INTRODUCION

LIGHTING AND ILLUMINATION:

Lighting is one of the major uses of electrical energy .Sun is the biggest source of natural light. Where there is no natural light, use of artificial light is made. Artificial light may be electrical or non-electrical. Artificial lighting produced electrically has advantages.

These are given below

Electrical Lighting Non-Electrical Lighting

1. Clean in operation 1. Dirty in operation2. Easy to control 2.Contol is difficult3. Reliable 3. Non-reliable4. Steady output 4. Varying output5. High efficiency 5. Low efficiency6. Low cost 6. High cost7. Less hazardous 7. More hazardous8. Low possibility of fire 8. High possibility of fire9. e.g. LED lamps, fluorescent lamp, arc lamps etc.

9. e.g. candle, oil lamps, fire, fireworks etc.

Electrical lighting is also hazardous but if proper precautions are taken its hazardous and dangerous level is less as compared with the non-electrical lighting.

Definition:

When light falls on the surface, the surface is illuminated and the process is called illumination. I.e. light is the cause and illumination is the result n the surface which it falls. When the light falls upon the surface, the phenomenon is known as illumination.

Colour of object we see:

The sunlight consists of seven different colours namely Red, Orange, Yellow, Green, Blue, Indigo and Violet. When light falls on the object, the object by its quality, absorbs certain colours and reflects one or more. The colour which we see is that which is reflected by the object. Thus, if the grass is green, it is due to the fact that it absorbs all other colours except green which it reflects. The object which looks white reflects all colours in equal proportion.

Importance of lighting safety considerations:

There is some safety factors which should kept in mind while designing, maintaining, locating and installing the lighting system.

The workers working in industry exposes to different types of safety risks due to not taking into consideration of safety factors. The lighting affects both physical and mental level of workers.

Improper Lighting effect:-

1. Eye irritation

2. Headache

3. Reduction in mental alertness

4. Discomfort

5. Reduction in productivity & quality of work

6. Injury to person

Injury Trend Based On Lighting Level:

The fig.1 shown below shows injury incident trend based on lighting level. Illumination level in lux is shown on X-axis while numbers of persons injured are shown on Y-axis. The different types of injuries are shown by different colures like red shows the factures. The general trend shown by black colour shows that as illumination level increases the number of injured person decreases. So lighting safety is very important issue and all precautions related to it should take into account.

Fig.1 Injury Trend Based On Lighting Level

Source: Lighting safety considerations by Mathew F. (IEEE Transactions on Industry Applications)

Before going in detail of lighting safety considerations we should understand some basic terminologies related to lighting.

Terminologies:

Luminous Flux (Lumens): Total quantity of light energy radiated per second.

Illumination (Lux): Luminous flux received by a surface per unit area of surface.

Lamp efficiency (lm/w): Ratio of luminous flux to power input.

Depreciation factor: Ratio of illumination with clean lamp to illumination under working conditions.

Space to height ratio: Ratio of horizontal spacing between two lamps to the height of the lamp above working plane.

Glare and Shadow

Safety Aspects:

Following are the safety aspects which we will see in detail

Lighting Design: - Adequate lighting, glare & shadows, flickers

Maintenance Issues: - Re-lamping, de-energize, environmental factors

Location and Installation:-

Hazardous Locations: - Flameproof & explosion proof lighting, restricted breathing

Maintenance Ergonomics: - Static load, body postures

Indian Standard Code for Lighting

LIGHTING DESIGH

In lighting design topic we will cover adequate illumination, glare, shadows and flickers and their effect on safety of workers.

Adequate illumination:

The purpose of industrial lighting is to allow for adequate performance of visual tasks. The most common question when it comes to lighting design is “How much light is necessary?” Over illumination is as undesirable as inadequate illumination. Adequate lighting will improve productivity of workers and reduce workplace accidents by increasing the visibility of moving machinery and other safety hazards.

