Chapter Corner

Is the Lamp in Your Metal Halide Luminaire a Safety Concern?

Posted in: Features, May/June 2017

shutterstock_lights.jpgA recent fire that engulfed an industrial site in New York is said to have been caused by the ignition of highly-combustible cardboard. One hundred members of the local fire department responded to the blaze, which had caused the roof and some of the walls of the building to collapse. The fire quickly took over the six-block-long building and prompted the authorities to issue a shelter-in-place order for all nearby residents. What caused the ignition of the cardboard? The failure of a single light bulb.
 
Metal halide lighting, a popular form of high-intensity discharge (HID) lighting, is commonly used as the light source in high bay luminaires located in warehouses and factories. Over time, the strength of a metal halide lamp decreases; and all lamps eventually fail. Failure comes in two forms:

1. The lamp will no longer ignite when powered up by the ballast.
2. The lamp will suffer from non-passive failure. Non-passive failure happens when the tube inside a lamp explodes.

Metal halide lamps contain high-pressure gases in the arc tube. In the case of non-passive failure, the pressurized arc tube within the lamp causes the explosion. When the arc tube explodes, molten glass can fall from the fixture, which presents an obvious issue if a fixture is installed above flammable materials. This risk can be reduced if the high bay luminaire is enclosed, but fixtures are often left unenclosed; we call these open fixtures. Open fixtures that experience non-passive failure will rain molten glass down and out, potentially leading to serious damage.

There are multiple factors that can cause the non-passive failure of a metal halide lamp. Two of the most common reasons for non-passive failure are use of the lamp beyond its rated life or the lamp not being cycled through the proper on and off periods. Both causes are seemingly inevitable. While the lamps could be monitored for these two issues, very few facilities actually keep track of them. The reality is this: While the causes of non-passive failure go beyond these two reasons, even managing these two risk factors is usually infeasible. If that is the case, then what can be done?
 
Start by Performing a Simple Safety Check
Determining if a high bay fixture with a metal halide or a pulse start metal halide lamp is safe is as simple as 1-2-3. Start by performing a quick and easy safety check to ensure you and your property are protected.
 
If any of the following is true, your high bay fixture is safe:
 
  • The high bay has a glass or acrylic lens.
  • The lens will stop molten glass from falling after a non-passive failure.
  • The mogul socket that holds the lamp is pink. If the mogul socket is pink, it will only accept an open-rated lamp.
  • The lamp in the fixture is an open-rated lamp. Open-rated lamps are designed for open luminaires and are designed to prevent non-passive failure.
Don’t be remiss. Be sure to inspect all luminaires with metal halide lamps today. These simple checks will ensure that a non-passive failure doesn’t injure your team members or destroy your facility.
 
Preventing Non-Passive Failure
What should you do if you identify luminaires in your facility with lamps
that cause non-passive failure? Combine the following two procedures,
which are recommended when using any metal halide fixtures.
 
  • Institute a program to properly cycle metal halide lamps. Completely shutting off all metal halide lamps for 15 minutes every seven days is essential. Even if the establishment requires round-the-clock performance, metal halide lamps must be cycled.
  • Establish a schedule to group relamp. Document when metal halide lamps are installed and replace the lamps before the end of their rated lives. Replacing all lamps before the end of their lives helps mitigate the aforementioned safety concerns. An easier way to ensure safety and compliance is to group relamp the facility and immediately schedule a time in the future for the next group relamping.
 
If you are already preventing non-passive failure by properly cycling lamps within the required on and off periods and by following an appropriate relamping schedule, here are other ways to effectively prevent non-passive failure:
 
  • Enclose the fixtures. Depending on availability of parts, it may be possible to add acrylic or glass lenses to your existing high bay fixtures. A lamp that suffers non-passive failure in an enclosed luminaire will not be as harmful as one in an open fixture.
  • Change all sockets to open-rated sockets. Open-rated sockets are pink and will only accept protected metal halide lamps that contain quartz shrouds to keep hot particles inside the lamp. If the socket is pink, the lamp installed in the socket is not susceptible to non-passive failure. In the event of a non-passive failure, the explosion remains contained in the lamp. The lamp will need replacement, but the facility will remain safe.
  • Replace metal halide luminaires with LED. LED high bay luminaires may be a better and more permanent solution. LEDs eliminate the risk of non-passive failure. LED high bays also reduce energy use, eliminate maintenance, and improve visibility.
 
To learn more about which lighting technology used in high bay luminaires is the best choice for your application, check out “Which Industrial Warehouse Lighting Technology Should You Choose: T5, PSMH, or LED High Bay Lights?”
 
Access Fixtures offers factory direct commercial, industrial, hospitality, and sports lighting for less. Access Lighting features light fixtures with LED, induction, PSMH, and fluorescent light sources. With custom manufacturing capabilities, Access Fixtures builds luminaires and poles to the performance specifications our
clients require. Luminaire types include wall packs, area lights, bollard lights, garage lighters, vandal resistant  lights, exit and emergency lights, high bays, low bays, and vapor-tight luminaires.
For more information, visit Access Fixtures at www.accessfixtures.com.