DIN Vs Yoke Regulator Fittings
By Keith Lawrence
One of the regular questions on the group is about the two different regulator fittings in common use in the UK, which is "best"?, do I have to convert my cylinders? can I use my regulators abroad? Well, I haven't found a definitive divers guide yet - so here's one...
What is a Yoke Fitting?
The yoke fitting is the 'normal' method of fitting a regulator to a cylinder valve. As well as being known as a "yoke" fitting the same system is often called an "A-Clamp" or sometimes an "international" fitting. This system is well tried and tested, it does work, but is being slowly replaced by the superior DIN fitting.
What is a DIN Fitting?
The regulator part
A DIN fitting is a screw fitting, simple as that. Instead of the regulator clamping onto the outside of the the cylinder valve, it screws into it. The picture shows a 7 thread DIN fitting on a Spiro (US Divers) regulator. This regulator and the DIN fitting can be used at pressures up to 300 BAR. This regulator will fit onto a 300BAR cylinder, which has 7 threads in it, or the more normal 5 thread 232 BAR fittings.
The only difference between the 5 thread 232 BAR and 7 thread 300 BAR fittings is the number of threads, it is designed that way to stop you making mistakes! A 7 thread 300 BAR regulator will fit into either a 300 BAR 7 thread or a 232 BAR 5 thread fitting. A 5 thread 232 BAR regulator fitting will not screw into a 300 bar cylinder, it wont reach the end and it wont make a seal.
Why Use One?
There are two main reasons for using DIN fittings -
- They are safer, the 'O' ring is trapped inside the fitting and it is very difficult for it to squeeze out.
- It is neater and more streamlined, there is not a large screw knob sitting on top of your cylinder waiting to catch on bits of rope etc.
The vast majority of the technical divers use them with their twin sets and stage cylinders, quite simply they are a better design of regulator fitting. But you don't need to be a technical diver to benefit, more and more ordinary divers are now using DIN fittings, they are very common on the continent.
The only problem with a DIN regulator is what happens on holiday when you are given an A-Clamp cylinder? That is not a problem, just an inconvenience - see later.
How Do I Convert My Regulator?
View of the regulator with DIN fitting,
the old A Clamp fitting (shown)simply
The simple answer to that is buy your regulator with a DIN fitting already fitted. Despite what dive shops may tell you (they often stock only A-Clamp regulators), many regulators are available with DIN as an option at no extra cost. If you've already got an A-Clamp regulator then you will have to get the fitting changed, it may cost you £50 or more for the fitting though!
Best is to get your local dive shop to do it for you, but it's actually very simple - the old A-Clamp screws out and the DIN fitting screws in. Remember to keep the old A-Clamp, when you sell the regulator, somebody might need it.
What About My Cylinders?
What a lot of people don't realise is that the majority of cylinder valves available in the UK, even the 232 BAR ones, are in fact DIN valves - the manufactures simply screw a small "insert" into the valve to make it into an A-Clamp valve!
A standard 232BAR cylinder valve
(this one is a MDE valve). Note the
hexagonal hole, that's the insert.
Remove the insert and you are left with a DIN
thread in the cylinder valve. A DIN regulator will
then screw straight in.
The insert removed from the cylinder, you are
looking at the "inside" end.
All you have to do is remove this insert with a hexagonal key and what is revealed is a 5 thread (count them) DIN fitting. The number of threads is again a safety thing - you can only get 5 thread inserts so you cannot convert your 7 thread 300 BAR cylinders to A-Clamp!
Note that there is no 'O' ring in or on the actual cylinder valve, the 'O' ring on the regulator DIN fitting does the sealing.
Keep hold of the insert, put it in your spares box. You will need it if the fill station hasn't got a DIN filling whip or you want to use your cylinder with a normal A-Clamp regulator.
The DIN Fitting In Use
A DIN regulator fitted to a DIN cylinder.
Check the 'O' ring on the regulator as you would with the 'O' ring on an A-Clamp cylinder valve, make sure everything is clean and just screw the regulator straight into the cylinder valve. It only needs hand tightening.
What About Diving Abroad?
The only place I've found where I can't get a DIN fitting cylinder is the Caribbean, anywhere frequented by mainly American divers may be limited to A-Clamp only. Anywhere frequented by the Europeans, especially the Germans (e.g. the Maldives) and you sometimes have to ask for an A-Clamp fitting as all of their cylinders are DIN by default.
If you've converted your regulators from A-Clamp to DIN then you could always put the old fitting back, but I don't bother - I don't like constantly changing regulator bits. So I use an adapter, the adapters A-Clamp fits onto the cylinder, my DIN regulator screws into the adapter.
An A-Clamp to DIN converter, it's
just a normal A-Clamp with a DIN
thread in the end.
A DIN regulator fitted to an A-Clamp cylinder via
An adapter is not ideal, it is actually the worst of both worlds with the snag points and two 'O' rings to worry about, but because I so rarely need one (I've needed it on one trip in the last three years) it's something I put up with.
Which is best? The DIN fitting of course - if you buy all your equipment with DIN fittings then there is no expense in changing later. The only problem you're likely to come across is holiday diving, that is easily overcome by carrying an adapter. All of my regulators and cylinders have been DIN for the past three years, I just don't use A-Clamp any more.
© Keith Lawrence (February 2000)