Why you need to verify valve thread

[Leadking]

It could have ended very differently ...




He crawled through the eye of the needle. French Meijaard Dive Shop Oktopussy in Wemeldinge is glad he lived to tell about what happened in his filling station.
After the diving world a few weeks ago was rocked by a fatal accident because of a whipping crane, it went wrong again. This time, fortunately without casualties are regrettable. On 7 October, at Dive Shop Oktopussy in Wemeldinge 4 bottles offered to fill. One of the bottles is the knob broken and the request was to update it. Meanwhile, the bottles are filled to 200 bar. Just when French Meijaard was about to turn off, this bottle happened. With a loud bang shoot the tank valve.


French says: «You flashes with your eyes and see the enormous havoc around you.The ceiling is down on the floor in a jumble of insulation and other issues.

Through the open door pulls the dust away and slowly the realization back. I come to the conclusion that there is nothing corporeal hit, just a little deaf in one ear by the pressure wave. And the customers who are a little further on,'re fine and are only very shocked. »The bottle stands upright and the crane is next and is still attached to the hose that has become about 30 cm longer. Then also immediately see the cause. It appears that the (club) bottle with reinspection mrt2013 is threaded 3/4G while the crane has M25x2 thread.This of course does not engage well put together and is therefore a time bomb that could go off any time.


French continues: "Here I have long been 20-25 years afraid that once could also happen to me. As long ago that is about all bottle suppliers have decided to all go to the same thread M25x2 make in their bottles. Before that,

there are also those 3/4 G used. And that is the problem, because a tap M25x2 fits in a 3/4 G bottle, and have yet to be put on the last part a bit to get him. Closed I've heard many times over the years that in this way a crane bottle is fired with more or less injury. And as long as the bottles with 3/4 G remain in circulation may therefore happen again. Especially since the tap 3/4 G is no longer commonly available, and there are always new divers will not know of the existence of these bottles with different wire. »
To finally to deal with this problem, these bottles 3/4 G, all older than 20 years are not eligible to be located. reinspectionThrough the inspection company has submitted this to the French regulator, the Department of Stoomwezen, but this he was told that it does not intend here to give. Implementation It is suggested that an approved bottle with a well-mounted crane is safe! Exactly, but so that we do not come from the risk.
French calls everyone in the diving world to do the following:

• Make sure your old bottles with 3/4 G have. This is always stated on the bottle.
• Check that the correct crane mounted. This is stated on most taps
• Let this bottle did not recognize hours and do not sell it further.

French: "I hope that everyone who has a old bottle with 3/4 G thread has to take responsibility and not let the bottle labels. For as long as these bottles remain in circulation, the weather can happen again a wrong valve is mounted. And it should not be that there are more victims. "

: Incidentally, the following applies with immediate effect at Dive Shop Oktopussy

• As long as it is not shown that this actually happens, all bottles with 3/4 G thread are filled only through our automatic filling unit itself. The same goes for bottles with small conical thread W 19.8
• Oktopussy shall not cooperate more to bringing these bottles. Retesting to

Fellow Martijn Hanson Duikcentrum the Gravelines was shocked. He decided almost two years ago with small bottles, grootkonische and 3/4 gas taps not fill out after an earlier accident in which the owner of a filling station was seriously injured,
security for the customers as its own staff.
Martijn Hanson: "The incident with our colleagues from Dive Shop Oktopussy indicates that our policy is applied correctly and prevent this type of accident. Especially considering the number of visitors in and around the Diving Centre, we are aware that such accidents can have disastrous consequences.
If diving center we like to see this old standard of bottles with small, grootkonische and 3/4 gas taps as soon as possible is phased out. » Read more about cranes and wire in the article The right valve on your bottle?

 

[Wookie]

Is 3/4G the same as our 3/4 straight thread used in the United States and in much of the world? Good luck condemning all of those...

 

[Hickdive]

In the UK, prior to EU standardisation to metric m25, many cylinders had 3/4" BSP neck threads. However, this is not the same as the 3/4" NSPT thread still commonly used in the USA. Thus US cylinder valves cannot be used with older UK cylinders. It might well be that 3/4" G (which I've not come across) is yet another 3/4" standard that is incompatible with UK and US ones.

It should also be borne in mind that EU standards now mean that the neck thread size must be marked on the cylinder AND the valve, making it much easier to check they are compatible. Previously on the UK the neck thread did not have to be shown on either but usually one or the other would be marked. I now
work on the principle that I won't put a 3/4" BSP valve into a cylinder unless I have personally removed the one I am replacing and either it OR the cylinder are marked with the neck thread AND the cylinder is marked as being manufactured to the old standard BS5045/1 or /3 which permitted 3/4" BSP threads.

 

[Bob DBF]

It would seem that verifying and marking the valve thread on the neck at hydro as a retrofit would solve the problem for any but the most impaired.



Bob
-----------------------------
There is no problem that can't be solved with a liberal application of sex, tequila, money, duct tape, or high explosives, not necessarily in that order.

 

[ajduplessis]

I have previously highlighted this issue in various valve treads. Good to see all ended well but things could have turned out much worse.

 

[Cave Diver]

Are the two threads so close, that they can be interchanged accidentally and without difficulty?

 

[Wookie]

To my knowledge, the M25 will go in a 3/4 straight thread hole, but it's not right, it's loose, and the threads aren't the same pitch. The 3/4" straight thread will not go in a M25 hole.

 

[Doc Harry]

Many cylinder inspectors are complacent and don't take their job seriously.

 

[Hickdive]

Are the two threads so close, that they can be interchanged accidentally and without difficulty?

A 3/4" BSP threaded valve will appear to screw into a M25 threaded cylinder neck but will meet resistance on the last couple of turns, at which point an unsuspecting person might just add a bit of grunt to get it down to seat. The problem is at this point it is only those last couple of turns that have engaged the cylinder threads. The one or two threads that are holding the valve in will eventually fail. I suspect that may be what has happened here.

When fitting valves you should be able to use your index finger to spin the valve down the threads (even if you've already checked the cylinder and valve markings tally) until the valve seats and then torque it in. Any resistance means you're either cross threading or there is something wrong with the cylinder neck or valve thread. Not so long ago a rogue batch of M25 cylinder valves that were slightly out of pitch were released onto the market in the UK. The markings on the valves and cylinders tallied so some people spanner fitted them, not noticing the resistance they would have got from finger spinning them in. The cylinders were then used happily and without incident until their first visual inspections at which point the cylinders were failed and condemned because the neck threads had been stretched by the faulty valves. That particular distributor now has all the valves they import run through a thread-test gauge before sending them out to retailers.

 

[halocline]

Amazing photo, I wonder if this sort of technique would work for me when it comes time to demo my kitchen?