4.1 Industrial

10-94 I E S LIGHTING HANDBOOK

like character of the hotel and are flexible and easily coordinated with anydecorative scheme.

INDUSTRIAL LIGHTING

In 1915 the Illuminating Engineering Society prepared and issued a

Code of Lighting Factories, Mills and Other Work Places. According to the

procedure of the American Standards Association, revisions of the Codewere made in 1921 and in 1930. The 1942 American Recommended Practice

of Industrial Lighting, which is condensed here, is a development of the

earlier codes.

Illumination is an environment factor that affects every industrial es-

tablishment. The advantages of good illumination to employees and man-agement are many.

Production and Quality Control

Under good illumination it is possible to see an object of much smaller

size than is discernible under poor illumination. Continuous quality

control throughout the manufacturing process, made possible by goodillumination, permits early discovery and rejection of defective parts prior

to further processing or final inspection.

Floor space utilization. A uniform level of general lighting such as

shown in Fig. 10-66 makes possible the most efficient arrangement of

machinery and conveyors and better utilization of floor space. Manu-facturers have learned that in many cases more work can be achieved with

less floor space when the work flows in straight lines through assembly or

inspection sections. Good general lighting facilitates the arrangement of

straight .production lines.

FIG. 10-66. A uniform level of general lighting permits the optimum utilization

of floor space and increases the flexibility of the production line plan in this shop.

INTERIOR LIGHTING 10-95

Cleanliness. Industry has found that cleanliness pays. Poor illumina-

tion makes it difficult to see into corners or under machinery and these dark

areas collect dirt and waste that would otherwise be cleaned out. Wheredirt can be seen it is more likely to be removed. In a well-lighted plant

dingy areas do not exist and much more sanitary conditions prevail.

Light and safety. Engineering for safe plant operation consists es-

sentially of preparing a safe working environment. The environment

should be designed to match and to compensate for the limitations of humancapability. However, as revealed by an analysis of accidents and their

causes, this is but one phase of the safety problem. Most personal injury

accidents involve a combination of personal and mechanical causes. Thechain of circumstances or series of causes which has led a workman to a

potential injury frequently can be broken only if be can see quickly andaccurately the causes and act to prevent the accident.

Factors of Good Illumination

There are many factors involved in good illumination. These can be

summed up under the headings quality, which includes the direction anddiffusion of light, its color, etc., and quantity. Separately and in conjunc-

tion they have significant effects on the ability to see easily, accurately,

and quickly.

Quality of illumination: light diffusion and distribution. Some directional

and shadow effects are desirable in general illumination for accentuating

the depth and form of solid objects, but harsh shadows should be avoided.

(See Fig. 10-67.) Shadows are sof-

ter and less pronounced when manywide-distribution diffusing lumi-

naires are used. Alternate light

and dark areas in strong contrast

are not desirable because the adapta-

tion of an observer's eye to first

one and then the other of the twobrightnesses is fatiguing. For this

reason, purely local lighting re-

stricted to a small work area is

unsatisfactory; there should be suf-

ficient general illumination through-

out the room. High (30 to 60 per

cent) reflectance surfaces serve

several purposes. They reflect light

toward the working areas, they

reduce contrasts between walls,

ceilings, windows, and luminaires.

Machinery with a high-reflectance FIG. 10-67. Uncontrolled shadows

finish reflects light to otherwise sha- usually interfere with vision. How-, ,

ever, in some cases shadows may bedowed areas. utilized also to simplify seeing tasks.


Clearly defined shadows, without excessive contrast, simplify the seeing

task in certain types of operations such as engraving on polished surfaces,

scribing on metal, and some textile inspection. (See Fig. 10-67.) Con-trolled shadows may be provided b^y supplementary luminaires.

Many of the seeing tasks in industry are on vertical or nearly vertical

surfaces. Hence the amount and the distribution of light on vertical sur-

faces often are important. (See Fig. 10-68.)

.

jf

.

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FIG. 10-68. In many industrial areas the visual problems occur on vertical as well

as horizontal planes. In such cases uniform illumination should be provided on thevertical.

