Re: Limit stop in Piping stress analysis

From: <trajyagu@ltcis.ltindia.com>
Date: Sat Apr 20 2002 - 01:19:00 EDT

Right, no one will go for more than one axial stop if there is feasibility to accomodate expansion loop. But in some very very special cases it may become inevitable.

Lets take a system with a sraight pipe length of 20 m , then a 90 bend and a 2 m perpendicular piece which is directly connected to eqipment nozzle. I don't have feasibility for loop or changing the route. only thing i can do is to adjust supports. Now whole expansion of 20 m lenght will hit the nozzle and best thing one can do is to provide an axial stop at bend with trunion in the direction of 20 m leg. The axial stop will take this load due to thermal expansion and nozzle will be safe. In case of high temp lines sometimes axial force on stop becomes so high that it becomes very difficult to design such support. In such cases it becomes necessary to reduce this force on stop and in such special cases partial restraint before the stop can play important role though it's difficult to execute at site but not impossible.

Cocept of partial restraint is quite new because rarely one gets trapped in such situations.

"KAUSTUBH JOSHI" <kvj@epc.ltindia.com> on 04/19/2002 01:19:28 PM

Please respond to <a href="/group/PipingDesign/post?postID=TlL36b-6uBy9359C_xxjYco6761y-O65QoiPwptwkMJniv09vchmf3ZTd9dXintm1X8MsEJKs4rimg2WPxwGXfnYw6G5og">PipingDesign@yahoogroups.com</a>

To: <a href="/group/PipingDesign/post?postID=TlL36b-6uBy9359C_xxjYco6761y-O65QoiPwptwkMJniv09vchmf3ZTd9dXintm1X8MsEJKs4rimg2WPxwGXfnYw6G5og">PipingDesign@yahoogroups.com</a> cc: (bcc: TUSHAR K RAJYAGURU/L&T-CHIYODA) Subject: Re: [PipingDesign] Limit stop in Piping stress analysis

Dear Steve,

I did not get you exactly.

What I think, it can not be possible with rigid restraints. In case of rigid restraints the line would be overstressed due to not allowing thermal expansion. In case of multiple restrictions in a straight line, The supports can be sheared off or it can damage the pipe as well.

With rigid supports, we can achieve the distribution of load theoretically, as suggested by Tushar, but this system will be very very difficult to be implemented at site. And more over, the performance of the system could not be evaluated exactly due to deviations at site.

I case of springs, being the low stiffness, supports absorb the thermal expansion of the line and reduce the thermal stresses. But this certainly can not work with conventional rigid limit stops.

Regards,
Kaustubh

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