Arc source above average service life hours

I almost hate to ask, and I've already ordered new lamps, but how worried about the timer on my Lycian 400 (http://www.stagespot.com/downloads/1266 specs.pdf) being SIGNIFICANTLY over the average service life on the data sheet for the lamp (Datasheet & application note database, pdf, circuits, cross reference, data sheet, datasheets | Datasheet Archive hti 400 24-datasheet.html ((second data sheet)) ) should I be? By 100-300 hours?

I've never dealt with these follow spots before. Is there a chance that the previous person in my position just didn't reset the timer?
 
Arc lamps usually don't just up and die. They used to rate the Satellite I (575 HMI) at 400 hours. In most cases, we ran them close to 1000 hours. Depends how much drop-off you are willing to accept. When you pair spots, then it becomes more important to keep their look balanced.

As the HMI type lamps age, the envelope goes from being crystal clear to a heavy frost. This knocks the output down. There is also a color shift. Eventually, the lamp will begin dropping out and requiring re-strikes. The lamp rating is based on usable output and variance from specs. (Unlike an incandescent where the rating is the average burn-out time.)
 
... Is there a chance that the previous person in my position just didn't reset the timer?
Are you sure that the Lycian 400's "odometer" IS resettable? Most followspots' timers aren't. One usually just writes "Lamp changed on <date> at <meter reading> by <technician>" on a piece of tape affixed to the back or side of the unit.

The HTI 400/24 lamp (your link doesn't work) has a rated life of 250 hours. Once you exceed that, nothing really bad will happen, but you may notice a gradual loss of intensity and shift (toward "brown") of color temperature. It happens so gradually that you may not even notice, unless comparing to a new lamp. Some users replace their gaseous discharge lamps at 75% of rated life, others religiously AT the rated life, still others wait until the lamp no longer functions. All approaches are situationally valid.

Short answer: Don't worry, be happy. :lol:
 
Awesome.
I can deal with aesthetics, I was just worried about it's potential to throw shrapnel increasing. I noticed we were really having to crank the watt watch meter on one, and then jumped when I saw the timer.
 
:) Pardon my cursory explanation :)
There is an externally controllable power supply with a gauge that this particular model labels the "watt watch". One of our two spots maintains a high color temperature on a lower setting. The other, with many more hours logged on its time meter, is much warmer and must be turned up to compensate. This seems to go along with the above explanation of HMI's fading out rather than blowing?
 
Exactly! An HMI lamp has a mix of metals in it. As it ages, some of these metals are more prone to be deposited into the envelope glass (quartz) which changes the mix and alters the color temperature. Also, the electrodes erode which effects this as well. Although the HMI lamp operates at a pressure, it is no where nears what is found in a xenon lamp.

On xenon lamps, heat stress alters how stable the envelope is. Also, deposits increase the temperature of the envelope. Because of that, old xenon lamps become a bit of a time bomb as they get old.
 
Explosions are more of a xenon think. HMIs usually just fade away until you can't keep them lit.

Key word here being "usually" they occasionally will have a "non-passive failure". In a moving light this often causes $300-$1000 in damage to the heat shield, Reflector, and occasionally color wheels/Flags.

Just thought I would point out that running lamps much past 2x their rated life can cause more problems than dim output.
 
Another thing to bear in mind, the manufacturer defines the rated hours through their own duty cycling of the lamp, i.e. lamp ON, run 60 minutes, Lamp OFF, wait 15 minutes, repeat to failure, deduce the "rated lamp life."

As we in this industry tend to run, say, a followspot from the time doors open to the close of the last curtain call, our duty cycle may be 4 to 6 hours. Given this, one can interpret the manufacturer rated life to define the number of strikes. I have seen HTI1200 with 1200 hours on them and still look fine, even though the rated life is 750 hours.

The above cannot be taken as a hard and fast rule, obviously. There will certainly be instances of premature "energetic decomposition," or what lay people might call explosions, but to run over hours is not unheard of and may not necessarily be a "bad" thing. "Brown" light, or a noticable degradation in output, are your best determinants on replacement. (IMHO)
 
Regarding rated life:
Projection arc lamps use different metrics to establish lifespan. That "life" is determined by how far outside of specifications the lamp operates as it ages as compared to the "burn out" point. Best example was my prior post. In one case, the spot was out on the road for 5 years before it came back with the complaint that the lamp was dropping out. When I checked the meter, it had 1800 hours since the last re-lamp! (Rated life 400 hours.) It was quite dim, but the group had been using it for club work and didn't notice! Never had one blow, but they tend to have better ventilation in a followspot. Movers, on the other hand, are tight quarters and the lamps often have more thermal stress. Can one explode in a followspot? Sure. Even the incandescent/halogen ones do.

HMI is at a slight vacuum at room temperature, and a slight pressure when on. Xenon, on the other hand is at many atmospheres pressure even when cold!
 
