IT HITS THE TARGET TWICE!

An important saving in a critical war metal

A big step-up in fluores- cent lamp performance

A LL fluorescent lamps are alike in that each requires the use of mer- cury—an essential war material. But lamps differ widely in the way that material is used.

Through the newly patented ‘“‘mercury bomb,”’* Hygrade Lamps now get twice

the good out of the same volume of

mercury—they stretch this scarce and vital metal 100% further.

But more than that—this remarkable new device lifts Hygrade performance to a new high level.

You see, too much mercury in a fluor- escent lamp means more than waste—it means that the excess deposits itself on the surface in the form of dark streaks and splotches that cut down light out- put. On the other hand, too little mer-

cury may cause the lamp to grow dim after a short period of service.

The “mercury bomb” rigidly controls— to the thousandth of a gram—the amount of mercury used in Hygrade Lamps; assures precisely the right quantity to keep them “‘bright to the last inch.” There are four other good reasons — easily verifiable — why Hygrade Sylvania Lamps can best serve war- time lighting needs. They give more light; they have a smoother coating texture; they’re uniform in color; they last longer.

These fine lamps work well in any type of fixture. They’re at their best when operating in fixtures made for them —‘‘Miralumes” — complete Hygrade fluorescent units in which each part teams up with the rest.

If you haven’t yet received our free file- size kit —containing catalogs, prices and complete technical specifications on all Hygrade Fluorescent Lighting Equip- ment—write today to Dept. ES-8, Hygrade Sylvania Corporation, Salem,

Mass. U. S. Patent No. 2,283,189

BRIGHT TO THE LAST INCH

FINER : LONGER raed Gal ict LASTING

HYGRADE SYLVANIA CORPORATION

SALEM, MASS.

Makers of Hygrade Incandescent Lamps, Fluorescent Lamps, Fixtures, Starters, Sockets and Sylvania Radio Tubes

This panelboard is especially designed for use in shell loading plants, coal mines, coal storage rooms, flour mills and other places where dust is a hazard. It is approved by Underwriters’ Laboratories, Inc., for ‘Class II, Groups F and G, Hazardous Locations,”” covering atmospheres containing carbon black, coal or coke dust and grain dust.

Instead of the usual steel front, consisting of trim and door, this panelboard has a solid steel front plate, gasketed all ‘round, and secured with screws to the extra- wide flange. It is further rendered dust-tight with welded hubs for con- duit outlets, welded box-corners, and

handle bushings riveted directl

_ aka he ” BLT PELTED) Hectic Co ais, | % > || ELECTRICAL PRODUCTS - for War Industry

wane : e

wees

ari

a 4

to the steel cover plate. The brackets are welded at the back.

The circuits are externally operable by a mechanism of new @ design. The handles operate through the dust-tight bushings. and engage the regular handles on the circuit breakers inside the cabinet. ON and OFF positions are indicated on the front of the cabinet.

The panelboard is of the circuit breaker type, with either @ Type AC or @® Dublbrak circuit breakers; also other types of lighting branch-circuit circuit breakers. . Capacities: 50 Amperes or less, for 3 wire, single phase, or 4 wire, 3 phase mains, with lugs only. Available with 4 to 42 circuits . . . Frank Adam

any

FRANK ADAM ELECTRIC CO. ST.LOUIS, MO.U.S.A.

ELECTRICAL SOUTH is published monthly by W. R. C. Smith Publishing Co., Marietta, Ga., and Atlanta, Ga., U. S. A.

Subscription rates, United States and Possessions, $1.00 for one year; $2.00 for three years; Canada, $1.50 per year; Foreign Countries, $2.00 per year. Entered as second class matter at the postoffice, Marietta, Ga., under Act of March 3. 1879.

Volume 22

Number 8

Tops personally, he and his staff are the nemesis of all incoming materials that do not measure up to Anaconda quality standards: they check them all.

In these critical days, no one can afford to make mistakes, no matter how trifling, in so vital a product as electrical wires

and cables. &

from

Relentless guard over the quality of products going into the manufac-

This familiar trade-mark symbolizes the best ef- forts of modern research

ture of Anaconda wires and cables, is tl.is “‘bogey man.” He and his group of expert associates check every item against Anaconda’s rigid speci- fications (tougher by far than those stipulated by government agencies), to the end that every wire and cable bearing the Anaconda name can be trusted for long, efficient, and eco-

nomical service. pane

DA GENERAL OFFICES: 25 Broadway, New York => CHICAGO OrFIcE: 20 North Wacker Drive Subsidiary of Anaconda Copper Mining Co.

