Some question about Root gap"R" in Fig.3-4(TC-U4a-GF).

Date 02-28-2013 06:14

As shown in fig3-4 (TC-U4a-GF) of D1.1:2008. If the fabricator choose process FCAW. The theoretical dimension of root gap"R" is 6mm. How to understand the tolerances of "R".
For example the As Detailed tolerance is +2,0. So the Range of R shown in the shop drawing can from 6 to 8mm.

And is it Fit-up means shop trail-assembly? So during shop trail-assembly, the Range of R can be from 4 to 14mm. Am I correct?

I mean the tolerance during assembly can be the accumulation of As Detailed tolerance and As Fit up tolerance. Am I correct?

Attachment: TC-U4a-GF.jpg (81k)

By 803056

Date 02-28-2013 17:32

The "as detailed' tolerance is the tolerance the designer can incorporate into his design. In this case the designer is afforded the latitude of increasing the root opening by 2 mm. The designer would have to indicate the required root opening in the welding symbol.

The as "fit-up tolerance" is added to the dimensions indicated by the welding symbol. If the welding symbols specifies the root opening of "X", it could be as small as "X-t" or as large as "X+t", where t is the as fit-up tolerance.

Best regards -Al

By yyq4794 (**)

Date 03-01-2013 00:32

Further question, Is Fit-up tolerance used for shop assembly. Other word is it the tolerance after fabrication?

By eekpod

Date 03-01-2013 01:17

yes.
The as-detailed is for the drawings to have a tolerance.

the as-fit up is for the work performedin the shop by the fitter and or welder.

By 803056

Date 03-01-2013 04:17

Think of it this way; the as-fit-up tolerance is to to accommodate those situations where the fabricator cut it twice and it is still too short.

Al

By yyq4794 (**)

Date 03-04-2013 05:19

Thanks a lot. I understand it clearly now.