On 6 Feb 2006 07:35:13 -0800, "jcarlyle" wrote:

George, I'm very surprised. All of the pressure vessels I've ever
worked on over the last 30 years that were located inside the USA have
had either DOT or ASME certification. I don't have a reference for you
at the moment, but I've written a note about this issue to a past
president of ASTM to get his input. I'll get back to you with his
response.

Meanwhile, could you tell me exactly what the stamped ratings on the
shell say that you are taking on trust?

Ishould have prefaced my comments with "I work in INDUSTRIAL AND
MOBILE FLUID POWER, not aerospace", so our situations may be very
different. Other than the QA requirements, a hydrotest is a
hydrotest, and I'm not sure that breathing oxygen cylinders for use in
a plane have any different requirements than on the ground ... but I
DON'T KNOW THAT. I have performed a hydrotest on SCUBA cylinders; we
didn't use certified gauges or anything; our criteria was recovery
from 5/3 "rating" confirming plastic deformation was not reached.

They will always have a maximum working pressure stamped in either PSI
or bar. They will often have a minimum termperature.

I did a little digging and find that most today for US use design to
Section VIII Div 1 and either stamp (U) all or upon premium payment
(which I suspect is an indicator of QA costs).

I found that those with IDs of less than 6" do not fall under ASME
criteria. That appears insignificant as the "standard" for common
bladder accumulators is 9" OD; I'm sure the shells are under 1/2 inch.

A quick look at Tobul, Vickers, and Hydac suggest they routinely stamp
theirs. Parker has an extra charge for it.

What I have _NEVER_ seen is one subjected to hydrotest.

MOST of what I run into are between 1 and 15 gallon, either 2000,
3000, or 5000 psi "rated", and of diaphram, bladder, or piston
construction. ALL use N2 as the specified gas. I've had customers
use Argon against my recommendation.

Have a good week,

George