electric shock and riggers

[janitor]

I would like to raise awareness in our community of the potential hazards to riggers from malfunctioning control gear and hoists.
One useful approach would be to try to stop people from making electrical connections to chain hoists while the riggers are still working on the point.
A rigger recently told me that a shackle pin flew out of his hand as he received a shock when a member of the road crew connected a pickle to the motor that he was hanging.
He said that he couldn't even get the word 'heads' out of his mouth due to the shock, and only managed "Huhhh..."

I've heard many examples of rigging steel arcing to the building steel due to electrical problems below, and know of another rigger who rolled off the beam and onto his lanyard as a result of being shocked.

I'd like people to also be aware that when they run one (three phase) motor on an eight channel motor controller (for example), the other seven motors are all hot - have three phase electricity going to them, so if any of those points are being worked on, the potential exists for a shock event.

I'm probably preaching to the choir on this site, but don't know how to go about getting the word to people who may not have realised the potential hazards created by their behaviour.
Thanks for any help that you can provide.

 

[Les]

Seems that there are some opportunities for better engineering controls regarding chain motor maintenance and testing prior to use. Remove the hazard completely rather than trying to work around a hazard which does not need to exist in the first place.

...Or am I just being dense in not realizing that chain motors are for some reason inherently electrically flawed?

I do agree with your point however, I just think a better approach might be to target the problem areas themselves and educate users on proper gear maintenance and grounding procedures. When it comes down to it, there will always be some residual risk of working on the high steel around energized equipment, whether it be from another trade or your own - but the best mitigation technique might be to focus on the unsafe condition rather than the act which exposes it.

 

[de27192]

I am simply of the opinion that you should not operate lifting equipment until it is anchored securely to the building.

That's not even an electrical thing. Yes I am aware that you can run the excess chain through the hoist whilst the rigger is doing his thing... I just feel that for the minimal time saving, one false move, unthinking moment or distraction on the ground could see an unfinished point taking the full weight of the motor, causing both a lot of metal to fly out of the roof, but also potentially that metal could still have a rigger attached to it. It's just not worth it, as far as I am concerned. My own practice is just not to run a motor until it is attached to something solid.

 

[DuckJordan]

Either way, if you chain motor is inducing an electric charge through the chain to the building steel its likely a fault in the motor and needs to be addressed. All Electronics should be isolated from the case and the chain to avoid such issues in a properly maintained motor.

 

[FMEng]

It's the law that when someone is working on any kind of machinery, piping, or electrical equipment that has enough energy to harm it should be locked out and tagged out. A chain motor would certainly fall into that category. Both the venue and the workers are responsible to conduct LOTO.

 

[RonaldBeal]

....
I'd like people to also be aware that when they run one (three phase) motor on an eight channel motor controller (for example), the other seven motors are all hot - have three phase electricity going to them, so if any of those points are being worked on, the potential exists for a shock event.
.....

Just a minor nit to pick. This is not universal. While it is often the case with CM motors, some systems only energize the motor that is running (such as the chainmaster motor systems)
Also some motor controllers leave motors "hot" regardless of if a motor is being run. (Indeed it is necessary for pickles to function on CM hoists)

RB

 

[janitor]

Thank you everyone for your responses.
I agree with de27192 and FMEng - we should never be running motors until the work is done. I'd like this to become standard practice throughout the industry.
Thanks for the LOTO point FMEng, it gives this opinion a little more weight/legitimacy.

 

[rigstar]

Hi "Janitor", I have read good comments on here.
Just a brief background on who I am before I comment on your concerns of the electric chain hoist.
I have been involved with the CM hoists since 1968 when we had to invert the gravity reversing contractor in the hoist so it wouldn't automatically run when we used the hoist climbing up the chain. Using the hoist in the inverted position of the normal factory use having the hoist stationary on a beam clamp to an I-beam and the chain running up and down. There is nothing I do not know about a Lodestar hoist. My company has owned a few thousand hoists in years past for sale and rental and even had our own private label hoist called the Rigstar Stage hoist and the Rigstar Little Rigger 1/4 ton hoist. We also manufacturing multi hoist control systems.
I have also been a head tour rigger for many many years on major concert and production tours throughout the world and I have seen a lot of things happen in my time.
I'm also the head rigger and safety officer in my stagehand local 53 IASTE as well as an OSHA authorized outreach trainer and a CM certified hoist technician.

Now then, I personally have been shocked by touching a chain while being up on a lighting truss to focus lights. Not a good feeling. I have been shocked being up on the steel structure in a building rigging points. Not a good feeling.
Here's what happens when that happens, There is a hot leg wire that is touching the hoist casing which then will travel to the path of least resistance and that ground when it touches the casing. Even though the hoist may have the ground wire from the electrical cable attached to the hoist body the power can still flow through other directions as well such as the chain of the hoist and to the building steel structure and the lighting truss itself.
It is important to never pick up a hoist out of the road case by grabbing on the electric cable of the hoist which I have seen many stagehands do, which could cause a hot leg in the hoist come loose and touch the casing. Also when taking off the end covers of the hoist and then putting the end covers back on to be careful not to pinch a wire between the end cover of the hoist and the body of the hoist. That can also cause a short.

I was up on a lighting truss running a spot light for a U2 concert in from of the stage and during one of the songs one of the end motors on the truss started to run down.
At first I thought is was part of the show until I asked the LD if this truss I was on was suppose to move, and he said NO! Good thing I was only a few feet away from the hoist and knew what to do, so I got out of my seat and unplugged the power cable to stop it from traveling any further. No one knew how the hoist started to run on it's own.
But I had them turn the main breaker off on their control system.