Sales Offices in Principal Cities

and production.

ANACONDA WIRE & CABLE COMPANY

ELECTRICAL SOUTH for AUGUST, 1942

AUGUST, 1742

Volume 22 No. 8

AREER LL SIE L AE AN

J. C. MARTIN, Manager

RICHARD P. SMITH, Promotion Manager

W. E. COOGLER, Production Manager

Editorial and Business Offices GRANT BUILDING ATLANTA, GEORGIA

Member of A. B. P. Member of A. B. C.

ANNUAL SuBSCRIPTION—$1.00 THREE YEARS—$2.00 CaNADA—$1.50 ; ForEIGN—$2.00

Business Representatives: L. E. ALLEN, 189 West Madison St., Chicago, Ill. Tel.: Lakeview 10282. L. R. McCarty, 8325 Winding Way, Merion, Pa. Tel.: Merion 1066. W. A. McGez, P. O. Box 562, Charlotte, N. C. Tel.: 8-49382.

e Published Monthly by

W. R. C. SMITH PUBLISHING CO.

Marietta and Atlanta, Ga.

. J. Rooke, President,

- W. MCALLISTER, Vice-President and Editorial Director,

. W. O’Brien, Vice-President,

. W. Pup, Vice-President, ICHARD P, SMITH, Vice-President, . A. SHARPLESS, Treasurer,

. C. Martin, Secretary,

OFrm 4

Publishers Also of CoTTON SouTHERN HARDWARE SOUTHERN AUTOMOTIVE JOURNAL SOUTHERN POWER AND INDUSTRY

egrets

> oh pik RRR A SOQ yaa

Entered as second class matter at Marietta, Ga., U. S. A., under Act of March 8, 1879.

T. W. McALLISTER, Editorial Director CARL W. EVANS, Editor

NAT M. JOHNSON, Southwestern Editor

Contents

Keeping Your Welders Welding

Planning for Industrial Lighting Maintenance Electrical Features of Plantation’s Longest Pipeline Eliminating Industrial “Machine Camouflage” Mass-Production Methods on a Wiring Project Industrial Wiring Practice—Part 8

Time-Saving Technique for Housing Project Wiring Promoting Your Appliance Service Sales

How Dealers Are Meeting the Emergency

New Fluorescent Circuit Saves Critical War Metals Factors Causing Meter Failure Disclosed

Emergency Overloading of Power Transformers

Departments

News of the Electrical Industry Personal Notes About Men You Know

New Electrical Equipment and Materials

Copyrighted 1942, W. R. C. Smith Publishing Co., Atlanta, Ga.

PSE UR?

These A.C.S.R. overhead ground wires, installed during 1925-7, are being removed for use.as power conductors on a new line.

IMAGINEERING IS GETTING POWER

A.C.S.R. overhead ground wires have protected parts of this line for seventeen years. But they’re being taken down now—for more urgent service—to be used as power conductors on a new line.

New conductors could not be obtained, so Imagineering by this power company’s engineers found a way of serving additional vital war industries.

Imagineering is taking care of the future, too.

TO VITAL WAR INDUSTRIES

Spans, towers, insulators and fittings are all planned so that this new line will accommodate new and larger conductors, when they again become available. Alcoa engineers are assisting in all of this design work.

When you have the problem of getting more work out of old lines, or of keeping them on the job, Alcoa engineers are always here to advise you. Write ALUMINUM COMPANY OF AMERICA,

2164 Gulf Building, Pittsburgh, Pennsylvania.

ELECTRICAL SOUTH for AUGUST,

Sie SS

1942

rec an ke] tio

in | we fai tim ten der per

Keep Your Welders Welding

HILE arc welding sets to-

day represent the highest in simplicity and reliability, they require attention from a mainten- ance standpoint if they are to be kept in the best operating condi- tion.

With the accent on production in shipyards, ordnance plants, and welding shops of all types, the failure of even a few sets is some- times costly. A systematized main- tenance program will pay divi- dends in terms of better welder performance and longer life.

