UNITED STATES 

DEPARTMENT OF THE INTERIOR 

/ 

BUREAU OF MINES 

INFORMATION CIRCULAR 

PROTECTION AGAINST LIGHTNING AT SURFACE AND 

UNDERGROUND MINING PLANTS 

D. HARRINGTON, D.J. PARKER, AND L. H. HARRISON -------- - 
I. C. 7447, 

April 1948. 

INFORMATION CIRCULAR - -- 

UNITED STATES DEPARTMENT OF THE ImRIOR - BUREAU OF MINES 

By D. Harrington,g/ D. J. ~arker,l/ and L . H. ~arrisonL/ 

. INTRODUCTION 

The necessity for protection against the hazards of lightning manifests 

itself from time to time in the mining industry by reason of loss of life, 

damage to electrical equipment, fires in surface s%ructures at mines, and 

accidents in the handling and use of 'explosives. This paper is intended to 

assemble, correlate; and present some of the salient points embodied in the 

available literature on the subject and at the same time give some factual 

data concerning instances of such loss of life and damage to property, with 

special application to the mining industryc 

The annual loss of life and destruction of property by lightning is 

considerable; the former may be prevented to a limited extent, though use of 

common sense as to exposure is required and not always followed; the latter 

can be prevented to a considerable degree. The manufacturers of electrical 

equipment, through improved types of lightning arresters,, have done much toward the protection of electrical equipment, with consequent safeguarding of 

life and of property. Education based on unfortunate experiences has gone 

far to discourage the handling of explosives and blasting accessories during 

thunder storms, especially in open pits and quarries, and to a much smaller 

extent in underground workings. The lowly lightning rod plays an important 

role in the protection of certain types of buildings (especially isolated 

buildings), stacks, monuments, and other structures. 

LIGHTNING PHENOMENA 

In 1751, Franklin proved that lightning was simply a visible display of 

electricity - an extended spark; and until a generation ago little had been 

added to his exposition, to define the various phases of the phenomenon. 

Matters pertaining to lightning are discussed in the following references: 

- 1/ The Bureau of Mines will welcome reprinting of this paper, provided the 

following footnote acknowledgment is used: "Reprinted from Bureau of 

Mines Information Circular 7447. " 

- 2/ Chief, Health and Safety Division, Bureau of Mines, Washington, D. C. 

- 3/ Former supervising engineer, District D, Health and Safety Division, 

Bureau of Mines, Birmingham, Ala, 

- 41 Mining-electrical engineer, Bureau of Mines, Birmingham, Ala . 
Lightning discharges are initiated by invisible pilot streamers or 

leaders propagated from the cloud toward the fin, forming a path for the 

discharge. Regarding this, Wagner and McCann, %"i state: 

As the leader strikes the ground an extremely bright streamer 

propagates upward from the earth to the cloud following the same 

path as the main channel of the downward leader. The charge distributed along the leaders thus is discharged progressively to 

ground, giving rise to the very large currents usually associated 

with lightning discharges - currents varying between 1,000 and' 

200,000 amperes. 

With currents of such magnitude, even though spread over a considerable 

area of the earth's surface, voltage gradients a r e b u i l t up owing to the resistivity of the earth, which can provide sufficient potential difference to 

set off explosive charges primed with electric detonators and produce definite 

shock hazard. Such valtage differences are not confined to the earth's surface but have caused premature explosions in underground mines, and instances 

- 6/ Wagner, C. F., and McCann, G. C., ~ightning Phenomena: Chap. 12, Electric 

Transmission and Distribution Reference Book, Westinghouqe Electric & 

Manufacturing Co . , Pittsburgh. 
I.C. 7447 

are on record in which persons have received severe shocks at remote locations 

underground during lightning storms. 

Below are some abstracts of'letters and reports giving data on instances 

in ~hich~lightning isknown or suspected to have caused premature explosions 

or electrical shock in mines and quarries. 

I have in mind an occurrence at the Wakefield Pit of the M. A. 

Hanna Co. at Wakefield, Mich., about 1922 when two well-drilled 

holes were loaded to be detonated with electric blasting caps; and 

while the men were at lunch a lightning storm came up and these 

holes were set off without damage to anyone. There was always a 

question as to whether the wires were properly "shorted" when 

left. * * * 

On May 22, 1908, at Caimito Mulato, Canal Zone, during a 

thunder, storm, lightning exploded 31 tons of dynamite in a number 

of drill holes. The charges were all pldced and the legs of the 

electric detonators were being connected to the leading wires. 

