RE: PSV Tailpipe, 45 Degree Cut?

Paul,
Could you please comment on to what will happen to the horizontal component of velocity if the pipe end is square cut at 90 degrees. Thanks and kind regards,

Hasim SAKARYA
Dow Turkey

-----Original Message-----
From: PipingDesign@yahoogroups.com [mailto:PipingDesign@yahoogroups.com] On Behalf Of Paul Bowers
Sent: Thursday, February 08, 2007 8:19 AM To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] PSV Tailpipe, 45 Degree Cut?

Nozzle/twister writes at
http://www.eng- <http://www.eng-tips.com/viewthread.cfm?qid=156173&page=6:> 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

[Non-text portions of this message have been removed] Received on Thu Feb 08 02:48:00 2007