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#130 - 07/05/00 04:53 PM Un-tied expansion Joints - guide loads
Andrew Weighell Offline
Member

Registered: 01/15/00
Posts: 52
Loc: England, UK
Does anybody know of papers / references that would give specific details of guide loads adjacent to untied bellows.

In EJMA, guides are required within 4 and 14 D of the untied expansion joint to maintain stability. EJMA mentions loads on the supports of 7-15% of the pressure thrust.

EJMA does not say mention the alignment tolerances, type of bellows (rubber or metal) all of which will greatly affect the load on the first guide.

e.g.

"Support design loads of X % of pressure thrust assuming < Y % of Diameter axial misaligment of connecting pipes and < Z degrees of angular misalignment". We would want Y and Z to be very small but in a real world they won't be zero.

Many thanks

Andrew Weighell

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#131 - 07/26/00 03:39 PM Re: Un-tied expansion Joints - guide loads
Dan Edgar Offline
Member

Registered: 03/03/00
Posts: 89
Loc: Pine Valley, Ca, USA
The reason for guiding the expansion joints at 4D & 14D is because when you introduce an unrestrained expansion joint, the pipeline changes from a tensile member to a compressive member. As a compressive member, the pipeline is subject to buckling the same as a column with a compressive load. As such, a perfectly straight & infinitely rigid pipeline would not require any guiding, however, for "real world" applications guiding is required and the load is unknown. The industry has settled on the 7%-15% of pressure thrust value.

In regard to misalignment, if the pipe is installed in accordance with either B31.3 or B31.1 then the alignment is considered in the above factors. If the alignment because significant, i.e. say over 1/4" then the compressive load will begin to cause eccentric bending in the pipe. This would require a more rigorous analysis with CAESAR II.

Hope this answers your question, if not please contact me at pipesol@connectnet.com for a private conversation.

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#132 - 08/22/00 05:36 AM Re: Un-tied expansion Joints - guide loads
Alvin Zhu Offline
Member

Registered: 03/04/00
Posts: 7
Loc: Singapore
The code is a guideline. The purpose of guides on pipe is to keep the system stable.to keep the system stable, an anchor close to joint and guides are required. So these restrains will take the force induced maily by thermal expansion and friction. So just make a piping stress analysis,you will get the restrain loads on guides


Regards

Alvin Zhu

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