Two fatalities and a number of injuries resulted. * + * 

On August 11, 1908, at Macachin, Canal Zone, a number of 

holes had been charged, and the legs of the electric detonators 

had been connected up to the leading wires when lightning struck 

the circuit and exploded the whole charge. Four men were injured. *** 

On November 7, 1911, at Miraflores Locks, Canal Zone, lightning set off 12 35-foot holes, in which were 1,100 pounds of 60- 

percent straight nitroglycerin d--mite. Electric detonators were 

in place in the holes but the legs had 'not been connected to the 

leading wire. The evidence is that all of the holes exploded, 

and it is possible that a number of these holes were fired by influence from adjacent holes. A number of men were injured but no 

fatalities resulted. *** 

In June 1913, in an open-pit iron mine in the United States, 

during a thunder stom, lightning struck a bench near 34 charges, 

14 of which exploded prematurely. Thirty-four charges had been 

placed in chambers which were reached by "gopher" holes. Two 

electric detonators had been placed in each charge, and the mn 

were placing the stemming in the gopher holes, when a severe 

electrical storm occurred. A number of the men took shelter in 

an unfilled "gopher" hole. A lightning flash was seen to strike 

the bank near the charges, and a blast occurred immediately. 

Eighteen men were killed in this accident. *** 

In August 1918, in an open-pit mine in the TJnited States, 

lightning exploded prematurely two "springing" charges, which 

contained five sticks of 40 percent dynamite. Each charge contained an electric detonator, and the leading wires were lying 

on the surface. No one was injured. **+ 
where electric blasting is employed and especially where the charge 

is placed in part or whole sometime before it is fired. 

In the case of the Brockville, Ontario, explosion, it is not 

known whether the legs of the electric detonators or the shotfiring circuit were electrically short-circuited by twisting the 

wires or otherwise, but in the other cases mentioned, it is reasonably certain that this was not done in any case. This would 

be a wise precaution to take in any event, though the degree of 

protection afforded by it cannot now be definitely stated. 

Notable features of this premature explosion are the fact 

that it was the custon of this drill boat to bring the explosive 

for charging in the holes to the drill boat immediately before 

charging and in this case it appears that but little or no explosive was on the drill boat at the time of the explosion. That 

11 survivors were rescued was due to the fact that the United 

States Cutter CG. 211 was nearby; a flash of lightning aras observed from it, as was the explosion, whereupon it proceeded 

promptly to the site and started the rescue operations within 

about 3 minutes. * * .* 
I.C. 7447 

The Sliver mine in St. Louis County, Minn. was first developed 

as an underground property in 1908 but later as an open-cut by removing 40 to 60 feet of glacial drift. The major ore body extended 

in an east to westernly direction. The ma,jor portion of the steam 

shovel operations had been conducted in the south portion of the 

open-cut leaving a bank of ore on the north shore line approximately 

500 to 600 feet long, 40 feet high, and 100 feet wide. Old sublevel 

drifts from the underground operations extended from east to west in 

the b3nk, and during 1918, it was decided to drive crosscuts to the 

shore line in an attempt to mine the ore and stockpile it in the pit 

for later loading by steam shovel, This attempt was unsuccessful and 

it vas then decided to blast the entire bank in one operation by 

driving coyote holes and drift, then load the ore by the steam 

shovels. 

Timbered coyote holes were driven 50 to 60 feet into the bank 

at 50-foot intervals about 5 to 7 feet above the open-cut bottom. 

Drifts were driven in an east to westernly direction, connecting 

up all the coyote crosscuts. After the drifts were completed, a 

half carload of granular black blasting powder and 45 percent 

dynamite were distributed throughout the drifts. Primers consisting 

of electric detonators and 45 percent dynamite were placed in each 

charge and the wires were extended to the coyote hole openings. 

Stemming consisting of ore materials in bags was piled as close to 

the explosives as possible and the coyote holes were packed with 

loose ore. 

The work was almost completed on Thuro -day, June 27, 1918, and 

it was decided to fire the blast on the following Sunday, when adjacent rnfnes would be idle. 

An electrical storm passed over the mine about 10 a.m. on 

June 27, 1918, and the heavy rain dccompanying it caused the opencut operation to be stopped; however, 13 men engaged in placing 

stemming in the coyote holes continued working during the storm. 

