Absorbed air can also cause pressure drop during hydrotest and has caused
confusion on more than one occasion.
-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=DCmJhPT3VNxUJg_H1kuwdhrlp2jkF-ejLayfzB38lNbFszHjuqqIx6xJMrGVASVTgtSkQXOttvVS7vZO79uvnzX7otXry7c">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=DCmJhPT3VNxUJg_H1kuwdhrlp2jkF-ejLayfzB38lNbFszHjuqqIx6xJMrGVASVTgtSkQXOttvVS7vZO79uvnzX7otXry7c">PipingDesign@yahoogroups.com</a>] On
Behalf Of John Luf
Sent: Friday, May 12, 2006 12:11 PM
To: <a href="/group/PipingDesign/post?postID=DCmJhPT3VNxUJg_H1kuwdhrlp2jkF-ejLayfzB38lNbFszHjuqqIx6xJMrGVASVTgtSkQXOttvVS7vZO79uvnzX7otXry7c">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] presure drop during hydrotest
Visual examination of all welds/joints is a must in the field of piping, the results of the visual examinatrion for leakage is in many ways more important than minor pressure drops.
Did you do a close 100% exam of all these connections during your test?
Christopher Wright <chrisw@skypoint.com> wrote:
On May 11, 2006, at 10:31 PM, Wutt wrote:
> Any calculation to support my hydrotest.
> The pressure is drop according to temperature, I want to use the
> calculation to prove to client that this is not cause of leak.
The material inside the vessel changes with temperature according to
the principles of thermal expansion = CTE x length x (temperature
change). So does the vessel itself. If the volume change of the
contents is different than the volume change of the vessel, the
pressure changes. Note that the volume change of the vessel (say a
cylinder) is found from the relationship between volume, diameter and
length: V = piD^2L/4 delV = pi (2D delV +delL)/4
del L and del D are the changes in vessel geometry from thermal
expansion del L = CTE x L x temperature change. The volme chance of the
contents, presumably water is the bulk coefficient of expansion x
volume x temperature difference.
If you were doing this for me I'd also want you to prove to me what the
actual temperature change of the vessel is. It won't be the same as the
ambient temperature change because the vessel changes temperature much
more slowly than the surrounding air. You'll have to do a heat transfer
calculation to estimate that. A measurement of the tank wall will help,
but it won't telll you the whole story.
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
____________________| John Sedgwick, Spotsylvania 1864)
<a href="http://www.skypoint.com/~chrisw">http://www.skypoint.com/~chrisw</a>
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Best Regards,
John C. Luf
Cleveland Ohio U.S.A when I'm not in Austria
Member B31.3, Piping Engineer - Stress Analysis, Pipe Supports, Component Design, and Surge Analysis... according to my daughters master of unimportant trivia
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Yahoo! Groups Links Received on Fri May 12 16:01:00 2006
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