Local isolator near drive, good or bad?

I have only used the Marechal Decontactors on two separate occasions, for two very different reasons. However, I found them to be the ideal solution on both occasions with no reliability issues. The first application was as mentioned on a group of four mixing vessels with large Ex-d rated motors. This was getting on for 15 years ago so exact size eludes me but I would say around 22kW. The decontactor was fully-rated for this application. 

The vessels were subject to a regime of regular internal inspections but the inspectors wouldn't enter the vessels unless the tails were disconnected from the motor terminals... they weren't about to take any chances with the incorrect vessel being isolated. Trouble was they might have to wait 20, 30, 40 minutes for an electrician to become available and then another 20 minutes for the isolation to be completed (and of course it was a similar story when the vessel was reinstated again afterwards). Apart from the time wasted my main concern was the potential for compromising the integrity of the flame-path and mis-connection / loose connection when reinstating the terminals. After the isolator was installed, the inspectors were able to isolate for themselves. The four plugs/sockets were keyed differently to prevent misconnections. There were no downsides I recall.

The other application was on an overhead crane with a electrical hoist conversion but manual long travel. Since the crane was originally designed for manual operations, there were no busbars and no collectors so the supply to the hoist was on an umbilical cord with plug. The bay was extremely long so a number of socket outlets were installed to allow the hoist to be plugged in at strategic points along the bay. Operators were not supposed to use the manual long travel unless the hoist was unplugged. Trouble was, there was always a chance that they might forget to unplug and the umbilical cord / sockets could be stressed or damaged. We replaced the standard industrial sockets with a Marechal decontactor with a self-ejecting mechanism of the type used by fire and rescue vehicles. If the umbilical cord was put under any strain the plug popped out of the socket before any damage was done. This was maybe 7 years ago, again no reliability issues.

Thank you - very interesting indeed. Sounds like a  name I should keep to hand.

Mike

jbrameld said:

The local isolators can be lockable and the operatives can all have their own padlocks - which all adds to your safe system of work.

Those from an industrial background should be very familiar with safe working. e.g. As you are probably aware, the first person to attach a padlock must also affix a multilock caliper to ensure other parties can also attach their personal padlock, to a formalised permit to work system.

Jaymack