Opinions on older HP80?

[fishmunger]

I am considering picking up a used HP80 (in hydro). It's an '89 and I think it might be a pressed steel, it has a sherwood 6300 din valve (that angled back one). It's galvanized and looks pretty nice. I was wondering:

1) What's the current deal with the exemption on PST tanks, should I avoid it?
2) Is there anything stopping me from changing out the DIN for a YOKE valve? All of my other tanks have yoke and I don't want to swap around. Do you think I'd have any problems putting a yoke on it and just having it filled to only 3000 psi (~70cu/ft gas)?
3) Presuming it is a PST, I've searched and found 2 sets of buoyancy traits. -3 empty and -1 empty, anyone know the true stats?

any other advice would be appreciated. thanks

Nate

 

[spectrum]

Hi Fishmunger

There was a release a while back that the surviving PST operation would take care of the exemption paper work in time. The fall back is a personal request for one. In general the consensus seems to be that they will continue to be usable. I have 6 and I'm sleeping nights

If you have the older PST HP Steels they probably have the small necks with a 7/8" machine screw thread and have a stamped pressure rating of 3500 PSI. These are true HP cylinders and as such can not be fitted with a yoke connection. As an 89 I believe this has to be what you have.

The next generation known as the E series are rated at 3442 PSI, just a few atmospheres below the 3500 PSI threshold. These have the more common larger 3/4" Pipe thread. Being under 3500 PSI you find these equipped with the Thermo-Pro valve which will do yoke and DIN duty.

Based on this chart I believe you have an empty buoyancy rating of 3.3 pounds. My E7-80s are -2.5 pounds.

Pete

 

[Scared Silly]

Edit: removed post because the post refered to in Post 8 clears things up. Thanks.

 

[Alian1]

I believe what Spectrum meant is that the outside of the tank looks much narrower than a regular tank, like it has a small longer neck. I cant speak of the thread size but I have seen the long thin necks on "real" HP tanks (3500psi instead of 3442)

 

[spectrum]

The 7/8 thread is a 7/8 machine thread. This means that the fitting that screws into it is essentially 7/8 in diameter and the hole is tapped to match

The more common 3/4 thread is a pipe thread. Being a pipe thread the male thread that is on the valve it is a thread that would be on the outside of a threaded pipe that has an inside diameter of trade size 3/4.

Since the 3/4 pipe thread is based on an inside pipe dimension whereas the 7/8 is actual the 3/4 is physically larger. In short they are 2 distinctly different thread families.

If you dig back far enough you can find a post where I made the same incredulous remark.

Pete

 

[fishmunger]

the neck on this tank definitely looks narrower than normal. It's not a pipe thread or anything. So I take it this is a different size then?

Nate

 

[fishmunger]

i just reread your post spectrum and now I understand....

 

[spectrum]

In fact here is my faux pas. The power of searching!

Pete

 

[fishmunger]

cool stuff, so now the question is: any way to put a yoke valve on that tank? If not, I think I'm gonna pass...

thanks Spectrum

Nate

 

[spectrum]

cool stuff, so now the question is: any way to put a yoke valve on that tank? If not, I think I'm gonna pass...

Not to my knowledge and if there is a way to physically do it then it would not be on the up & up.

Pete

Edit, If you want I will do my best to keep them utilized for you.