Reprinted below is some safety related and manufacturers (Philips) operating instructions for UHP type projection lamps. The article contains information regarding the deleterious effects of bulb operation under unstable AC power supply voltage conditions:
HAZARDS OF AND SAFETY PRECAUTIONS FOR UHP LAMPS
Projector lamps have numerous hazards. They do not make good toys.
The arc light is about as intense as a welding arc or a carbon arc. One should not look directly at the arc. If your eyes are already adapted to bright light, you may get away with looking at the arc for up to a few seconds with no permanent eye damage - but doing this is NOT a good idea. You won't hurt your eyes looking at the arc through #12 welding glass - but there are other hazards. All projectors have a series of filters installed between the light patch to ensure an efficient block of UV radiation. Filters made for looking directly at the sun will also make the arc safe to look at directly. Most other dark transparent materials will not protect your eyes since they let through enough infrared to risk cooking spots on your retina - an eye damage phenomenon notoriously lacking warning signs.
The arc emits almost every kind of ultraviolet in the book, including large amounts of UV-A, UV-B, and some UV-C. These different ultraviolet bands are bad for different parts of your eyes. Number 12 welding glass and sun-viewing filters will protect your eyes. However, the UVC, UVB, and the shortest UVA wavelengths can sunburn your skin. Serious sunburn and increased risk of skin cancer may result from significant exposure to this radiation. These wavelengths are blocked by ordinary glass, but for other reasons below it is HIGHLY RECOMMENDED to only operate UHP lamps in fixtures designed and made for them by qualified personnel - typically engineers and technicians who work for the fixture manufacturers.
The shortest ultraviolet wavelengths emitted by UHP lamps can generate ozone. Operate the lamps in an adequately ventilated area. If you can smell the ozone, it can noticeably irritate your lungs within hours.
UHP Projector Lamps operate at red-hot temperatures of up to 900, sometimes even 1050 degrees C (approx. 1650-1900 degrees F) and contain very high pressure usually in excess of 160 atmospheres and often near or over 200 atmospheres, and in a few cases 300-plus atmospheres. They can explode. Rarely, but who knows how rarely, they explode when nothing can be detected as wrong. If operated in any way other than as specified or past their intended life expectancy, the risk of explosion increases. Explosions can be dangerous since they can result in red-hot (or hotter) pieces of glasslike quartz being shot out in all directions, possibly with considerable force. These lamps should only be operated in fixtures made for these lamps and designed to contain a lamp explosion. These lamps contain mercury, so you might not want one to explode in your home even if there was no risk of fire or red-hot glass shrapnel.
UHP Projector lamps require forced air cooling. This is another reason to operate them only in fixtures designed for the particular lamp being operated.
UHP lamps have pressure well above 30-50 atmospheres even when they are cold. You don't want to drop one and have it break......... think of a hand-grenade!
UHP Projector lamps have quartz bulbs operated under stress at high temperature. The usual halogen lamp rules for bulb cleanliness apply. Carbon and oil deposits can absorb light and make hot spots. Traces of any sort of ash, salts, metal oxides, or alkalis can leach into hot quartz and cause strains which can weaken the quartz.
You should not touch the bulb. If you touch the bulb, you can clean it with alcohol so that no skin oil traces are left on the bulb. It may also be a good idea to rinse the bulb with distilled water.
Do not operate a UHP lamp that has been scratched or chipped.
UHP Projector lamps should be operated only at the wattage they were designed for and with the type of current they were designed for. Overpowering them is obviously bad. Underpowering an UHP lamp can also be bad, since a slightly-too-cool electrode does not emit electrons easily, and the voltage drop in the cathode region of the arc increases and causes positive ions to hit the cathode harder, which "sputters" off cathode material. This will discolor the bulb and may cause the bulb to overheat or have an abnormal temperature gradient somewhere and could make the bulb explode. Discolored bulbs as well as abused electrodes can really overheat if operated at full power.
UHP Projector lamps are designed for AC, and typically have two identical main electrodes. Operating an AC lamp on DC will overheat and/or excessively age at least one electrode. Aging electrodes have limits in the peak rate at which they can emit electrons without overheating or sputtering, and peak current has to be minimized. Excessive peak current may accelerate aging of electrodes that are in good shape.
UHP Projector lamps may have to be operated in a specific position so that convection currents - internal and external - don't cause vulnerable parts of the lamp to overheat. This is another reason to use them only as directed in proper fixtures designed specifically for the lamp being used. Follow all directions that come with the lamp and all directions that come with the fixture.
With all this trouble and the high cost of UHP Projector lamps, it is no wonder why they are only used where there is no substitute for a small, very intense light. UHP lamps are not good toys for casual experimenters.
Do not touch or handle this lamp without wearing glove.
If this lamp touched by bare hands, the lamp must be cleaned with towel and alcohol solution.
Do not touch a lightened lamp or a lamp immediately after off-operation; High heat may cause sever damage.
The lamp generates UV radiation, do not look directly into the light; Avoid directly exposing skin to the light.
The lamp may only operates properly in an approved and appropriately operated projector.
Fast on-off switching may cause short lamp life.
For lamp replacement, the power must be switched off when operating in equipment.
Safety protection is needed for the lamp area because of high ignition pulses.
Surrounding temperature should be less than 55 C
Operating voltage : The average operating voltage should deviate from the rayed voltage indicated on the type plate by no more than 3%
Sudden voltage deviations of more than +/- 10% may cause the lamp to go out.
Permanent operation at a voltage above or below the rated supply voltage may lead to changes in the light color and a reduction in the life of the lamp.
The lamp take about 2-5minutes after being switched on to reach its full luminous flux.
Color variations : As with all metal halide lamps, there may be difference in color from lamp to lamp. This may be due to external factors such as mains voltage, control gear and luminaries design.
When a lamp comes to the end of its life it must be replaced as soon as possible to prevent damage to the control gear and radio interference.
These lamps can be considered to have come to the end of their service life if:
the light color of the lamp changes dramatically or-
there is an appreciable loss of brightness or
the lamp periodically goes out and restarts or
the lamp no longer ignites
Sometimes a UHP lamp end it's life with a explosion or a big pop.
Also in general:
The high pressure lamps require an incrementally higher start voltage at each start. At the end of life the lamp might still be capable of firing, but requires more voltage than the ballast can provide. It explains the cases when a set would not start for several days, then it starts the first time but maybe not again until the lamp is replaced.
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