The use of LED sources in the lighting systems of factory plants represents a major step forward in the field. In addition to guaranteeing significant energy savings, LED lighting improves the quality of the light output in terms of colour rendering, including remarkable safety benefits, while increasing the productivity of workers.
The technological evolution of LEDs and the design of new lighting fixtures have helped overcome the issues connected with the initial stage of their application, such as, for example, the problems caused by insufficient heat dissipation. However, due to a greater diffusion of innovative technology, new criticalities connected with special situations have emerged. One of these criticalities concerns the installation of LEDs in environments with a high concentration of some kinds of volatile chemicals.
To learn more, we met experts from major LED manufacturers. Our first interview is with Mauro Ceresa from Cree.
“At present – explains Mauro Ceresa – there are two factors that can damage or shorten the lifespan of LED sources: electrical stress and a phenomenon that we call chemical incompatibility. The latter is a process that occurs inside the LED and that is caused by external contaminants. Let me explain this in detail.
The structure of a white-light LED (the one used for lighting systems) is made up of a chip that produces blue light, which is covered by a layer of phosphors that converts it into white light, and protected by a silicone encapsulant. This silicone is a special, highly transparent kind of silicone which is particularly resistant to thermal exchanges, extremely stable and does not decay when exposed to UV radiation, guaranteeing a longer lifespan to the LEDs. This silicone, however, is permeable to gas and can be damaged by some chemicals.
What are the substances that can damage a LED?
“High concentrations of volatile organic compounds may alter the silicone inside the LED. At first, we found this phenomenon with several adhesives that were used to seal the lighting fixtures. When LEDs began to be used for outdoor lighting systems, we discovered that some of the sealants employed to ensure water-tightness released volatile organic compounds (VOC) that interfered with the silicone. The intervention of other factors, such as the wavelength of blue LEDs (particularly powerful) and the heat produced by the fixtures, would trigger a phenomenon called discoloration.
This problem has been overcome by subjecting sealants to lab tests to check whether the sealant contains substances that could cause LED light degradation.
The Cree website contains special kits, supplied by our partners, which allow lighting manufacturers to carry out tests to reveal any incompatibility with a LED’s chemical compounds.
Chemical incompatibility can also be caused by a high concentration of particular substances present in the environment surrounding the lighting fixture, such as, for example, in workplaces where particular solvents are used in paintings and coatings. In this case, too, for the LED light output to decay, there should be special conditions, such as a certain level of saturation or a temperature that can accelerate the process.”
How can we prevent these criticalities?
“To make a LED completely impermeable to gas, in theory we need to encapsulate it, as we do with very low power LEDs used in light indicators, but this would impair much of the LEDs luminous efficiency, therefore losing the advantages over traditional sources. The same applies to lighting fixtures that cannot be manufactured with special protections, because they are mostly used in environments where these problems do not exist.
Therefore, the keyword is information and it must concern the entire manufacturing chain.
Manufacturers must equip their fixtures with warnings regarding the possibility that some substances in high amounts can determine these phenomena; and it would also be useful that buyers provide the manufactures with the information necessary to develop any special protections. The issue should also involve other stakeholders, such as designers and installers.
LEDs offer great advantages in the industrial sector and it is important to prevent wrong applications from slowing down the diffusion of such an innovative lighting technology.”
- Posted by Redazione
- On October 14, 2016
- 0 Comments