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Thread: European Tank Valve Threads

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    RBW Member txdiver is an unknown quantity at this point txdiver's Avatar
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    European Tank Valve Threads

    Going through the BtS catalog I noticed that steel cylinders in Europe seem to have 3 different type of neck threads: M25/2, M26 and G5/8 - or are all the neck threads M25/2 but when the valve is an expandable valve (H-valve etc.) it has the G5/8 designation and when a M25/2 is O2 clean its called an M26. I am a bit confused. Could someone please educate me, please.

    Thanks

    Andy

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    RBW Member michael-fisch is on a distinguished road michael-fisch is on a distinguished road michael-fisch's Avatar
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    Re: European Tank Valve Threads

    Tank Valves have the following threads on the end that gets screwed into the tank:
    M25x2
    M18x1.5
    Small tapered threads (at least 15 years old, no longer used)
    Large tapered threads (used on storage bottles)

    The end that connects to the regulator is usually:
    G5/8 (232 or 300 Bar) DIN for breathing gasses with less than 23%O2
    M26 for breathing gasses over 23%O2
    Nobel gasses use a special valve that I can't remember the dimensions of.

    Other fitting are also in common use.

    Michael

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    RBW Member Paul S is on a distinguished road Paul S is on a distinguished road Paul S's Avatar
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    Re: European Tank Valve Threads

    Quote Originally Posted by michael-fisch  View Original Post
    Tank Valves have the following threads on the end that gets screwed into the tank:
    M25x2
    M18x1.5
    Just to add on to what Michael said, I think the M25x2 is the most common, with the M18x1.5 being used for small cylinders where the neck isn't large enough for the larger thread.

    There's no actual facts behind that statement, it's just based on what I've observed.

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    RBW Member Paul S is on a distinguished road Paul S is on a distinguished road Paul S's Avatar
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    Re: European Tank Valve Threads

    Quote Originally Posted by txdiver  View Original Post
    ...and when a M25/2 is O2 clean its called an M26. I am a bit confused. Could someone please educate me, please.
    Just a note on the designations which makes understanding a little easier. When someone talks about a M25x2 thread, it's a 25mm diameter and a 2mm pitch. If the pitch is missing, then it defaults to some standard value for that diameter. I think it's 3mm for M26, but I could be wrong.

    So no, M25x2 and M26 are not the same thread by different names. The diameters are close, but the pitches should be different.

    G5/8 is an imperial sized thread, as is probably obvious.

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    RBW Member michael-fisch is on a distinguished road michael-fisch is on a distinguished road michael-fisch's Avatar
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    Re: European Tank Valve Threads

    Please be very careful with 3/4x14 neck threads and M25x2 Valves

    They will seal perfectly until 150Bar, then the tank flies in one direction and the valve in the other direction.
    Almost always with severe bodily harm or death, the dive shop or boat usually has to be rebuilt too.
    BTS was bright enough to talk Luxfer into making AL80s for them with M25x2 threads, using the wrong valves has already caused a few deaths.

    Michael

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    Re: European Tank Valve Threads

    Quote Originally Posted by txdiver  View Original Post
    Going through the BtS catalog I noticed that steel cylinders in Europe seem to have 3 different type of neck threads: M25/2, M26 and G5/8 - or are all the neck threads M25/2 but when the valve is an expandable valve (H-valve etc.) it has the G5/8 designation and when a M25/2 is O2 clean its called an M26. I am a bit confused. Could someone please educate me, please.

    Thanks

    Andy
    Of the threads you mention only one is a neck thread and that's M25x2.
    The G5/8 is the thread that the DIN reg screws into and is the standard
    regulator thread, the M26 is also a regulator thread but it is supposed to
    be used for nitrox, with a nitrox regulator also having M26 thread.
    The M26 was introduced by the EU to stop confusion of cylinder contents
    but it has never really taken off though nitrox regs have to have the m26
    fitting to get CE aproved, most people change it to G5/8 standard DIN thread
    or use an adaptor.

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    RBW Member txdiver is an unknown quantity at this point txdiver's Avatar
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    Re: European Tank Valve Threads

    Awesome info and clarification - thank you everybody very much!!!

    So all neck threads are M25/2. Correct?
    There is 2 types of DIN reg threads: G5/8 and M26/3(?) - the later which is not too common and designated for higher O2 usage.

