Longitudinal Seamer Backup Bar Groove

admin

We use an automated longitudinal seamer to fabricate tank shells from steel and aluminum. A question recently arose concerning the shape of the groove in the seamer's backup bar. For many years they used a square shaped groove, which produced square shaped drop-through. Several years ago they switched to a half round shaped groove so that the drop-through shape looks more like the weld bead shape on the topside.So my question is: Are there any guidelines, recommendations, or studies available regarding backup bar design, and specifically the shape of the groove?
Reply:If you are producing the vessels to a code or specification, it may (should) provide the requirements for drop-thru.  The customer should specify what they want.It's difficult to see any logic in using a square edge prep on the backing bar groove.  Just from common sense, in order to minimize stress risers produced from sharp notches, I would use a slightly rounded configuration, probably not fully half-round as there is no reason to have excessive buildup.