Does anyone know how to estimate SIF and flexibility factors for a 45 degree Y-piece tee ? It is a one-piece tee with integral reinforcement and has an octagonal cross-section . It is made of titanium and is in a line with design pressure 5.5MPa and temp. 221 deg C. I don't know whether it is a standard vendor design or not.

To get the valid SIF for the unlisted components in ASME B31.3, the best way is experimental methods. This methos is, however, very difficult task. Alternatively you can use the finite element analysis method but I am not sure how much this method is valid in view of the Code requirements. Therefore ; you would be better ask to fitting manufacture. The qualified fitting manufacture can show and have the SIF for their products.

If all abve is not available, I think you may use conservatively the SIF of fabricated unreinforced tee in ASME B31.3, Appendix-D since normally the SIF of fabricated unreinforced tee is larger than the lateral tee's one. However I am afraid that this is how much conservative since your fitting is not carbon steel and not circular section. You have to know the SIF in Appendix-D are based on 4x4 branch fittings, D/t ratio is less than 100, with Markl's fatigue test. When your client insist you to verify the valid the SIF, you would be better refer to the following paper ;

"ASME publication, Determination of Stress Intensification Factor for Integrally reinforced 45 lateral Branch Connection, D.J.Wallsh and G.E.Woods, June, 1972, ASME Conference"
This paper shows ;

1) For r/rb larger than 0.5, integrally reinforced 45 degree lateral branch connections, ; the flexibility characteristic(h) are as follows ;

i = 0.9/h^2/3
h=2.29 t/r for in-plane
h=4.01 t/r for out-of-plane

2) For rb/r equal or less than 0.5 integrally reinforced 45 lateral branch connections ; the stress intensification factors(i) are as follows ;

i = 0.307 (r/t)^2/3 (rb/r)^1/2 for in-plane
i = 0.537 (r/t)^2/3 (rb/r)^1/2 for out-of-plane

You remember above paper is based on carbon steel pipe. If you have futher questions and want to discuss the valid SIF calculation, I will introduce someone who is specialist in the SIF calculation.


[This message has been edited by Soon Ryang, WEE (edited December 26, 1999).]

Can you please introduce me to a specialist in the SIF calculation ?
If you have that guy email address , can you please proide me ?

it will be very much helful.

Beside the man, maybe you will need the pdf file too at the link below:
http://www.coade.com/ubbthreads/ubbthrea...=true#Post17079

and the web:
http://www.paulin.com/FESIF.aspx

Hi Martin,

The SIF is irrelevant because beam theory computer programs cannot calculate stresses for the "block Y" fittings. The fitting at issue is not round on its exterior surface and since it is irregular in cross section software designed to calculate stresses in pipe (round in cross section with uniform wall thickness) cannot be applied. The "block Y" fitting is illustrated in Chapter 2 of the B31.3 book by Glynn Woods and Roy Baguley (CASTI Publishing). Since the "Block Y" fitting is designed for very high internal pressure it is very robust when compared to pipe.

The "block Y" fitting is very much more rigid than the pipes that are attached to it and we typically model the fitting as three rigid elements meeting at a node at their point of intersection. We might include an SIF for each of the three butt welds where the pipes meet the fitting but if they are rather "normal" butt welds the SIF would just be 1.0.

Regards, John

Thx Sir Breen for your valuable information...