    So now my next question is based on the fact that my buddy and I are joining a trip in Denmark in the fall next year. We are currently sourcing tanks for our DIR Megs (very similar to the GUE-JJ configuration). We know what we can work with - courtesy of the BtS catalogue - but just have to make sure that the European Lola valves we are about to buy, will accept our Apeks DS4 DIN regs. Here in the states DIN is DIN and no difference in thread pitch or diameter - only in the length: 7 threads for 200bar DIN and 9 threads for 300bar DIN. So the question is: is the G5/8 just a lower pressure designation and not higher O2 content designation vs. M26 but the share the same diameter, pitch and thread count?

    Sorry this is a bit confusing to us non-metric folks.

    I really appreciate all your help.

    Andy

    Upon re-reading it: I wanna make sure that we rent tanks with M25/2 necks threads and G5/8 300DIN reg threads to accommodate our US DIN regs. M26 is too exotic ...
    Last edited by txdiver; 5th November 2015 at 19:34. Reason: Confusion - clarification

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    RBW Member Brummkreisel is an unknown quantity at this point Brummkreisel's Avatar
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    Re: European Tank Valve Threads

    Quote Originally Posted by txdiver  View Original Post
    Sorry this is a bit confusing to us non-metric folks.
    To confuse you a bit more you'll might find old G3/4 for oxygen tanks which are the predecessor of M26x2 valves
    Another topic is the country you are visiting, some countries allow mixes up 40% oxygen when using air valves. In Germany to have use M26x2 for gas above 21% oxygen.

    Happy diving in Europe
    Michael

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    Re: European Tank Valve Threads

    All cylinder threads are not M25x2, there are other sizes, some tapered, some not, but in Europe all new 3, 5, 7... etc litre cylinder neck threads should be M25x2 - so buy a standard cylinder and it ought to have this thread, however this is largely irrelevant as normally you would buy the cylinder with a valve fitted. In which case the valve to cylinder thread should be sorted by the supplier.

    (especially as if it is used for oxygen or partial pressure blending, as the supplier will clean/mark the cylinder as suitable for oxygen - if you buy a bare cylinder and separate valve, it would not be marked as oxygen clean, and some/many shops/centres will not fill it)

    The only real important thing, is how your regulators connect to the valve, and there are a number of types, firstly there is the A-clamp style, which is still used, albeit somewhat antiquated, I don't think you will have this on your rebreather or bail out regs. These are likely to be some form of DIN standard fitting, of which there are many - many gasses have different forms so they can't be mis-connected, for example acetylene has a left-hand thread, whilst oxygen is a right-hand thread etc etc.

    In diving cylinders however there really are just three forms:

    1. A g5/8 or 5/8bsp thread having 5 threads, and a large recess where the O-rings seals. This is used for 200/232 bar, the regulator will NOT fit in a valve type 2. below, both because of the thread length and the recess size.

    2. A g5/8 or 5/8bsp thread having 7 threads, and a small recess where the O-rings seals. This is used for 300 bar, the regulator will fit in a 200/232 bar valve .

    The above two are the most standard ones around - most regulators will be 300bar and will fit in either 300 or 200/232 bar valves - 300 bar valves should only be fitted to 300 bar cylinders

    3. The last one is a bit of an oddball, and that is almost the same as a 300 bar fitting, except the thread is M26 - only a M26 regulator will fit in a M26 valve, technically any high O2 gas should use this, so normally a rebreather sold in the EU must have this fitting on the oxygen side. The diluent would have the standard DIN style and must not have M26.

    If you are bringing your rebreathers over I assume both sides have std DIN therefore you need standard DIN valves.

    One final note, normally the format of a rebreather valve is different to a standard cylinder valve - the handle normally opposes the regulator thread, whilst a standard valve like the a-clamp is usually at 90degrees - again if you are ordering a cylinder and valve, just state that it's for a rebreather
    Last edited by BlondeBimbo; 6th November 2015 at 07:13.

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    RBW Member txdiver is an unknown quantity at this point txdiver's Avatar
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    Re: European Tank Valve Threads

    More great info ... and the plot thickens even more. I will check with the trip organizer about the Danish rules.
    We were planning on renting 7L or 8.5L cylinders hopefully with Lola valves and a flexible manifolds already attached. But we are not too hopeful in finding the combo so we were thinking of buying European Lola valves here and simply bringing them over. But after going through all the info this may be more complicated than originally thought ...

    Just for the illustrations sake we are diving an All-DIL/B/O backgas set-up ... very similar to the GUE's GUE-JJ (see attached picture of the valve/manifold configuration) and carry the O2 off-board ...

    Our regs are 300bar DIN so they should fit on standard G5/8 valves. I am a bit concerned about the M26/2 since our regs will not work with those valves ... I am glad I am starting this quest early ...

    Andy

    Lola Valves with Flexible Manifold.png

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