A shovel crew of six men sought shelter in an old timbered drift 

in the east end of the area which was to be blasted; this drift 

intersected the open-cut bottom and extended into the bank for 

60 to 70 feet. 

Eye witnesses are said to have testified that lightning struck 

the mine, and a terrific crash was heard when suddenly the ore bank 

seemed to open and slide away from the north shore line caving all 

openings. 

Rescue work was started immediately, but of the 19 men in the 

drift and coyote holes, only 1 was saved and the other 18 lost 

their lives. The company haa a complete map of all coyote holes 

but it was of little value due to the shifting and sliding of the 

bank. * * * 
from ourfcompressor and exposed to the weather. Shortly after 

Anderson and his crew came out of the mine there was considerable 

thunder accompanied by sheet lightning, and the loaded holes were 

all discharged. The pipe line, in this case, was unquestionably 

the conductor, there being enough electrical energy in the air to 

detonate the E. B. caps. The Jightning did not appear to strike 

in this case, but the whole atnlosphere was charged. . . 

Y** 

~hk "Explosives Engineer" of October 1933, page 294, gives an. ' 

account cf a premature firing of 16 out of 36 holes in an underground 

linestone mine of the Washington Building Lime Cc., Bakerstown, 

Jefferson County, W. Va. The account states that the men had charged 

36 holes and were some distance from the surface, that the firing 

lines were all'disconnected, and the cause of the premature blast is 

attributed to lightning. *** 

Early in the season, bush fires threatened to do much damage in 

northwestern Quebec, but large crsws;and a heavy rain checked the 

blazesin time. The OrBrien rhine at Cadfllac was shut down for a day 

because of the nearness of fclre and in Joadnes Township, near Rouyn, 

200 fire fighters succeeded in quelling the first "green bush" fire 

of the year. 
I.C. 7447 

The same storm that helped to put out the fires was responsible for the loss of three minersf lives at the bottom of Sladen 

Malartic's shaft, then at a depth of 700 feet. It was the third 

time a supercharged atmosphere had set off an electric blast premturely in northwestern Quebec, although it has never happened 

in nearby Qntario mines where no ot$er precautions are taken, 

Holes for the "squere-up" round iri the shaft-sinking operation had 

been completed, and all but the blasting crew of three had been 

taken up. Loading was completed, and the electric blasting caps 

had been connected, Fifty feet above, on the safety bulkhead, 

the circuit was broken. On the TOO-foot level, the circuit was 

broken in two places, one of them a locked switch to which only 

the chief blaster had a key, The men were j~ist ready to come up 

in the bucket when a flash of lightning crossed overhead, at least 

50 feet from the headframe. The charge at the shaft bottom went 

Two died instantly and the third man lived 20 

minutes .:! *** 

Lightning Explodes Dynamite 4,000 Feet Below Ground 

- Johannesburg, December 13. - Eight native mine workers were 

killed in a Rand mine December 12, 1937, when lightning struck a 

bell wire on the headgear of the Central Shaft and detonated 11 

dynamite charges 4,000 feet underground. The men were in a party 

of 15, preparing dynamite charges under the supervision'of two 

Europeans. Four other natives were seriously iqiured. One of the 

Europeans, 1W. J. J. P. Pretorious, was saved from serious injury 

and perhaps death, by the action of a relative, who p~shed him 

aside in the first explosion, The mine is owned by East Rand 

Proprietary Mines Ltd .5/ * * * 

In the summer of 1929 in the Machusett-Coldbrook Tunnel in 

Massachusetts, after a round had been charged and the men had 

left, and while both safety switches were open, lightning which 

accompanied a thunder storm on the surface, struck the shot-firing 

line, followed it down the 411-foot shaft and toward the face of 

the tunnel about 1 mile distant, ,jumped across both of the open 

switches, and fired the shot. Nobody was in,jured. Subsequent to 

this occurrence eight-foot gaps were introduced into the shotfiring line as a protection against premature explosion from 

lightning. *** 

A fire completely destroyed a fan installation about 3:30 a.m. 

on August 8, 1944, at the Carbon No. 3 mine, Carbon Fuel Co . j Carbon, 

We Va. An electrical rain storm was raging during the afore-mentioned 

date, and it is the opinion of the rranagement that the fire was 

- 7/ This item was taken from the Canadian Mining Journal. July 1938, vole 59, 

NO. 7, P* 407. 

