ASME Section 1 fitup Criteria

Date 06-26-2002 04:07

I would welcome your input as professionals in the arena.....Consider this a survey as it were
1) ASME Section 1 Subsection PW does not provide a specific dimension for circumferential piping weld internal misalignment, only that the weld joint provide for complete penetration.

With joints of differing inside diameters it states that tapering at 3:1 may be performed to assure complete joint penetration.

Based upon this information I have established a maximum fit up internal mismatch of 1/16 " maximum (Circumferential) for ASME section 1 piping connections. I based this on a fitup gap of 1/8" plus or minus 1/16". A root weld in this instance would be close to 3/16 in width (which is 3x the offset). The resulting taper across the weld therefore....3:1
What criteria are you using at your project? Im interested on feed back on this issue. It has been stated that this is too strict a tolerance and that 1/8 circumferential mismatch is acceptable for welding.
By the way this project also has 10% random RT all pressure welders...

I thank you in advance for your replies....

By Seldom

Date 06-26-2002 11:49

I suggest your 1/16” misalignment tolerance is unduly restrictive. My company’s specs (WPS’s & engineering specs) have permitted an internal, maximum misalignment of 1/8” or 25% of the wall thickness for many, many years without compromising integrity for weldability. It is also included in the specs that internal tapering may be authorized but it shall comply with the governing code, standard, or regulation.

If some of your welders blow an x-ray because they missed an edge, they need to do a better job of fitting-up or learn the technique required to tie-in a 1/8” mismatch.

By M-Squared (**)

Date 06-26-2002 12:35

I would agree with Seldom. Imposing a 1/16” restriction on internal misalignment is excessive. If you have incorporated this into your specification it must be costing you an “arm and a leg” as far as time and money.
I assume that your welders are involved with the fit-up or, at a minimum, check the fit-up prior to welding. If so they are aware of what they are faced with. If they are faced with a misalignment (1/8’ or less) they know they will need to make some adjustments to their technique, and welding variables (within WPS limits) to ensure they have full penetration and they tie-in the edges.

My company also has a 1/8” maximum misalignment tolerance that has worked well over the years.

Good Luck

MM

By boilermaker (**)

Date 07-03-2002 01:01

I'll add my two cents...just imagine if the tube or pipe isn't a true circle? you're dead on with two points 180 degrees from each other, but the tube could be "egged" and have internal misalignment. Then it's just a process of keyhole welding and pushing wire.

By pipeliner1 (*)

Date 07-16-2002 04:14

The hi-lo you are talking about is not bad ,, I assume you are a welder ,, if you think it is to bad to pass x-ray ask your fitter to transition the smaller pipe to match the bigger , and if they are only shooting , 10% of the welds ,, hell ,, just cut the shoulders , when ya run the bead ,, it a be good ,, !!!!!!!!!!