Quality of illumination: color. With equal illumination (footcandles)

variations in color quality of light have little or no effect upon the visibility

of tasks that do not involve color discrimination. However, in certain

industries color discrimination is important and in these the spectral quality

of the light on the work may be critical. Some manufacturers paint sta-

tionary and moving parts of machines different colors to increase contrast

and prevent accidents.

Quantity of illumination: recommended levels. The illumination recom-

mended for an installation depends upon the seeing task. The degree of

accuracy required and the size of detail to be observed, the color and re-

flectance of task and surround materially affect the brightness distribution

required for optimum seeing. As illumination on a task is increased, its

brightness and the ease, speed, and accuracy with which it can be accom-

plished usually are increased.

Surface brightness measurements may be made with a brightness meter

(see Section 5). Brightness may be computed by multiplying the illumina-

tion by the reflectance of the surface.


Most of the recommended illumination levels in Appendix Table A-lapply to the average room. If it is desired to determine the level produced

by an existing installation, the measurement procedure outlined in Section

5 should be followed.

The majority of the recommended values of illumination shown in Table

A-l refer to the general lighting measured on a horizontal plane 30 inches

above the floor. In some cases where an illumination level of more than

50 footcandles is necessary, it may be obtained by a combination of general

lighting plus supplementary lighting at the point of work.

The Illuminating Engineering Society in recent years has been studying

the illumination needs of specific industries. If a more detailed discussion

of the lighting specifications for a specific process is desired than it has

been possible to include in the handbook, the reports referred to should be

consulted.

To ensure that a given illumination will be maintained (even where con-

ditions are favorable) it is necessary to design the system to give initially

at least 25 per cent more light than the required minimum. In locations

where the dirt will collect rapidly and where adequate maintenance is not

provided, the initial value should be at least 50 per cent above the minimumrequirement.

Where safety goggles are worn, the light reaching the eye is likely to be

materially reduced and the general level of illumination should, therefore,

be increased accordingly in these locations.

General Lighting in Industry

Modern industrial lighting practice is to provide a uniform illumination

level throughout every work area. This is called general lighting. Thegeneral-lighting level should be uniform so that light will be available,

when needed, at any point. This is particularly desirable for interiors

where the production layout may be changed. If the general lighting

has been designed for uniform illumination, tables, machines, and con-

veyors often may be moved without necessitating a change in lighting

installation.

The purpose of a general-lighting system where there is also supple-

mentary lighting is to keep the brightness ratios between the task andthe surround within a range that is comfortable to the eyes (not over 10

to 1) in order to provide sufficient light for safety and to illuminate second-

ary visual tasks.

Luminaire Spacing and Layout

The lumen method of design described in Section 8 is used to design

general-lighting installations intended to provide reasonably uniform il-

lumination over a given area. The footcandle level calculated by this

method is the average for the entire area. The level in a well-designed

system at any specific point near the center of the room may vary 5 per

cent even in an empty room with no equipment or other obstructions.


The variation may be as great as 30 per cent if points next to the walls are

considered, unless special attention is given these areas.

Layout suggestions. The conventional arrangements of electrical outlets

for lighting (one, two, or four per bay) have been adequate for a wide

range of footcandles because of the many incandescent-filament lamps

available in the 150- to 1,500-watt range with outputs of from 2,600 to

33,000 lumens each. By comparison, the fluorescent-lamp range, encom-

passing only a few ratings between 15 and 100 watts with outputs of 495

to 4,400 lumens each, is limited. To obtain a lumen output per fluorescent

luminaire comparable with that of a 500- or 1,000-watt, incandescent-lamp

luminaire, it is necessary to use many lamps.

Fluorescent lamps, by virtue of their tubular form, suggest new layout

and installation methods: continuous rows of lamps and "troffer" systems.

