Concerning lateral tees and their reinforcement requirements...

This is on a geothermal gathering system which is being qualified against ASME B31.1. The customer wishes not to buy fabricated laterals and instead wants to weld together two pipes to form the branch and header connection. This method of construction requires reinforcement as calculated from an area replacement calculation (BPVC). The area replacement calculations are only applicable if the branch connection diameter is <= half of the header diameter. I believe this is correct so far, please correct me if I am wrong here.

Now my question: What happens if the lateral violates the diameter ratio rule, say if the branch connection is the same size as the header...?

1) The code is violated and the tee cannot be built and satisfy the requirements of B31.1

Or

2) The lateral violates the diameter ratio rule and the area replacement calculation simply does not apply here. However the lateral can still be built if it is qualified by FE analysis.


Which approach is appropriate: 1 or 2?

Thanks for your time...

I suggest that the area replacement conforms to ASME VIII Div. 1 as per nozzle calcs and this is ok as you suggest for O.D. ratios less than 1:2

Unless you have proven examples above this ratio of diameters (of which there are probably many) you should design by analysis i.e. ASME VIII Div. 2 and as you state, FEA will cover this.

Tbh, I don't see why the client doesn't buy fabricated laterals for these higher dia. ratios, FEA is costly by comparison unless these are high dia. pipes.

The sizes of the piping vary from 18" to 36". The client is concerned with cost and does not want to procure fabricated laterals...as much as I wish they would.

I would agree with you that the correct approach would be to use Div 2 - design by analysis. I have two senior stress analysis engineers telling me varying things on the subject.

There are clearly different approaches to the subject, collaberate potential directions towards the solution and let the project manager make an informed decision whilst liasing with the client.

Basically remove the opinion engineering from the situation and it becomes simple again.

If you have a preference then phrase the possible solutions that way - cost/ease of solution/ability factors.

Excellent. I will do that. Thanks for your response on the subject.