Re: Welding a small pressure test vessel...
- From: "Pete C." <aux3.DOH.4@xxxxxxxx>
- Date: Fri, 11 May 2007 09:08:23 -0500
Bruce wrote:
On Thu, 10 May 2007 22:08:57 GMT, "Pete C." <aux3.DOH.4@xxxxxxxx>
wrote:
I'm not a certified welder in any way, shape or form. Mostly self taught
though I did take an evening class at a tech school once. I do 95% TIG
on steel with my Syncrowave 250.
I have a project that I need to do which is a small pressure test
vessel. Max operating pressure is 150 PSI, air only, at least two safety
valves. Rough design is about a 12" length of 8" dia .5" wall steel
pipe, fixed welded on base plate and a removable top cap.
Figure the top cap should have say six bolts to secure it, most likely
hand knob style on a loosen and swing to the side out of slot in cap
type arrangement for convenience. The top cap will also need to have a
view port, presumably 1" lexan well reinforced with a couple steel cross
bars.
Recommendations on how to do this safely? Am I crazy to attempt it? It's
fairly low pressure and small enough to be overbuilt without excessive
cost. Were I able to do this as a hydrostatic chamber I'd be perfectly
comfortable, but as an air type chamber the potential catastrophic
failure mode makes me nerv
Thanks,
Pete C.
You are talking about 8" schedule 80 pipe. I did a quick calc and if
the material strength is 18,000 psi, which seems conservative, and
using a safety factor of 4, the working pressure would be 600 psi and
the calculated burst pressure is 2400 psi.
Normally pressure vessels have either domed heads or a standard flange
and blind so to be technically correct you should either locate a 8"
schedule 80 dome or flange and blind.
Having said that I might comment that you are grossly over designing
for a 150 psi system.
8" schedule 40 has a wall thickness of 0.322 and using a conservative
strength of 18,000 psi and a safety factor of 4 the working pressure
is 400 psi.
8" schedule 10 with a wall thickness of 0.165 with other data the same
has a working pressure of 200 psi.
The fixed and removable ends are another story. If I were building
this for my own use I'd probably use schedule 10 pipe and a 0.5" plate
for the closed end, which would be the base of the chamber. For the
end that is removable I would try to locate a manufactured flange (I
don't know where you are but here in Asia you can buy low pressure
weld neck flanges. Check the pressure rating to be sure what you are
buy though.
As you want a viewing port I would make the flange blind out of 0.5"
material also and machine a stepped hole in it for the lemon:
Top______
__ |
_______|
Since the lemon is held in by pressure I'd just mount it with some
kind of sealing gunk.
When I had the thing finished, if I felt nervous at all, I'd hydrostat
it. Fill the vessel completely full of water, clamp on the lid and
pump it up to 300 psi. Close the valve and come back tomorrow. You
will probably have some pressure variance because of temperature but
if you've still got about 300 psi in the pot your good to go.
Bruce in Bangkok
(brucepaigeatgmaildotcom)
--
Posted via a free Usenet account from http://www.teranews.com
Grossly over designing makes me more comfortable :) If I could do this
as a hydrostatic chamber I wouldn't be concerned since that doesn't have
a potential for a catastrophic failure mode.
Pete C.
.
- Follow-Ups:
- Re: Welding a small pressure test vessel...
- From: Steve B
- Re: Welding a small pressure test vessel...
- References:
- Welding a small pressure test vessel...
- From: Pete C.
- Re: Welding a small pressure test vessel...
- From: Bruce
- Welding a small pressure test vessel...
- Prev by Date: Re: Welding a small pressure test vessel...
- Next by Date: Re: Welding a small pressure test vessel...
- Previous by thread: Re: Welding a small pressure test vessel...
- Next by thread: Re: Welding a small pressure test vessel...
- Index(es):
Relevant Pages
|
