welding plugs

[bergie]

hi sparks
theres 2 plugs on a circuit : 63 amp 4 pin with 16mm cable and 80 amp 3 pole. the cable is about 10m. its been working fine for years ,but they need a coc. 2 welders on a 1 circuit trips a 63 amp breaker if they strike at the same time.they have 400 amp busbars(sealed ) running along the factory and they tap off circuits where they want with a breaker+ earth leakage under the busbars. some places are fuses under the bus bars for other machines.
i dont like the system,but i cant fault it. for interests sake,they have a huge 1500 amp oven with its own mini sub. factory dates back to 1950,s i think.

[Sparks]

With such big welders I suggest you check what the actual maximum load is with a simultaneous strike and let that be the deciding criteria. From what you have said so far I would consider having each plug on it's own circuit. There is no control as to when the welders will strike at the same time and it would cost them more to keep resetting a breaker that will not last long. Cater for startup load not running load unless you use a delayed breaker. That will cater for occasional simultaneaous strikes. Measure it & know the exact demand. Then you cannot make an expensive/dangerous mistake.