Input for two horizontal trunnions at the same point.

Srs,

I would like to known the best way to codify an intersection with two horizontal trunnions as support to a vertical line.

When I do that he program show one warning saying that there are 4 pipes framing into an intersection.

That message is normal or I can do better?

Regards.

The warning is trying to call to your attention that you have an unusual geometry in your model so the warning has served its purpose.

Warnings are trying to call something to your attention, fatal errors are inputing mistakes and must be corrected for the model to run.

For this case, I used the branches 1 millimeter apart and define SIF in every branch. Is this correct assumption according to code, e.g B31.3?

Even though I sit on that codes design committee I must admit I have never seen a SIF for a trunnion let alone a pair of trunnions of undefined size, and thickness as well as an undefined header size.


My sarcasm notwithstanding you are all on your own... but I can tell you that if any part of one trunnion is within the (R/t)^0.5 distance they will have overlapping stress fields and are definitely undefined by the code.

Try some FEA instead of relying on a simplified program and a simplified code!

I recently saw a "solution". There was only one trunion. In P91 MS line. We did quick FEA. Over the limits off cause. Trunions fail on lines operating in creep range even without any support load. On lines in creep range:
- don't use trunions
- never weld support item on outside surface of the bend
- never even think of welding something on longitudinally welded elbow/bend outside surface
- If you still do any of the above please let me know the plant. We are considering starting a company to remove such items :-)