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Re: Welding on pressure vessels

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Patrick ---

Before you mess with a LOX vessel, be aware that it must be an
ASME-certified pressure vessel under OSHA regulations.  The appropriate
code is not UBC or AISC, but ASME.  The welding you are contemplating
will require a) special welding license, b) a special ASME inspection,
and an engineer or manufacturer with an ASME R-stamp license.  That
entity then must issue a certification report, which remains in the
active vessel file retained by the owner/user.   Any less than that is

  One suggested source of such expertise is General Physics Corporation,
with a west coast office in San Diego.  Jim Gill is the Director of
Operations for that office.  Call 760-233-9880, or try his cell phone at

An alternate approach which I have employed successfully is to utilize
the existing anchor leg, but span over it with an added plate or short
member.  The new anchor bolts are then installed through the new plate,
not the existing.  With some care, the original tank design is not
altered, but anchorage is assured.   If this can be done, it will be less
costly than the ASME code route.

Russ Nester

On Fri, 30 Mar 2001 18:45:36 -0800 Patrick Rodgers
<prodgers(--nospam--at)> writes:
> Dear All,
> As part of California's hospital upgrade, bulk medical (lox) gas 
> tanks
> must have there anchorage verified.  Given a large number of tanks 
> were
> installed without permits, or at least we have not found any, we 
> have to
> check the anchorage.
> My questions
> Since these tanks tend to have three legs with a single anchor bolt, 
> we
> are finding that additional anchors are required.
> 1.    Are the ASME approved tanks allowed to be modified in the leg 
> area
> without voiding the ASME approval?  Modifications would include 
> welding
> gussets, welding plates to box the channel shape of the leg, or 
> drilling
> holes.
> 2.    Is welding on the legs of a tank filled with liquid oxygen a 
> good
> idea?
> 3.    Are there any  other items to be reviewing.  Such as does
> strengthening the legs for lateral loads cause problems in the outer
> shell of the tank?
> Thanks in advance.
> Patrick Rodgers