Over-illumination:

Definition: Over-illumination is the presence of lighting intensity higher than that which is required for specific work or activity.

Health Effects:-

1. Headache

2. Fatigue

3. Stress

4. Performance effect

The over illumination can be reduced by using low brightness lamps.

The fig.2 shows an over-illuminated industrial area.

Under-illumination:

The under illumination is exactly apposite to that of over-illumination. Definition: Under-illumination is the presence of lighting intensity lower than that which is required for specific work or activity.

Health Effects:-

1. Headache

2. Fatigue

3. Stress

4. Performance effect

Also under illumination is reduced by placing the lamps below 2.5 m from the surface which has to be illuminate. The fig.3 shows an under-illuminated industrial area.

Fig.2 over-illuminated industry Fig.3 Under-illuminated industry

Design factors:

Lighting design calculations are based on recommended values depending on locations and tasks. The recommended illumination levels are not to be interpreted as initial measurements, but the actual in-service values. The system must be designed such that allowances are made for the collection of dirt on luminaries, lamps, walls, ceilings, as well as the lamp lumen depreciation (LLD). The design will not be required to have an extra allowance compared with a light with a higher LLD, which may result in the system having more fixtures and possible over illumination for much of the lifecycle of the lamp.

Glare and Shadows:

Glare: While designing lighting system, glare and shadow effect should be considered. Glare is caused by over-illumination and it can be avoided by using low brightness lamps. Glare may cause momentary blindness and stress on eyes.

Shadows: Shadows are also undesirable. They are responsible for accidents on moving machines. They can be avoided by placing lamps below 2.5 m and using different light fixtures.

Flickers:

Definition: Flickers are the result of poor power quality from the supply which gives fluctuating voltage as an input to the lamps. It may results in the flickers which mean quick, repeated changes in the light intensity which is unsteady.

Effects: It may result in eye strain, headache and eye discomfort.

Solutions: They are different types of ballasts can reduce flickers specifically new types of electronic ballasts requires low power and produce low humming noise. Also, replace bulbs on scheduled basis. Old bulbs tend to flicker more and they are not as bright. Ensure that all parts of the light fixture, especially the ballast, are functioning properly.

Design Procedure:

The best design procedure of lighting by taking into consideration all above factors is given by:

1. Identify the requirements

2. Determine the method of lighting

Fig.4 different methods of lighting

3. Select the lighting equipment

4. Calculate the lighting parameters and adjust the design as required

5. Determine the control system

6. Choice of luminaries

7. Inspect the installation upon completion

Maintenance Issues

The factors related to safety of maintenance worker in lighting system are discussed in this section.

Relamping:

Relamping means replacing lamp at the end of their life cycle.

Frequency of relamping: The frequency between this relamping mainly varies depending on the type of lighting used. There are a variety of lighting sources that offer different ranges of life ratings. Fig. 5 is of frequency of relamping and shows the characteristic relamping occurrences over a five year period for different light sources, assuming continuous operation and typical lifetime ratings. By reducing the need for more frequent relamping, users are gaining both economical and safety benefits. Maintenance labor and material costs are reduced. Maintenance workers replace lamps less often and are less frequently exposed to the different risks involved such as shock hazards and elevated work.

Fig.5 Frequency of relamping

Improper servicing:

Another issue that is not always taken into account is the Improper servicing of equipment during lamp replacement. Some examples include missed seals and gaskets

and not using internal components in accordance with manufacturer recommendations, etc. These can be very serious concerns, particularly in classified areas. Reducing the possibilities of improper servicing is another benefit of using longer life lighting technology.

Fig.6 Improper Servicing

In the fig.6 shown in first case, maintenance operator cannot replace lamp since guard is in one hand and another hand is used for holding ladder. Bus as per manufacturer’s recommendations if we use guard tether, then operator can remove guard, let it hang by tether and replace the lamp easily. This method improves safety of worker since it is elevated work and also replacement is done easily and in less time.

