UV Light Bulbs

<...change the bulb every now and then coz the UV lighb bulb actually have a life span. why?...>

To maintain a level of biological resilience that the supplier can warrant as safe.

Would it be acceptable to wait on the old bulb until the protection level was low enough to make someone ill, before replacing it? If so, whose fault would it be <rhetorical question>?

Thanks for the advice and yes, definitely changing the bulb is a must in order to protect me and my family's health.

The question I have is, why will it degrade? what is the physic behind it?

Over time, the filament will age and parts of it will evaporate and migrate to elsewhere in the envelope. So the resistance of the filament will change, so the current through it will change, so the light output from it will change.

Thinner filament means more electrical resistance, which means less current, which means less light.

The next time the lamp is changed, compare the difference in outward appearance of the new lamp and the old lamp (obviously with the power turned off!). It is not uncommon for a metallic stain to deposit itself on the inside of the glass envelope close to the filament over time. The material was when new part of the filament. This stain indicates the lamp is in less-than-optimal condition, and in itself also presents an obstruction to the passage of light.

Just a small question. You mention degradation of the filament. I am not a EE and I have only seen UV bulbs that look like fluorescent lamps. Are there physically filaments in the tubes as in incandescent lamps?

Yes, fluorescent lamps have filaments (coils) used to act as an electrode between the gas plasma and other conductors. The filament also supports a quantity of emitter that reduces the work function of the lamp (makes it more efficient) by emitting electrons into the buffer gas and plasma.

The fluorescent blacklights that use a powder coating on the inside are not suitable for killing germs. They emit mostly a lower frequency UVA with a little UVB. The type of glass used filters out any UVC in this application.

Fluorescent lamps that are used in germicidal applications and for erasing memory in an integrated circuit use a type of glass that permits UVC to be radiated. They will have no powder coating. The glass appears to be clear. They are harmful to human tissue and eyesight if they are intended to emit UVC.

This sounds like it may be a good application for UV LED's.

Do you know the lumen output of the bulb?

UV LEDs are just over the visible spectrum. In fact they are not UV, they are Violet, ventered at 405 to 406 nm (Visible light is considered to end somewhere at 400 nm). Anything lower than 370 nm will have no chance at passing through the PMMA housing of LEDs. Normal glass would cut off around 300, and silica (pure quartz crystal glass) I believe starts to significantly cut off at 220 nm well in the UVC band as I remember.

This is why plastic sunglasses offer the best protection for your eyes, but with the worst picture clarity unfortunately.

At the moment, solid state electronics have not produced an efficient enough device, or one with a long enough lifetime, that emits in UVC. The GaN ones (blue/violet Leds and lasers) were a huge breakthrough in 1998, and we are just starting to witness the effects of it.

In terms of intensity, I am sure that one could couple a few hundreds of diodes or a few tens of laser diodes in and get to some good levels.

Saying that, people have always suggested UVC as the best band to work in because each photon will do its job quick and easy in ionising. Considering the last post about entropy, I am not sure if anyone has tried really intense blue light on smaller amounts of water flow to see the results.

Good Luck!

Do you know if uvc light is safe for human or not? UVC light is recognized that it is useful for disinfecting coronavirus.

That question is worth a phone call to the manufacturer.

http://www.uvcomparison.com/uvscience.php

Nice website for your answer.

There are methods and devices for measuring the effective output of UV lamps. These devices are used for calculating the amount of time, based on output intensity, necessary to erase UV Eraseable memory devices so they can be reprogrammed. This is not the same spectral frequency as the filtration application.

If there is a simple method of testing the affect of the UV lamp of the filtration system you would know when to replace. For example seeing how long it takes to make a change in a controlled water sample when the lamp is new and later when it is old.

The water flow rate can be reduced to increase exposure time as the lamp gets older too.

A filament in the UV Lamp is a "starter". It is not used after the lamp is on. Over time material from the starting filament can migrate onto the glass of the lamp and affect its ability to shine through. The gases themselves can "wear" and migrate too.

Jon

To sterilize water, the light must be of a fairly wide UV spectrum and of a sufficient intensity to penetrate the water. I haven't researched UV LEDs lately but their intensity is nowhere near bright enough and they certainly don't have a wide spectrum. Remember the most biologically damaging spectrum of UV light is the short wavelength light. Maybe one day LEDs will be capable of producing this. Then someone will go through the steps to prove its sterilization effectiveness. Then and only then will LED sterilizers be available.

While others here have answered the OP question quite well, there is one Physical principle that they used but did not state. That is the concept of entropy. In brief, given only enough time anything will eventually fall apart.

I read everywhere that only UV rays can kill germs. Well, I beg to differ. About a year ago I developed an ugly infection on my right hand. I waited too long to seek medical attention, thinking I could make it go away. Finally, I could not hold out any longer and went to the ER. To make a long story shorter, I made 3 or 4 trips, over several weeks to the ER (due to not having good insurance) and went through almost 3 equal batches of 2 kinds of antibiotics and the infection was still there. I decided to see what was available on the net and discovered 'light therapy'. This little know area of medical research seemed way to simple to be effective but I decided to try it anyway. With 2 days the remaining patch of my infection was dead by shining a violet/blue led flashlight on it for about an hour for the 2 days. The first night, it started itching--first time in 5 or 6 mos. On the 3rd day, the white bubbles that were spreading around my hand were all brown. By then, I had been told by one of the nurses at the ER that I had MRSA--that they had been having quite a problem with it lately. I had also been referred to an infectious disease Dr. also. By the 2nd visit with him, 2 weeks later, he told me the infection was GONE. It had also started spreading under my arm pits. I shined a blue led light on them too. BELIEVE IT OR NOT.

