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Here we answer the questions that we are often asked about BlueLine NDT's blue light solutions for fluorescent magnetic particle and fluorescent liquid penetrant inspection.
How do the BlueLine lights work? BlueLine NDT's blue lights work the same way that ultraviolet lights do - they make the fluorescing material, whether mag particle or penetrant, emit fluorescence. Instead of using wavelengths of invisible ultraviolet radiation, though, they use visible blue wavelengths. Where do the BlueLine lights come into the inspection process? You use the BlueLine lights to look at the fluorescent indicating material you have applied to the surface to be inspected. Does anything about the inspection process change beside the light? No. No. How intense are the BlueLine lights? The BlueLine lights produce far more than 1,000 microwatts per cm squared at 18". Whether this is sufficient to make the fluorescent indicators glow brightly enough will depend on the indicator. BlueLine is measuring the fluorescence properties of existing magnetic particles to determine whether they will work well with the BlueLine lights. How can the blue light intensity be verified? BlueLine offers the BLR-1 Blue Light Radiometer that measures the blue light intensity in radiometric units (microwatts per cm squared), similar to the meters used now with UV lights. Do the BlueLine lights work with all fluorescent magnetic particles and liquid penetrants? We haven't checked every single one, but so far the answer is yes. We recommend that you test the light in realistic conditions to be sure that the lights will give you the results you need. So far, though, we have not found any indicators that the lights don't work with. Can you use the blue light to photograph indications? Yes, and BlueLine offers a customized Fluorescence Photography System. Will any source of blue light work? Any blue light has the potential to make things fluoresce, but that doesn't mean they are good for the job. BlueLine starts with carefully selected high intensity LEDs and then adds a custom made interference (dichroic) filter. This trims the wavelength output so that the lights work in combination with the BlueLine yellow filter glasses to achieve the high contrast needed for quality inspections. Do you have to use filter glasses when you work with the blue light? Yes. When you illuminate a surface with intense blue light a lot of that light can be reflected back to your eyes. If you don't block it from reaching your eyes it will degrade or destroy the contrast between the indication and the background that you need for good inspection performance.
Do you have to use the BlueLine yellow filter glasses? Yes. The BlueLine filter glasses are carefully selected to work with the BlueLine lights. If you use just any yellow glasses (shooting glasses, blueblockers, etc.) it is possible that you will have either reduced fluorescence intensity or reduced contrast. To avoid this, use only the filter glasses supplied by BlueLine.
How can I be sure that I am using the right glasses? The BlueLine filter glasses are clearly imprinted with the BlueLine NDT name on the right earpiece.
Are the BlueLine filter glasses certified as safety glasses? Yes, all the filter glasses conform to ANSI Z87.1 impact standards. Do indications look any different under blue light? As long as you use the yellow filter glasses, no. They will look the same as they do under ultraviolet. How often do I have to replace the bulb? The BlueLine lights use high intensity light-emitting diode (LED) technology, not bulbs. LEDs will not break if dropped, and should not ever burn out in normal use. LEDs do lose some portion of their intensity over time, but will provide years of use. Do the BlueLine lights contain any hazardous substances? No. There is no mercury or any other hazardous substance that could be emitted from the light under any circumstances. Do the BlueLine lights conform to existing standards? If a standard specifically calls for the use of ultraviolet light then the answer is no. We are working on having the standards modified to allow the blue lights, but that will take some time. Do not simply substitute blue light for ultraviolet if you are working to specifications that do not permit it. For more information click the CODE link here or at the top of any page. If the lights don't conform to standards, how can you use them? There are several ways that you can make use of the lights immediately: Dual-use mag particles
Informational inspections
Inspections conducted according to in-house standards
Does the blue light cause contrast-reducing fluorescence within the eye? BlueLine's blue lights would produce even less fluorescence in the eye than ultraviolet. But since you do inspections looking through the blue-blocking yellow filter material, none of the blue even reaches your eye to cause fluorescence. How much white light leakage is there? This is a common question because there is a specification for allowable visible light leakage from ultraviolet lights. This question doesn't really make sense for the BlueLine lights because ALL of the light coming out is visible, blue light. The true issue, though, is not how much visible light is reaching the surface, but how much visible light that is not coming from the indication reaches the eye of the inspector. It's about viewing contrast. If an ultraviolet light leaks too much visible light then both the fluorescence AND the visible light leakage will reach the eye, and the leakage reduces the contrast of the fluorescence. In the case of the BlueLine blue lights, the yellow filter glasses prevent the intense blue light that reaches the inspection surface from reaching the inspector's eye to reduce contrast, while still efficiently passing the wavelengths of the fluorescence emission. The result is that indication are seen in high contrast, without interference from the visible radiation emitted by the light source. Do you have to do fluorescence inspection in the dark with the BlueLine lights? It is always true that a darker environment helps to see fluorescence. But the BlueLine lights will greatly enhance the visibility of dual-use magnetic particles even in well-lit environments. The blinking capability of the BlueLine FL5000 enhances the detectability of fluorescence of any indicator even further, especially in the presence of ambient light. How does the BlueLine flashing mode help you see fluorescence in ambient light? The flashing mode takes advantage of two aspects of human vision. One is that we notice flashing lights more easily than we notice steady lights. This is why all sorts of lights for warning applications blink - like police cars and road hazards - and why flashing text on a web page catches our attention. The other is that a short pulse of light appears brighter than a steady light of the same absolute intensity. These two factors combine to make the flashing a powerful tool for finding fluorescence when there is ambient light. As long as the excitation source and the blocking glasses are well matched, as they are with the BlueLine products, then as you scan the flashing light over a surface any flashing you see comes from something that is fluorescing. There are limits even to the power of the flashing to overcome ambient light, but even if you are in bright sun you can generally work successfully just by casting a shadow over the area you want to inspect. You can do this by using your body, your hand, a clipboard, or a co-worker. Are the blue wavelengths safe for your eyes and skin? Yes, the blue wavelengths are safe unless you stare directly into the light without the filter glasses on. The blue light is very intense and it would cause an afterglow if you looked right into it even briefly, but that is not dangerous. How careful do you have to be with the lights? The lights are rugged and there should be no damage even if dropped from a reasonable height (although we don't recommend doing this). The BlueLine lights are completely sealed against normal environmental exposure, and most models can even be used up to 500' underwater. Contact BlueLine NDT by telephone or e-mail if you need more information about our blue light inspection technology.
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