it is stated, or shoot me a PM. One can never stop leaning, and I would like to know if he is right. Im not above swallowing my pride and saying "Ill be Da**ed, he was right".

 

[duckbill]

I'll try asking him again. I know he'll hem and haw, and roll his eyes, but if he makes such a statement, he should be able to qualify it, right? I mean, I know he doesn't have to; He can refuse to do business any time he wants and for whatever reason. Besides all else, I do respect that right of a business owner. The sad thing is that it is something like this that strains the relationship, and the next nearest LDS's are an hour further away.

Thanks for the offer on the valve, northcoastdiver. If worse comes to worse, I'll PM you. I appreciate the offer.

What pescador says makes sense. The 1/2" threads on my manifolds have 9-11 threads. So, if 7 threads need to be engaged, that would mean that 2-4 threads MAXIMUM would show. Average of 3? Pescador, did you see this in a code somewhere?

 

[duckbill]

CGA C-6, the last word on steel tank inspection, says this:

"Cylinder neck threads shall be............ More information on threads can be found in CGA V-1."

I don't have CGA V-1 handy, but it isn't one of the publications hydro shops are required to have, so it is unlikely to add anything that would contradict C-6.

I have to wonder. I'm just thinking here, and could be way off. If I assume (which I am- please correct me if this is wrong) that the "C" in C-6 is for "cylinders", could the "V" in V-1 be for "valves"? Then maybe the answer could be found in CGA V-1 regarding valve threads? Just guessing.

Anyone?

 

[pescador775]

The CGA don't care about "exposed threads". They concern themselves with thread engagement. The old USD valves which were used with 2000 psi tanks had 9 threads. The Healthways valve was standardized with 10 and the Nemrod had 11. The "three thread" thing is a good rule of thumb. For example, it could be dangerous to fill a tank fitted with a USD valve which had 4 threads showing. Speaking for myself only, I would inform the owner of this and request that he allow me to empty the tank, secure the tank in a vise and attempt to tighten the valve. If it could not be tightened, then remove the valve and find out what was going on with it. If a Nemrod valve were secure in a Healthways tank, four threads showing and did not leak, I would probably go ahead and fill it. Only an old timer would know these things but the three thread rule is better than nothing. There is no minimum exposed thread number. So long as the valve can be secured without leaking, even if only one thread were showing, it should be safe to fill. If the valve was bottomed, even if not leaking, it tends to indicate that the valve threads are pretty worn. I would not fill above 2200 psi.

 

[oxyhacker]

Unlikely, for reasons already mentioned. We are talking about inspecting a tank not a valve, and he wants to condemn, as I understand it, the tank not the valve.

V-1 is pretty obscure,as far as CGA publications go. I've seen a copy, but don't have one. Best I can recall, it is just about the different CGA valve specs, with drawings and dimensions, and nothing "hands on" about inspection or servicing.

I have to wonder. I'm just thinking here, and could be way off. If I assume (which I am- please correct me if this is wrong) that the "C" in C-6 is for "cylinders", could the "V" in V-1 be for "valves"? Then maybe the answer could be found in CGA V-1 regarding valve threads? Just guessing.

Anyone?

 

[duckbill]

We are talking about inspecting a tank not a valve, and he wants to condemn, as I understand it, the tank not the valve.

No. That's the weird thing about it! He said that the tank/valve system/package is condemned because of the valve itself.

Mark wasn't in today. I'll try him again tomorrow.

In the meantime, I went to the LDS to pick up my tank today and talked with the owner about this again. I have to say he was more cooperative than I had anticipated. Anyway, he said it has always been that way, it is a DOT regulation, and after he talked with someone on the phone about it, said he'd get a copy of the regulation to me. He said it was a CGA flier/memo (can't remember the exact word used). He said that anyone who says differently has obviously never been through the PSI course, which is where he learned about it. I really hope he can come up with the document. I look forward to one of the two of us learning something new. I predict he misunderstood whatever it is. We'll see.

I totally agree that it is the number of engaged threads that is the critical factor as long as they are loaded sufficiently to prevent leakage. This just makes sense. I just don't see the Feds sweating it over how many unused threads are showing, unless there is some concern about vulnerability and breakage due to the extra length.