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Up Topic Welding Industry / ASME Codes / Groove Welds - Unequal Wall Thickness
- - By TMC Date 10-17-2015 09:12
The welding job is a 20" pipe SA106 Gr B Carbon Steel with 0.375" nominal wall thickness to a 20" SA 105 Carbon Steel valve body with 0.75" nominal wall thickness; the joint configuration is a vee groove weld.  Construction code is ASME III.  From Fig NB-4233-1 (1972 Ed), it appears that there are 2 criteria: 1) The welded joint needs to be filled to the top of each bevel 2) The maximum taper up the joint can be no more than 1:3 for a distance of 1.5*t, then up to 45 deg angle.

Based on the groove angle and the root opening of this joint, IF the joint is filled to the 0.375" pipe and a 1:3 taper has been achieved to the valve bevel, but there is still some of the bevel on the valve showing, what options are available?  Leave it alone?  Machine the remaining bevel to a 45-deg angle?  Fill to the top of the valve bevel and add more weld to the top of the pipe to maintain 1:3?  I'm new to the industry and trying to understand the details of this requirement.  I look forward to your responses.
Parent - - By In Tension (**) Date 10-17-2015 21:19 Edited 10-17-2015 21:25
Is the offset only on the OD? 
I'm not sure what the figure looked like in 1972 but in the current edition the figure I believe you reference is NB-4250.  If you're working to the 1972 edition then you must use the requirements therein but if you're working to the current edition the below applies.
Here is the text that goes along with the Figure:

The welding ends of items shall provide a gradual change in thickness from the item to the adjoining item. Any welding end transition which lies entirely within the envelope shown in Figure NB-4250-1 is acceptable provided:
(a) the wall thickness in the transition region is not less than the minimum wall thickness of the adjoining pipe;
(b) sharp reentrant angles and abrupt changes in slope in the transition region are avoided. When the included angle between any two adjoining surfaces of a taper transition is less than 150 deg, the intersection or corner (except for the weld reinforcement) shall be provided with a radius of at least 0.05t min; and
(c) if the weld is subject to preservice inspection, the length of the counterbore shall be 2tmin for pipe and 1tmin for components and fittings, as shown in Figure NB-4250-2 or Figure NB-4250-3.
(d) Transitions more severe than those stated herein are acceptable provided the requirements of NB-3200 are met.

The way I read it, after a few beers, is that:
The maximum slope of 1:3 only applies to ID offsets.  The maximum taper up to 1.5t is 30 degrees (not 1:3) with a max taper of 45 degrees beyond that.  The figure appears to allow transitions between included angles of 150 and less provided you include a radius of at least 0.05t at the transition.  If I understand the question correctly, your weld reinforcement is tapered to 3:1 (hopefully not 1:3) and then transitions into the exposed bevel.  Depending on your bevel angle and the angle you've achieved with your 3:1 taper you should be able to use as-is, either with or without the radius as appropriate.  You can also weld beyond the joint on the thinner pipe to achieve the required slope, if necessary.
I never use Section III, so it may be somewhere else and I wouldn't know it, but I'm not seeing the requirement to fill to both bevels.  Was that in the text that goes with the Figure in that edition?  Is that what (a) above is implying to you?
Parent - - By TMC Date 10-18-2015 01:24
Yeah the offset is only to the OD.  I got a hold of ASME III-1992 and it looks like the details I'm referencing in NB-4233-1 (1972) did move to NB-4250 in later editions.  And some of the details changed, as you pointed out; the max slope of the transition in 1972 Ed is 1:3, but in 1992 Ed the max transition angle is 30-deg.  The axial distance over which that transition takes place is the same in both editions: 1.5*t.  I did not see anything in the 1972 Ed that requires both bevels to be filled.  But unless you have a very large included angle for the vee groove (180 - 2*30 = 120 deg), if the bevels are not filled, then the 30-deg angle likely will be violated (using the 30-deg criteria b/c the math is easier).  So in my example, it seems to me that you either have to 1) fill up to the pipe and valve bevels maintaining the proper transition angle, and if required add filler metal to the pipe side of the weld to maintain the transition angle or 2) fill to the pipe bevel, maintain the transition angle to the valve bevel, and remove the extra material on the valve bevel to maintain the transition angle to a distance of 1.5*t.
Parent - By In Tension (**) Date 10-18-2015 16:44
In this Figure the definition of included angle is not the traditional included angle of the V-groove but the included angle between transitions.  For example, if you've faired to 30 deg (measured from the pipe axis) and the included angle of your V-groove is 60 then the included angle of the weld to bevel transition should be 150, and not require a radius.
Up Topic Welding Industry / ASME Codes / Groove Welds - Unequal Wall Thickness

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