Aaron, Michael, Chris -
My apologies, out of town and slow to answer, so I'd like to reply to all here.
I sent two files to Paul to upload. File Clamps&PipingSketch shows a typical high pressure clamp type union and a typical use of the union in a piping system. File ZST shows a typical zero static tee which is designed to eliminate dead flow spaces in the piping system.
Aaron addresses many of the questions asked. Welded joints are preferred, but can not be completely avoided without sacrificing cleaning, maintenance, and inspection, in this high purity water system.
The problem with using some of the products suggested such as braided hose, Bradford clamps, or flexible yoke style couplings, is that these are not ASME BPE compliant in terms of surface finish and elimination of static flow areas in their design. I am not sure of the hoses though, and will do a follow-up on available options with hoses.
We are negotiating with one of the manufacturers for testing the clamps. It may offer an advantage to them if they can publish what their clamps can withstand while others do not have the data. It seems an industry standard may be an option here because the design of the clamps are so similar across manufacturers and there are only three manufacturers, I believe.
The code I am most concerned with is B31.3 which states the pipe flexibility requirements, the BPE code is mostly addressing dimensions and issues relating to sanitization. B31.3, para. 319.1.1 requires a leak free system. As Aaron comments, the unions usually work initially, but often leak. If the system is designed to cycle thermally, and will leak after "x" number of cycles, does that meet B31.3? It seems to me since the intent of B31.3's flexibility requirements is to end up with a system that can cycle thermally and still not leak, these joints can not be shown to comply.
Ken A. Nisly-Nagele, P.E.
Project Engineer, Mechanical
Applied Engineering Services, Inc.
7999 Knue Road
Indianapolis, IN 46250
317-585-8920
-----Original Message-----
From: Aaron Wolfe [mailto:aaronwolfeman@hotmail.com]
Sent: Friday, May 21, 2004 8:46 AM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Modeling Hygienic Unions
Ken,
In my experience the clamps hold up well to thermal expansion....If the line is designed with sufficient change of direction to handle the force. The MHP style could be used in high pressure situations. But over time they just leak. I work in mostly bio-pharm systems. And the places where clamps are required are for removable spools for sterilization, calibration of an instrument, or connection to a piece of equipment. It is standard practice to minimize the use of such clamps because like I said, eventually they just leak. This is due to the gasket being repeatedly fatigued by clamping and unclamping. A quick replacement and they are good for another round. Being Autoplant users, we use AutoPIPE for the "stress test" and it seems to handle the clamp fitting just fine.
Regards,
Aaron Wolfe
Piping Designer
Paul Mueller Company
P.O. Box 828
Springfield, Mo 65801
(417) 575-9780
E-mail: awolfe@muel.com
-----Original Message-----
From: Ken Nisly-Nagele [mailto:knislynagele@applied-e-s.com]
Sent: Thursday, May 20, 2004 5:43 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Modeling Hygienic Unions
These clamps are made by Tri-Clover, Waukesha, or Swagelok, and are
rated to
200 psig. By meeting code, I mean to demonstrate that the unions will
not
leak during sterilization. I'm not concerned about the clamps working
at
the design pressure, but rather, I'm concerned with the clamps leaking
when
the piping in which they are installed undergoes bending during thermal
expansion and causes the faces of the ferrules to spread apart and
result in
leakage. With standard flanges there are tools to predict leakage, but
I am
not aware of a way to check for leakage with a union of this type. It
may
be that the only solution is to ask the manufacturers to test and
publish
the data as a group or individually.
Ken A. Nisly-Nagele, P.E.
Project Engineer, Mechanical
Applied Engineering Services, Inc.
7999 Knue Road
Indianapolis, IN 46250
317-585-8920
-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com]
Sent: Thursday, May 20, 2004 5:00 PM
To: â¡
Subject: RE: [PipingDesign] Modeling Hygienic Unions
>My apologies, my initial posting was not sufficiently clear.
No problem. Are you talking about clamps like the Grayloc or Tri-Clover
variety?
>The question is one of
>applying the unions and demonstrating compliance with the code.
I think the easy for doing this is to show that your clamp meets the
code
rules for a pressure which produces a unit axial load equal to the
(calculated axial pressure stress + the calculated bending stress)/pipe
wall thickness. This is fairly conservative, but it'll meet the U-2(g)
requirements without a lot a extra work.
Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen. ___________________________| John Sedgwick, Spotsylvania 1864)http://www.skypoint.com/~chrisw
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