Since the lamp lengths and ballasts are different for each of the fluorescent

lamp sizes, these lamps are not interchangeable. However, future increases

in illumination may be provided for by a wiring layout that will accommo-date added luminaires or rows of luminaires to co-ordinate with the original

installation. (See Fig. 10-69.) It is possible, also, in some two-lampluminaires to add a third lamp of the same size, with an increase in illumina-

tion of approximately 50 per cent. Where such luminaires are spaced

closely, or in continuous rows, the two extra lamps in adjacent luminaires

can be served from a two-lamp ballast located in one of them. Two-lampindustrial units with reflectors punched for lampholders for a third lampare used. This potential capacity may serve several useful purposes. Byadding the third lamp almost 50 per cent increase in illumination may be

made available over a small area for especially difficult visual tasks, or

throughout the installation for a general increase in illumination. Il-

lumination levels from a general-lightin"; system are low near walls when not

FIG. 10-69. This luminaire installation is arranged to minimize the complexityand expense of future increases in illumination. Spacing plan permits addition of

units without disturbing existing installation.


supplemented by natural light from Avindows. The latter cannot be de-

pended upon at all times. It is possible to compensate for the daily andseasonal variations in natural illumination by using the third lamp in out-

side end rows and in the two end reflectors of the rows between. In large

installations this can be accomplished by having all the luminaires in out-

side bays fitted with a third lamp. In incandescent systems, lamps of

higher wattage than in the center of the room should be used in

the outer bays.

Mounting height. For practical purposes the average illumination level

produced by general-lighting installations of spread distribution lumi-

naires in large areas (room index > 5) is independent of luminaire mounting

height. In small areas the average varies in proportion to the coefficient

of utilization, not inversely with the square of the distance from luminaires

to illuminated plane. Spacing between luminaires usually should not

greatly exceed their mounting height.

Supplementary Lighting in Industry

Extremely difficult seeing tasks require illumination levels which are

not always easily or economically obtained by standard general-lighting

methods. To solve such problems supplementary luminaires often are

used to provide high levels for small or restricted areas. Also, they are

used to provide a certain brightness or color, or to permit special aiming or

positioning of light sources to avoid shadows caused by workmen or ma-chinery. A reasonably comfortable interior usually results when the gen-

eral-illumination level is at least one-tenth that of the supplementary

level. Employees using their eyes for critical visual tasks glance away from

their work at frequent intervals for momentary relaxation. If the bright-

ness contrast between task and surround is too great, instead of being

rested, the eyes are fatigued.

Supplementary luminaires. Two types of supplementary equipment will

take care of almost all requirements: (1) Small, concentrating projectors

augment the general lighting on a seeing task and provide directional

quality. (2) Large-area, low-brightness diffuse sources may provide

either general lighting for small areas or "plus" lighting for a more difficult

seeing task such as inspection. (See Fig. 10-70.) All supplementary

luminaires and projector lamps should be shielded, louvered, or mountedso as to minimize the possibility of glare. Where adjustable fluorescent

luminaires are used, they should be of the two-lamp type to minimize

stroboscopic effects.

Portable luminaires. Portable equipment can be used to good advantage

in airplane hangars and garages and wherever internal surfaces must be

viewed. A typical unit consists of five angle-reflector luminaires mountedon a portable rack with outlets for electrical tools. Two-hundred-watt,

inside-frosted incandescent lamps are recommended. A "trouble light"

consisting of 50- or 100-watt rough-service lamps in a guarded socket

attached to an extension cord often is provided for internal inspection.

Similar devices have been developed for fluorescent lamps.


FIG. 10-70. Typical supplementary- and portable-lighting equipment designsPortable-lighting equipment often is useful for repair work and for increasing illumi-

nation on surfaces which are inaccessible and not reached by general lighting.

Hazardous locations. Vapor-proof, explosion-proof, and dust-tight

uminaires each are designed for a specific type of location where either

corrosive vapor, inflammable gases, or explosive dusts are likely to be en-

lcountered from such processes as oil refining, paint and varnish making,

or lacquer spraying. (See Fig. 10-71.) Special equipment such as this

usually is mandatory also in locations with moisture-laden atmospheres

such as steam processing, engine rooms, and shower baths. The National

Electrical Code requires the use of these special types of luminaires in cer-

INTERIOR LIGHTING 10-10)

VAPORTIGHTGLASS GLOBE"

GLASSREFRACTOR

FIG. 10-71. Luminaires for hazardous locations: a. dust-tight; b. vapor-proof;c. explosion-proof.

tain areas. Both angle and symmetrical types of reflectors in the 75- to

500-watt size range are used.

