Torque Value

Most of the problem with the LV breakers is that damage can occur easily by racking with too much torque. Most plants rely on the experience of the electrician to recognize when the force is too much. The racking tool usually has no way of measuring torque, but the lever arm is short enough that normal people will notice if the racking force is too high. Big Bruisers can cause a lot of problems. I was once mentor to an engineer who didn't have any idea of his strength and broke a lot of things, really expensive things. Talking didn't seem to do much good. My manager and I couldn't figure out what to do. Then one day he went off to a required company class and fell in love with a Female VP of a TV network we owned and became a house husband, we were sure glad!

The major thing is to require use of the specialized devices if provided. When they are not, the torque required should be measured when the mechanism is clean and lubricated and then posed on the equipment with a warning not to exceed a small percentage over that. If the manufacturer gives a value then that should be posted. It is a matter of training. I have seen a lot of switchgear and motor starters destroyed with too much torque. Not just breaker racking, but also bus bar distortion due to over-torque on the joints. Many craftsmen have to be educated that a torque spec is not to get the item tight enough but to prevent it from being overtightened.

I have even seen the racking screws of the old Magnablast Vertical racking 15KV breakers broken during manual racking and/or the chain drive between the sides. There are some people out there with more strength than they need.