ARC BLOW
In certain cases depending upon where the return path connections are given for the arc current, the arc may be deflected towards a direction of weaker electro magnetic field. This phenomenon will become a nuisance with high current DC arc. The arc will be deflected away from the weld zone if proper earth connections are not given. Some guide lines are useful to avoid this problem.
1) Give return connection on the ends of the weld, not in corner of plates.
2) Start welding from the return cable connections.
3) It is better to have both the ends of welding connected to return cable for long welds.
4) For fillet welds if it is possible connect the return cable to both the corner of the fillet.
5) For circumferential seam weld connect both the pipes to the return terminal to reduce arc below.