whats better ?

[Luis H]

This is true, technically.

In the real world, I have seen a LOT of o-rings blow on people trying attach yoke regs to their HP tanks. No big deal if you have a spare, but a hassle nonetheless... and a dive-killer if you don't have a spare handy.

I prefer DIN, and all my regs are DIN (tho I always carry a yoke adapter).

That said, I would choose the pro valve in a heartbeat, because there have been a number of times when I would like to dive a second dive, and have a spare tank filled and ready to go (DIN only), but the only other people up for a dive only had yoke regs, so I was unable to share my tank. If my tanks had the newer pro valves, I could have screwed the yoke donut back in for them and gone diving.

DIN connections are very good, but there are pro and cons to both.

I have been using both yoke and DIN valves for over 35 years and all I can tell you is that they both have there benefits. I have European tanks that I have owned since the early 70’s (one set was first hydro in 1957) with DIN valves. You can see them under this thread: http://www.scubaboard.com/showthread.php?t=153541

I have witness a few O-ring blow out, but with the modern valves with the small O-ring yoke connection (versus the old fat O-ring), an O-ring blow out should never occur. With the modern valves (if the connection is not damaged) when you properly seat the regulator or the filling attachment, there is metal to metal contact leaving no room for an O-ring to be extruded. The key words are “properly seat” and “the connection is not damaged”.

At this point I have developed a preference for a yoke connection because they are easier and quicker to connect and in the long run the DIN threads tend to wear more (particularly if you are regularly mating it to filling stations with less than perfect threads).

I totally dislike the use of seven threads. The five thread can handle any pressure, is less screwing, less threads to get damaged, and the cavity in the female end is not as deep so it is more robust (less chance of being deformed when banged). I don’t know when the seven threads DIN became popular, but I hope it goes away.

I don’t want to high jack this thread further so let me point you to an older thread of mine were I discussed some pros and cons of DIN connections (some of the pros have been discused heavely by others):
http://www.scubaboard.com/showthread.php?p=1861813#post1861813

IMO, I totally agree that a valve that has the ability to make either a DIN or a yoke connection is the best choice.

 

[pescador775]

Luis is correct.
I have used yoke valves on 3500 psi tanks for 15 years and never had an O ring blow. (To do this, I machined standard 3/4 Sherwood valves to 7/8 machine thread). Blown O rings are due to several things; use of old fashioned valves with crush type O rings (fat O rings), damaged valve orifice, soft or cracked O ring. Damaged valves are common in the rental business. Usual cause is ice pick to remove and replace an O ring. A high pressure O ring needs to be fairly hard (90 duro). Blown O rings in DIN valves are probably due to a grain of sand becoming lodged in the socket or due to a bad O ring. Generally, this happens less frequently because the crucial component, the O ring, is located on the regulator which is generally handled and serviced more carefully than a tank.

In addition to the comments pertaining to the valve and O ring, the yoke system must be of a newer type. This is due to a problem not anticipated 50 years ago when some of these yokes were manufactured. At high pressures, the old type of yoke will stretch enough to cause the regulator to stand off from the valve orifice. The actual measured stretch of the brass in an old yoke is about 0.007. In contrast, they stretch induced in one of the newer US Divers or Scubapro yokes is about 0.002, not enough to cause a problem.

As to preferences, either DIN or yoke are satisfactory for high pressure service (240 bar for our Euro readers).