Selection and Installation

The right welding set must be selected for the job, because a maintenance program will be dis- couragingly difficult if misfit equipment is being used.

To insure proper choice of the rating of a single-operator set, the maximum current, load voltage, and duty factor (ratio of arc time to total time) must be taken into account. Except in the smallest sizes, most sets are rated on a one-hour load. Their rating is the current which they will deliver

*Mr. Wyer is welding engineer for General Electric Company, Schenectady, N. Y

ELECTRICAL SOUTH for AUGUST, 1942

By R. F. Wyer*

for one hour without interruption, without exceeding a_ prescribed temperature rise.

Since this method of rating, chosen as a simple standard for comparison, does not take into ac- count actual operating conditions, it is not always’ economically sound to choose the size next larg- er than the maximum operating current contemplated. However, for this same reason duty factor should be taken into account when new equipment is being consider- ed to make certain that the set is big enough for the job.

Proper installation can do much to keep the welding equipment at work and troubles to a minimum. In wiring up a welding set, care should be taken to provide ade- quate branch circuit conductors, and fuse clips large enough to ac- commodate the necessary fuses. It should be observed that motor- generator type welding equip- ments have _ full-voltage motor starters almost without exception, so that due consideration must be given to the starting current of the motors.

Care should be taken to ground

the frames of all welding equip- ment in order to avoid shock or annoying tickles when a ground- ed person touches the frame of the equipment. Even with equip- ment in perfect operating condi- tion, under some conditions, it is possible to receive a harmless but irritating sensation of shock from ungrounded equipment due to the passage of infinitesimal capacity or leakage currents. In addition to protecting against this annoy- ance, adequate grounding of ma- chine frames is also a desirable safety precaution against harm resulting from insulation failure in equipment or leads, or im- proper connections. Grounding Precautions

Regardless of the type of safety ground connection which is in- stalled, adequate low resistance work leads should always be used, and care should be taken to se- cure good connection between the work lead and the work. If this is not done, it is possible under some circumstances to overheat the safety ground connection by the passage of welding current through it.

In the location of welding equip- ventilation is a very im-

ment,

portant consideration. The life of electrical insulation is seriously shortened by overheating, and overheating is bound to result where insufficient ventilation is provided. Particularly where large numbers of welding equipments are to be located in small enclos- ures, considerable study should be given to the problem of supplying clean, cool ventilating air.

Where small houses or tempor- ary sheds are located in hot sun- shine, the heat absorbed from the sun added to the heat dissipated by the welding equipments may raise the ambient temperature above 100° F. and cause severe overheating. In such cases, large louvers or other ventilating open- ings should be provided in the building not only at the bottom but near the roof to give good air circulation and keep the ambient temperature below 100° F. In some instances, it is desirable to provide exhaust fans to assist in Sanding brushes to a good fit with the commutator is essential whenever removing heated air from the up-

new brushes are installed. This operation is described in detail in the per part of such enclosures. accompanying text on welder maintenance practice.

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Inspection and Regular Servicing

The competent maintenance man will have a record of all weld- ers under his care. One of the most useful and easy-to-handle references is a card file. All re- pair work, with its cost, can be entered on the record, and any welder requiring excessive atten- tion or expense can be investigat- ed and causes determined and cor- rected.

Inspection records will also serve as a guide to tell when weld- ers should be replaced because of high cost to keep them in oper- ating condition. Misapplications, abuses, and the like will also be disclosed.

A systematic and periodic in- spection of motors and generators is necessary to insure best oper- ation. While some welders are in- stalled where conditions are ideal —where dust, dirt, and moisture are not present to an appreciable degree—most machines are locat- ed where some sort of dirt accum- ulates on the windings. This low- ers insulation resistance and cuts down creepage distances.

Steel-mill dusts are _ usually highly conductive, if not abrasive, and lessen creepage distances. Other dusts are highly abrasive and actually cut the insulation in being carried through by the vent- ilating air. Fine cast-iron dust quickly penetrates most insulating

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The blowing of dust out of welder should be done carefully with low- pressure air to avoid driving abrasive dust into insulation. Metallic dust

can be most damaging to electrical coils. materials.

an mee 2 eee Se

ELECTRICAL SOUTH for AUGUST, 1942

Hence the desirability of in- specting motors periodically. If conditions are extremely severe, weekly inspection and _ partial cleaning are desirable. Most mo- tors require a complete overhaul- ing and thorough cleaning about once a year.

