# Chain Hoist Electrocution Hazard



## WooferHound (Aug 3, 2010)

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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## epimetheus (Aug 4, 2010)

Do you happen to have a part number, manufacturer, or series for the connectors of concern? 7-pin and 4-pin circular are incredibly generic...

Sent from my Incredible using Tapatalk


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## MNicolai (Aug 4, 2010)

I've actually seen this happen before. Nobody got shocked, but the wrong phases were hitting the wrong pins and a few guys spent a good hour and a half tearing one of their motors apart to figure out what was wrong it. Eventually they realized that they had plugged it in improperly. The connectors had seemed to mate so naturally when they were plugging it in that they didn't think twice about that connection being the fault.

They spent a lot of time trying to figure out why their voltage readings internally within the motor were as off as they were, but the motors had worked fine the night before so it really threw them for a loop.


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## mrb (Aug 4, 2010)

its usually the older socapex brand connectors that do this. there is a little tab on the phenolic insert that holds the male pins that goes into a keyway in the shell. over time impacts to the connector can cause this tab to break. better connectors such as veam VSC dont have this problem. It really boils down to the equipment being in poor condition and not well maintained. A cable with a loose insert should be discovered and removed from inventory before it ever makes it out of the shop. 

on a sidenote, I am suprised (i was not previously aware) that different pins are used for ground by different vendors. What happened to make first / break last for ground? Big liability theyre taking on....


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## derekleffew (Aug 4, 2010)

mrb said:


> ... I am suprised (i was not previously aware) that different pins are used for ground by different vendors. ...


This is what happens when no standard exists for things such as fly cable. Companies are free to use whatever connector happens to suit their purpose, and make up their own pin-out, with interoperability and sometimes safety suffering.

From TMB FAQs - Connector Questions :

> What is the pin out on a 7-pin Socapex?
> 
> There is no standard wiring on a 7-pin connector for motor control. Normally the center pin, (#5), is used for the ground. However, the pins used for control and the pins used for power vary from rental company to rental company. Usually they are in groups - [1,2,3, control], [4,6,7 power], or [1,2,3, power], [4,6,7 control]. There is no industry standard, so you should always double check the wiring of any equipment that is sub rented and used with your gear. The reason to double check your gear is that 7-pin connectors carry power and control together and there is a potential for harming the equipment or the operator if the wiring configuration is not confirmed.


From TMB Trussing/Rigging Questions :

> What are the standard twist-locks for chain motors?
> 
> There is not a standard.


However, our industry does have an organization committed to remedying situations like this, and anyone can participate in the process. I don't know if _BSR E1.6-3–201x, Selection and Use of Chain Hoists in the Entertainment Industry_, addresses cabling or not, but it should.

Note that the "spinner" situation probably occurs more frequently (due to total number of connectors in use) with 19-pin Socapex-style connectors used on lighting multi-cable. Circuits will either not work at all, or will come up in the wrong sequence. The notch, tab, or pin, should always be between pins/contacts 6 & 7.


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## WooferHound (Aug 4, 2010)

I realized that I never gave credit for the warning I posted above. It was originally written by Ed Kish owner of Kish Rigging in Moorpark California. 
Dated June 6 2010

The president of our Union is very well known for rigging the world over with the biggest acts, his name is Mike Weisman. He is the person trying to spread this information because he had a good friend killed from electrocution by this very problem.


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## Rideoften (Aug 6, 2010)

I'm glad to see this problem getting the attention it deserves. I hope someone does come up with a "standard of the industry" for the wiring of motors and controllers. Without hijacking the thread I would like to open a discussion with one other problem with these same 7 pin connectors. That being the occasional violent "flare up" from trying to make the connection while hot. We all know the gear should be powered down before making or breaking connctions, but sometimes when it's very busy someone forgets and makes the connction while hot. I've personally seen about a one foot flame shoot out of the 7 pin connector from this and know of many more. What is the cause of this. Why does it happen. Even when the connectors are not spinners it can still happen. This has never been answered to my satisfaction. Always willing to learn.

Rideoften


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## derekleffew (Aug 6, 2010)

Rideoften said:


> ... What is the cause of this. Why does it happen. Even when the connectors are not spinners it can still happen. This has never been answered to my satisfaction. ...


Peculiar. The only thing I could say is poorly maintained cables/connectors. Unless the hoist is running, no current is flowing. One doesn't usually turn off the circuit breaker before plugging in to a duplex Edison outlet at home (or really anywhere else), does one? Note that I'm NOT advocating/condoning hot-patching, as with an incandescent load. But I know of no rigger who regularly powers down a circuit before plugging/unplugging a hoist.


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## WooferHound (Aug 6, 2010)

I have never seen one of these connectors arc like you are describing, but there would need to be a large current draw or short circuit for this type of arc to occur.


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## Footer (Aug 6, 2010)

derekleffew said:


> Peculiar. The only thing I could say is poorly maintained cables/connectors. Unless the hoist is running, no current is flowing. One doesn't usually turn off the circuit breaker before plugging in to a duplex Edison outlet at home (or really anywhere else), does one? Note that I'm NOT advocating/condoning hot-patching, as with an incandescent load. But I know of no rigger who regularly powers down a circuit before plugging/unplugging a hoist.


