RE: PSV Tailpipe, 45 Degree Cut?

From: <Arif>
Date: Thu Feb 08 2007 - 05:28:00 EST

I always thought that the bevel is to increase the surface area to decrease the back pressure at he time of discharge.

A J

-----Original Message-----
From: PipingDesign@yahoogroups.com [mailto:PipingDesign@yahoogroups.com] On Behalf Of Steve McKenzie
Sent: 08 February 2007 11:28
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] PSV Tailpipe, 45 Degree Cut?

Paul
I would think the idea is to take the sharp edge out of the noise generated
by the pulse when the valve unseats. The effect on directionality would be
negligible.You will also see slash cuts on auto and bike exhaust headers. I
think the real reason is that it looks cool. Would be horrified to think that the squareness of the cut is the difference
between reliable operation and failure.

Cheers

Steve

>From: Paul Bowers <pbowers@pipingdesign.com>
>Reply-To: PipingDesign@yahoogroups.com
>To: PipingDesign@yahoogroups.com
>Subject: [PipingDesign] PSV Tailpipe, 45 Degree Cut?
>Date: Wed, 07 Feb 2007 23:18:30 -0700
>
>Nozzle/twister writes at
>http://www.eng-tips.com/viewthread.cfm?qid=156173&page=6:
>
>=============================
>
><<What I've been taught is that the bevel is to deflect the release and
>noise away from the structure or operating area. In the old days it was
>common to see short tail pipes at the edge of a structure at mid-level.
>Now most vent pipes exit at a minimum of 7 or 8 feet above the highest
>nearby access level.
>
>The bevel does create a horizontal component (on a vertical pipe) that
>serves to increase the bending moment on the tail pipe dramatically,
>increasing stresses and complicating the support/guide scheme. There is
>a good discussion of this in ASME B31.1, Appendix II.
>
>The bevel does not increase the capacity and has outlived its
>usefulness. A bird nest is not going to slow down a release, though the
>bird may get the ride of his life.
>
>As a Pipe Stress Engineer who is responsible for supporting and
>restraining these vent pipes, I always request the ends to be square
cut
>at 90 degrees unless the client has dictated otherwise.>>
>
>=============================
>
>See the URL above for more discussion on the subject.
>
>Paul
>
>
>

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