- 8/ Mining Journal o on don) vol. 199, No. 5339, Dec. 18, 1737, P. 1124. 
was jued. ts case, dg 

s doe odayst, te 

holes are loaded with electric primers in the evening, and the 

blasting is carried out at daybreak the next morning. The blast 

was fired by lightning in the middle of the night, and no one xas 

in the vicinity. Necr North Bay, Ontario, in the course of some 

constructisn.work, rnen narrowly escaped serious in-jury when lightning set off a row of primed holes. 

I believe that our operators are very careful to avoid the 

.connecting up of electric blasting wires in a stono, 3ut in two 

fatal accidents which have occurred in this district as a result 

of induced currents caused by lightning, no one had previous cotice 

that a storm was im~inent. In both csses, the sky was cloudy, and 

it had rained to some extent, but the sudden lightning discharges 

cane without werning. This evidgnce was checked with the power 

corr.pariyfs substation records, and as you know, their instruments 

record even minor surges. 

There is very strong evidence to indicate that the induced 

charges were led underground by the hoisting cables. A cable 

stretching from the drum of a hoist over the head sheave offers an 

ideal collector, i.e., condenser, as it is not grounded to unlim; 

ited capacity. Also, in case of a nearby discharge, it would pick 

up stray currents by induction and transait or create secondary 
I.C. 7447 

induced currents in parallel conductors. In view of the many and 

severe storms in this district, I favour the following practice: 

When the explosi.ves and ele~tric~primers have been delivered 

to the shaft bottom, the bucket shall be rung up to the blasting 

set. The men will then load theholes, and connect-up the wires 

between holes. When completed, they will ascend to the blasting 

set via the ladder, the last man unreeling the lead wires.. ,men 

they reach the blasting set, they will test their circuit, and 

connect up to' the blasting wires as. in ordinary practice. If a 

chain ladder is used, it would be advisable to hang this laader, 

in a part of the shaft.as far as possible from the hoistiG, CO* 

'*. partment and the blast'ing wires ; a wooden ladder would b'e 

preferable . 

The suggestion contained. in the abme paragraph wo,uJd, I believe eliminate the danger from unexpected lightning discharges. 

Cf course, handling blasting caps during an electrical storm is . 

clearly dangerous. *** 

The details of this Shenango incidRnt were as follows: Four 

"jump" holes had been drilled in an ore bank ahead of a shovel for 

the purpose of blasting the cre. These holes were about 30 feet 

'deep. The blasters had placed one stick of dynamite with an electric blasting cap attached in each hole, which was the customary 

practice at that time in "blowing out" the holes preliminary to 

placing the regular charge of powder used in blasting the ore. 

These four holes were not wired together. The ends of the 

blasting wires were lying upon the ground under a rock at the 

collar of each hole. The ends were not twisted to€ether, which 

is bur practice today in order to close the circuit 2nd guard 

against stray currents and premature explosions , 

While the holes were thus charged with one stick of dynamite 

each, an electrical storm came up during which the blasters and 

others in the pit sought shelter from the rain. When the men returned to the holes they discovered that all four sticks of dynamite had been discharged, presumably by lightning, although no 

one heard any definite report. No one noted that any particular 

flash of lightning struck in the or?:; nit, but there was much 

lightning accompanying the stom. )J.) one was injured. 

We are unable to find any otFe2 i~stance of premature blasts 

at cur properties due to lightnimg. It is the general rule today 

cot to charge holes during an electrical storm. 

With ~ordeau fuse this danger of blasts being set off by 

lightning is minimized since no electric blasting cap is attached 

to the fuse until immed5ately before the blast, and'this is not 

done if the weather is stormy. In ordinary electric blasting the 

ends of copper lead wires are always kept twisted together -until . 
amounting to 90 lbs. of Gelignite had been prepared and >rimed 

in the face of a tunnel 1,000 yards awsy from t'ne entrance, when, 

whilst the men were returning to the firing battery, the charges 

suddenly exploded. At the time a severe thunderstorm raging, 

and it is believed that lightning fired the charges. At the same 

moment a man, vho 'was standing at the entrance of the tumel with 

spanner in his hand, received s shock which wrenched the spanner 

frcm his hand and caused im to fall. Eight men were injured as a 

result of this accident 

The chief coal-mine inspector of the Province of Victoria, Canada, wrote, 

in part, on ~ulg 21, 1938: 

On July 5th, 1938, an explosion occurred in "B" mine, Michel 

Colliery, in the solltheastern part of this Province, and caused 

the death of three men. 

