Osram Opto Semiconductors GmbH of Regensburg, Germany says that 19,500 of its Oslon SSL series LEDs have been installed in 975 lamps in the 63.1km2 Xishan Duerping coal mine in Shanxi Province (China’s ‘home of coal’). Replacing traditional fluorescent lamps, the LED lamps enable energy savings of 61% (from 427,050kW-hr down to 170,820kW-hr annually), as well as reducing maintenance requirements and accident rates significantly, the firm reckons, resulting in an annual saving of more than RMB220,000.
Osram Opto notes that, as a low-reflectivity, low-contrast, high-temperature and highly corrosive environment, the underground coal mine is one of the most difficult lighting applications. But, with the use of LEDs in place of traditional incandescent lamps, coal mine lighting has become less challenging.
The 20W LED lamps come in two designs: round-shaped ones for general lighting in the underground coal mine; and square-shaped ones are for long-distance lighting inside the tunnels. Because of the low reflectivity in coal mines, the output of light sources needs to be much higher. With a luminous flux of 104lm (warm white) to 130lm (cool white), the Oslon SSL LED suits this application, reckons the firm.
“We have chosen Osram’s Oslon SSL LEDs for their high reliability and efficiency,” says Zhong-hua Li, chairman of Shenzhen General Technology Co Ltd, which makes the coal mine lamps. “More importantly, the light output of these LEDs is high enough for good designs. The average luminance is 82 lux, compared to 45 lux of the previous incandescent lamps,” he adds. “With the use of advance optics, we are able to reduce glare to a minimum in this low-contrast environment.”
In addition, the Oslon SSL LEDs include coal mine safety certification, explosion-proof certification, salt spray and waterproof testing, impact testing and 1000-hour burn-in testing.
“The use of LEDs in coal mine lighting is definitely taking off,” reckons Kai-chong Cheng, senior marketing director APAC at Osram Opto Semiconductors Asia Ltd. “These are the most compact 1 W LEDs on the market,” he claims of the Oslon SSL LEDs. “As LEDs do not use any glass envelope and cannot break, we hope the use of these LED lamps will reduce hazards for the people who work underground.”
Also, compared with up to 3000 hours for an incandescent bulb, the LEDs can provide useful light in excess of 50,000 hours of operation, reducing the maintenance interval from once every three months to once per year. According to a study by the USA’s National Institute for Occupational Safety and Health (NIOSH), most accidents (53%) happen during the maintenance and repair work of light bulbs or light fixtures. The longer life and glass-envelope-free packaging of LEDs can hence reduce exposure to these hazards, it is reckoned.
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