All very valid points- Xenon lamps are at ~30 atmospheres of pressure when cold, that increases to almost 90 when hot. This is why you should ALWAYS-- ALWAYS use safety gear when handling them. This is also why you shouldn't run them beyond their rated life. At least not significantly. Most Xenon lamps for Followspots/Cinema projectors have a full warranty up to their rated life, so there is definitely value already built in which provides you incentive to change it at that point and not take the risk.

HMI/HTI/MSR/CSR types are USUALLY under very low pressure (1-3 atmospheres at most. There are some exceptions). Double-jacketed ones have either a vacuum in the space between the outer envelope and inner capsule (to prevent oxidizations of the pinch seal and help them achieve longer life)-- which will result in a "pop" sound as they implode slightly when broken-- and some of the higher wattage ones use Nitrogen as a fill gas between the envelopes to assist in the hot-restrike capability of the lamps.
Some lamps can rupture at the end of life due to what is called a “dropped electrode”. What happens is the tungsten on the electrode begins to mushroom at the tip due to the halogen cycle in the lamp. While the Halogen cycle causes the Tungsten molecules to redeposit on the filament, they don’t redeposit equally or in the same spot they came off of- they tend to gather on the hottest part- the tip. So over time you have a very narrow electrode at the area coming out of the quartz, and very fat electrode tip, and eventually it just falls and breaks, and if it does it while hot, it will melt the quartz and rupture the envelope, causing a small “non-passive failure”.


Again- the key people to ask when you want to know about a fixture and how it tracks life is: The Fixture Manufacturer!
The person to contact at LYCIAN is: Steve Costa [email protected] , he’s a great guy and will be happy to answer any questions for you regarding how the fixture calculates or tracks life of the lamp, and risks on replacing them after life.
 
All very valid points- Xenon lamps are at ~30 atmospheres of pressure when cold, that increases to almost 90 when hot. ...

From XBO® :
Depending on lamp design, cold XBO® lamps are filled to a pressure between 5 and 15 bar.
In order to obtain this positive pressure in the lamps, the xenon is frozen into the lamp body
during manufacture. The pressure in the lamp rises during operation to about four times the
value because of the temperature.

1 atmosphere=1.01325 bar.
 
So, to put into terms that we use day-to-day, atmospheric pressure at sea level is about 14.7 pounds per square inch.
( Atmospheric pressure - Wikipedia, the free encyclopedia )
A lamp pressurized at 15 bar, would be 220.5 psi. When hot, four times that would be 882 psi !!! (numbers rounded off)
:excitable:
Of course, since we don't live in a vacuum, you probably should subtract about 14 psi from those numbers.

Still, that is an awesome amount of pressure in a little glass (quartz) globe !!

Makes me hopeful I will never have to change another (retired.)
 
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wait, also, speaking of all these explosive, shrapnel throwing Xenon lamps, how does one typically dispose of such things??
 
From the same source cited in post #13:
Burnt-out XBO® lamps can either be returned to the manufacturer for appropriate disposal
by methods consistent with modern recycling, if possible in the original transport packaging
or in that of the replacement lamp, or they can be destroyed by the user.

Observing all the precautions given in the section on “Mechanical installation” on page 39, it
is advisable to wrap the lamps up in the safety cover and to seal the ends tightly with the en-
closed hook-and-loop strips. The hook-and-loop strips have to press the fleece tightly onto
the lamp bases. The lamps can then be discharged safely by free fall from an height of about
1–2 meters onto solid ground (put on safety goggles and protective clothing!). The xenon
gas that escapes is not poisonous and returns to the atmosphere from where it came. The
remains of the lamp can be disposed of as rubbish and the electrodes and rods (i. e. tungsten
material) sent for recycling.

Alternatively, one can take the lamp outside to a clear area and, wearing all appropriate PPE, wrap the globe in a towel and hit it with a hammer.
.
 
The peak danger is the time between when you open the fixture and have the lamp back in its packing material. Very old lamps can be VERY unstable. Had a projectionist tell me about a time that as soon as he loosened the clamp screw the lamp blew. (Movie theaters are know for running past life.)
 
The peak danger is the time between when you open the fixture and have the lamp back in its packing material. Very old lamps can be VERY unstable. Had a projectionist tell me about a time that as soon as he loosened the clamp screw the lamp blew. (Movie theaters are know for running past life.)

That's why we ship ours with a ballistic cloth "wrap" that velcros around the lamp for while you are inserting/removing it. should it explode, this will contain the glass.

And sheesh, Derek... way to call me out on my mis-remembering/exageration. :) Who has time to look up the hard #s? Someone once told me 30 atm... so I guess shame on me for not looking it up myself in the XBO Xenon guide in my bookcase.
 
follow spot watt meter

So I have a pair of Lycian 1266 with an HTI 400/24 lamp
the lamp Ballast has a LED meter that guides you setting the ballast output using a hi/lo range switch and a 6 position dial.

On one fixture the meter was pegged at the high end, with the output switch & dial set to the lowest value. the lamp was working.

being that the lamp was well past its rated life. I changed the lamp.

the new lamp works fine but the meter is still pegged at its highest indicator. with the lowest ballast output set.

Any thoughts on this?

not much to be found on the lycian web pages.
 

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