pipingdesign: RE: pocketed line

From: <Bruce>
Date: Wed Dec 12 2001 - 16:39:00 EST

In the USA, this is one of the intents and purposes of Process Safety Management (PSM, 29CFR1910.119 for those who aren't familiar). The reg specifically requires that procedures be developed and reviewed for startup after emergency shutdown, after turnaround or extended shutdown, and others. The problem is that so many engineers and supervisors don't understand that utilities are just as much a part of the plant operation as the systems and components that are use to take feed and output product.

Sorry if this isn't an expected reseponse, but this is one of my "hot buttons".

                                         ... Bruce D. Bullough ...
                                         Sebesta Blomberg & Associates
                                         2381 Rosegate
                                         Roseville, MN  55113
                                         651-634-7344 (office)
                                         651-634-7400 (FAX)
                                         www.sebesta.com

-----Original Message-----
From: geoff stone [mailto:blenrayaust@yahoo.co.uk] Sent: Wednesday, December 12, 2001 3:28 PM To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] pocketed line

If you do a search using Google on "waterhammer" you will come up with an interesting number of papers related to steam hammer. These describe some catastrophies in the USA where a steam valve was cracked open to bring a header back into service. The line hadnt been blown dry, drain valves were not open or under sized. The steam condensed in the cold line. The condensate couldnt drain quickly enough and a slug of condensate was picked up by the high velocity steam. The result was a tragic death as a valve ruptured in a pit scalding workers with high temperature steam and condensate.

Start up of steam headers needs a task risk analysis undertaken by experienced operating engineers and operators. It shouldnt be taken lightly by enthusiastic amateurs.

"SARE, RALPH H." <SARERH@YANPET.SABIC.com> wrote:
<HR>
<html><body>

<tt>
 
 

> 1. In case of condensation during shutdown, water will accumulate in the 
> pockets. When the line is charged with steam, this water will be carried 
> along with the high velocity steam. When such a mixture passes through 
> bend, it creates unbalanced dynamic forces, which can damage the 
> supporting and in some adverse conditions, the piping itself. 
> 
Joshi - it is almost routine procedure during any startup or commissioning 
to blow the line dry. beside this is the reason why a bootleg is installed 
on the main steam header . 
 

> 2. In case you line is having pockets, after hydro test, water will be 
> there in the pockets, which will be like added mass and can cause damage 
> to supporting arrangements. 
> 
Again, a proper startup procedure will ensure that this dont happen. 
 

> 3. The pockets are created due to improper supporting. Improper supporting 
> lowers the frequency of the line and hence, where frequency is one of the 
> criteria of the analysis, pockets can not be tolerated. 
> 
If proper QC is in place, pockets observed by certified inspector not shown 
on the drawing approved for constrcution should have been reported as a 
non-conformance and corrected prior to commissining. This is standard 
practice during the mechancal completion phase of the construction. 
 
 
</tt>

 

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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Received on Wed Dec 12 16:39:00 2001

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