I'm guessing they might be free handing the welding of the smaller diameters since its 6G. If not they're working too hard. I'm also guessing that the fusion problems are probably concentrated most in the mid diameters. The smaller diameters don't really have a side wall to speak of, and with the larger diameters you can walk the cup, which helps.
I would also say its not a heat input problem per se. The puddle is viscous and so you have to give it time to fuse. It can help to even cool your parameters and allow you to slow down.
The might also be humping the root and then cold lapping the cover. If your roots and fills are concave you should have no trouble.
If specs allow I'd knock a slight bevel on the smaller diameters and autogenous the root. Then one pass fill and cap. No side wall problem.

Hi Nalla

This problem often occurs in welding of duplex stainless steel, especially when low heat input parameters are asked for. It is normally caused by the welders laying the filler wire in the groove and then fusing it in. A better technique is to establish a weld pool, and then "dip" the filler into the moulten weld pool, so that you are sure that the filler is being fully melted.

Let the welders try that, and see if your problem goes away.

Regards
Niekie

Hi Nalla

Got any feedback on this? Did you manage to sort out your problems, and if so, how?

Regards
Niekie