Description of Driving Event:
A metal halide high intensity light bulb in the O&C high bay ceiling inadvertently exploded. Glass fragments were spewed to the O&C high bay floor, which was clear of personnel and flight hardware at the time of the incident. The subject light fixture was inspected and cleaned of all debris. Metal halide bulbs are very bright and increase the amount of available illumination by 50%.
The explosion of the metal halide bulb caused concern so the bulb's fragments were collected and sent to NASA's malfunction lab for evaluation. The malfunction lab observed discoloration of some bulb fragments. According to the lab the discoloration suggests that the lamp was reaching the end of its useful life. It is not known what the manufacturer's recommended life for these particular lamps is, but once they reach that particular number of hours, under continued use, they have an increased propensity to explode. In addition, the lab studied the interface area between the lamp bulb and the metal housing, no anomalies were noted.
Metal halide bulbs provide good illumination but require specific mounting hardware for operation.
To protect personnel and flight hardware, all metal halide bulbs should be covered with a lens assembly capable of withstanding the impact produced when one of these bulbs explodes.
Evidence of Recurrence Control Effectiveness:
Several O&C facility support personnel were interviewed regarding the exploding bulbs. One person said protective covers/lenses had been installed to contain the bulb fragments if one were to inadvertently explode. This person said he knew of at least one bulb that had exploded since the installation of the protective covers and said the bulb's fragments were contained with no problem. After contacting several more O&C facility support personnel, no other evidence of additional bulb explosions was found. The last time burnt out bulbs were replaced approximately 125 bulbs had burned out and not one of them had exploded.
Comments: NASA document number SPP 0-01 titled "Shuttle Payload Ground Operations Contractor Standard Practices and Procedures", Section D Requirements and Responsibilities: Tool, equipment, and material control (paragraph #43) states: "Glass is forbidden in/on or over flight hardware unless the glass is equipped with a shatterproof protective cover that will contain all fragments in case of glass breakage. Unprotected light sources are not allowed in/on or over flight hardware."
Documents Related to Lesson:
Additional Key Phrase(s):
- Energetic Materials - Explosive/Propellant/Pyrotechnic