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Chain Hoist Electrocution Hazard


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USA calling, I'm not sure what you guys are using for Chain Motor power and control connectors, but this is a real issue over here.



To Users of rigging equipment that utilize 7 pin circular connectors to connect chain hoists and other electrical equipment, combining the Power & Control wiring in the same connector.


This type of connector is subject to mechanical failure of the plastic insert that supports the pins within the connector shell. This failure allows the connector insert to rotate relative to the connector shell. A connector with this type of problem is often referred to as a "Spinner".


It is possible to connect a spinner connector to a non-spinner connector, effectively cross-wiring the equipment in the electrical path from the controller, to cable, to chain hoist.


Many companies use pin 4 as the ground pin which is on the outside circle of pins.


When the ground pin is any other than the center pin, a spinner may cause the ground path to be interrupted unless the connector shell is electrically bonded to the ground pin. Most companies do not bond the shell to the ground pin, a typical design making a good bond difficult.


Depending on the wiring configuration used to wire the connector, it is possible to lose the ground as described above. It is also possible to simultaneously connect Line Voltage to the hoist and the object being rigged.


This makes the hoist and object being rigged "Hot" with line voltage. The upstream circuit breaker will probably not trip as the ground has been interrupted. An unsuspecting worker who touches the Hot equipment and a ground may receive an electrical shock. The severity of the shock can vary depending on the specific conditions in place at the time of the fault.


Two employees were recently shocked on a job where sub-rented equipment was wired with a Pin 4 ground. This incident points to the serious nature of this problem.


It has been found that connecting equipment with differing wiring configurations can establish the same condition and hazard as the spinner condition described above. There is not a standard connection scheme in place for chain hoist wiring using multipin circular connectors. Since mixing gear from different suppliers is a common practice, one should examine the equipment and not assume the wiring is correct or has been changed.


This information is being provided in the interest of safety and appropriate action should be taken to eliminate this hazard.

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Thanks for the heads up.


Most hoists in the UK will either use a switched phase for the direction control so only have a three phase Ceeform style connector, or have control circuits carried on a separate 4 Pin Ceeform Style connector, so there is little risk of this happening, as the power and control connectors will not mate.

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There are a few users in the UK who utilise 7-pin Socapex connectors for motor control, ourselves being one company with ELP and Bandit being the others that I am aware of.


Both Pearce Hire and ELP and I'm reasonably sure Bandit (never used their motors so can't confirm) use Pin 5 (centre pin) as Earth.


In addition to this we earth the metal shell of the connector as you should any metal shelled connector carrying mains voltage, regardless of the 'spinning' issue a termination failure could cause a conductor to come into contact with the metal shell thus rendering it live.


Worth bearing in mind however for those on here who tour across the pond so a worthwhile heads up all the same! There may of course be UK users who adopt a different pin configuration but I'm not aware of any and either way I'd still expect them to earth the shell.

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