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Pipe Clamps That Break

Published : 14th September 2003


I'm working on a job right now where two days ago, one of my guys was hanging a light. We heard a bad noise and looked up and he was just catching a light (he was on a ladder).

Then we realized what had happened :

The pipe clamp he was tightening onto the pipe simply broke in two! Very scary, I'd never seen this happen before ever, and we were all lucky that he managed to catch it and that it didn't crash to the floor or onto somebody's head.

I didn't know it was possible to break these things, short of shooting them out of a gun or something. Someone mentioned he'd maybe over tightened it, but I'd always been confident you could tighten those things up onto the pipe as much as you wanted without any fear of them breaking.

Anyone ever seen one of these break before? Is it possible to over tighten them? I'm not a grip, but I've always just screwed those babies into the pipe almost as tight as I possibly could.

The equipment all came from a very highly regarded rental house.

Phil Badger, gaffer, LA
http://home.earthlink.net/~badger111/index.html



I am assuming that this was the sort of pipe clamp with cast jaws.

Castings are prone to fracturing if hit hard enough...A pipe clamp thrown down from a scissor lift that hits the floor wrong can be cracked. The crack may not show up until it is stressed...like when it is being tightened. The same is true of the cast iron pipe hanger clamps...I have had them crack when tightened which can be really scary and dangerous.

No rental house can test all the clamps before each job. Very few technicians will bother to look at castings or test them on the ground first...there is never enough time.

Not sure what the answer is...other than be ready for that horrible noise and don't fall off the ladder

Mark Weingartner
LA based



>Not sure what the answer is...other than be ready for that horrible noise >and don't fall off the ladder

This would be a great reason for the use of safety chains on all suspended
lamps.

Nick Paton
Film & Digital Cinematography
www.npdop.com



>Not sure what the answer is...other than be ready for that horrible noise >and don't fall off the ladder

I cop to being tongue in cheek without applying the necessary emotion. Aircraft cable safeties are cheap...I still have 4 dozen of them in my set-box back from the days...And while we are on the subject, a piece of sash cord or 1/4" manila line tied from the yoke (bail) of the light to the pipe does not much of a safety make...unless it is pretty short, by the time the fixture fetches up against its leash, it will probably have enough momentum going to snap it. This is an obvious further reminder that putting a cotter pin in the clamp to hold the light to the clamp does you no good if the clamp is no longer holding on to the pipe. acceleration due to gravity: 9.8 m/sec squared (32 ft/sec squared)

It's not just a good idea, it is the law

Mark H. Weingartner
metric or imperial wizard
LA based
Mark Weingartner



>acceleration due to gravity: 9.8 m/sec squared (32 ft/sec squared) It's >not just a good idea, it is the law

This reminds me of a question on a physics midterm : if you wanted to find out the height of a building, and the only instrument you had to use was a barometer, how would you use it to determine the building's height?

All of my classmates thought the solution was to measure the difference in barometric pressure from the ground floor and the top floor of the building, and spent way too long trying to derive a formula that could be used to determine distance.

I thought it was a joke question and wrote "I'd drop it off the top of the building and count how long before it hit the bottom. D= 1/2A*(T)squared". And I did get partial credit for my silly answer.

The correct answer (according to the instructor) was "knock on the building supervisor's door and tell him you would give him the barometer if he told you the height of the building".

The instructor's point was that sometimes you have to think outside the box and not try to use a tool for a job it wasn't designed to do.

Jessica Gallant
Los Angeles based Director of Photography
West Coast Systems Administrator, Cinematography Mailing List



>I didn't know it was possible to break these things, short of shooting >them out of a gun or something.

Oh yeah, they will definitely break being cast. I've seen it happen while an electrician was hanging a lamp. And they can easily be over-tightened. These clamps are designed for the lamp to be hung straight down and not offset at any angle. So there is no reason to be unnecessarily tightening them other than snug.

Another point to be made is that the light should have the safety line installed first but that is something that most often never happens. It could be something that the rigger may want to consider in the future as a personal work habit. The way I see it is that the most opportune time for the lamp to fall is when it is being handled on the grid, so install the safety first. The safety is not simply for the actors but for everyone on the set.

That's my 2 cents...

Jim Sofranko
NY/DP



Phil Badger writes:

>The pipe clamp he was tightening onto the pipe simply broke in two!

On theatre stages this comes up every once and a while. The cast clamps have been know to be brittle and will break under stress. I have also seen C-clamps spread an open and extra 1/2 inch or so that were deformed and did not break. The clamps do not have to tightened to within an inch of their life to be effective. The standard of use for stage work is to use safety cables for all units because of this possibility.

Richard C. Bakos

Studio One
South Bend, IN 46619



Phillip Badger writes:

>I didn't know it was possible to break these things, short of shooting >them out of a gun or something. Someone mentioned he'd maybe over >tightened it,

There are many types of cast iron, some types are extremely brittle and are not at all suitable for pipe clamps. Pipe clamps should be made from malleable iron, which is cast, but then under goes an annealing process which fundamentally changes the its characteristics. At the end of the process, which that can take several days, the malleable iron is basically quite different than grey or white cast iron. The annealing process provides toughness, impact resistance, ductility, high resistance to corrosion, and machinability.

