Smallest allowable groove angle - 1/4" plate field weld 2

[canwesteng]

I'm having a 1/4" plate welded to a bin cone (angle of 15 degrees to the vertical). I'm wondering if 15 degrees is sufficient for a CJP weld of relatively thin material, or if joint prep is required to take it to 30 degrees

 

[racookpe1978]

Adequate at that thickness. Not great, a bad welder might screw it up, but certainly good enough for medium and high-skilled welders. (Assume a 1/8 to 1/16 gap for the butt weld.) Thicker metals? You'd need a greater total prep anlge (15 + 15 = 30 degree total. Most common industry average for pipe prep's is about 66 degrees total.)

 

[canwesteng]

I was thinking it would ok. If the contractor squawks about it we can always go to 30 deg.

 

[racookpe1978]

No, not what I meant.
If you absolutely HAVE TO, you can use a 15 deg prep angle IF you have a good welder with good access, then you can expect an adequate weld most of the time.

You SHOULD allow (require!) two 30 deg angles so an average welder can do the job under average access conditions without significant failures IF YOU CAN do so.

 

[Metalfixer]

GMAW can be used verses SMAW with smaller prep angles for easier access, if allowable.

 

[DekDee]

If you don't know what is the right angle and you are coming on here for advice why state you will change it if the contractor "squawks" ?
We used to hang a noose from the workshop beams on the slim chance a design engineer who seemed to be from another planet actually visited our workshop.
Give your contractor (who probably has a much better idea of what he is doing than you have) a perfect option.
Nominate the joint as CJP and let them decide the included angle.

 

[gtaw]

I concur with DekDee. However, that approach will require the contractor to prepare the edge in the field, which is always the more expensive route in terms of time and labor.

I suggest taking a look at AWS D1.1 for a prequalified groove detail that suits your needs. Any of the details listed for SMAW can be used with either FCAW, GMAW, as well as SMAW.

If you do nothing else, if possible, consult with the contractor that will be doing the work. Ask the contractor if he has a preference.


Best regards - Al