HP or LP double

[BigTuna]

On the subject of overfilling LP tanks, I think I've read that in Europe an LP tank can be filled to higher pressures than the same tank in the US, due to differences in the European and US certification specs.

Can one of you experts state the correct version of this? If it's true, doesn't it make us think differently about what is safe?

I don't know for sure if this refers to the very same tank certified under different rules, but that's the impression I have.

 

[dsteding]

The other fly in the ointment here is the buoyancy characteristics of the HP tanks. They are made of a different metal and may have completely different trim than their LP volume bretheren. So yes, the 104/130 share similar volume at similar pressure, but they may trim very differently because of dissimilar construction methods and materials. Hence my question to XS Scuba.

This is my biggest consideration in which tanks to double up-I am looking at either Faber 98s or buying one more Worthington 119. Having dived both of these tanks as singles rigs, it is clear that the 98s are much more top heavy . . . I like that as a single rig, but I'm not sure it would be good for a doubles rig.

 

[PhilEllis]

On the subject of overfilling LP tanks, I think I've read that in Europe an LP tank can be filled to higher pressures than the same tank in the US, due to differences in the European and US certification specs.

Can one of you experts state the correct version of this? If it's true, doesn't it make us think differently about what is safe?

I don't know for sure if this refers to the very same tank certified under different rules, but that's the impression I have.

Everything I say in this post is the result of several discussions I had with an engineer at Worthington about a year ago. It is all from my recollection and it was a fairly lenghtly conversation, so I could be "mis-remembering" much of it, but we did discuss the differences in USA and EU pressure cylinders............

If I remember correctly, the engineer told me that there was NO TRUTH to the common rumor in the scuba industry that the IDENTICAL cylinders that were approved for 2650 PSI fills in the United States were approved for higher fills in the EU. He said that the most popular cylinder in the EU (Faber) did not market the same cylinders in the United States and the EU. While they look alike, he stated that there were completely different alloys of steel used in the two cylinders. I believe he said that the EU standards also require a cycle test and a "leak before burst" failure for certification. If this is the case, it would be impossible to submit the EXACT same cylinder for approval to two widely different working pressure levels.

Maybe XSScuba will chime in on this issue. I know he knows a great deal about this area of cylinder certification, maybe more than any other routine participants on our board here. Anyway, I hope this helps.

Phil Ellis

 

[lamont]

If I remember correctly, the engineer told me that there was NO TRUTH to the common rumor in the scuba industry that the IDENTICAL cylinders that were approved for 2650 PSI fills in the United States were approved for higher fills in the EU. He said that the most popular cylinder in the EU (Faber) did not market the same cylinders in the United States and the EU. While they look alike, he stated that there were completely different alloys of steel used in the two cylinders. I believe he said that the EU standards also require a cycle test and a "leak before burst" failure for certification. If this is the case, it would be impossible to submit the EXACT same cylinder for approval to two widely different working pressure levels.

That is my understanding as well. Different metals, different metallurgy on paper, different certification test.

The overfilling of LP cylinders really rests entirely on the track record and the assumption that under normal use that any cracks would be found on hydro before the tank ruptured. They are different tanks from the HP/E/X tanks and different tanks from those in the EU...

 

[cerich]

Different tanks between EU and US for sure.

I had spent some time in 2002 reviewing all the different specs and regs when doing some SOLAS, LLyods.and MCA certification for a unique (at the time) installation/application of HP CG in a 100 meter plus yacht. I was the Project Manager and the owner of the yacht wanted as much air in his tank as possible without overfilling or being "illegal" (actually the legal aspect concerned the insurance company and Captain much more than the owner). Bottom line the tanks were purchased in Europe. (shipping cost more than the tanks...)