Maintenance principles of lighting equipment

The illumination of lighting equipment initially declines gradually over its lifespan due to: (1) the gradual attenuation of the output of the bulb (tube); (2) the accumulation of dirt in the bulb (tube), lamps and interior decoration. If the illumination decreases by 20% after a period of use, it is equivalent to wasting 20% of the lighting electricity bill.

When the average luminous flux wasted due to dust or attenuation of the light output of the bulb (tube) is equal to the cost of cleaning or replacing the bulb, then this cleaning or replacement of the bulb is the most economical maintenance cost.

Many industrial and commercial lighting systems are designed to illuminate the room evenly. The British Lighting Engineering Association regulations in 2000 recommended that the minimum allowable limit of attenuation be less than 80% of the uneven use value. The average use value is set for lighting design purposes and is the average value required over the entire lifespan. It varies with visual work and indoor conditions. Therefore, before planning maintenance procedures and formulating the most appropriate economic calculations for cleaning and replacing bulbs, it is necessary to first understand the luminous flux attenuation rate.

Sufficient life test data shows that most light decay curves are non-linear for dirt and bulb (tube) light output, because the initial luminous flux loss caused by the combination of dirt and light output decay is often two or three times the average loss rate. Therefore, if after 10 months, the total decay of light output is 40%, and the monthly average rate is 4%, the decay in the first month will be about 10%.

In fact, the design lumens used in lighting design have taken into account the impact of bulb (tube) output decay. For example, discharge lamps normally use a value of 2000 hours, which is equivalent to the average light output of the bulb (tube) in the first 5000 hours of use. If fluorescent tubes or high-pressure discharge bulbs can still be used after 5000 hours of ignition, the lighting design lumens should be reduced by 2% to 4% for every additional 1000 hours of use, depending on the type of bulb (tube).