Precautions for UV Lamp Failures

Reduce the supply voltage.

Check your phase to neutrel & neutrel to earth voltege

Neutral-to-earth is not relevant!

The earth conductor is there for personal safety.

if neutrel coming from dg or transformer is not of accurate value then what

how can you differ earth and neutral .Neutral is also a type of ground earth.as you see in transformer which is star delta connected we not use only neutral creted by star connection but with that neutral we also connect grond earth

GA from me...

Still not slacking Mr Slack!

There are many differences, check this CR4 thread on that subject. CJM

Reducing the supply voltage to what level? It's rated voltage is 230V. We are operating at 220V.

Er, simply to the voltage at which excessive failures do not occur!

then why rated voltege is given on lamp

So that the user can match the rating of the lamps to the voltage of the supply.

Thats what my doubt, it is rated at 230V, still we are operating at 220V. Simply we can not reduce it and check on trial & error. There should be some rule or caluculation.

Check #9 first.

voltege flactuation and not proper fitting may cause failure

Yep. Another thing for CHARAGONDLA to check!

Mr.Pandit & Mr.PWSlack,

Thanks for your suggestions! Infact these are all basic points to check the failure of any bulb. Other than this is there any thing special precautions we have to take for the UV Lamps?

The manufacturer probably advises not to touch the glass envelope of the UV lamp, as perspiration from the hands can potentially shorten the life of the lamp. So they should be handled carefully, perhaps with a piece of the plastic bubble-wrap they are supplied with?

Good point you rised Mr.Slack. But it is not supplied with bubble wraped packing. Just supplied with rectangular corton box.

Then do what the manufacturer says in the leaflet that accompanies them.

Er, PWSlack has no gender.

Where did you put your gender?

Hello Charagondla,

I was in the lamp making business for about 17 years. But from the description, I can not determine exactly what kind of bulb you have described because it is possible that two or three types fit that description.

Can you tell me what kind of UV bulb you talking about? Incandescent, Fluorescent, High Intensity Discharge (HID), or High pressure mercury?

Can you tell me what is the failure mode? Pre-mature end of life? Crack? Damaged electrode (coil or other)?

Can you tell me what the life rating is, compared to what you are seeing?

Can you describe the fixture or operating environment?

I may be able to help, but I need to know the answer to these questions.

I am talking about High pressure mercury vapour lamps

Failure is like intensity coming down below 1000 micro-watt within short period of 5-10 days and Fusing of coil.

We are using these lamps for inspecting the cracks on crank-shafts

Do you switch them on and off during the day? Are they over heating? Could a cheaper, more robust UV lamp do the same job? Is there heavy equipment nearby being used/switched on/off? Have you put a voltage monitor on the supply?

What more can you tell us?

We have practically no useful info from you up to now........

To my knowledge mercury vapour lamps are not used for producing UV. In fact it purposely contains precaution to avoid UV rays coming out of the bulb, by using a borosilicate outer bulb and also a mechanism to deliberately burn up if outer glass is broken.

If you are using UV lamp for inspection, you may find many irritated operators with irritated eyes!!

You also talk of 1000 micro Watts that is 1 milliwatt or 0.001W, This seems to me impossible. Please check and revert.

Please also check the power supply unit. If your power supply unit is overrated than the lamps, they may burnout after a very short period of extra brightness!

It may also be helpful if we know the format and voltages of the electrical source, Wye, Delta, 2, 3, or 4 wire, neutral involved? There are possibly other issues that can cause this. CJM

The problem is two fold. The UV bulbs that use tungsten filaments run them at a higher then normal temperature and they then have a life of less than 100 hours. They also get blackened on the inside due to tungsten vapour so their output falls over their short life. This type of bulb is also very sensitive to vibration. They are made with quartz glass to let the UV out and it is tinted to block most of the visble. This also exacerbates the problem by keeping in heat. Vibration is also their enemy as they are far more sensitive than common bulbs.

Suggest you use a zinc arc for UV light. or find a fluorescent source

Never ever touch a UV bulb with bare hands. Always use rubber gloves or some such when you're changing them out. Also, if you do not have a surge suppressor at the UV system control panel, get a good one. In my experience, UV bulbs are very sensitive to the slightest voltage fluctuation.

GA back at you , this would also extend the life of the Tungsten filaments types. CJM

Well ...You have received 2 GAs. There must be something I do not understand but you and those 2 understand. My opinion is UV lamp needs a certain operating voltage. When you have 2 lamps in series 2nd lamp will only get half of the voltage. So either it may not work at all or may work at low emission.

Please kindly clarify. I am asking this because I do not understand the logic.

Imagine connecting 2 Fluorescent lamps of 40W either in series or parallel to one 40W choke (ballast)! Joining 2 lamps in series or parallel in my opinion is incorrect as the power supply unit may not be able to cope up and burn.

Its at least 3 people who do not understand the problems fully and are less than capable where electricity and UV lamps are concerned.

Do not worry yourself, "shit happens" as Forest Gump (might have!) said!!

Same problem as with Photo bulbs. Keep them as cool as possible by removing unnessesary covers, venting, or increasing air circulation.

Hi Charagondla,

Can you tell us which type of UV lamps you are using, UV-A, UV-B or UV-C? Are you using ordinary ballasts (chokes) or electronic ballasts? If you are using former switching over to electronic ballasts will definitely help you.

As you also may be aware there are many brands of UV lights. Price difference can be as much as 5-10 times.

We manufacture UV-c Water sterilizers and I can share some of our experience with you.

The usual life of UV bulb is 1000 hours. Every switch on and off reduces its life by 8 to 10 hours.

During the work if bulb is switched on and off then there is considerable loss of life span of bulb.

It is better to switch off the lamp when all work is finished, let it remain on when there is no work. Switch it on at the beginning of the shift and switch off at the end of the shiift.

I'm still unsure of the intended use of the UV lamps. If they are for exposure testing or some other laboratory function (like comparing plant growth rates) then while all the suggestions given may help extend the life of the bulb, you need to monitor and be aware of the ACTUAL output from the lamp.

We run testing with UV type "A" spectrum. Lamps are replaced at the nominated service times and while yes, they are expensive, that's their role in the testing. They are a "consumable" within the process.

If you're not using them for laboratory work, then you still need to consider the trade-off between performance and replacement costs.

OK, a weekend has gone by and the forum still cannot eliminate an extraneous earth connection from the list of possibilities, nor the way the lamp has been handled. It's time to give up on it.

GA from me.....

I use Sankyo Denki-Japan UV bulbs which are rated for 9000hrs. Actually we get more than 9000hrs bulb life. But we change bulbs after 1 year as UV output decline with time and not because of bulb failure.

As you rightly said a ballast that allows to much current will destroy it soon. It also will not give correct emission during that short period.

We also should consider whether UV-a, b or c. Experimenting with unknown can be pretty dangerous which may cause DNA damage and risk of cancer.

Thanks for the tip. I had not heard of LED UV lights. Must investigate to see whether UV-c is available as I am involved in that product. You get a GA from me.