Bottom line here is about training and education of the proper use and maintenance of electric chain hoists and control systems.
The normal 3 phase hoist that we use in our industry is usually 208-230 volts A.C.. If you meter between any two hot legs you will get a reading of the 208-230 depending on the power output in the building. If you meter from any hot leg and the casing of the hoist you will get a reading of 110-120 volts A.C.. So when one of the hot leg wires is touching the casing and you touch the chain or casing you will get shocked with 110-120 volts A.C. power.

Electric hoist should no be operated while the chain of the hoist is being rigged to the steel structure by the high rigger. That is a normal practice during a load in of a show.
Before any hoists are to be operated by a stagehand they are to ask the ground rigger if it is O.K. to run the hoist. The steel cables that are suspending the chain of the hoist must be completely attached to the building steel structure before operating any hoist and that must be confirmed by the ground rigger.

When walking away from any multi hoist control system the systems should always be turned off by the KILL switch or the main breaker on the distro panel or remote control handle. This will cut the power off from getting to any of the hoists.
Once the equipment that is being supported by the electric hoists is at trim height the main power needs to be turned of while not needed to be used so there is no possibility of power getting to the hoist.

I would agree that a common standard should be implemented but you have to gather all the stagehands together to educate and train them.
It would seem simple and a no brainer for anyone off the street to run a chain hoist. Give them a hoist control pendent ( Pickle ) and tell them to push the button and run the hoist up. There is more to it than that!!!!!!
Never let a stagehand operate running any hoist without going over the basic operation of using the equipment first, Bottom line!!
I can't say it enough, it's all about training, education and I don't mean just reading a book but by hands on practice. It's not just the old saying that "Practice make Perfect" because if you are practicing the wrong ways of doing something, then it's not perfect but could be very dangerous. It's "Perfect Practice makes Perfect"

The Rigstar Training and Testing Center teaches all aspects of live entertainment rigging in a 7 days "Complete Rigger" course that is over 82 hours of class room and hands on training. www.rigstar.com/school1.html www.rigstar.com http://www.rigstar.com/schooloutline.html

http://www.rigstar.com/Certification.html

If there is anything else that I can be of help please do not hesitate in contacting at: [email protected] or call 1-413-585-9869

 

[derekleffew]

I don't mean to make light of anything thus far in this thread, but some of the suggestions (LOTO) are just not practical, nor IMHO necessary provided proper procedure is implemented. No hoist should be run while the up rigger(s) is still on the point. Waiting until all riggers are clear of all points, however, is not going to happen. Especially on the load-out, when a ground rigger will often run out a chain (excess spilling on the deck) while the bridles/slings are still being lowered.

Again, IMO, a more dangerous situation, but apparently one that has received little attention due to its infrequency of occurrence is discussed here http://www.controlbooth.com/threads/chain-hoist-electrocution-hazard.20975/ .

 

[LavaASU]

I don't mean to make light of anything thus far in this thread, but some of the suggestions (LOTO) are just not practical, nor IMHO necessary provided proper procedure is implemented. No hoist should be run while the up rigger(s) is still on the point. Waiting until all riggers are clear of all points, however, is not going to happen. Especially on the load-out, when a ground rigger will often run out a chain (excess spilling on the deck) while the bridles/slings are still being lowered.

Agreed. LOTO is for when someone is accessing an area with dangerous sources of energy (electrical, mechanical, hydraulic, ect) for repair/inspection/ect. Its NOT for using items in their normal use. A chain hoist is not inherently an electrocution hazard. It should be perfectly safe to handle in that respect. If not that is a dangerous fault with it due to abuse/failure/poor design/whatever just like anything else thats electrocuting people. Do you unplug the amp rack before touching the front panel of the amp? I think not. Also, a hoist should be grounded. If the hoist is grounded, and the hot wire gets pulled lose like was mentioned, the current will flow to ground, and pop a breaker (same thing that would happen with the Amp rack, or a lighting console, or your TV).

 

[janitor]

We appear to agree that it would be good practice to not energise a hoist until the up work on it is completed - this would be a great practice to implement industry-wide, right now.
More specifically I would say that the hoist should not be connected to anything until the up work on that point is done, thus avoiding the situation where other hoists on the controller are operated, and power is supplied to all hoists connected to that controller ( chainmaster control systems notwithstanding ).

Thanks Derek for reminding us of the Socapex Spinner situation, definitely something which everyone should be aware of, and a serious hazard, but really it is a subset of the overall shock topic. It isn't relevant how the electricity gets loose, or even what kind of electricity it is (Steve) - just that it happens.

LavaASU you are correct, hoists become shock hazards due to many factors, but abuse and failure are the wild cards in your list, because no matter how well designed and maintained the product is, these factors can cause it to become hazardous while it is being installed, and before anyone is aware of it.
Of course a hoist should be grounded, and almost all probably are, but wires break and fall off on their own schedule, service grounds can be installed poorly, or accidentally (incompetently) disconnected, and of course rather perversely, a grounded hoist would be a hazard to someone touching a live truss, or building steel which is poorly grounded and has floated to a higher potential due to a faulty light fixture, for example.
In other words a very wide variety of circumstances can lead to electrical shock. Although one would hope not to actual electrocution.

The difference between an amp rack, a television and the chain hoist in question, is that the shockee is at height, and probably in a moderately unstable position.

Finally, breakers are designed to protect equipment and not personnel, they are not likely to open unless their current rating is exceeded by a fairly good percentage.
The low level arc which results from a fault condition where current flow is insufficient to trip a breaker has caused plenty of house fires, and was the motivation for the introduction of the Arc Fault breaker requirement for bedrooms, into the NEC.
This amount of current flow would be quite sufficient to injure someone.
Even when current flow is high enough to trip them, these breakers are nowhere near fast enough to protect personnel.