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#72937 - 03/05/19 04:29 AM Anchor Loads for Loop
sharu Offline
Member

Registered: 04/09/13
Posts: 16
Loc: india
Hi All,

May i know the practice followed by stress guys for providing loads at Axial stop (Point A) location for the below shown configuration.
[img:left]https://imgur.com/a/o4CmHnb[/img]

Ideally, if the distance on Right hand side and left hand side of point A are equal(Equi-distance loops), then zero loads will be shown at location A. This condition is achieved when line gets heated up completely and reaction forces are generated.

In real, due to time taken to get the line charged, this phenomenon may not happen. In this situation what loads may be transferred to Civil for safe design.

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#72954 - 03/06/19 09:38 AM Re: Anchor Loads for Loop [Re: sharu]
Michael_Fletcher Offline
Member

Registered: 01/29/10
Posts: 709
Loc: Louisiana, US
Ultimately, it should not fall on the pipe stress analyst to direct CSA how to design their supports, and they should take loads from piping stress and develop their own philosophy.

However, in order to remain civil with Civil, I would offer the suggestion to look at all identical or comparable supports and find the one with the maximum load (that isn't designed with a special purpose in mind, such as nozzle protection), and design all supports based on that.
_________________________
Ver: 9.00.00.5900 (Build 160721)

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#72955 - 03/06/19 11:34 AM Re: Anchor Loads for Loop [Re: sharu]
Bob Zimmerman Offline
Member

Registered: 12/29/99
Posts: 179
Loc: Houston,TX,USA
I have typically employed the following philosophy for line stop loads (limit stops, bumpers, stoppers, ...):

"The design load shall be the greater of the net load or 25% of the maximum load from either side. If one side of the bumper can be isolated/ambient, the design load shall be the higher one sided load."

Zero load shall not be given to Civil. I have seen some folks use 20% or 30% versus the 25% stated.
_________________________
Bob Zimmerman, P.E.
Vice President of The Piping Stress International Association (The PSI)

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#73025 - 03/14/19 06:44 AM Re: Anchor Loads for Loop [Re: Bob Zimmerman]
sharu Offline
Member

Registered: 04/09/13
Posts: 16
Loc: india
Thanks Michael and Bob for throwing some light on this.

I agree with you point Bob. I discussed the same with some seniors and released that we can find out the maximum axial load acting on the loop in a simple way from Global element forces report. It provides FROM and TO forces for a particular node. From here we will get maximum forces acting on axial restraint.

Note: In restraint summary report we get the combined effect which cancel each other.

Thanks to your efforts.
_________________________
sharun

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#73034 - 03/18/19 07:19 AM Re: Anchor Loads for Loop [Re: sharu]
engineer001ch Offline
Member

Registered: 12/21/18
Posts: 11
Loc: China
I think in your situation the special factor k=0.8 can be used for anchor loads as described here: http://www.whatispiping.com/how-to-avoid-zero-anchor-loads-from-piping

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#73036 - 03/19/19 01:40 AM Re: Anchor Loads for Loop [Re: engineer001ch]
Chakot Offline
Member

Registered: 05/01/09
Posts: 61
Loc: Italy
Interesting.
What's the best way in your opinion to implement this strategy in CAESAR II?
Would you use some special load case, or maybe Excel?
Thank you

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#73185 - 04/20/19 08:19 AM Re: Anchor Loads for Loop [Re: sharu]
sam Offline
Member

Registered: 02/25/04
Posts: 641
Loc: Maharastra, India
Very easily it can be done in load case editor by making new load case for anchor load.

In piping stress analysis and support specifications, such core issues need to be fixed at basic design stage. If anchor is used only for thermal load, not for any seismic or accident load like steam generated water hammer, some gap at axial stop can reduce thermal load.

But, issue of design of anchor is not the responsibility of civil only, piping stress owns the design when they sign the anchor design. After all, piping stress and supports design is a team effort of civil and piping!
Reg,
Sam
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#73221 - 05/01/19 10:04 PM Re: Anchor Loads for Loop [Re: sam]
NiTiN Stress Offline
Member

Registered: 10/22/09
Posts: 37
Loc: india

hi,
One thumb rule is that you can take middle anchor load as 1 /3rd of end anchor load ( end anchor having max axial load)
Regards,
Nitin Lonkar

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