Home of Professional Cinematography since 1996

Exploding HMI’s & Crank Stand’s

Published : 29th November 2003


1/. Has anyone experienced exploding HMI bulbs, especially 575's? Would you please describe the experience, damage, noise, etc?

Also interested in 1200's. Have heard tales of larger bulbs blowing out whole fixtures.

2/. The fairly new American brand crank stand is beautifully designed and apparently well engineered as well. Take a look if you are in the market.

Jerry Cotts
DP/LA




I gaffed an MOW a few years ago, and had a courtroom scene on the second floor of the local art gallery. Two condors, with a 4K Xenon and an 18K in each bucket. The DP asked me to set the one condor's lights to rake the background, while he set the other condor for the foreground via the Key Grip. We quickly and efficiently worked this way for hours, until in the middle of shooting there was a tremendous boom from outside as the foreground light died.

We rushed to the window to find the DP had set his condor bucket about three feet above my bucket. The heat from the lower lamps had caused the glass of the bulb to weaken (at least that's my theory), and the bulb eventually blew spectacularly. The reflector was melted in places, and there was absolutely nothing left of the lens.

Poor kids in both buckets were scared to death, with the one below having to go to one of the trailers to take a shower. Thank god for safety glass!

I guess the moral is : Beware Heat!

Phil Klapwyk
Gaffer
Vancouver, Canada


>1. Has anyone experienced exploding HMI bulbs, especially 575's

I have experienced a 575 exploding in an LTM Fresnel. For a few seconds before, there was a visible flicker, which a crew member was drawing my attention to just as the lamp blew. I was standing behind the fixture, and there was a noticeable flash at the moment of explosion. I don't really remember the sound - so it couldn't have been THAT loud a bang, although there was definitely a bang... The globe itself was shattered, there were small slivers of glass throughout the fixture, and the Fresnel lens was cracked. However, the glass did seem to be well contained by the fixture, nothing really came out until we moved it a few minutes later.

I should say that it was later discovered that the lamp head had defective electronics (a bad coil, I think, although I'm no electrician so I may not be remembering correctly), which were probably responsible for the globe going, so this may be somewhat different from other HMI bulb explosions.

George Hupka
Director/DP
Downstream Pictures
Saskatoon, Canada



Jerry Cotts wrote :

>1/. Has anyone experienced exploding HMI bulbs, especially 575's? >Would you please describe the experience, damage, noise, etc?

I will never forget it! An LTM PAR - 1,2K exploded in my hands, as I was trying for the "perfect-bounce-angle" off a foamcore(beadboard). Of course the electrician had set it "raw" without the first protective glass, in order to get the maximum punch out of it. We were all lucky, actors and crew, because it was a bounce. It truly is an explosion of shuttered glass, it goes everywhere! It's scary. Of course I learnt a lesson.

It's been eight years now and whenever I ask for a Par, I always make sure on the kind of lens that's in front of it.

All the best,

Dimitris Theodoropoulos
DP, Athens Greece



I will second Jerry's endorsement of the American Roadrunner crank stand - I can say without shame that this stand is the best stand of it's type I've ever owned. In fact, all of the American gear is great - they make the best baby stand, the best combo, the best high roller...even the best knob.

On my Matthews high roller, I replaced the handle that always whacks into the 4x4 you're trying to set with American's version, and they work great now. I think I'm starting to gush - I better stop before I get the keyboard wet with tears...

Ted Hayash
CLT
Los Angeles, CA



Jerry Cotts wrote :

>Have heard tales of larger bulbs blowing out whole fixtures.

Jerry,

I have first hand experience with a large fixture exploding nearby. A quick background. It is 1989. This was my 3rd or 4th movie, but first time as an Electrician. I was the greenhorn of the crew so the best boy decided now was as good a time as any for me to learn to fly a Condor. In I go never having seen the controls, a quick 30 second review and up I go.

This was a 60 footer carrying an ARRI 6 K Fresnel with the basket turned sideways to face the building. This was one of those older model construction condors where the controls are mainly toggle switches ( No Feathering). Needless to say I was like "Buck Bronco" at the controls trying to maneuver it into position. The Condor settles and I strike the light, the 6 K burns for probably 20 minutes and then Explodes right next to me ( I was standing in the Basket) shattering the fresnel lens in the process. This scared the "bejezuz" out of me, I thought the condor was going to fall over, I couldn't hear, both ears were just ringing. Everyone was yelling not to touch anything, "you will get Poisoned" I was radioed to hurry down, so I bucked my way down.

The best Boy was Pissed off, the grip /electric crew thought it was hilarious and continually busted my balls and I thought this job kind of sucks. The best theory I have come up with is the Basket being turned sideways was not level, making in turn the Arri 6k fresnel not level causing one side of the HMI Bulb to overheat and explode?

Was it the Bronco ride up? Any thoughts? Surely Mark W. has a theory.

Best to all,

Ted Wiegand
D.P.
Pittsburgh, Pa



George Hupka writes :

>I should say that it was later discovered that the lamp head had >defective electronics (a bad coil, I think, although I'm no electrician so I >may not be remembering correctly), which were probably responsible >for the globe going . . .

Uh-oh, did it cost you another lamp to find out the choke had failed?

If a choke burns out it often passes much more current than is desirable, and this can cause instant lamp failure with possible shattering.

Clive Mitchell
http://www.bigclive.com



Ted Wiegand writes :

>Was it the Bronco ride up? Any thoughts? Surely Mark W. has a theory.

I reckon it was just bad luck.

Clive Mitchell



>Uh-oh, did it cost you another lamp to find out the choke had failed?

Fortunately, no - I think there was an old emergency backup on the truck, and when they swapped it out and sparked the light, the flicker was again extremely visible, so they immediately shut down the fixture and sent it away...before history could repeat itself!

George Hupka
Director/DP
Downstream Pictures
Saskatoon, Canada



>Surely Mark W. has a theory.

Am I that predictable?

I would guess that the "out of level" was not enough to cause the problem (which is basically a problem of lack of cooling on the high side of the globe with the older double ended ones).

On the other hand, all the bucking around, especially with the earlier fixtures which did not have very good shock mounting, it is quite possible that one of the long "legs" of the bulb may have cracked from the bouncing around and finally failed after it had heated up for a while.

The double ended bulbs were electrically quite sound, but prone to physical damage.

Mark Weingartner
Always with the theory
LA based but not home



>1/. Has anyone experienced exploding HMI bulbs, especially 575's? >Would you please describe the experience, damage, noise, etc?

I've had an old style 1200w PAR HMI explode. It popped, but continued to illuminate! I went into the next room, and found pieces of glass all over the room, melted into the carpeting. It had exploded "thru" the lens in front of it, but the filament continued to burn. Of course I turned off the light, let it cool down and discarded the globe. I'm insanely thankful that none was near the light when it happened.

Roderick
Az. D.P.
www.restevens.com
12on12off



Roderick wrote :

>I've had an old style 1200w PAR HMI explode. It popped, but continued >to illuminate!

HMI filament?

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614



…It had exploded "thru" the lens in

> front of it, but the filament continued to burn.

There ain't no filament there...

The old 1200 PAR HMI's had a double ended HMI globe built into a PAR glass enclosure. My guess is that the front lens of the PAR globe fractured dramatically, but the internal HMI globe soldiered on
unbothered by the fuss.

Mark Weingartner