Thanks again for all the answers guys. I was right in that there us little difference whether it's DC or AC  except as was said when unplugging with a heavy load. I thought that the 15 amp plugs pins were capable of carrying a lot more than 15 amps the plugs of old were well built to hear of one being used at 25 amps makes me think they were over engineered  and then some! A friend of mine told me they had a workshop in the dockyard that was all 220 volts DC using 15 amp sockets throughout with heavy duty switches mounted above sockets and the cooker in the canteen  all makes sense now. 

Thanks again for all the answers guys. I was right in that there us little difference whether it's DC or AC  except as was said when unplugging with a heavy load. I thought that the 15 amp plugs pins were capable of carrying a lot more than 15 amps the plugs of old were well built to hear of one being used at 25 amps makes me think they were over engineered  and then some! A friend of mine told me they had a workshop in the dockyard that was all 220 volts DC using 15 amp sockets throughout with heavy duty switches mounted above sockets and the cooker in the canteen  all makes sense now.