Recommendations on type of weld to use
Recommendations on type of weld to use
(OP)
Hi
I have attached a sketch to show the situation. Basically we need to split a shell due to manufacturing reasons at the location of an internal plate. Can anyone give a recommendation on the type of weld to use to at the joint?
This is an ASME VIII Div.1 vessel. The shell OD is 22 in so it is possible to get inside to add an internal fillet weld on the open end.
Has anyone encountered this situation before?
What is of concern is that if shell sections are attached by full pen "V" groove weld full penetration, the shell sections would be reliably joined, but the flat plate will have welding only around its outer edge. Not ideal to me!
Thanks
I have attached a sketch to show the situation. Basically we need to split a shell due to manufacturing reasons at the location of an internal plate. Can anyone give a recommendation on the type of weld to use to at the joint?
This is an ASME VIII Div.1 vessel. The shell OD is 22 in so it is possible to get inside to add an internal fillet weld on the open end.
Has anyone encountered this situation before?
What is of concern is that if shell sections are attached by full pen "V" groove weld full penetration, the shell sections would be reliably joined, but the flat plate will have welding only around its outer edge. Not ideal to me!
Thanks





RE: Recommendations on type of weld to use
Regards,
Mike
RE: Recommendations on type of weld to use
you have a very thin 1/4 round plate of diameter 20 inches being joined to a 20 in dia flat plate 1/2 inch thick with a large (but unspecified) hole in the middle of the flat plate.
So: there is no pressure difference across the flat plate. A 1/4 fillet weld (one sided or even two sided) could hold the flat plate in place and be far stronger than the wall of the pressure vessel.You report there is access inside for welding - REMEMBER TO VENTILATE AND PROTECT THE WELDER.
There is little pressure inside the 1/4 inch thick pressure vessel. (If there were, you'd need a thicker wall PV.)
There is very little wall thickness for a weld prep at all - best would be a simple V-bevel with a 1/16 - 3/32 flat land and a 45 deg bevel on the remaining 3/16 thick wall.
The 1/2 thick plate could easily and very conveniently serve as the "backing ring" for the outside weld for simplicity and added strength of the 1/4 wall weld. If so, then add a single-sided fillet weld (staggered fillet weld even) to finish supporting the 1/2 plate on the inside.
RE: Recommendations on type of weld to use
I’m not exactly sure what the “ASME VIII Div.1 vessel” means in terms of the allowable welding details, you guys know that better than I do. But, I would want the outer shell to have the best weld integrity. Is there any pressure difference across that internal pl., what does it do, how is it loaded? I’d make that internal pl. o.d. the same as the shell i.d. and use the pl. as a sort of backer bar. Then the issue becomes edge prep. on the shell halves. If you use your .5" pl., and 2-.125" lands and leave a .25" gap btwn. the shell edges, you probably want to put a 10-15̊ bevel on each edge and fill the groove on the shell. Maybe you could get by with a .125" chamfer on the outer corners of the shells. If you used a .625" internal pl. and left a .375" gap btwn. the shell edges (that means 2-.125" lands), you could probably get by without any shell edge prep. and still have good welding access. The one potential problem with SnTMan’s suggested detail is that welding to opposite faces of a pl., as I think he is suggesting at his joint, can sometimes cause lamellar tearing in the plane of the pl., due to weld shrinkage.
RE: Recommendations on type of weld to use
SnTman, I like your suggestion, and it is a viable option to consider. Seems to solve a lot of issues for me. Due to the method of assembly, we want to do the internal coating as complete as possible on the lower section and then attach it finally to the upper part (which per your idea can have the 1/2" plate pre-welded to the top shell section) and finish it off with a single full pen groove weld. We will then touch up the paint in the heat affected zone.
racookpe1978:
You are correct as there is less pressure differential across the 1/2" thick plate (a filter element fits in the hole) than as contained in the vessel. We would normally take about percentage of the shell pressure as a DP across the plate as a design basis. The shell contains 150 psi.
Your recommendations for weld prep and treating the 1/2" plate as a "backing plate" would surely suffice for the low(ish) delta P, with added strength by fillet welding.
RE: Recommendations on type of weld to use
Regards,
Mike
RE: Recommendations on type of weld to use
now I have options, earlier I had issues...
Cheers
RE: Recommendations on type of weld to use
RE: Recommendations on type of weld to use
RE: Recommendations on type of weld to use
I think the point is that the circ. weld between the shell sections is the critical weld.
RE: Recommendations on type of weld to use
The outside circumferential weld is the pressure boundary, and the 1/2 plate serves as a good available backing ring for that closure weld with a V-prep and 1/16 (nominal) flat landing.
RE: Recommendations on type of weld to use
RE: Recommendations on type of weld to use