Rank: Forum user 
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Our head office have just had four out of twenty eight tubes replaced as they were faulty. As you can imagine there is a distinct difference in the light levels. I have instructed that the remaining tubes are replaced.
Can anyone tell me or point me in the right direction to find out when tubes should be replaced, without the use of a light meter it is difficult to guage and no doubt when the bill comes in I'll will need an answer!
I can remember years ago as a young apprentice that all the tubes in our workshop were replaced every three years.
Thanks in anticipation
Clive
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Rank: Forum user
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I think I'm correct in saying that every light source, whether it be a tungsten, halogen, LED or flourescent lamp has a reccommended life expectancy, given by the manufacturer.
Flourescent lamps seem to have a longer life expectancy due to the fact there is no filament to heat up to create the light source.
You may find that cleaning the remaining tubes will have a huge effect on the light output as will washing the diffuser/reflectors.
I hope this leads you to a successful conclusion
Tom
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Rank: Forum user
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Tom,
thanks for the reply, we have already cleaned all the tubes and diffusers. There was little change in the light levels.
Whilst the old tubes do not appear to the naked eye to be su-standard, ie" Blackened Ends" or "Pinking" of the tubesthere is a marked difference, hence the decision to change them all. I was just curious if there was anything written down to justify my decision when the bean counters ask?
I'll look at the manufacturers guidance when the new ones arrive.
Cheers
Clive
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Rank: Super forum user
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In fact they have two filaments, one at each end.
More correctly called "emitters", or cathodes, their purpose is to generate electrons by thermionic emission.
The tube contains gases at low pressure, and mercury vapour, and are coated by a compound that fluoresces when excited by ultraviolet radiation.....
The filaments run at a lower temperature than incandescent bulbs....much lower...which accounts for their longer life.
Failure is usually due to the cathodes losing emission.
Their disposal should be as for hazardous waste, and not in a dustbin....each tubes contains a few milligrams of mercury.....
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Rank: Forum user
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JohnMurray wrote:In fact they have two filaments, one at each end.
More correctly called "emitters", or cathodes, their purpose is to generate electrons by thermionic emission.
The tube contains gases at low pressure, and mercury vapour, and are coated by a compound that fluoresces when excited by ultraviolet radiation.....
The filaments run at a lower temperature than incandescent bulbs....much lower...which accounts for their longer life.
Failure is usually due to the cathodes losing emission.
Their disposal should be as for hazardous waste, and not in a dustbin....each tubes contains a few milligrams of mercury.....
ZZZZZZZZZZZZZZZZzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz........................
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Rank: Super forum user 
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ptaylor14 wrote:JohnMurray wrote:In fact they have two filaments, one at each end.
More correctly called "emitters", or cathodes, their purpose is to generate electrons by thermionic emission.
The tube contains gases at low pressure, and mercury vapour, and are coated by a compound that fluoresces when excited by ultraviolet radiation.....
The filaments run at a lower temperature than incandescent bulbs....much lower...which accounts for their longer life.
Failure is usually due to the cathodes losing emission.
Their disposal should be as for hazardous waste, and not in a dustbin....each tubes contains a few milligrams of mercury.....
ZZZZZZZZZZZZZZZZzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz........................ Took me back to my HNC days in the early 80s! The zzzzzz made me laugh out loud but after the recent 'Curb your enthusiasm' I can't bring myself to put LOL!
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I dont think there is any manufacturer who would be prepared to suggest that tubes need replacing earlier than there recommended life span.
Has the correct colour type of tube/s been selected correctly in the first instance because this can have a massive impact on how light affects rooms. There are specific codes on the tubes.
If you scan the internet you can find which codes relate to which colour.
Standard (Halophosphate) fluorescent tubes have a colour rending index of 50-70% whereas the Triphosphor fluorescent tubes have a colour rendering index of 85%.
The numbers given on your tube show the colour code reference eg. F18W/35 refers to the 18 watt halophosphate fluorescent tube with the colour 35 (White).
Check out what you have and speak to a lighting design company for there specialised recommendations..
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Rank: Super forum user 
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For what I am about to post is in no way connected with the manufacurer.
Clive
Have you tried NET lighting? They are L.E.D strip lights that last longer than the mercury tubes and when its time to dispose then all you have to worry about is the WEEE above your head, nowt hazardous. Accepted they do cost more but the investment does payback so I'm told.
Badger
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So glad I only posted what I did.. as I too could easily have put together ZZZZzzzzz edition.
To reiterate a couple of replies, for very little extra outlay, just go for what they call "day light" tubes, which hopefully will overcome the triphosphoric halo thingy whatevers.... however as Clive rightly indicates... LED is the way forward, however, I think we are getting away from the initial topic of how money can be saved and some method of justifying the expenditure on tube replacement.
If, as a result of a risk assessment, the hazard of insufficient light is apparent, a control measure could be.... the replacement of the existing tubes to a more suitable and sufficient tube with appropriate light emissions
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Rank: Super forum user
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Seperate question.
Is there any legislation or regulations about the need to cover the actual tubes themselves.
A few of our offices have the bare tubes (older sites) which have lost (probably removed by the staff still working there) their covers.
We've also got some new lighting which again are nigh on bare tubes that come as pairs with the mirror type casing (not sure on the terminology) but have no covers as such.
I know regarding the electricity regs etc but wondering if there is something specific apart from best practice to actually state they need physical covers in case of breakage etc (not that i've ever seen one break in almost 40 years on this planet).
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Rank: Super forum user
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With designing lighting, the wall surface, floor surface and maintenance of the fittings is considered along with the required level of lighting for the design task. The light output of the tubes will fall-off as they age and to maintain light levels they are best replaced once a year to give max level. If the wall covering is darkened along with the floor the reflected light will fall off and so the design needs to be changed to keep levels to the design requirements
Re the 'regs' the type of fitting should be suitable for its use. Totally enclosed types in kitchens, garages etc
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Rank: Super forum user
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And another thing..At the ends of the tubes are heaters. They warm up the gas inside to tubes and make it conductive as well as heating up the emitters/collector (ac so both acts as each f you see what I mean).If you were to take the powder off the inside of the tube no 'light' would be visible (mercury oxide etc)
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