Weekly and Yearly Cleaning

For the weekly cleaning, the motor and generator should be blown out with dry compressed air (about 25 to 30 pounds per square inch in pressure). Where conducting and abrasive dusts are present, even lower pressure may be necessary, and suction is to be preferred, as damage can easily be caused by blowing the dust and metal chips into the insulation. On most motors the windings are fairly accessible, however, and the air can be properly directed to prevent such damage.

About once a year, welders should be overhauled. First, the heavy dirt and grease should be removed with a heavy, stiff brush, wooden or fiber scrapers, and cloths. Rifle-cleaning bristle brushes can be used in air ducts. Dry dust and dirt can be blown off, using dry compressed air at moderate pressure. Care must be taken to direct the air so that the dust will not cause damage and will not be pocketed in the various corners. Grease, oil, and sticky dirt are easily removed by ap- plying cleaning liquids such as carbon tetrachloride.

If the welder can be spared from service long enough, the in- sulation of the motor should be dried out by heating to from 90° to 100° C. While the motor is still warm, a high-grade insulat- ing varnish should be applied.

The varnish may be sprayed or brushed on. After applying the varnish, the best results are ob- tained by baking for 6 or 7 hours at about 100° C. If the machine must be put back into service quickly, or if facilities are not available for baking, fairly good results will be obtained by ap- plying one of the varnishes whicn dry in a few hours at ordinary room temperatures.

Lubrication Instructions

Manufacturers’ instructions re- garding lubrication of bearings should be carefully noted. These instructions should be kept near the welder so that they are readily accessible. Usually grease-pack- ed bearings have sufficient lubri-

ELECTRICAL SOUTH for AUGUST, 1942

The resistance measuring instruments now available provide a convenient means of determining the condition of the insulation by indicating its resistance to leakage currents.

Hand-operated grease guns should always be used on pressure-relief lubricated bearings. Grease should be added slowly to permit excess to vent from relief pipe or plug. (Latter not visible here.)

cant when shipped from the fac- tory to last about a year under normal conditions of cleanliness and temperature. When sets are operated in unusually dirty at- mospheres, run continuously 24 hours per day, or exposed to ex- tremes of temperature, it would be well to shorten the bearing in- spection and lubrication interval down to six months, or less if ex- perience warrants.

An occasional check of bearing temperature by feeling with the hand may disclose undue _ heat- ing before damage is actually done. Once a lubricating routine has been established, it should be carried out, and by reliable men who will follow instructions.

It is pretty generally establish- ed that outside of gross neglect for long periods of time, the major causes of bearing troubles are overgreasing and dirt. Overgreas- ing results in excessive heating of the bearing, frequently with churning and breaking down of the grease with consequent loss of its protective qualities.

Dirt occasionally gets into a bearing through the use of grease that is carried around or stored in uncovered containers. Quite as frequently it gets in through carelessness in protecting parts while bearings are disassembled or opened for inspection.

Only a high grade of grease should be used on ball bearings.

Brushes and Commutators

Brush inspection is important. The first essential requirement for the satisfactory operation of brushes is the free movement of the brushes in their holders, Uni- form brush pressure also is neces- sary to assure equal current dis- tribution. Adjustment of brush holders should be set so that the face of the holder is approxi- mately 14%” up from the commuta- tor; any distance greater than 14” may cause brushes to wedge, re-

sulting in chattering and excessive -

sparking.

It is essential that the correct grade of brush for a _ specific application be used. Recommend- ations as to the correct grade of brush should be obtained from the manufacturer of the welder only.

Broken brushes imply two pos- sibilities: incorrect brush grade, or mechanical defects (such as un- balanced, rough, or eccentric commutator). To eliminate brush

breakage, both factors should be corrected.

