Can you please help me in eliminating the stresses in the following job which i am sending by email to you. Its a small job.

I am emailing you the required files. Please email me the job on gsakhardande@yahoo.com

Thanks.

Guru

Your problem is the pressure multiplier m. It is calculated as m = 1.4 lambda^0.25, where lambda = Di / 2tm. Of course he can't change Di.

tm is defined as the wall thickness of the header pipe for fabricated (set-on or set-in) tees or the minimum thickness of the reinforced portion of the moulded tee. (In most cases this will correspond to the thickness of the matching pipe.) Calculations are further based upon the requirements that (1) the thickness of the pad on the fabricated tee is also equal to tm (giving a total thickness of 2tm), and that the crotch thickness of both the reinforced fabricated and the moulded tees is 1.5tm.

Since these pad and crotch thicknesses are mandated by the code, CAESAR II ignores any entries in these fields, assuming that the requirements of the tee are met when the tee type is selected (tm is taken from the wall thickness specified on the main spreadsheet, since normally the thickness of the matching pipe is what the user should be using).

If you want to go out on a limb (it would be your responsibility to "extend the code"), and if the wall thicknesses of your tees exceed these requirements, you may be able to back calculate an "equivalent tm" as:

tm = min(thickness of matching pipe, 1/2 of minimum thickness of reinforced portion of moulded tee, pad thickness of fabricated tee, 2/3 of crotch thickness of either)

Then you would have to build the tee as three piping elements with wall thicknesses specified as tm and diameters specified as Di+2tm (or di+2tm). (Note that this is not exactly correct, as the non-pressure stresses -- bending, torsion, etc. -- are supposed to be calculated from the "Design thickness of the reference laminate" -- in other words, from the matching pipe dimensions. But it should be a close enough approximation for those tees where hoop stress nearly totally dominates.

I modelled the tees as three elements with 1.5 times the main pipe thickness. This way the stresses are eliminated. My tees are set-in tees, so is this the correct way of doing this. Or is there any other approach.

Thanks

Where did the 1.5*Tmain come from? The code references 4 different thicknesses for "tm", these are:

a) thickness of matching pipe,
b) 1/2 of minimum thickness of reinforced portion of moulded tee,
c) pad thickness of fabricated tee,
d) 2/3 of crotch thickness

In my post above, I suggest that if you want to "extend the code" based on "your engineering judgement", use the minimum of (a) through (d).

Here I have modelled the Tees as 3 elements joining at a junction as per Figure 7.15 BS 7159 code.
I have put the thicknesses as shown in the figure & we manufacture the tees in the same manner.
Hence the crotch thickness is 2.5 times that of the body (page 7/14). The lamination thickness on the sides is tm + tm i.e 2tm.
We laminate these elements overall with 1.5xtm as this is uniform & more stronger than the code requirements.

Is this approach correct for modelling the tees. Please confirm