Thursday 14 May 2015

Butt Fusion Fittings

Still buried with work and not sure if I’ll be able to do a video but at least you will have some quick info on how to do but fusion fittings and routes in general.

Depending on the complexity and detail you need there are a couple of approaches to take here. The simplest one would be to ignore the discrepancies before and after the pipe welding but you can take it all the way and create your excess welding material as ifeatures that you can drop on each fitting you author.
On my plant layouts I always ignore them because we tend to have plenty of space and discrepancies can be ignored. Quite simply on a 10 meter pipe the assemble tolerance will incorporate any variation from welding or thermal expansion.
So unless you’re into designing medical equipment or any other precise, tight tolerances equipment I would not bother. Keep this as a reference if every once in while you need to do renderings, or the client asks for these welds to be in place and ignore them the rest of the time.
On the simple side, quick and dirty if you do need to have proper, exact cut-to-length dimensions and BOM reports then you need to over-define your engagement dimensions so that the parts interfere therefore reporting correct pipe length and correct route dimensions, node to node.

If you do need to get all that detail exact and you have all the time in the world I would suggest you do the fusion as a ifeature that you can drop on each fitting. Make that ifeature table driven so you can choose and change size on the fly. You can take it down another level and calculate the lost volume from the cutout (melting) and generate your weld bead based on that but that’s way too granular for me.

If you need to author ipart fittings like elbows, tees, or anything else that has a table and might go to Content Center then define new planes driven by the fusion distance and set your engagement to plane/point so you can drive the engagement for each fitting diameter separately.

I recommend that you don’t change or re-author the pipe because you might use that pipe on different connection style (socket welding, jointed, etc.) and it will mess those up. Do all these changes on fittings and it will drive the pipe engagement as well.
Don’t just stop here use the over-engagement on compressed gaskets (thank you Chris Benner for the solution), expansion joints etc.
Here are a couple of links on Fusion Welding, general info and dimensions to help you on the process:
-          Local Head Loss in Polypropylene andPolyethylene Pipeline Joint Welded by Butt Fusion - Ing. Jaroslav VeselskýSupervisor & Prof. Ing. Jan Melichar, CSc.
-          Polyethylene Pipeline Systems - Avoiding ThePitfalls of Fusion Welding - Dr Chris O’Connor

And the post on Autodesk forum that generated this idea.

I have managed to do a video for my youtube friends. Not my best of works, you can hear I am tired and out of focus, apologies for that.


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