Maintenance Check Chart for Electrical Welding Apparatus

Machine Fails Causes

Rough or dirty commutator

Brushes may be worn down to limit of ad- justment or life

Brush springs may have lost adjustment or may be broken

Field circuit may have variable resistance connection or intermittent open circuit

Electrode lead or work lead connections may be poor Wrong grade of brushes may have been in- stalled on generators

Field rheostat or tap switches may be mak- ing poor contact and overheating

Brush-shifting or other mechanical current- adjusting mechanism may have loose or worn links

to Hold Heat

What To Do Commutator should be trued or cleaned Replace or readjust brushes Replace or readjust brush springs

Cheek field current with ammeter tw dis- cover varying current. This applies to both the main generator and exciter if used

Tighten all connections

Check with manufacturer’s recommendations

Inspect rheostat and clean and adjust finger tension on switches

Check = current-adjusting mechanism for

backlash and play

Welder Starts but

May be running the wrong way

Generator or exciter brushes may be loose or missing

Exciter may not be operating

Field circuit of generator or exciter may be open

Generator may be reversed in polarity due to another machine or incorrect operation in parallel with another machine

Series field and armature circuit may be open-circuited

Fails to Generate

Check direction of rotation with manu fac- turer’s instructions or direction arrow. On 3-phase motors, direction of rotation may be changed by interchanging any two leads Be sure that all brushes bear on the com- mutator and have proper spring tension

Check exciter output voltage with voltmeter or lamp

Check for open circuits in rheostat, field leads, and field coils. Also check resistors and rectifiers, if any. Some machines give low output when fields are open

*Flash the field with a storage battery or another generator first with one polarity and then with the other to see if it builds

up | (Flash exciter field if set has separate ex-

citer)

Check circuit with ringer or voltmeter

Check the brushes to make sure that they will not wear down too far before the next inspection. Keep extra sets of brushes avail- able so that replacement can be made when needed. It is false economy to use brushes down to the absolute minimum length be- fore replacement. Cases have been known where brushes have worn down until the metal, where the pigtail connects to the brush, was touching the commutator. This, of course, was causing damage to the commutator.

Make sure that each brush sur- face, in contact with the commu- tator, has the polished finish that indicates good contact, and that the polish covers all of the sur-

ELECTRICAL SOUTH for AUGUST, 1942

face of the brush. When replac- ing a brush be sure to put it in the same brush holder and in its original position. It has been found helpful to scratch a mark on one side of the brush when removing it, so that it will be replaced properly.

New Brush Installation

When installing new brushes, fit them carefully to the commu- tator. Sand only until the curve of the brushes is the same as that of the commutator. Be sure that the brush shunts (pigtails) are fastened securely so that current will not overheat the brushes and brush holders.

Check the springs that hold the

=“ oo

Machine Fails to Start

Power circuit may be completely dead

Look for open disconnect switch, fuses re- moved from clips, or blown fuses

Power circuit may be single-phased

Leek for one blown fuse or one dead line

Power line voltage may not be suitable for motor, or may be extremely low; may be by ch ring of the motor

starter

Check voltage —- ee particularly at the rting

Machine may be jammed

See that armature turns over easily by bend, and leok for foreign material in air gaps

Motor starter may be single-phased

Check to see that all fingers on starter make contact when closed

Overlap protecting relays may be tripped

See that relay contacts are closed and that starter picks up when push button is p Be sure te remove cause of tripping

Motor Trips Off Line

Power circuit may be single-phased

Check for one blown fuse or dead line

Welder may be operating above current capacity

Welding electrode or work leads may be too long or too small in cross section

Check load against welder nameplate Check duty cycle

Check terminal voltage while machine is loaded; it should not exceed 30 volts on small machines or 40 volts on large ma- chines when operating at rated current

Ambient temperature may be too high

Make sure that temperature in motor-gen- erator recom or housing does not exceed 100 F and that there is no interference with normal ventilation of the machine

Welding Arc is Loud and Spatters Excessively

Current setting may be too high

Check setting and current output with am- meter

Check polarity

Polarity may be wrong

Try reversing polarity or try an electrode of the opposite polarity

*“Flashing” the field of a generator or exciter is a

thed of blishi the residual

magnetism of the field structure with the proper ——_. to cause the machine to *‘ build-

ly heavy current through the

up,” or generate voltage. It i of field windi

rily, using an external source oa direct current te supply the power.

If a low-voltage source, such as a storage battery, is used, the series field of the generator should be flashed; if a higher voltage source such as another generator or exciter is used,

the shunt field should be flashed.

brushes against the commutator. Improper spring pressure may lead to commutator wear and ex- cessive sparking. Excessive heat- ing may have annealed the springs, in which case they should be re- placed and the cause of heating corrected.