Lighting for Industrial Inspection

In most production processes there are one or more inspection operations

that involve checking some characteristic of a material or product against

a previously established specification or standard. Although inspection

or checking sometimes is accomplished by the use of devices requiring little

visual effort or skill on the part of an operator, acceptance or rejection

often depends on the accuracy of the visual observations of a skilled in-

spector. Usually, because of the importance of the inspector's decisions

in such cases, it is worth while in planning a lighting installation to treat

an inspection area as a special problem. The following examples suggest

ways in which a variety of typical inspection problems have been solved.

Highly polished surfaces. Chrome or tin plate, aluminum sheet, andother specular surfaces frequently are inspected visually to detect scratches,

dents, bare spots, and other flaws. It has been found that an inspector

can locate such flaws when he views an image of a low-brightness luminaire

in the polished surface. The image should be at least as large as the area

to be inspected and its brightness should be not more than 400 footlamberts.

(Surround brightness should be not less than 1/10 image brightness.) Thearea to be inspected should be so screened that images of other sources,

windows, machinery, or personnel are not in the inspector's field of view.


FIG. 10-72. Flaws such as grindmarks in highly polished surfaces formdistorted images of regular patternssuperimposed on the low-brightnesssurface of the inspection table or in-

spection luminaire. They may bedetected easily by this method.

Opaque bands of uniform width

equally spaced in parallel lines, rec-

tangular grids, or concentric circles are

of assistance in detecting surface con-

tour irregularities. These are revealed

by a distortion of the image pattern

which in some cases may be notice-

able only when the inspector moveshis head. (See Fig. 10-72.)

Printers' imposing stones, type com-position cases, and metals used for

scribing present similar seeing problems

which may be solved in this manner.

Refractive flaws in transparent ma-terials may be detected by viewing the

image of such a source or the source itself through the material.

The following rules of thumb are applicable to the inspection of plate glass

:

1. The glass should be viewed against a combination of light and dark

areas.

2. The light source should have a brightness of less than 1,800 foot-

lamberts (4 candles per square inch).

3. The light source preferably should be rectangular in shape with a

width of 5 to 6 inches and a length of 24 to 30 inches. "With luminaires of

this size the width of the dark spaces between should be of the order of 2

to 3 feet.

Trough-shaped luminaires are located approximately 6 feet behind the

support for the glass plate. The supporting framework for the glass plate

should be raised or lowered to bring the glass area between the eyes of the

inspector and one or more of the luminaires.

Open-weave fabrics and

other translucent materials.

The location and removal

of any defects in open-

weave fabrics previous to

the final finishing process

is accomplished best by ob-

serving the defects in sil-

houette against a large-area,

uniformly low-brightness

panel such as shown in Fig.

10-73. The brightness of

the panel should be suffi-

cient to show up defects.

It should not exceed 400

foot lamberts. The sur-

round brightness should notFIG. 10-73. Low-brightness source for silhouette v , .,

1/10 ,, .

finspection of translucent materials such as fabrics,

De iess Inan i / iU /na; 0I

glass, plastics, paper, liquids, etc. the panel. For the best


silhouette vision the illumination on the cloth from the observer side times

the reflectance of the cloth should be not more than one-tenth the bright-

ness transmitted by the cloth.

Light transmitted through translucent materials such as glass, paper,

plastics, and liquids also may reveal certain kinds of faults, foreign material,

and defects. Large luminous panels can be built in conveyor lines over

which, or past which, the material flows. The illumination level required

varies with the task. A panel brightness of the order of 100 footlamberts

often is adequate. Bubbles, blisters, cracks, chips, and whorls may berevealed as highlights or distortions caused by refraction when transparent

materials such as glass jars, bottles, bulbs, clear plastics, etc., are seen

moving before a large-area, low-brightness panel. Alternate dark andluminous backgrounds or black strips laid on a luminous background aid

in locating and identifying defects.

