weldment dimensional tolerances

[Tmoose]

We have a few internal "standards" for dimensions we expect when a component is fabricated by welding. It dates back to the days when we had our own fabrication shops.

Is there a modern day guideline of accuracy that can realistically be expected when multiple components are welded, then welded together?

An example might be two or three 1/2 inch thick rolled rings and partial cones, 6 to 10 feet in diameter and several feet long, stacked together and welded to a 1 inch thick top plate.

Like a hopper or cyclone.

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[gadkinsj]

We do alot of weld-ments and we usually just put extra material anywhere we need to locate something precisely and have post welding machine processes to get it there. But if you put a tolerance on a drawing it is up to the fabricator to meet that tolerance for the cost that they quoted you.
I am way behind the times with this also but we are starting to use more laser cutting of pieces and do the insert tab A into slot B type assembly so that things are placed pretty well when it is assembled.
I find that Vendors want your business and are always willing to share what they are capable of with you if you discuss it with them.

 

[SnTMan]

Tmoose, if there is an industry association for type of work you are doing, they may have standards. Examples are TEMA and HEI for exchangers, HEI for surface condensors, etc.

Dennis Moss's PV handbook is available online to ASME members. Megyssy's (sp?) PV handbook should also. Any thing related to process towers etc. should be applicable.

Probably on something like you describe +/- 1/2 OAL and +/- 1/4 to interface features such as connections, supports, etc. would be in the ball park.

Regards,

Mike

 

[KENAT]

Tmoose, there are so many factors affecting it - tolerance of individual parts, what type of fixture/self fixturing if any is used... that I doubt there's any true 'industry standard' or similar.

In fact what you have may be more than most folks. You could perhaps update it for the improved accuracy of the part cutting material, if any.

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