RE: TRUNION TEMPERATURES

B31.3 talks about two type of Stress categories. Primary and Secondary.

Glynn Woods (in a book published by CASTI)explained. An example of the a secondary stress would be bending of an elbow that joins two lenghts of pipe subjected to a temp increase. The bending in the elbow will reach a maximum value as the temp stablizes at its new increased value. Thus, the reduction causing the stress to increase stops. The elbow, now in this new higher stresses state, will expreince local yielding or deformation which will reduce the stresses in the elbow.

319.2.3 talks about the same thing. This is a secondary stresses and its basic characteristics is that it is self-limiting (loads dissipate as the system deforms). The study made by Markl's on fatigure failure of the bends made a reference to the effect of the ovalization.

-----Original Message-----
From: KAUSTUBH JOSHI [mailto:kvj@epc.ltindia.com] Sent: 19 April, 2002 3:56 PM
To: <a href="/group/PipingDesign/post?postID=dZJVQ8h1PUWyg_wyylBmq9h_HTKol4gFk041mEkndPfLN2vQNlHz0I5GM2NDf1s0B4zDFfwF8F7NOmC5MM0PH847nDRDAcM">PipingDesign@yahoogroups.com</a> Subject: Re: [PipingDesign] TRUNION TEMPERATURES

Dear Steve,

As a non stress(ed) engineer I have a question for the more highly stressed guys.Say we have a 1.5D bend at exactly 90 degrees cold. As it warms, the angle will decrease because there is more metal on the outside of the bend than the inside. Does C2 allow for this?

Ans:
CAESAR-II is based on the principle of "Guided Cantilever Method", in which the end rotations are not allowed. Hence, in CAESAR-II the inward bending of a bend due to increase in thermal expansion, is not taken into consideration. The solver takes into consideration of flexibility factor to calculate end displacements and sif for calculation of bending stress.

Similarly, it is worth noting:
when we have increase in temperature the bend bends inward and due to warping of fibres, we have a SIF assiciated with the bend. Does this mean that when the system is having negative increase in temperature due to opening of bend we should have Stress RELEAVING factor ?

Regards,
Kaustubh Received on Sat Apr 20 03:46:00 2002