The following is from GE Lighting for their 400 Watt Metal Halide Lamps:
"CAUTION: THE FOLLOWING INSTRUCTIONS MUST BE COMPLIED WITH TO HELP AVOID POSSIBLE SHATTERING AND EARLY FAILURE OF THE LAMP."
General Electric Company will not be responsible for poor lamp performance, personal injury or property damage resulting from failure to follow these instructions.
Metal Halide lamps are constructed of an outer bulb with an internal arc tube made of quartz. The arc tube operates under high pressure at very high temperatures (as high as approximately 1800ºF). The arc tube and outer bulb may unexpectedly rupture due to internal causes or external factors such as a system failure or misapplication.
– Lamp must only be operated in specified burning position with compatible electrical equipment in the types of fixtures prescribed in the applicable specification bulletin. Fixture lens/diffuser material must be able to contain fragments of hot quartz or glass (up to 1800ºF). If in doubt, contact your fixture manufacturer.
– Electrically insulate any metal to glass support in fixture to avoid rupture of the glass.
– Protect lamps from direct contact with liquids (such as rain, sleet or snow) to avoid breakage from thermal shock.
– In continuously operating systems (24 hours/day, 7 days/week), turn lamps off once-per week for at least 15 minutes. Failure to comply increases the risk of rupture.
– Screw lamp firmly but not forcibly into the socket to minimize loosening due to vibration. Do not use excessive force as the glass bulb may break.
– Do not scratch glass bulb, because it may break during installation or during operation.
– Turn power off and let lamp cool before removal to avoid potential burn and electric shock hazard during lamp replacement.
– Relamp fixtures at or before the end of rated life. Beyond rated life, light output diminishes while energy consumption and risk of rupture increase.
LAMP OPERATING CHARACTERISTICS – This is a discharge lamp and requires some time to restart and come to full brightness after a power interruption. For total load, add auxiliary watts to lamp watts. In service, color variation from lamp to lamp is an inherent characteristic of metal halide lamps. It is further influenced by variations in operating conditions and is not an indication of system or lamp failure. As lamps age, a gradual shift to a warmer color normally occurs.
– If outer envelope of the lamp breaks or is punctured and lamp continues to operate, immediately turn power off and remove lamp after it has cooled.
The following is from GTE for their 400 Watt Metal Halide Lamps:
In November 1985, GTE's lighting business revised its warnings for Sylvania Metalarc lamps. The warning advised the end user of the potential danger of operating metal halide lamps in open fixtures and REQUIRED enclosure under every circumstance to prevent the possibility of personal injury or property damage caused by arc tube rupture. The revised warning also advised the user of the inadequacy of the standard for determining suitability of enclosure materials.
During the past five years, GTE has continued to address this issue. It has taken a leadership position in educating the industry, regulatory bodies and end users regarding the precautions to be followed to minimize the risk of injury or damage and to reduce the possibility of arc tube rupture.
Another important action taken by GTE was the development of new Sylvania Metalarc lamps that can be used in open fixtures. These lamps were specifically designed for those fixtures where enclosure is impractical and are called the Sylvania MP Metalarc lamp.
A third action taken by GTE was to strengthen its operating instructions for metal halide lamps advocating the replacement of lamps that have operated for rated life. In addition GTE recommends that end users cycle lamps once a week by turning them off for a minimum of 15 minutes.
As a result of our action and in concert with regulatory and industrial organizations, the standard for enclosure suitability has been revised. Today, new lens/diffuser materials are available from fixture manufacturers, which have been designed to contain hot glass particles resulting from an arc tube rupture. The standard for determining the suitability of these materials is contained in UL1572, revised December 26, 1988.
Because of these leadership actions and five years of monitoring the performance of Sylvania Metalarc lamps, GTE is revising its containment policy.
For certain applications where the customer decides the associated risks are sufficiently remote to not justify the additional cost of the MP Metalarc lamp or fixture enclosure, they may now elect to operate the Sylvania 400 watt and 1000 watt Metalarc lamp in an open fixture. Where an extra measure of safety is desired, the customer can use the Sylvania MI Metalarc lamp or in specific applications, may choose a fixture that is suitably enclosed.
We will be revising our lamp warning notice and catalog information to reflect this change in policy. A copy of the revised warning notice is attached for your information. Let me assure you of our continued dedication to meeting the high standards of quality and safety that we have set for all our products.
This Metal Halide lamp is constructed of an outer glass bulb with an internal arc tube made of quartz. Metal Halide arc tubes operate under high pressure (up to 50 psi) and at very high temperatures and can unexpectedly rupture due to internal causes or external factors such as a ballast failure or misapplication. An arc tube rupture can burst and shatter the outer glass bulb resulting in the discharge of glass fragments and extremely hot quartz particles (as high as 1832ºF, 1000ºC). In the event of such rupture, there is a risk of personal injury, property damage, burns and fire.
This lamp may be operated in any burning position. When this lamp is operated more than 15 degrees off the vertical position it must be operated in a suitably enclosed fixture.
A suitably enclosed fixture uses lens/diffuser material able to contain fragments of hot quartz or glass (up to 1832ºF). Enclosed fixtures which comply with UL Standard 1572 (revised December 26, 1988) should withstand an arc tube rupture. If you do not know whether the enclosure in your fixture can safely withstand an arc tube rupture, contact your fixture manufacturer.
To reduce the risk of personal injury and property damage as described above, especially when used in open fixtures; the user must follow the proper care and maintenance instructions in section IV.
To further reduce the risk of personal injury and property damage resulting from an arc tube rupture occurring in an open fixture, and depending upon the application and operating environment, Sylvania recommends the use of a suitably enclosed fixture or the use of an "MP"/"MPT" lamp. For example: If the lamp is located near flammable or combustible material, a suitably enclosed fixture or "MP"/"MPT" type lamp is recommended.
Sylvania "MP"/"MPT" type lamps have an internal shield designed to contain an arc tube rupture and are commercially available from GTE Products Corporation.
PROPER CARE AND MAINTENANCE:
To reduce the possibility of an arc tube rupture and optimize lamp performance:
1. Operate lamps only with compatible equipment (ballast, starter, capacitor and socket).
2. Turn lamp off for a minimum of 15 minutes at least once a week.
3. Replace lamp at or before the end of rated life.
4. Protect lamp from contact with liquids and moisture.
5. Replace lamp if outer glass bulb has been scratched, cracked or damaged in any way.
6. Electrically insulate anything in contact with the outer bulb to avoid glass rupture.