Industrial buildings, like all workplaces, require well-planned lighting systems to support various activities. Industrial lighting is where the necessity of light meets the challenges of environment, dirt and practicality. Mounting and ceiling heights vary from close-in task lighting to out-of-the-way locations 20mtr or more, above the floor. Moreover, lighting costs are critical, and there is an expectation of efficiency in every way. While hardly glamorous, industrial lighting is a demanding design problem. One has to answer various issues related to lighting quality, Lighting quantity, Lighting Efficiency, Luminary arrangement and Lighting controls. The article is an attempt to highlight these critical factors while designing Energy Efficient Lighting for an Industrial application.

Lighting quality

Appropriate quantities of light are essential, but“Lighting Quality” issues are just as important in providing a comfortable and safe working atmosphere. When the lighting meets both quantity and quality needs, it adds measurably to worker performance and productivity. Various industrial operations have various LUX requirements. These are specified in the related IS standard. However, using conventional HID lighting, maintaining the lighting level according to these IS standard is extremely costly. (Sometimes it is costlier than the lighting cost itself). It is more prominently observed at many industrial segments where roof height is more than 8 metres. Some of the important quality issues for Industrial Lighting are tabulated in the next page.

Quality lighting contributes to the comfort productivity of the personnel working in manufacturing / warehouse facility. It also contributes to their safety especially around moving machinery. Glare control, balanced brightness, no flicker, minimum shadows, long life and sustained lighting levels must be taken into account to ensure safety and security in the work place. Outdated HID lamps are poor at colour rendering. A high CRI (more than 75) will allow people to see colours accurately and work in a comfortable environment. Abilty to see the objects is based on several conditions including the age of the worker @ 40 year old person needs double the lux than a 20 year old person. The size of the task and the speed of the task also change the lighting requirements dramatically.

Lamp efficiency

Lamp efficiency is measured in Lumen per watt (Lm/w). Various technologies offer different levels of Lm/w. Every designer tries to use maximum efficient lamps. (e.g. LED, T5 etc.). In this effort to make the design optimised by Lm/w, other important parameters are often compromised. Lighting efficiency is not the only point of importance.

Some of the important quality issues for Industrial Lighting are tabulated below…

Using HID lamps is a current standard practice for industrial lighting. Although the efficiency is improved by various other technologies, taking a closer look, it shows that they have faster lumen decay, which means faster re-lamping in order to up keep the lighting levels.

One has to select the lighting source depending on the operating conditions in the workshop. They are very sensitive to ambient temperature, which affects the lamp life very badly. Lighting quality with respect to colour shift, drop in CRI, flickering etc are also affected by the ambient temperature. In case of heat processes the ambient temperature is much higher and it is still higher at the roof area, where the lamps are actually mounted. Similarly, the dust deposition on the luminaries, heat sink and other parts of the lamps reduces the efficiency. Overhead crane operators often have to look upwards. If a very high glare lamp is mounted, it would make the operator blind and can result in a serious accident. There are other important factors that would change as per the industry type and operations being done there. Hence Lumen / watt is not the only criteria for selection of the lighting technology for Industrial application.

Lighting arrangement

Lamp arrangement is equally important as it would decide the uniformity of the light on the workshop. Due to various overhead structures like, air vents & pipes, Cranes, cable trays, utility lines, there are many obstructions to the light. While in design stage these structures are often not available or ignored. (as lighting is the last item on priority !!) Hence lamp locations are not synchronized with such structures resulting in un-uniform lighting. Selection of lamp model based only on electrical or efficiency related information also leads to the dark and light patches on the workshop. Lamp –photometry is very important as it decide the number of lamps, location of lamps and wattage per lamp.

Existing workshop: 400 W /lamp, Lux level = 90-120 Lux…
New workshop: 200 W /lamp, Lux level = 200-250 lux…

Lighting controls

Right amount of light when and where required is important.

When an area is not in use, reduced light levels would save a lot of energy. With modern techniques there are several ways of doing it. Occupancy sensor, automatic or equipment driven internal timers, diming controls etc. Simple technique such as forming proper well thought control groups according to the work station (instead of ease of wiring!) is important. A user friendly lighting control can be done by dividing the workplace according to usage area (High usage, low usage etc.) and forming these control groups to align the on/off switches accordingly. Occupancy sensors are very effective in warehouses, storage areas and other less used areas.

Induction lighting technology, explained on the next paragraphs, provide very well satisfactory answers to all the points mentioned above. It is best suitable for industrial lighting applications due to its unique features such as long life, extremely low lumen decay and a stable performance under varied environmental conditions. Coupled with excellent electrical properties (Lowest THD, High Power factor, no noise generation) Induction lighting is the ideal solution of Indian industrial conditions.

Existing Lighting 250 Watt / lamp, Lux Level = 90-100 lux…
Induction Lamps 150 Watt / lamp, Lux Level = 180-200 Lux…

Now see, some case studies from variety of industries where these issues are resolved using Induction Lighting.

1. Castings plant

Existing Lighting Conditions (Before the changeover to IL) : Use of 250 W and 400 W HPMV lamps, Lighting levels 60 to 90 much below the standard requirement. Frequent failures of lamps due to heat treatment process.

Challenges – Maintenance of lamps at 12 mtr++ height, Lux level of 100 – 150 to be achieved with minimum electricity cost and investment.

Solution – 240 pcs Induction lamps of 150 W & 200 W used to replace 300 pcs of 250 W & 400 W HPSV / MHL lamps. Scheme designed to give Lumen considering type of work in each section.

Results – Freedom from lamp replacements for last 4 years, desired Lumen achieved with 30% energy bill saving, paradigm shift for foundry ambience.

Comments by user – “I have never seen a foundry with such good lighting in last 25 years of experience“

2. Small parts manufacturing plant

Challenges – Improve visibility in shop to enable inspection of dark coloured pressed parts, lot of localised task lighting giving uncomfortable vision due to high contrast spots.

Solution – 25 Induction lights of 150W replaced 25 Metal halide lamps of 250W.

Results – Average illumination levels doubled (100~150 changed to 200~400), localised task lighting eliminated, eye comfort for operators, easy for inspection.

Comments by users – “Now we can work without eye strain and output quality as well as volume improved.“

3. Forging plant

Challenges – overcome variation in lumen across shop caused by varied life point of exiting lamps. Achieve across shop 250Lumen lux, reduce glare.

Solution – 100Induction lights of 200W replaced 100 Metal Halide lamps of 400W.

Results – Uniform lighting of 250 Lumen with no fringes, Lighting load reduced from 40 to 20 KwH, Saving of 4.3 L /A, Freedom from Glare and maintenance

Comments by users – “Very comfortable lighting, we can see micrometer reading more clearly and there is no glare from machined job making inspection very easy.”

Satish P Nanadikar
Deputy General Manager
Mahindra CIE Automotive Ltd