The fluorescent versus LED debate
17 May 2010
When it comes to selecting light fittings for use in hazardous areas, there is still some confusion over whether users should opt for the latest LED lamps or for the more conventional fluorescent lights. A recent independent report published by the US Department of Energy sheds some interesting light on the debate, says Willi Steckel of Cooper Crouse-Hinds.
Shedding new light on the fluorescent versus LED debate
For many companies, replacing traditional fluorescent light fittings with LED lamps is now a very real possibility. However, when it comes to replacing lamps installed in hazardous gas or dust areas, some of the ‘facts’ about LED lighting can be misleading, particularly in terms of a lamp’s performance, reliability and the availability of replacements or spare parts. End users must therefore be extremely cautious when considering the replacement of conventional fluorescent lamps, particularly in hazardous zones.
For manufacturers of ATEX-certified light fittings, new product development cycles are relatively long. From initial product development through testing and certification and on to final product launch, the process can take anything from 9-24 months to complete. The testing phase alone – which for a light fitting involves extensive temperature, ultraviolet corrosion and impact resistance tests – can be as much as 60 per cent of the total time required to introduce a new product to the market.
Applying for the appropriate ATEX Zone 1 certification is a lengthy process, which requires an independent test body (such as SIRA or BASEEFA in the UK) to approve the application. The independent test body has to verify all the product’s documentation and test reports, and will repeat the more critical product testing itself. Only then is a light fitting considered safe for use in a hazardous area and ready to be certified and launched into the market. For these reasons, any new technological advances that affect hazardous area light fittings should be treated with caution, since any technological advancement or change of component will require the lamp manufacturer to begin the testing and certification process again (or to apply for an amendment).
As a leading manufacturer of light fittings for use in hazardous gas and dust areas, Cooper Crouse-Hinds understands the product development phase better than most suppliers. The company has already invested millions of pounds in the construction of its own LED research and development centre in the USA. Built two years ago, this R&D centre combines the LED efforts of all the various Cooper lighting divisions into one common LED platform, using this know-how to build reliable LED lighting systems and to constantly remain on top of this emerging technology.
However, while LED technology has developed very rapidly and will continue to do so, there are certain areas in which LEDs or solid state lighting (SSL) products are not yet ready to replace all conventional light fittings, particularly when it comes to fluorescent tubes installed in hazardous areas.
A report published by the US Department of Energy (DOE) in October 2009 stated that when it came to 4’ linear replacement lamps, solid-state lighting products "were still not competitive with T8 fluorescent lamps".
The report is based on Round 9 of the DOE’s Solid State Lighting CALiPER (Commercially Available LED Product Evaluation and Reporting) program, conducted from June 2009 to September 2009. In Round 9, 30 products that represented a range of product types and technologies were tested using absolute photometry. All SSL products were tested following the IESNA LM-79-08 testing method. Testing also included measurements of surface temperatures, which were taken at the hottest accessible spots on the luminaire.
The four primary focus areas for testing were downlights; 2’x 2’ recessed and flat panel luminaires; 4’ linear replacements lamps (tested as bare lamps and in 2’x 4’ recessed); and small replacement lamps including 1,000-hour continuous operation test. The report summarised the performance results for each product and discussed the results with respect to similar products that use traditional light sources.
In addition to basic photometric testing, CALiPER periodically performs additional testing that examines dimmability, reliability, thermal management, or in situ performance. Directly applicable published standards are not available for these additional tests, so CALiPER works with standards organisations, industry trade groups and independent test laboratories to explore and determine appropriate testing methods. For example, linear replacement lamps are tested using absolute photometry, both as bare lamps and in situ: installed in typical recesses to determine fixture losses and measured distribution. Also, a limited number of products were selected from each round of CALiPER testing to be subjected to long-term testing. Preliminary results from recent long-term tests are also included in the report.
According to Willi Steckel, Product Line Manager Lighting (IEC) at Cooper Crouse-Hinds GmbH, the DOE Round 9 report has important implications for developers and users of hazardous area fluorescent light fittings. "Over the last four years, there have been conflicting opinions in the press with regard to LED lamps and conventional fluorescent lights. The information being given to buyers ranged from fact to fiction. This is what prompted the US Department of Energy to investigate by starting its CALiPER testing program, which is purely independent and not influenced by any single light fitting manufacturer."
Aside from the DOE report, there are other barriers to companies investing in LED light fittings. Many end users, particularly those involved in hazardous area oil and gas installations, have already invested significant sums of money in conventional fluorescent or HID lamps, which have performed very well, often over many years without failure. For this reason alone, many end users are unlikely to switch to a relatively new technology such as LED straight away, particularly if budgets are tight and the purchase price is so high compared to fluorescent or HID.
"In hazardous areas, the cost of labour is very high," said Steckel. "So users need to make sure that the lighting they use is very reliable. The last thing they want is for a lamp to fail and to have to send in a maintenance engineer to replace or repair the problem. The customer may be very happy with the reliability of their existing T8 fluorescent light fittings and so the risk of changing to an LED version is deemed too high."
Another issue for some end users is simply that LEDs are a relatively new lighting technology, which could indicate a less reliable source of supply. As Steckel explained: "Four years ago, we started developing an LED exit light for hazardous areas. However, during the last four years, we were informed on three separate occasions that the LED components were no longer available due to further technological developments and improvements in solid-state devices. This meant we had to repeat our new product development, testing and certification process three times for the LED exit light."
"By establishing our LED research and development centre two years ago, Cooper Crouse-Hinds is now able to ensure that issues such as these never arise. Through the knowledge and experience gained and by using common LED development platforms, we can guarantee the future compatibility of our products, even as new SSL technologies are developed. On an oil platform or refinery, for example, where many of our CEAG fluorescent fittings are installed, having a future-proof light fitting with readily available replacements, is absolutely critical to the customer’s operation."
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