Kaia,

Regarding your point number 4 on the life expectancy of the lamps. As 
previously mentioned there can be detrimental effects from variations in 
voltage on performance.

Tungsten halogen lamps behave in a similar manner to other incandescent 
lamps when run on a different voltage. However the light output is 
reported as proportional to V^3, and the efficacy proportional to V^1.3. 
The normal relationship regarding the lifetime is that it is 
proportional to V^-14. For example, a bulb operated at 5% higher than 
its design voltage would produce about 15% more light, and the efficacy 
would be about 6.5% higher, but would be expected to have only half the 
rated life. Another way to look at it, is if your bulbs are rated at 
120V and line voltage in your building is averaging 130V, that is a 
nearly 2% increase over design voltage, or roughly a 20% reduction in 
life expectancy. I'd have your line voltage checked and/or monitored for 
spikes or excess voltage. This can often be an issue that is caused by 
factors outside your specific space such as buildings with shared tenants.

One should also note that manufacturers life expectancy numbers are 
based on continuous burn tests, not cycle tests. Turning lamps on and 
off reduces the life expectancy because of the initial heat requirement 
to evaporate the tungsten filament. This "shock" effect causes the lamp 
to momentarily burn inefficiently each time it is "started" or turned 
on. Some lighting control systems incorporate a start up sequence where 
bulbs are turned on at 90% of design voltage and then ramped up to 100% 
after a short period of time to allow the lamp to warm up. This effect 
is more pronounced in halogen lamps due to their higher operating 
temperature.

To one other point. Wearing gloves when changing lamps is good practice 
and I would strongly encourage doing so. In your case though, with R30 
bulbs, oils on the glass bulb are not likely to be your problem. The 
larger form factor of the bulb and the method of construction generally 
would not lead to catastrophic failure if contaminated by oils from your 
fingers. This type of failure is usually found when oils are transferred 
directly to the clear quartz envelope surrounding the filament. These 
are the type of lamps you find inside auto headlamps, reading lights, 
inside fixtures such as your range hood in the kitchen, etc. It would 
generally take a larger transfer of oil or other material to the bulb to 
cause the failure you describe with the R30 bulbs. Your facility people 
may want to review your cleaning procedures though, as some cleaning 
practices or solutions coming into contact with the lamps may cause the 
failure you describe.

Good luck,

Larry Fisher



On 2/29/2012 5:40 PM, Kaia Landon wrote:
> Thanks everyone who has weighed in so far. Our maintenance/facilities 
> guys will be checking into things more in the morning before we open. 
> So far their best guess is some sort of power surge.
> To answer some questions:
>
>   * No, we've not been in the habit of wearing gloves to change bulbs.
>     We'll definitely start! (Am I the only one who'd never heard of this?)
>   * The fixtures are rated up to something like 100 watts. We're
>     significantly under.
>   * The bulbs we've been using are GE Halogen Edison Flood, 60 watts.
>     PAR 30. (Here's the exact bulb, if this helps:
>     http://www.amazon.com/85116-Indoor-Floodlight-Halogen-60-Watt/dp/B00291WZTW/ref=sr_1_5?s=hi&ie=UTF8&qid=1330554039&sr=1-5
>     <http://www.amazon.com/85116-Indoor-Floodlight-Halogen-60-Watt/dp/B00291WZTW/ref=sr_1_5?s=hi&ie=UTF8&qid=1330554039&sr=1-5>)
>   * In general, these bulbs have not been lasting the 3,000 hours
>     promised on the packaging. Based on the number of bulbs we've
>     purchased in the past year, I'd say they're lasting, on average,
>     less than half that long, although whether we're replacing bulbs
>     from 10 fixtures monthly or 100 yearly is unclear. We've recently
>     started tracking when we replace the bulb in any given fixture so
>     we can (hopefully!) eventually figure out whether the problem is
>     with our hardware, or with the bulbs themselves.
>   * We're located in northern Utah - definitely no lightning strikes
>     we could attribute anything to recently. Today's weather is wet
>     and windy. I don't recall the weather the day the other exploded.
>   * Vibration is a possible concern. We share a building with the
>     Senior Center (we're City funded), and they are upstairs. While
>     things are generally pretty tame, they do sometimes have clogging
>     and/or square dancing classes up there which rattle the whole
>     building quite a bit. Bulbs exploding do not seem to correlate to
>     building vibrations, however.
>   * We have not switched brands recently.
>   * There's not a dimmer on any of these.
>   * No recent construction or additions to the building's electrical
>     system.
>
> Thanks again for all the helpful suggestions. Please keep them coming 
> if you think of anything else.
>
> Thanks,
>
> Kaia
>
>
> On Wed, Feb 29, 2012 at 2:11 PM, Regan Brooks 
> <[log in to unmask] <mailto:[log in to unmask]>> 
> wrote:
>
>     Hi Kaia,
>
>     Agree with Marc, this problem has several variables that need to
>     be considered – however, I will say (speaking as a former theatre
>     person now in museums) that getting fingerprint oil certain lamps
>     (as the bulb is properly called! ;) ) can and will cause them to
>     explode. First thing theatre techs are taught that I’ve noticed is
>     lacking in museums, depending on your lamps – never ever touch the
>     actual bulb portion!
>
>     */Regan Brooks/*
>
>     Registrar
>
>     Gaston County Museum of Art & History
>
>     PO Box 429
>
>     Dallas, NC 28034-0429
>
>     704.922.7681 ext. 107 <tel:704.922.7681%20ext.%20107>
>
>     */www.gastoncountymuseum.org <http://www.gastoncountymuseum.org>/*
>
>     */Become a fan of the Museum!/*
>
>     */Visit us on our Facebook page and see what we are up to!/*
>
>     www.facebook.com/GastonCountyMuseum
>     <http://www.facebook.com/GastonCountyMuseum>.*//*
>
>     /" Be nice to the archivist, or she'll erase you from history!" -
>     Anonymous/
>
>     *From:*Museum discussion list [mailto:[log in to unmask]
>     <mailto:[log in to unmask]>] *On Behalf Of *Kaia Landon
>     *Sent:* Wednesday, February 29, 2012 3:33 PM
>     *To:* [log in to unmask]
>     <mailto:[log in to unmask]>
>
>
>     *Subject:* [MUSEUM-L] Exploding Lightbulbs - cause and prevention?
>
>     We've got track lights, and each can holds one 60 watt halogen
>     floodlight. We always use the same lightbulbs. About a month ago,
>     one exploded. Just now another (on a different track/circuit,
>     about 50 feet away) did the same. The explosion is quite loud, and
>     resulted both times in a few small pieces of glass burned into the
>     carpet.
>
>
>     Any suggestions on what might be causing this, or how we might
>     prevent it?
>
>     We are now tracking each of our lights to keep track of when the
>     bulbs were replaced, which package they came out of, etc., so at
>     some point we might be able to connect the exploding bulbs, but
>     right now we've got nothing.
>
>     Luckily, in both cases, there were no visitors in the immediate
>     area, but there is clearly a possibility that someone could be
>     injured if they were within about five feet of an exploding bulb.
>     (They're far enough away from the walls that there is no damage of
>     art being damaged.)
>
>     Thanks!
>     Kaia
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