De-energize:

It is always a good practice to de-energize the lighting fixture prior to replacing lamps toeliminate shock and burn hazards. Working on lighting circuits is one of the leading causes of work-related deaths among electricians. The hazards of servicing luminaries are made worse by the fact that they are elevated work tasks by nature. There are two methods of de-energizing a lighting fixture: removing power at its source or removing power at the individual fixture itself. There are different types of devices that enable the fixture to be disconnected from live wiring without having to disable power at

the source. Maintenance workers have the ability to perform their field wiring/installation without being exposed to un-insulated energized conductors.

Fig.7 Fixture with circular finger-safe quick disconnect

Such devices provide a finger-safe female connection on the line side that prevents the worker from making contact with the line voltage. Providing a local disconnecting means at the fixture eliminates the need to identify the correct source and shut off the entire circuit.Advantages:-

1. Quick removal

2. Safe and quick replacement

3. Eliminating shock and burn hazards

Environmental Factors:

Frequency of maintenance is affected by environmental factors. This is often over looked when selecting lights. Corrosion, moisture, and dust can increase the maintenance frequency of the luminaries.

Corrosion: Lighting fixture corrosion is quite common in any outdoor application. Today, manufacturers use specific alloys to construct their enclosures to provide the best corrosion resistance. Most commonly

used is copper-free aluminum. The exterior also be finished with an epoxy powder to provide additional corrosion-resistant properties.

Moisture: To combat moisture issues, choosing a fixture with a NEMA 4X rating is ideal. In addition, note that design requirements for NEMA 4X are similar to Division 2 and therefore provide better ingress protection.

Dust: In an environment prone to dust, one preventative method is to choose a cone top fixture, minimizing dust buildup on top of the fixture

(see Fig. 7). Fig. 8 Cone top fixtures used for reduction of dust accumulation

LED with heat sink: When dealing with LEDs, it is very important to consider dust particularly when the fixtures utilize an external heat sink. Dust build up will insulate the cooling fins from the air, inhibiting the heat exchange. The inevitable result is reduced lumen output and a shortened lifecycle.

Location and installation

Frequency and accessibility of future maintenance requirements:

When designing a new lighting system or retrofitting an existing one, consideration should be given to the frequency and accessibility of future maintenance requirements. In industrial facilities, it is common to see light fixtures installed in hard to service locations. In many of these cases, new equipment was installed and the existing lights were not relocated. In other situations, fixtures may be placed over equipment or on structures that are impractical to maintain. This may have achieved the necessary illumination levels. However, the maintainability was not taken into account.

Fig. 9 Lights located above process equipment.

Fig. 9 shows lights located above process equipment. Expensive and time consuming man-lifts may be required to reach such fixtures. In other cases, it may not be possible to reach a fixture without putting worker safety at risk.

Space restrictions and temperature relations:

Other location considerations that must be made are space restrictions and temperature conditions. Lighting fixtures that are confined to a small restrictive area experience a reduction in air flow which does not allow the fixture to operate at its designed conditions. Shortened fixture life due to the inability to dissipate heat is likely to occur. When specifying lights, ambient temperature must be considered because different light sources are affected by low and high temperatures. Some fixtures may not be able to start,

have reduced output, or experience reduced life. This may introduce a safety risk by not providing adequate illumination levels when required.

Maintenance Ergonomics

Maintenance ergonomics means that maintenance process should be so as to reduce operator discomfort. The importance of maintenance ergonomics is often overlooked when designing lighting systems. Fixtures placed in hard to service locations place workers in difficult and strenuous positions that increase the likelihood of injury while performing maintenance on the fixture. Musculoskeletal disorders (MSDs) include a wide range of inflammatory and degenerative conditions affecting the muscles, tendons, ligaments, joints, peripheral nerves, and supporting blood vessels [6]. Some common risk factors associated with MSDs include rapid work pace, forceful exertions, and non-neutral body postures. The three major factors that contribute to work-related MSDs include static load, awkward working positions and body postures.

