1000w metal halide bulbs at end of life blow the end out of the bulb.

[the electric guy]

I am working with 1000w metal halide lamps that are over indoor tennis courts. These lights are anywhere from 15 feet to 40 feet high. Because of this we only have the oppertunity to change them once a year. Because there is appox. 160 fixtures we change the bulbs once every two years unless they burn out faster. What we have noticed is that the bulbs will sometimes blow the bottom out of itself. When this happens we have noticed that the scoket will be damaged also, and require changing also. I was thinking about fusing the input to the amperage needed on start up so that at end of life it would blow the fuse before damaging the bulb or socket. Is this a good idea or will something else work better?

 

[don_resqcapt19]

I have not heard of that type of failure for MH lamps other than ones that are left on 24/7. A few percent of those tend to have a violent failure at end of lamp life.
Are the correct lamps being used as to the base orientation?

 

[mgookin]

The ballasts should be limiting the current. How old are those ballasts and how often do you replace them?

Are you finding it occurs randomly, or have you noticed it repeating only on certain particular lights?

What's the chance they're being hit by tennis balls and the players are not fessing up to it?

 

[rt66electric]

lightning ???

lightning ???

lightning ???

 

[GoldDigger]

1. Any chance that high temp surface areas of the bulb were handled improperly during installation and were contaminated with skin oils, or something else that could have weakened the glass or quartz envelope?
If they were all handled in the same way that might explain similar blowouts.

2. Can you tell whether the socket damage was electrical/heat damage from high current at the time the bulb blew up or mechanical damage from the blowout? That will tell whether fusing is likely to make any difference. If the failure occurred just from high pressure or temperature at the time the bulb failed, current limiting will not help you.

 

[the electric guy]

more info on 1000w mh

more info on 1000w mh

I am working with 1000w metal halide lamps that are over indoor tennis courts. These lights are anywhere from 15 feet to 40 feet high. Because of this we only have the oppertunity to change them once a year. Because there is appox. 160 fixtures we change the bulbs once every two years unless they burn out faster. What we have noticed is that the bulbs will sometimes blow the bottom out of itself. When this happens we have noticed that the scoket will be damaged also, and require changing also. I was thinking about fusing the input to the amperage needed on start up so that at end of life it would blow the fuse before damaging the bulb or socket. Is this a good idea or will something else work better?

I am guessing that the damage is from the lamp trying to light and the amperage going up. I am not sure though. The ballasts are appox.17 years old. Once I change the ballast it only works for a year or two then they fail. It happens randomly. The fixture could be hit with a tennis ball and I would not know unless the ball ends up on the top of the fixture which does happen to only one or two fixtures. The fixtures are on for a max. of 13 hours a day, when no one is using the courts they are tured off.We have dropped the wattage from 1000w to 950w but the problem was there before we did that. Yes the bulb is in proper orientation.

 

[GoldDigger]

I am guessing that the damage is from the lamp trying to light and the amperage going up. I am not sure though. The ballasts are appox.17 years old. Once I change the ballast it only works for a year or two then they fail. It happens randomly. The fixture could be hit with a tennis ball and I would not know unless the ball ends up on the top of the fixture which does happen to only one or two fixtures. The fixtures are on for a max. of 13 hours a day, when no one is using the courts they are tured off.We have dropped the wattage from 1000w to 950w but the problem was there before we did that. Yes the bulb is in proper orientation.

If the situation got worse when you replaced the ballasts, chances are you are using the wrong rating ballast.

 

[mbrooke]

Are these pulse start or probe start? What is the bulb code and what is the ballast code? Are you using cheap bulbs?

It could be a slew of things, overheating caused by the fixture, balls hitting the light, high line voltage bulb ballast mismatch ect.


Best thing to do is order type "O" rated lamps regardless and use those. They have an arc tube shroud and the outer envelope does not break when the arc tube fails violently. Unlike MV or high pressure sodium, metal halide arc tubes like to grenade when something is bothering them or are past the printed life. Its a good investment especially in HI bays in that the hot glass can start a fire, not to mention the mercury being released isnt good either.