To detect small fire cracks and bubbles in glass jars and the pin-point

bubbles caused by foreign material in carbonated beverages, a narrow beamsource is recommended. The mirror action of these defects reveals their

presence.

A modification is the arrangement employed for the inspection of inner

tubes for air leaks. The partially inflated tube suspended from an over-

head conveyor is passed through a trough filled with water under the sur-

face of which there are light sources on each side of the inspector's stand.

Any air bubbles coming from the tube are made visible by the light they

refbct.

Polarized illumination. The detection of internal strains in glass,

mounted lenses, lamp bulbs, radio tubes, transparent plastics, etc., maybe facilitated by transmitted polarized light. The nonuniform spectral

transmittance of strained areas causes the formation of color fringes that

are visible to an inspector. With transparent models of structures andmachine parts, it is possible to analyze strains under operating conditions.

Nonspecular materials. Surface flaws, irregularities in surface shape, pit

marks, scratches, and cracks in nonspecular or mat materials are mosteasily seen by lighting which strikes the surface obliquely in such a mannerthat nonuniform surface contours cast shadows. Wrinkles in roofing

materials are revealed by small shadows which the wrinkles cast when the

sheet is illuminated by a narrow light beam incident at a grazing angle.

Directional light also has been found useful for the inspection of sand-

paper and Venetian blinds. (See Fig. 14-6.) The light may be specular

for inspecting mat surfaces, but should be diffused at the source for ex-

amining polished or shiny materials.

Minute details and high precision. Careful inspection of very small

objects may be greatly simplified by viewing their magnified images. For

production work the magnified image may be projected on a screen. Be-

cause the projected silhouette is many times the actual size of the object,

any irregular shapes or improper spacings can be detected readily. Similar

devices are employed for the inspection of machine parts where accurate

dimensions and contours are essential. One typical device now in commonuse projects an enlarged silhouette of the teeth of a gear on a profile chart.


The meshing of these production gears with a perfectly cut standard is

examined on the chart.

Color control and classification. Many manufacturing operations in the

paint, lacquer, enamel, dye, textile, paper, tile, and printing fields include

careful color-control procedures. Section 4 includes detailed discussion of

these problems.

Moving parts. It is sometimes necessary to inspect and study movingparts while they are operating. This can be done with stroboscopic il-

lumination which can be adjusted to "stop" or "slow up" the motion of

constant-speed rotating and reciprocating machinery. Stroboscopic lamps

give flashes of light at controllable intervals (frequencies). Their flashing

can be so timed that when the flash occurs, an object with rotating or

reciprocating motion is always in exactly the same position and appears to

stand still.

METAL WORKING

Some very difficult seeing tasks are encountered in metal-working shops.

The difficulties are a result of many different causes, including the following

:

1. Low-reflectance metal surfaces result in low task brightnesses. Therapid collection of oil and dirt further reduces reflectance and makes goodmaintenance difficult.

2. Work and machine surfaces are of similar character and reflectance

and consequently provide poor contrasts.

3. Specular metal surfaces in the process of fabrication form images

of luminous areas in the surround.

4. Much metal-working machinery is bulky, and obstructs the distribu-

tion of light flux.

5. Dimensional tolerances often are extremely narrow.

In many industrial processes the seeing task may be greatly facilitated

by painting various parts of the working areas, including the machines,

in contrasting colors of good reflectance. (See Section 4.)

Lighting for Heavy Industry

The heavy-industry type of metal working is done in foundries, steel

and iron mills, and fabrication assembly plants in the manufacture of such

products as ships, locomotives, engines, turbines, structural steel, andautomobile bodies. This work is carried on in high-bay buildings covering

large areas. Materials are moved from place to place by means of traveling

cranes. General illumination usualh^ is provided by high-bay luminaires,

employing a high output light source such as the incandescent lamp or high-

intensity mercury lamp. (See Fig. 10-74 and Fig. 10-75.) Incandescent-

and mercury-lamp combinations sometimes are installed on alternate out-

lets. The illumination from this arrangement is whiter than that of either

source alone; radiation from the incandescent alone is yellowish and from

Documents

4.1 Industrial