This colliery is situated in the Rocky Elountains, at an elevation of 4,000 feet, and i.s located in a narrow valley above which 

the surrounding mountains rise several thousand feet. 

His Majesty's Inspec-cors of Explosiv6s: Fifty-eighth Rnnual Report, 1933, 

p. 20. 
I.C. 7447 

The measures are inclined from lo0 to 30' and outcrop on the 

mountain above the mine which have been developed by means of a 

cross-measure adlt drift and at present four minesrare in operation, in separate seams, and may be considered as entirely 'separate 

mines except that their returns all join one common main return to 

the fan; I 

I The intake of "B" mine is at the outcrop on the mountains.ide 

at an elevation of 600 .feet above main adit drift 'and at' a point 

some 4,.000 feet, by course of sir, from the mamain return. ' 

. h 

The "B" seam is 5 feet thick and is all clean coal; the system 

of minirig is to develop large pillars to a predetermined4ine and , 

recover the' pillars by a retreating longwall method. All the cod 

is machine-.cut and conveyed to the cars on the main haulage'eoadk: 

. 

This seam is quite dusty, but all the workings are well 

treated with lime dust, and the return air from this "B" mine 

shows, by analyses, variously from 1 percent to 1.25 percent k~~ 

content and it is very seldom that CHq is detected by flame safet? 

lanp tests in the working parts of the mine. 

On the day of the explosion only some 17 men were underground, 

as it was an "ldle" day; these men were engaged in repairs, moving 

machinery, etc., and were distributed as follows: 5 in "B" mine, 

6 in No. 3 mine, 2 in the main return and 4 on the main adit tunnel. 

~pproximatel~ 50men are employed on dayshift in "B!' mine, ' 

which produces 500 tons per day, and it is beyond doubt that had 

this explosion occurred during a working day mny, if not all, of 

these men would have been killed. 

At the time of the explosion (1:40 p.m. ) there was an intense 

lightning storm, and some witnesses who were engaged on construction 

work outside the mine reported that they had seen a lightning discharge strike the immediate vicinity of the intake portal of "B" 

mine and raise a cloud of smoke; other men who were working close to 

the portal of the maln tunnels were affected by lightning at the 

same instant . * 

There was no knowle'dge of an explosion at this the, but the 

above phenomena raised an alarm and on investigation it was discovered that an explosion had occurred in "B" mine. 

At the same time three men working at different points in No. 

3 mine reported to their fireboss that they had seen flashes of 

light running along the rails and making a moise like firecrackers; 

one man on an incline stated that he saw a light traveling up one 

rail for a distance of 250 feet towards him and appeared to die 

out 15 feet past him. None of these men experienced anything in 

the nature of an electric shock, but another man who was working 

on a +inch pipeline did suffer a &hock. (I may say that there ' 
pg

nificance to note, according to a farmer who lived nearby, that a 

severe stroke of lightning occurred simultaneously with the pipeline rupture. . . 

The break occurred in western Iowa, about 7 miles northwest . 

of Bed Oak and 7.4 miles east of our nearest compressor station. 

The country in the vicinity of the break is glacial drift known 

as. upland - in general, a gently undulating plan. The hills 

throughout the upland are smooth and rounded. The slopes are 

gradual and uniform and the landscape has a rolling appearance. 

The pipe rupture occurred on the top of one of these hills. The 

immediate field was under corn cultivation. 

Probably more important than weather conditions surrounding 

a-break su-cki as that with which we are concerned, are the detailed 

facts of the construction gf the line, the location of the rupture, 

and other contingent circumtances. 

. - 

When the 24-inch lino was laid in 1931, the composite type of 

construction was used; that is, two or three 33-foot joints of pipe 

were welded together to form 8 solid.weldea section. These sections 
I.C. 7447 

were joined by a.Dpsser-type coupling. The trench was excavated 

to a nominal width of 32 indhes and a minimum depth of 5 feet, 

which provided a minim-im cover of 3 feet. 

The pipe was completely severed by the rupture. The reaction 

which immediately followed the initial force contained sufficient 

energy to turn a 39-foot piece of the pipe section end for end. 