 

[kwired]

Are these pulse start or probe start? What is the bulb code and what is the ballast code? Are you using cheap bulbs?

It could be a slew of things, overheating caused by the fixture, balls hitting the light, high line voltage bulb ballast mismatch ect.


Best thing to do is order type "O" rated lamps regardless and use those. They have an arc tube shroud and the outer envelope does not break when the arc tube fails violently. Unlike MV or high pressure sodium, metal halide arc tubes like to grenade when something is bothering them or are past the printed life. Its a good investment especially in HI bays in that the hot glass can start a fire, not to mention the mercury being released isnt good either.

You mentioned it first - I don't know all there is to know about these lamps, but I was aware there are two different types of lamps, one rated for enclosed lamps only, and another type that can be used with open or enclosed lamps, and it was my understanding that the reason for designing the second type was because violent failures are fairly common, and the second one is supposed to contain the failed arc tube so that you don't have hot parts and glass falling on people that may be below an open lamp type fixture.

 

[mbrooke]

You mentioned it first - I don't know all there is to know about these lamps, but I was aware there are two different types of lamps, one rated for enclosed lamps only, and another type that can be used with open or enclosed lamps, and it was my understanding that the reason for designing the second type was because violent failures are fairly common, and the second one is supposed to contain the failed arc tube so that you don't have hot parts and glass falling on people that may be below an open lamp type fixture.

All metal halide lamps have an arc tube that can fail violently, most common cause being from run beyond the rated life. Risk goes up with 24 hour non stop operation in that metal halide lamps generally fail to start when the reach the end of life, however in 24hour operation the lamp will never get that chance to fail by not lighting when still cold. Burning them horizontally increases the risk more so because the arc actually bulges upward, weakening the arc tube more at the top than the bottom. Being over driven (bulb ballast mismatch) is another one as well.

Reason for the sensitivity, MH lamps have much shorter arc lengths (electrodes are closer) as apposed to Mercury vapor or High pressure sodium lamps which have long slender arc tubes. The arc tube as a result operates at a higher pressure (around 50psig) and temperature than the other two, combined with normal arc tube blackening and the ease of the arc instability at end of life you have the higher risk.


You are correct, violent failures are common and that was the reason for the creation of the open rated lamp. By far the worst offenders are the compact envelope lamps commonly used in bollards, wall packs and recessed HIDs. I have seen parking garage fixtures where literally every other 175 watt lamp was blown to fragments. At one point I was convinced the normal failure mode for 100 and 175 watt lamps was through self destruct. Much less so for the higher wattage versions but every now and then it does happen.


Anyways, there are 3 types of lamp ratings.

First is type "E". These must be operated in an enclosed fixture, and one that is rated to contain the hot glass from a rupture. The outer glass will shatter from an arc tube failure when lit.

The second is type "S". These have a bigger envelope but no internal or external shatter protection. These used to be allowed in open fixtures like high bays with the theory being the larger envelope would disperse arc tube fragments but truth be hold in some cases the outer envelope would shatter as well. These lamps by code are not allowed anymore in open fixtures like high bays with no glass lens.

The third is type "O" These have a thick shield around the arc tube in addition to some also having a thicker outer envelope. They can run in either open or enclosed fixtures and a violent arc tube failure even from a serve ballast failure will not break the outer envelope. These also have a special base. It will still fit into a regular socket no problem, however open rated fixtures are required to have a special pink socket. The pink socket will take a type "O" bulb base, but it will reject all type "E" and type "S" bulbs bases.

 

[delaware74b]

I have seen metal halide lamps and sockets loosen from high winds shaking the poles and heads from 40 to 70 feet up. I have also seen similar to the op's situation in sportslighter-type fixtures. The main problem is NOT changing the lamps when they are at the end of their design life.

My company maintains a small used car dealer who has 12 fixtures and doesn't want the fixtures blanket relamped. I am there about twice a year replacing the lamps that had the arc tube rupture from excessive hours. I have also found the fixtures themselves had loosened from their mounting poles. Just general preventive maintenance is all that is needed.