Inspect the commutator for col- or and condition. It should be clean, smooth, and glossy, with a color varying from straw to choc- olate brown where the brushes ride on it. A bluish or reddish color indicates overheating of the commutator. Roughness of the commutator should be removed by sandpapering or stoning. Never

use emery cloth or an emery stone. Use a “fine” stone or number 00

ELECTRICAL SOUTH for AUGUST,

1942

sandpaper unless the commutator is in bad condition, when the job may be started with a “coarse” stone and finished with “fine.”

For this operation, press the stone or sandpaper against the commutator with moderate pres- sure with the motor running, and move it back and forth across the commutator surface. Use care not to come in contact with live parts. Be sure to keep the dust out of the machine.

If the commutator is very rough as evidenced by pronounced up and down vibration of the brush- es, the armature should be taken out and the commutator turned down in a lathe. When this is done, it is usually necessary also

to cut back the insulation between the commutator bars slightly. If the commutator is found to be dirty when the generator is in- spected, it should be wiped clean with a piece of canvas or other cloth that is free from lint.

Never put oil on the commutator. Proper selection of brushes gives the commutator all the lubrication required to prevent excessive wear and to build up a good smooth operating glazed surface on the copper. The addition of oil re- sults in the development of a high resistance film which may cause undue heating and rough brush action. The oil will also have a detrimental effect on the internal parts of the commutator.

Transformer Maintenance

The are welding transformers of alternating-current welders re- quire a minimum of maintenance, but this fact should not be allowed to result in neglect. On fan-cooled units, fans should be cleaned and lubricated about once a year. Windings should be blown out at least twice a year in very clean locations, and more often in dusty places. At the time of this peri- odic attention, all connections and coil supports should be checked for tightness. Manual current ad- justing mechanisms should be lub- ricated often enough to prevent stiff operation of the handwheel or crank, making sure that a fair- ly high melting-point grease is uniformly distributed over the full length of screws and guides.

On motor-operated controls, lub- rication at more frequent inter- vals may be required, as evidenced by slowing down of the motor or noise from the gearing. This point should be checked at least three times a year, and more often if experience justifies it.

Abuses of Equipment

While most welding equipment is designed to stand up under un- usually adverse operating condi- tions, some not infrequent circum- stances will cause serious impair- ment if not complete interruptions of their service.

One bad practice, for example, is that of leaving weather-pro- tecting tarpaulins thrown over machines in operation, in such a way as to interfere with the free passage of ventilating air into and out of the equipment. Cases are known where welders have been equipped with canvas flaps perm-

(Continued on page 54)

PLANNING FOR INDUSTRIAL

Lighting Maintenance

By W. H. Kahler*

IFTEEN footcandles or 30 footcandles; which would you take if the cost was the same for either? Naturally, you will an- swer 30 footcandles, but how, you will ask, can I get 30 footcandles for the same cost as 15 footcan- dles. The answer is briefly ex- plained by the following example. Not long ago the author was called upon to survey the lighting in a large plant where the work- ers were complaining of poor see- ing conditions. It was found that the average illumination was about 15 footcandles and in some locations was as low as 5 foot- candles. However, when the light- ing equipment had been installed a few years before, the average il- lumination was 30 footcandles. It was soon learned that this drop in illumination was an accumulation of three causes:

1. Lamp outages

2. Dirty luminaires

3. Lamps of improper voltage rating.

By thorough cleaning and prop- er lamping, the original 30 foot- candles was obtained.

Recent surveys indicate that 40 to 60 per cent depreciation of the initial illumination is also com- mon in many other plants. The main reason for such high depre- ciation is due entirely to neglected maintenance. Dirty luminaires, lamp outages, improper voltage, and dirty walls and ceilings, are all enemies of adequate lighting.

These high depreciation factors which cause poor, inadequate il- lumination may actually be very costly to the owners because the workers are deprived of the use of the illumination for which the lighting system was. designed. Therefore, they must work under lower lighting levels which hinder the speed and accuracy of seeing and thus reduce the rate of pro- duction.

