I need help in modeling a large, refractory lined TEE.

The RUN is 18 feet diameter and the 90 degree BRANCH is 12 feet diameter. Both the RUN and the BRANCH are lined with 12 inches of refractory weighing 110 lbs/cu ft.

If I model the TEE as I would in smaller pipe, the BRANCH wall and the BRANCH refractory extend to the centerline of the RUN of the TEE. In most cases this may not be significant but in this case, with the refractory, the weight is significantly too high and that affects the sizing of the spring hangers used in this system. Also, the weights of the RUN shell and the refractory in the RUN where the opening is for the BRANCH is included.

How can I model this TEE accurately so the correct amount of the pipe wall and refractory is included in the weight calculations? I also need to make sure that the SIF calculations for the unreinforced fabricated TEE are correct.

You might be outside of Caesar / B31.3 limits ... check your D/t ratios.

See the User Guide and other documentation for modelling tees with a no-weight centre-line rigid element in the branch. Correct weight for the run with big hole could be calc'd and input as a custom refractory density for just that element.

SIF's ... see my first comment. Could be a problem.

You may need to think about using FEA such as FE-Pipe ?