Use yoke or Din on PST tanks?

[scubadobadoo]

I switched to PST's recently too after using Aluminum for some time and find myself asking this same question. I also dive a yoke (SP MK25/S600) with my PST tanks and have finally gone through a set of O-Rings. I bought some basic black ones but they just don't seem to work very well as air escapes when I try to attach my 1st stage sometimes. What is the deal? I had some of those purple ones but they are hard to find! The purple ones are harder and generally made for nitrox like the ones viton makes right? Please feel free to correct me here...

Anyway, I have used yoke for one dive season with my PST's without issue until I had to change the O-ring. So far the tank hasn't blown my 1st stage through the back of my head yet. However, If my regs were DIN I probably wouldn't be having this O-ring issue right? SO, will the purple ones help or do I just have to mess with the way the O-ring is seated until it works?? Thanks gang as usual!

I will also add that I went to a new shop in Jersey last month to have my PST's filled and the shop refused to fill the tanks past 3000 because I was using yoke. First time that ever happened.

 

[spectrum]

First let's clarify that these are E7 series cylinders rated at 3442, right?

The E7 s are psuudo high pressure in that theye are less than 3500 PSI and get under the radar of the DIN requirement. They are usually sold with the THERMO-K PRO valve that has the donut that allows the yoke connection.

If your PST 100s are the older 3500 model then they should be DIN, period.

Not all yokes are created equal, some vintage and even current production are not intended to be used over 3000 PSI. Remember also that you may be blessed with a genrous fill on occasion so the load may be over 3442 at times. Check your specs.

There are countless threads on the merit of the DIN connection, that's what we chose to use.

So for the 3442 cylinders IMO it comes down to the specs on your gear and how much you buy into the DIN justification.

Pete

 

[scubadobadoo]

First let's clarify that these are E7 series cylinders rated at 3442, right?

Pete

Yes, E7 series in my case.

 

[spectrum]

I bought some basic black ones but they just don't seem to work very well as air escapes when I try to attach my 1st stage sometimes. What is the deal?

The O-ring compound make a difference but torquing those inserts has an effect too. If they are too tight then they will cock in the threads ay will be out of square with the valve. I tighten them with an allen wrench just using 1 finger to push the wrench lightly.

I just use the donuts for the convenience of the fill stations that are mosty yoke arond here.

Pete

 

[CompuDude]

I switched to PST's recently too after using Aluminum for some time and find myself asking this same question. I also dive a yoke (SP MK25/S600) with my PST tanks and have finally gone through a set of O-Rings. I bought some basic black ones but they just don't seem to work very well as air escapes when I try to attach my 1st stage sometimes. What is the deal? I had some of those purple ones but they are hard to find! The purple ones are harder and generally made for nitrox like the ones viton makes right? Please feel free to correct me here...

Anyway, I have used yoke for one dive season with my PST's without issue until I had to change the O-ring. So far the tank hasn't blown my 1st stage through the back of my head yet. However, If my regs were DIN I probably wouldn't be having this O-ring issue right? SO, will the purple ones help or do I just have to mess with the way the O-ring is seated until it works?? Thanks gang as usual!

I will also add that I went to a new shop in Jersey last month to have my PST's filled and the shop refused to fill the tanks past 3000 because I was using yoke. First time that ever happened.

The MK25 first stage can easily be converted to a DIN connector. That's what I would recommend. Unless you are familiar with the maintenance, I would have your LDS do it. Exact same reg, DIN or yoke... mine was out of the DIN style when I bought, so he opened a yoke one, and converted it while I watched. No problemo. I'd much rather use a yoke connector on my DIN for when I use yoke tanks, than try to use a yoke connector on a tank with pressure that's borderline too much for it to handle, but happens to have an insert that might let me get away with it.