Pipe clamps made by reputable manufacturers such as Mole are made from malleable iron and are extremely strong and reliable. Unfortunately, some companies are importing pipe clamps which are made from inferior grades of cast iron by manufacturers who may not know what the clamps are for and that do not meet ASTM standards. This appears to be totally price driven. What's more, it is very difficult to tell one type from the other simply by looking at them. Although if it looks cheap and poorly finished, it is probably low grade.

Many responding have urged the use of safety cables. Obviously, that should be done no matter what kind of clamp is used. But be sure the cable is in good shape and that it has a load rated spring snap and not a hardware store "dog collar" swivel snap. Even aircraft cable won't be much good if the snap breaks under an impact load.

>Anyone ever seen one of these break before?

I got into film work through the theatre and have spent a lot of time rigging lights. I've never heard of a pipe clamp breaking never mind seeing one break that is until recently. My experience with them had been that the tightening bolt would shear long before any damage could have been done to the clamp. I think you could shoot a Mole pipe clamp at a concrete wall and only the wall, and not the clamp, would be damaged.

>Is it possible to over tighten them?

We routinely set lights upright on pipes, off set lights from pipes and off set more lights from the off sets without incident, and torqued the daylights out of them.

>I'm not a grip, but I've always just screwed those babies into the pipe >almost as tight as I possibly could.

They're designed for abuse by stage hands.

>The equipment all came from a very highly regarded rental house.

Not everyone in rentals is aware of what is happening with suppliers on the theatrical end. Also, it is very easy for these kinds of items to get mixed on jobs so that a rental house may start out with high grade clamps and wind up with a few bogies.

In the theatre we always sent the lights up with the safety attached and set the safety first, then tightened the clamp.

Brian Heller



>Yeah, does everyone here remember what happened to Curtis >Mayfield? Unless there was a safety chain and even that gave >in...tragically sad.

I am not aware of the Curtis Mayfield incident, could you further explain?

Thanks.

Jim Sofranko
NY/DP



Jim Sofranko wrote:

>I am not aware of the Curtis Mayfield incident, could you further explain?

A lighting rig fell onto him during an outdoor concert event in Brooklyn NY (1990?). He was permanently paralysed from the neck down as a result of his
injuries. I believe he died in 1999.

Tom Townend,
Cinematographer/London.



>I am not aware of the Curtis Mayfield incident, could you further explain?

Thanks.

Jim Sofranko
NY/DP



Jim, from what I've heard it was a light that fell on him while performing on stage. It paralysed him but he lived another 10 years or so, and sadly has passed away (2-3 years ago?)

It is a terrifying thought being hit by something falling from above without much of a chance to deflect it.

John Babl



>It is a terrifying thought being hit by something falling from above >without much of a chance to deflect it.

Tell me about it. About ten years ago I was working video playback on a commercial gig in a large studio in NYC. Each day went 17+ hours and on the start of Day 3 I was sitting with the Director and Script Supervisor going over footage when a stinger came flying from the grid 25' above and hit me right in the Family Jewels. I was out of commission for about half an hour and the Producer was a good guy who wanted me to go straight to the hospital and offered to pay me for the day and send me home. I was okay but the electric who had not asked us to move when he was working right over our heads nearly was fired (I didn't want that one on my conscience and knew it was because of the hours).

Far worse that the pain was the terror when something drops on you from outta nowhere. So the moral to the story is to ask people to move when you're rigging anywhere near them and to make sure you safety even the little stuff like cables.

Mitch Gross
NYC DP



Does anyone ever wear hard hats when rigging? They made us wear them in high school theatre, but that's the last time I've ever seen someone wear one on a studio or stage. In college it was a rare site to see someone wearing boots. For a few years I shot industrial construction videos, large bridge decks, parking structures, office towers. You weren't even allowed onto the site without a hat. The more I think about it, it's insane that's not standard policy (during overhead rigging) at studios and stages for liability reasons.

This list is great, thanks Geoff and CML.

Dave Winters
DP / LA



Brian Heller writes:

>There are many types of cast iron, some types are extremely brittle and >are not at all suitable for pipe clamps.

Ordinary hardware-store C-clamps used to bear the word "malleable" -- presumably to distinguish them from the ones that weren't.

Do Mole clamps say "malleable" on the side? Should one assume that clamps that don't say it, aren't?

Dan "doesn't happen to have a Mole clamp handy" Drasin
Producer/DP
Marin County, CA



Dan Drasin writes:

>Ordinary hardware-store C-clamps used to bear the word "malleable" --

No, they don't. The Mole clamps have Mole Richardson Hollywood, California cast onto them on one side, the other side says Type 1201. They do not say malleable.

>Should one assume that clamps that don't say it, aren't?

I don't think so. I don't know of any requirement for labelling, but we were talking about theatrical type "C" clamp lamp hangers.

As far as hardware store "C" clamps ("G" cramps) are concerned, there are several levels of quality (strength). Stamped metal, cast iron, aluminium alloy, malleable iron aka ductile, cast steel, and forged steel. Within each type there can be several classes, e.g., light duty, heavy duty, extra-heavy, etc. The variety can be bewildering.

We try to avoid buying tools from anonymous manufacturers.

Brian Heller
IA 600 DP