When I float motors I regularly break and make a hot connection without issue. I have never seen this happen.



sent from my HTC Incredible


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## janitor (Aug 6, 2010)

Regarding the 'flameout'
I think that many of the most popular brands of hoist controllers, have a tendancy to be left with their contactor turned 'on'. Whether it's contactor enabled for pickling, or someone just hasn't 'killed' it.
So now every output on that controller, and every motor cable connected to it is hot with three phase electricity.
If I now plug a motor into one of those outputs there will probably be a tiny arc as the control transformer in the motor is powered up.
I think that the flameout comes from the cumulative deposition of carbon at the arc site until there is enough for two of the phases to connect and strike an arc - the third will join in quite quickly and you will have that relatively slow burn (1500mS?) until there is enough current flow to trip the breaker. 
I wish that people were more religious about not allowing motors to be energised so much. In my opinion they should only have power applied to them when they are about to be moved.
My analogy is to a car left with the engine running, and the shifter in 'park'
The probability of someone being run over is far higher than when the engine is turned off.


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## Rideoften (Aug 6, 2010)

Janitor,
That's pretty much the same belief I have. Under magnification you can see traces of carbon arcing on connectors. People that have never seen this, think it's all but imposible, but I've had to repair damage from this phenomenon more than a dozen times. I've seen the face of the connector burned beyond recognition while the back side of the same connector shows no evidence of any damage whatsoever. Another strange thing about this problem is, I've only seen this problem on black connectors. The white face ones have never flared up. As if the black ones allow carbon build-up more easily than the white ones. I would like to hear from others that have experienced this problem. Again, I apologize for the thread hijack. I should have started a separate thread.
Rideoften


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## janitor (Aug 9, 2010)

With apologies for continuing this conversation in possibly the wrong place, but not knowing the correct procedure, and after further thought, I wish to amend my previous comment. It's true that people all day plug motors in to hot controllers without flameouts, so perhaps the more likely scenario, rather than a tiny amount of carbon per connection, is that somewhere in its history, the female connector on the controller met a spinner and this was the source of the bulk of the carbon. Then the tiny arc from the transformer could be the final straw.


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## Ezekiel (Aug 11, 2010)

Hello all,

I'm very happy to see this issue getting the attention it deserves, as I've seen both spinners and flare ups personally as well as seen people get both burned and electrocuted. My heart goes out to those who knew the rigger thats life was ended because of this issue and hope that he did not pass in vain. I agree with janitor in saying that the flare up issue is a direct result of a cable previously coming in contact with a spinner but only arcing and not shorting out completely. Hence, the true issue is the spinner. Just my 2 cents, as I have not done any investigating. Short of going to a different fly cable all together (dual twist, p14, etc) what actions should be taken to fix this problem that has gone on far too long?


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## janitor (Aug 12, 2010)

The most simple answer to ezekiels question is to make centre pin the ground on seven pin circular connectors (ceep or socapex), irrespective of the other pin assignments.
The spinner can then never cause a loss of safety ground.
Conversion can be very simple if two wires are swapped in the motor and the controller. 
This would cost almost nothing in hardware, the labour cost would of course be significant, but in the larger scheme of things, seems justifiable.


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## Rideoften (Nov 1, 2013)

Rideoften said:


> Janitor,
> That's pretty much the same belief I have. Under magnification you can see traces of carbon arcing on connectors. People that have never seen this, think it's all but imposible, but I've had to repair damage from this phenomenon more than a dozen times. I've seen the face of the connector burned beyond recognition while the back side of the same connector shows no evidence of any damage whatsoever. Another strange thing about this problem is, I've only seen this problem on black connectors. The white face ones have never flared up. As if the black ones allow carbon build-up more easily than the white ones. I would like to hear from others that have experienced this problem. Again, I apologize for the thread hijack. I should have started a separate thread.
> Rideoften


 
Well, it's been a couple of years. Has anyone experienced the "flameout" problem? It has not gone away and it's very dangerous.

Rideoften


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## Focus (Nov 1, 2013)

If you spray a CM contactor with electrical contact cleaner than try to run it, it will also burst into flames.

P14 is a better choice.

Sometimes cables get damaged, sometimes motors get damaged; bring spares. Fix the broken ones.


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## Wood4321 (Nov 4, 2013)

Focus said:


> If you spray a CM contactor with electrical contact cleaner than try to run it, it will also burst into flames.
> 
> P14 is a better choice.
> 
> Sometimes cables get damaged, sometimes motors get damaged; bring spares. Fix the broken ones.



Why would you spray contact cleaner into a chain hoist contractor? Those are a maintenance free item. Nowhere within the load star manual does it say it clean the contacts within the contractor. If one fails replace it. 

P14 while a good connector, it has it's own problems. It is much more fragile than 7 pin soco. They tend to get out of shape over time, and get difficult or impossible to plug in.
But they are better than dual twist.


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## mstaylor (Nov 9, 2013)

I have seen the spinner and flameout problem. I smoked a cable and the controller circuit exactly this way. This company routinely insists on the breakers being turned off when changing cables. I have also seen brand new cables do this. In my experience the truss end of the cable tends to break the wrong part of the connector, particularly when done by less experienced hands, causing the problem. I just bought 48 hoists and a ton of cable. I speced P-14s for that very reason.


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## mstaylor (Dec 4, 2013)

Same company just ordered new CMs at LDI and called me to give them the pinout on their cables, I was loading in a show with them at the time. Pins 1,2,3 hots;pin 4 was ground, pins 5,6,7 are control. For the record, pin 5 is the center pin. They own hoists from two other companies that use the same cables but have a special controler just for them so I can only assume that pins 5,6,7 are in a different order in some manner. The third manufacture uses the same cable but must be run in phase reverse to run in the proper direction.


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