This pipe came to rest about 30 feet from its original location 

in the pipe line. The remaining section of the pipe came to rest 

approximately 125 feet from its position in the line. This piece 

of pipe contained the 8O overbend. 

Ina~m~ch asa severe stroke of lightning was reported to have 

occurred simultaneously with the pipe-line break, it was decided 

to investigate the probabilities of lightning as an influencing 

factor. I) I 

Our first efforts in this regard were directed toward a 

search on articles or discussions on the subject of lightning 

and its contributing influence on pipe-line failures. Inquiries 

were directed to tho secretaries of the American Gas Association 

and the American Petroleurn Institute. The Industrial Arts Index 

was also reviewed. We found three specifi,~ citations with direct 

bearing on the subject. The following will briefly describe each 

incident. 

Mr. Fred M. Goodwin, vice-president of Distribution of the 

Boston Consolidated Gas Co., has related an experience which occurred in Boston in September 1903. This incident was reported 

in a letter dated September 27, 1938, to the American Gas Association. The construction of a 24-inch main had been completed but 

had not been placed in service. A 24-inch gate valve had been 

installed at the point of connection with the existing system. 

or three days following the completion of the line there was 

a severe thunder storm, during which lightning struck a drip 

stem; this resulted in blowing five ler.yths of 24-inch pipe out 

of the trench. The supposition is that the 24-inch gate valve 

did not make a tight shut-off, which permitted a leakage of gas 

into the newly completed section. A gas-air mixture was thus 

formed which was ignited by the lightning and resulted in the 

explosion. 

The issue of the Gas-Age Record dated August 30, 1324, contains an article entitled "Lightning Destroys a New 20-inch Gas 

Main." The failure occurred on the night of Auyst 6, 1924, at 

Worcester, Mass., during a terrific electrical storm. It was 

definitely determined that lightning had struck one or more times 

in the vicinityof the newly completed 20-inch cast-iron main and 

that 60 feet of the 20-inch pipe were damaged. The cast-iron pipe 

was completely shattered and gave the appearance of having been 

struck by a large stone breaker or steam hammer. The main had not 

been placed in service and was supposed to contain only air, with 
ceptible deflection. There were no evidences of fusion or of heat 

on the pipe. 

Representatives of thc Duquesne Light Co . , the ~estinghouse 

Electric & M!m.facturing Co., and the Genersl E:Lectric CO.-were 

zonslllted regarding the part lightning m~~g have contributed toward 

the pipe rupture. 

Mr. C. F. Fortesc~re (ciecczsed), Conszltin,~ Engineer of the, 

Westinghouse Electric & &nufscturing Co., together with his assistant, made a vsry careful study of the pipe and other conditions surrounding the strike. The studies which he made and thel conclusions 

dram seen to give ample confirmation of the theory that th? failure 

was caused by the pressure created by a lightning discharge through 

the earth and partly confined by it, The above incfdent is quite 

amlogo?ls to our own break. 

In a further effort to obtain more information on the ~henomena of lightning, we consulted a nub& of technicians who were 

well qualified to- discuss this subjcct. These men were representatives of General Electric Co., Westinghouse Electric & Manufacturing 

Co., Western Railroad Supply, U. ,E. Bure~u of Standards, U. S. 

Weather bureau, Amour Institute of Technology, and Kansas City 
I.C. 7447 

Power & Light Co. Several theories and opinions were advanced as 

to the influence lightning would have in the destruction of pipe 

to which we have referred. Some of the engineers were of the 

opinion that it wa8 possible but not prcbable for lightning to 

have suff,icient force to rupture such 9 steel pipe. Others were 

of the opinion that the lightning stroke could have had a current 

magnitude of 200,000 to 250,000 amperes, and since it would dissipate itseLf in microseconds of time, it would be sufficient to 

cause destructive distillation of the cell structure of the earth 

and thereby develop enough pressure to destroy the pipe in a manner similar in some respectis to giercing the pipe with a projectile. 

It may be well to review a few of the phenomena of lightning 

and its destructive forces. It is generally accepted that when 

lightning strikes a tree, the tree is splintered from the internal 

pressure developed by the formation of steam from the moisture in 

the tree. It is further possible that under the high current intensity and potential gradient of a lightning charge, some of the 

material itself is decomposed or distilled with the formation of 

gaseous products which develop a high pressure. 

