RE: Sustained Stresses

From: <Gopakumar>
Date: Mon Nov 26 2001 - 04:07:00 EST

Dear Mr. Joshi,

The configuration of piping support shall be the same when analysis is done for operating as well as sustained conditions. So if u are talking about removing support because of lifting of pipe that means the same condition needs to be applied in the sustained case as well so the same condition will apply to site.

The ideal case will be to ensure that all pipe supports are active during both sustained as well as operating condition. So if the pipe is lifting either the pipe support location needs to be shifted or else spring support is the option.

Regards

B. Gopakumar

Telefon: 91-6347990 Ext 1543
Telefax: 91-6347512
mailto:B.Gopakumar@pg.siemens.co.in

-----Original Message-----
From: KAUSTUBH JOSHI [mailto:kvj@epc.ltindia.com] Sent: 26 November 2001 09:59
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Sustained Stresses

• High Priority **

Dear Members,

This is regarding calculation of sustained stresses.

1. The sustained stresses are calculated in sustained load case (Lets call this as SL1) and we are also interested to know that the sustained stresses in operating conditions (Lets call this as SL2) are within the allowable limits. To calculate the sustained stresses in operating condition, we take the active support configuration from the operating load case run and carry out the sustained loading analysis. But sometimes the deflections at the support locations (which are there for calculation of SL1 and to be erected at site), which are removed in calculation of SL2, give unrealistic picture. So the stresses calculated also gives unrealistic values.

For example, if pipe is lifting at a resting support location (S1) by 5mm in operating load case, then this support (S1) is removed and sustained stresses, SL2, are checked. Let us assume that the SL2 are exceeding the allowable , Sh. But if the deflection at the support location (S1) for sustained stress run (SL2) is coming to be 10mm down, then it is an unrealistic deflection, as at site, the support (S1) will be present. The pipe will rest on that support in operating condition after deflecting down by 5mm.

How to take care of this situation? How to calculate the sustained stresses correctly for such situations? Since, in reality, the deflection will be only 5mm down instead of 10mm down, the bending stresses will also be lesser, than what is calculated in the analysis of SL2.

I hope I am clear in my question. In case of doubt please feel free to ask.

Regards,

K. V. JOSHI PRDH-A306,
L&T POWAI WORKS,
MUMBAI-400072
INDIA
TEL: 8581401 Ext. 2880
E-mail : kvj@epc.ltindia.com

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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Received on Mon Nov 26 04:07:00 2001