*Mr. Kahler is lighting engineer for the

Westinghouse Lighting Divison, Edgewater Park, Cleveland, Ohio.

This is the second of a series of three articles on the servic- ing of industrial lighting equipment. In this article, Mr. Kahler tells how to plan a reg- ular cleaning and lamping

schedule. &

Also, if only half the designed footcandles are received on the working plane, the cost per foot- candle is about doubled. If a lighting system is designed to in- clude allowance for neglected maintenance, a high depreciation factor will be used and many more luminaires will be required, thus’ increasing the initial and operat- ing cost. é'

Consider for example a _ build- ing of 10,000 sq. ft. To provide 30 footcandles in service with an al- lowance of 25 per cent for depre- ciation, sixty 500-watt units would be required. If, however, the ar- chitect allowed 50 per cent for de-

preciation because of anticipated poor maintenance, ninety 500-watt units would be necessary. This represents an increase of 50 per cent in the initial and operating cost because 50 per cent more units are necessary to compensate for poor maintenance. In dollars and cents, this would mean an ad- ditional annual operating cost of about $800 for an average plant using its lighting about 4,000 hours per year. Certainly, the 60 units could be properly and reg- ularly maintained for a small frac- tion of $800.

Of course, the architect does not have control of the building main- tenance, so it is the owner’s re- sponsibility to set up a mainten-

ance schedule that is practical and ~

that will enable the lighting sys- tem to provide the actually de- signed footcandle values in serv- ice.

Individual Responsibility

A number of plants realizing the importance of maintenance have set up regular schedules for serv-

MAZDA LAMP REPLACEMENT RATES (BASED ON THEORETICAL MORTALITY CURVES) 250 T T T w * fX \-——— FILAMENT LAMPS | vi a4 | —— FLUORESCENT LAMPS '. | J 3 bs | = 4 | ae ee | ee (8 d/o Ne ee « Vi Ne? pS | ag | < 4 AVERAGE REPLACEMENT RATE 50 - ¥ Vi a | wi } 0 100 200 300 400 500 PER CENT OF AVERAGE LAMP LIFE

Fig. 1. This Mazda lamp replacement rate curve will be of value in

estimating the probable number of lamp replacements per month for a

new installation. Note that few replacements will be required for the

first few hundred hours and that this rate increases and reaches a peak

at 100 per cent of average lamp life. Eventually the rate levels off to the normal calculated value.

ELECTRICAL SOUTH for AUGUST, 1942

icing the lighting and they find that such schedules are relatively inexpensive to keep up after a sys- tematic scheme is worked out. First, it is important that com- plete responsibility for taking care of the lighting system be given to one supervisor. In some plants, lighting has been a responsibility of each department head and he naturally considers lighting a sec- ondary item because his main job is to get out production, not to relamp and clean fixtures. As a result, lighting is neglected. Where all lighting is under the responsibility of one man, a light- ing maintenance crew can be

FILAMENT LAMPS

100 100%

90%

PER CENT LIGHT OUTPUT

$8 8 8

100 97 93 90 PER CENT RATED VOLTAGE

PER CENT LIGHT OUTPUT

93. 90.

100 97 PER CENT RATED VOLTAGE

FLUORESCENT LAMPS 100% 5 10 ne 90% 3 90 86% = 80 9 wf i 3 Ww 60 & a ata 100 97 93 go

PER CENT RATED VOLTAGE

Fig. 3. A few per cent drop in voltage will cause a considerable drop in light output. The reduc- tion in light output is most pro- nounced in the case of filament and mercury lamps but is consid- erable also for fluorescent lamps. These charts show per cent of rated light output at 100, 97, 93 and 90 per cent of rated voltage.

FILAMENT LAMPS

PER CENT LAMPS SURVIVING

10 20 30 40 50 PER CENT OF AVERAGE LAMP LIFE

. MAZDA LAMP MORTALITY CURVES

70 80 90

Fig. 2. Mazda lamp mortality curves.

These curves indicate the per-

centage of lamps that will be burning at the end of any given period

measured in per cent of average lamp life.

It is especially useful in

planning group replacements,

trained to do cleaning and relamp- ing on a regular predetermined schedule for the entire plant.

There are five fundamental re- quirements to a well planned main- tenance schedule:

1. Provide easy access to all luminaires.

2. Clean luminaires regularly.