First, I'm glad that you were capable of healing yourself. What you have presented is a classic anecdotal piece of evidence. You have a single incident with many unknowns and conditions. To conclude that blue LED was the root cause of your recovery appears to be specious, at best. Possibly you were exhibiting a mild allergic reaction to one of the two antibiotics that did succeed in killing your original infection. But your body could not not return to its natural non-inflamed condition until the allergen ran its course. Let's not forget that you might have also had a natural spontaneous remission. The human body is a miraculous resilient wonder that nobody fully understands, let alone the foreign bodies that invade it.

Having said that and again reiterating that I'm glad that your health has returned. The UV lamp in this system is designed to kill a myriad of microbe species, not just the ones you were infected with. UV is what this system is designed to use for sanitation. Replacing this lamp with anything other than the identical spectrum levels and intensity levels the design intends is to capriciously change the design.

You would have had to have been in my shoes at the time. I'm not an engineer but do have an advanced degree in psychology, so I understand the power and reasons for things that influence the mind/body connection. I'm not a big believer in miracles. If you had done a brief search on 'light therapy', I think you'd change your tune. It is still a developing technology for valid medical problems. One of its concepts is that violet/blue light is close enough to UV-B (I think its B, as opposed to A) on the frequency spectrum that it kills bacteria also. I had been taking so many antibiotics that it screwed up my gut for the next 9 mos. It was still not killing the bacteria. Then, as soon as I started hitting it with the flashlight it started dying. In 2 days it was all dead--a 2 X 3" patch on the back of my right hand, except that it had traveled to my underarms (I learned a couple weeks later). I hit those spots for 2 or 3 more days and they were gone, except for a little itching. I agree it is anecdotal but I still keep a few of the older blue led flashlights around the house--not because I believe in miracles, just what I witnessed with my own eyes. I think it is pathetic that our medical system can't get a little more creative when people are dying all over the place from bugs that our failing antibiotic system is failing to treat. Flesh eating bacteria and the MRSA. The latter is antibiotic resistent--by name, in fact, yet they still give out the pills. If the they don't work they triple the dose. Logical?

Hi Redfred,

I wanted to check to see what you mean by "fairly wide UV spectrum".

The effective spectrum for bug killing runs from about 2000 to 3000 angstroms (pretty wide) but peaks around 2537 angstroms. So for UV radiation to work best, a 2537 Angstrom units (254 nanometers) is best.
A UV lamp that produces 2537 Angstrom unit wavelength is the one to use. A low pressure quartz mercury vapor lamp. The spectral emission of a low pressure mercury vapour lamp is a line spectra with about 90% of its output at 254nm. The Ozone range peaks at 1849 Angstrom units and this same lamp produces that wavelength as well. Other wavelengths are minimal.

I just read that a 254 nanometer UV LED has been around since 2007. It is good for spot treatment of infections and skin disorders like psoriasis and eczema.

Was it mentioned that U.V. is most effective when the water has been pre-treated with another filtration system because pre-filters remove large particles, water cysts, odors and tastes. These impurities can interfere with the transmission of U.V. energy.

Jon

UV lamps do have a definate lifespan due to the "solorization" of the glass envelope of the bulb that reduces the UV output even though the bulb still produces visible light.The enuelope will turn progressivly darker as the bulb ages.These bulbs can be permanently damaged by touching the glass with oily hands or if any oils are present in the air. These type of lamps are used in ozone monitors and their lifespan is around 2 years of continious use. A blackray meter can be used to check the UV output of the bulb if required.

good answers notyouravderage guy #7, and Dr ozone, #13. When i took over an inspection company it had Magnetic particle inspection equipment. this is used with UV lamp and fluorescent indicator dyes. In school we were told not to turn the UV lamps off and on due to rapid deterioration of the lamps UV output. so just leave them on all day. this bulb had separate starter ballast and a spot light type bulb.

I was also told that the UV is so potent that there is also deterioration in the quartz crystal and that it will eventually turn milky/ cloudy. not sure if this is conductor deposition, it was referred to as the internal quality of the quartz crystal itself.

I changed a 36 inch tube type water sterilizer bulb recently at a food processing plant. I noticed it had a very thin conductor inside the tube going down to the far end of the bulb. at 2 years the seals may have allowed some water vapour to condense inside as the conductor had a small corrosion mark on it. I couldn't detect any other flaws or deposition. out of curiosity if I had the equipment and a safe way of doing it, I would have liked to check UV output on the old and new bulbs.

Could it have something to do with cold cathose ignition?

Jon

Just wanted to add another 'anecdotal' comment. Since I told my story about the blue/violet led light killing MRSA, a company has formed to explore and develop light technologies for hospital sterilization using light frequencies in the 'violet' range, stating they are effective and safer to put all around hospitals than UV systems. Here is the link:

http://physed.org/news/2010-11-technology-combat-hospital-infections.html