Hi Tim,
The question that was given did not indicate the type of joints (packed,
packless, bellows, pressure-balanced, etc.).
Following are a few things to consider for finding where the expected expansion has gone: Examination of the piping supports should include all anchors and guides intended to control movement. Also, include a check for buckling of the pipe between joints. An anchor and/or guide could have broken or moved.
If the joints are not pressure-balanced type, the anchors at extreme ends will see a large axial force due to pressure thrust, or up to 200 sq-in cross section x 60 psig = 12,000 lbs. Also add any resistance to axial deflection (stuck parts, spring rate, etc.). Lateral forces become somewhat high, and there should be multiple effective guide points near each joint. I do not expect typical soil would provide effective guiding in your case.
Ben
-----Original Message-----
From: PipingDesign@yahoogroups.com [mailto:PipingDesign@yahoogroups.com] On
Behalf Of Paul Bowers
Sent: Friday, June 24, 2005 8:03 AM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] [Fwd: Re: [STM] Re: Steam line intermediate anchor]
I think you'll find that with direct buried steam lines, the pipe will
expand inside the insulation. I would characterize the earth as being more
of a virtual support/guide system, as opposed to an anchor in this type of
installation. We tried to have manholes at street intersections contain the
main valves, drip legs & anchor points. The manholes in the middle of
blocks
would normally contain back-to-back single expansion joints, with a common
anchor point, with a drip leg between them. We found that trying to have
line valves and expansion joints in the same manhole structures caused
space
problems. Intersections are usually just full of existing utilities, and
trying to cram a large manhole structure in there was a big problem. We
also
found that a pair of single expansion joints installed back-to-back gave us
a lot more flexibility when it came to "threading the needle" through
all of
the existing underground utilities. It also allowed us to install a full
sized drip leg near the anchor point between the joints, which made for a
lot less fooling around when trying to deal with expanding steam lines
acting on much smaller drip leg piping.
>A comment from a pipingdesign.com listmember (I forwarded the original
>inquiry to the group).
>
> Paul
>
>
> -------- Original Message --------
> Subject: [PipingDesign] Re: [Fwd: [STM] Steam line intermediate anchor]
> Date: Fri, 24 Jun 2005 01:33:30 -0000
> From: jcluf
> To: PipingDesign@yahoogroups.com
>
> So as to clarify this layout.... The lines enter and exit manholes
> where there are slip type EJs located. After leaving the side of the
> manhole the line is immediately buried???? Or is it in a casing pipe
> ??????
>
> If the line is buried it will develop whats called and described by
> some as a virtual anchor... the ground will develop local
> plastic deformations but in essence will restrain the pipe.
>
> A chase pipe is another matter altogether.
>
>
>
>> From: Gephardt, Tim <gephardtt@m...>
>
>> We have a 16", 60 psig steam line constructed in 1955, and it
> was
>> placed in a chase type system with slip style expansion joints in
>> concrete manholes to compensate for thermal expansion.
Yahoo! Groups Links Received on Fri Jun 24 12:25:00 2005
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