Static Loads:

This condition occurs when muscles are kept tense and motionless for a period of time. Some examples of static load include holding the arms elevated and extending arms forwards or sideways. The weight of an object held in an outstretched position will add to the static load exponentially (see Fig. 10).

Fig.10. Examples of static load conditions

Awkward Working Positions and Body Postures:

This condition occurs where space is limited and access is difficult. These non neutral positions stretch the physical limitations of the body and can cause muscle fatigue or micro trauma to tendons or ligaments, and compress or stretch soft tissues and nerves.

Fig.11. Examples of awkward working positions and body postures

Hazardous Location

Flame proof and Explosion Proof:

Flameproof and explosion proof luminaries are very similar, but also different in other ways. We will only highlight the similarities here. Both are designed to contain an explosion within its enclosure. Their construction utilizes flame paths to cool the escaping gases to below the ignition temperature of the external atmosphere. The entire fixture assembly (lamp, driver/ballast, and connections) is housed in a flameproof or explosion proof enclosure or device. The light is transmitted through a heat- and impact-

resistant lens. Flameproof technology may allow the use of nonmetallic materials that may be useful in corrosive areas. Some other features may include flameproof contact chamber, increased safety terminals, and sand-filled ballast.

Restricted Breathing:

Restricted breathing is a method of protection designed to prevent the entry of flammable gases or vapors from entering the fixture housing. This is achieved through gasketing or sealing that restricts the flow of air both into and out of the fixture. Luminary designs with restricted breathing protection have their T-ratings determined by the hottest point externally. Although internal components may operate at a higher temperature, combustible gases and vapors will not be subjected to those temperatures. The benefit of restricted breathing is that it allows industry to specify higher wattage luminaries and reduce the number of fixtures required, while maintaining the necessary temperature class. Some designs require external seals; consult the luminary manufacturer literature for details (see Fig. 12).

Fig.12 Cross section of a fixture demonstrating restricted breathing principles.

Indian Standard Code for Lighting

Indian Standard CODE OF PRACTICE FOR INDUSTRIAL LIGHTING IS: 6665 – 1972

A good industrial lighting should take into account:

a) Adequate quantity of illumination, and

b) Good quality of illumination.

A general lighting system should be designed to provide a uniform distribution of light over the entire work area.

In locations where dirt will collect very rapidly on luminaries surfaces and where adequate maintenance is not available, they should maintain periodically.

Quality of Illumination: To reduce direct glare in industrial areas, the following steps should be taken:

1. Decrease the luminance of light sources or lighting equipment, or both

2. Reduce the area of high luminance causing the glare condition

3. Increase the angle between the glare source and the line of vision

4. Increase the luminance of the area surrounding the glare source and against which it is seen.

High reflectance surfaces are generally desirable to provide the recommended luminance relationships and high utilization of light. They also improve the appearance of the work space. It is also desirable that the background is slightly darker than the seeing task.

In uniform illumination, the distribution of light with a maximum and minimum illumination at any point should not be more than one-sixth above or below the average level in the area.

Colour discrimination and colour matching are a part of the work process, the light source selected should have the desired colour rendering properties.

Regular maintenance of lighting installations cannot be neglected without prejudicing the level of illumination and hence the benefits that proceed from good lighting. Attention is drawn to the progressive depreciation of the lighting installation depending on the locations of usage and hence the maintenance problem is an extremely important one.

Special mention should be made of group replacement of the lamps and starters in case of fluorescent lamps lighting fittings.

Required Illumination Level In Industry:

CONCLUSION

Lighting design is not as simple and straightforward as one may think. It involves more than just achieving the desired lighting levels. Lighting designs need to start with a

safety-centered approach. Safety is affected by the reliability, longevity, and maintainability of the designed system. It is important to research available products and consult with manufacturers and suppliers to achieve the best and safest design possible. This technology is changing rapidly. End users must do their research and should not settle for an inferior design.