Half pink fluoresent lamps

[eletrick]

when fluoresent fixtures are operating on batterys (normal power is off and the em gen set is off) some of the lamps are half pink and half white, just half of the same tube. not all tubes do this. and when power is restored the tubes are all white. any insight ? thanks

 

[broadgage]

Some types of lamp contain contain mercury amalgam rather than pure mercury.
These lamps do not operate properly at much reduced power as on battery emergency lighting ballasts, or on line voltage dimming ballasts.
These lamps have to run fairly warm to light correctly and most battery ballasts dont put enough heat into the lamp.
It is best to use non amalgam lamps in such fixtures.

Another less likely possibility is that the lamps are very near end of life. Sometimes nearly dead lamps still work at full power on line voltage but not at much reduced power on batteries.
The reason being that the mecury dose in the lamp is largely used up* For the lamp to work correctly it is not the actual weight of mercury that is important, but the partial pressure of mercury vapour. Even a less than proper amount of mercury in a hot lamp will work ok, but not in a lamp that is cold due to low power operation.

*the mercury is not actually consumed, but it tends in time to form compounds with the other materials in the tube and therefore not be available for correct operation.
Due to the toxicity of mercury, manufacturrers are reducing the dose per lamp, sometimes they overdo this and otherwise servicable lamps fail due to mercury depletion.

 

[eletrick]

Maybe these will help (any idea how hard it is to get a good picture of a lit fixture ?) The color separation is not as pronounced as the first time these were tested and now some do not have the color. everything else works fine when power is restored, full bright white , lamps and all are new.

 

[zbang]

You can see the same sort of effect on a really cold CFL. Saw one where the light started next to the ballast and over about a minute the entire tube warmed and lit up. Kinda fun to watch.

 

[steve66]

maybe they (the lamps) just need seasoned by applying full power for x number of hours.

They recommend that for dimmable lamps. Since a battery pack also operates at less than full brightness, I would assume a lamp should be seasoned before using with a battery pack too.

 

[Electric-Light]

Got a PM from someone to address this question...

The pink comes form discharging in argon gas. Some batch of lamps are plagued with this problem where they're first switched on, it starts off with the center dim until fully warmed up.

Normally linear lamps are not supposed to take noticeably long to warm up like CFLs, but lamps plagued with dosing issues at production stage will. The mercury gets bound up in phosphor coating after it is left of for some time with some lamps and only released after lamp runs for a while and the heat drives out the mercury into the discharge.

This is a challenge that surfaced with the use of low mercury lamps. The Philips Alto II is among the lowest and they only use 1.7mg (that's 1/40 of a grain).

Unfortunately, the emergency operation performance will suffer when it pinks out as argon discharge does not produce much UV that's needed to light up the tube.

If those lamps are AMALGAM T5s... then this is perfectly normal. They're not meant to be driven at 5-10% output w/o cathode heating.
You're not supposed to operate lamps like this as it dramatically reduces useful life, but they do it, because under normal design, the usage is limited to maybe 30 minutes every year.

 

[jeremysterling]

when fluoresent fixtures are operating on batterys (normal power is off and the em gen set is off) some of the lamps are half pink and half white, just half of the same tube. not all tubes do this. and when power is restored the tubes are all white. any insight ? thanks

Yes, the battery ballast is miswired.

 

[mivey]

Yes, the battery ballast is miswired.

In what manner? Two lamps instead of one? Wouldn't that cause an issue with the main ballast? Never replaced/retrofitted one of those ballasts so I never had to monkey around with the wiring.