HP steel tanks and yoke regs?

[paddler3d]

I thought that 3442 is the max working pressure of the tanks??? I know my lds does my HP 80's to 3000 and no more even though im 3442 tank rated only difference is I have a 3000 DIN with a Yoke adapter.

It is my understanding that this really is just a DOT limit. If I remember right my buddy went to Tobermory in Canada and they cranked his HP80's to 4500psi. A burst disk on a valve that is rated to 3442psi should go around 4800-4900psi.

Cave divers have been overfilling their LP tanks for years.

Around my market, two of my LDS's have a hard time getting to the rated pressure of 3442.

Do a search on SB. There is an account of some fire department that got board and tried to blow up some tanks. AL tanks did fail, but none of the steel tanks failed, even when they were getting to the point of blowing HP hydraulic hoses!

 

[walke121]

When a tank is hydro'ed it is filled with 5/3 of the working pressure so a 3000 psi tank is hydro'ed at 5000 psi. It is safe to do this because water is used and if there is a tank failure it is a minor problem since water doesn't compress (well the water compresses but in such small amounts that it isn't an issue). Most tanks can hold this pressure but I think it would be an foolish idea at best to do this. I am not even sure that a 1st stage could even work at 4500 psi. As for a 4500 psi fill I can't even imagine a LDS that would even consider doing that even if the compressor had the ability to reach that high psi.

PS overfilling a LP tank to 2800-3000 is a lot different than putting 4500 psi in a tank. That is just stupid.

 

[Stu S.]

The dive shop might have figured they did me a favor. Wow... 3900 psi. in a 3442 tank. Seconds later, BAM, the SPG hose expanded and split open.

Thanks to Mike and Jerry for letting me use that spare regulator.

 

[mksmith713]

The dive shop might have figured they did me a favor. Wow... 3900 psi. in a 3442 tank. Seconds later, BAM, the SPG hose expanded and split open.

Thanks to Mike and Jerry for letting me use that spare regulator.

I guess you didn't have a 5000 psi SPG

 

[Stu S.]

I guess you didn't have a 5000 psi SPG

Yes, it is a 5000 psi gauge. That hose was about 16 years old. I now know those hoses do not maintain "like new strength".

 

[StreetDoctor]

Yes, it is a 5000 psi gauge. That hose was about 16 years old. I now know those hoses do not maintain "like new strength".

So then the problem wasn't the fill but the improperly maintained equipment. My girlfriend routinely uses a HP130 with a yoke reg and has never had a problem. I've also had fills to 3800 and not had a problem with my DIN regs.

 

[Gilldiver]

Just so people get this:

2500 PSI = 172 BAR
3000 PSI = 206 BAR
3500 PSI = 241 BAR
4000 PSI = 275 BAR
4500 PSI = 310 BAR

So, pick your pressure, as modern yokes are good to 232 BAR (3364 PSI) , you are within 136 PSI of a 3500 (241 BAR) fill. What do you think the safety margin is?

 

[WD8CDH]

Cousteau routinely used the Yoke fitting at 5000 psi. Most modern regulators and many older ones work well even at 4500psi. Of course, o-ring extrusion is more prevalent the higher that you go, especially with too soft o-rings. Of the two most common yoke o-ring sizes, the valves that use the smaller diameter one will be more reliable at higher pressures because the o-ring is better captured. Sherwood even rated some of their small o-ring valves at 4000 or 5000 psi.

Even the DIN>yoke inserts come with different size o-rings. The ones with the smaller o-rings on the yoke face are generally more reliable.

 

[Stu S.]

So then the problem wasn't the fill but the improperly maintained equipment. My girlfriend routinely uses a HP130 with a yoke reg and has never had a problem. I've also had fills to 3800 and not had a problem with my DIN regs.

Hey, Doc.

Maintanance or fill? Maintenance may not be the word, as we never see directives to change the hose after so many years or dives. The hose always went with the regulator for annual service. I suppose the only way to know the burst strength of a used hose is a destructive test; and this test was unplanned.

Since 1977, the three gear failures I've had were HP gauge related. Two hoses, and a gage that blew right off its fitting (that one was new).

Happy diving - Stu.

 

[StreetDoctor]

Hey, Doc.

Maintanance or fill? Maintenance may not be the word, as we never see directives to change the hose after so many years or dives. The hose always went with the regulator for annual service. I suppose the only way to know the burst strength of a used hose is a destructive test; and this test was unplanned.

Since 1977, the three gear failures I've had were HP gauge related. Two hoses, and a gage that blew right off its fitting (that one was new).

Happy diving - Stu.

I may be speaking out of my #@$ here but I would *think* after 16 years a hose would show some signs of wear? Dry rot, etc. just from being used no matter how well it was taken care of. I was always told you should replace your hoses every few years no matter what they look like. There isn't much servicing that can be done to them.

-Nick