6 Lamp service life, aging and failure behavior. Osram HQI-E 150 W/NDL CL
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6 Lamp service life, aging and failure behavior
6.1 Lamp service life and aging behavior
All lamp-specific electrical and photometric data are ascertained after operating for 100 hours under laboratory conditions using reference ballasts (according to
IEC). The service life data are determined under controlled laboratory conditions with a switching rhythm of
11 h on/1 h off. In practice, noticeable deviations can occur due to deviating supply voltage, ambient temperature and other general conditions. For metal halide lamps, there can be individual differences in colour from lamp to lamp, caused by external influences such as supply voltage, control gear, burning position and luminaire design.
Unless stated otherwise, the specifications apply to
TS types for horizontal burning position and to T and
E types up to 250 W for base up burning position. For lamps > 400 W, the horizontal burning position applies for the T-lamp. For lamps with 400 W, the burning position depends on the type (as stated in the catalogue).
Should deviating burning positions be used in practice, this could cause changes in luminous flux, colour temperature and service life. The POWERBALL HCI ® with its round arc tube is less critical than conventional cylindrical ceramic tubes.
The economic life is obtained by including the decrease in luminous flux over the service life in the calculation. Multiplying the survival rate by the maintenance of the luminous flux provides the decline in luminous flux of the installation. These factors are considered when preparing a maintenance schedule according to EN12464 (see also 7.5 Maintenance of
lighting systems with metal halide lamps).
Data on lamp survival behavior and luminous flux behavior can be found in the corresponding Technical
Information.
One main reason for the reduction in luminous flux is blackening of the arc tube by electrode material which has settled on the tube wall throughout the service life.
Frequent switching, overload operation, use in confined luminaires or high ambient temperatures can add to this blackening process and thus clearly reduce the service life. Operation at reduced wattage also causes increased tube blackening, as explained in chapter 5
“Reducing the wattage of high-intensity discharge lamps”.
6.2 Storage of metal halide lamps
The luminous flux is generally independent of the ambient temperature itself outside the luminaire. However, too high ambient temperatures can cause increased arc tube blackening in the long run. Also, special ignition units are required for lower ambient temperatures down to approx. – 50 C°. HQI ® -2000 W lamps with integrated auxiliary discharge are only permitted to – 20 °C.
Incorrectly stored lamps (e.g. damp and warm) may suffer corrosion on the contacts after a while; this oxidation must be completely removed before the lamps are used. In unfavourable conditions, this may even result in ignition problems. Lamps with filler material may lose this filler material if stored incorrectly and the socket contacts may then become exposed. There is a risk of arc-overs during the ignition process or the risk of touching live parts.
For measurement of the electrical, photometrical and colour characteristics, HQI ® -TS and HCI ® -TS lamps shall be operated within a luminaire simulator. Details on luminaire simulator (Quartz tubes around the lamp) for determining the lamp data for HQI ® -TS and HCI ® -
TS can be found in IEC 61167, Annex B.2.
6.3 Failure mechanisms of metal halide lamps
The following failure mechanisms are possible for metal halide lamps and the probability increases as the lamp gets older.
• Leaking arc tube
• Increase in re-ignition peak, fi nally the lamp goes out
The mean service life stated in the documents (B50 value) is the burning time within which maximum half of the lamps can have failed, i.e. the survival rate at this point in time is at least 50%. This is a value normally indicated by all lamp manufacturers. Apart from the B50 value, it is also common practice to indicate the times e.g. at which 10% or 3% of the lamps failed (B10 or B3).
• Broken leads
• Leaking outer bulb
Mean service life (B50): max. half the lamps have failed.
• Ignition failure
• Breakage or wear of the electrodes in the arc tube
Economic life: on account of the decrease in luminous flux and the increasing failure rate, the illumination level of the installation has fallen below a required value.
• Scaling of the base contacts by arcing in the socket
• Bursting of the lamp
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