It is known that when lightning strikes an insulated copper 

wire, the wire will completely volatilize and disap2ear. There 

will be no indication of burned or fused metal. The insulation 

will remain intact with no appearance of having been heated. 

The June 12, 1936, issue of Science contains-a very interesting report of a lightning stroke which occurred near Dodge, Neb., 

on June 24, 1935. The families who lived in the vicinity reported 

a lightning stroke of eqlosive intensity. A few days later a hole 

was found in the earth in a corn field. The hole was investigated 

and was found to measure 8 inches in diameter at the surface. The 

hole extended downward 8 feet almost vertically with an average diameter of 8 inches and then became smaller for the next 7 feet and 

varied somewhat from the perpendicular. At a de?th of 15 feet the 

diameter had been reduced to about four Inches and the main hole 

branched out in three directions into 2-inch hcles which followed 

for 3 or 4 feet horizontally into the earth. The clay showed signs 

of fusion at a number of points, and the inside of the hole had a 

cormgated appearance as though moist clay had been forced violently 

back by high pressure. It is known that when lightning strikes sand 

or sandy soil, fused sections will result which are known as lightning tubes or fulgnrites. These statements represent interesting 

examples of the heat and action of the lightning stroke. 

The Oil World of ~e~bkmber 1939 has an excellent article entitled Fire 

Prevention, Protection Development in the California Oil Industry (pp. 3-7), 

and the following paragraphs taken from it indicate some of the problems of 

the petroleum industry due to lightning as well as other causes of fire: 

It takes a serious loss to create a sense of future caution. 

Prior to 1920 no such loss had occurred in the oi.1 ind;lstry on the 
Itwas naturd enough that the engineers who had been assigned 

by these several companies to the newly organized fire service should 

get together. One of the first activities was to study forms of 

lightning protection, and it is a fact that in la25 plans were well 

under way for the installation of lightning towers and Faraday grids 

for oil-reservoir protection under the direction cf Messrs. Frank 

Peeke and E. R. Shaffer. The interest in this form of protection was 

accelerated by two g~eat lightning fires in the fall of that year 

each involving a crude oil reservoir. 

Then on the morning of April 8, 1926, two 750,000-barrel reservoirs blew off their roofs simultaneously at San Luis Obispc, 

Calif., and an hour later another of the six reservoirs followed 

suit. In the ensuing fire all six reseryoirs were destroyed along 

with 15 steel, wood-roofed tanks in the same farm. California, 

which is practically lightning-free, had produced the greatest oil 

fire of all times. 

I wish that the story might end here, but unfortunately this 

was not bad enough, for on the morning after the ignition at San 

Luis Obispo, the same freak or un~sual storm reached Brea, Calif., 

250 miles to'the south, and there repeated on another tank farm of 

the same company. Here three reservoirs and a small refinery were 
destroyed. There was one other reservoir-lightning- Sire 3 weeks 

later, since which time the record has been perfect on all pr.0- 

te cted risks. 

It is needless to say that the five oil companies involved in 

the fires that have been mentioned have never lost their interest 

in fire protection. Lightning protection has become standard 

practice, It is however curious to note that the other companies 

on the Coast have not followed their example in setting up fire 

engineering departments. It is the goup which went through the 

great fires of 1923 to '26 that are today carrying the fire protection program. 

It is pleasant to be able to say that so far as the last ten 

years are concerned, the Pacific Coast and paraticularly the major 

companies, have pofited by the experiences of the past and that 

the whole subject of fire protection has been glven reasofiable 

backing by most companies. Lightning protection, eliminutiori of 

wood roofs and better housekeeping has helped. Losses have been 

small and as a result there has been time to consider the problems 

of community srotcction. 

PROTECTION AGAINST INJURY OR DEATH CUE TO PREMATUm EXPLOSION 

In mines and quarries, precautions should b~ tdcen to prevent as far as 

possible any chance of premature explosion due to lightning. Short-circuiting 

of the lead wires is a primmy precaution. In sorub open-pit mines, it is now 

the general practice not to charge holes during the ~pproach or 2rOgress of 

an electrical storm. In underground mines, howevcr, this would not be 

2ractical. 

In mines using electrical equipment, feeder cables from the surface are 

a necessity, Such feeders should be equipped with modem-type lightning arresters ncar -he point of entry to the.minc. These arresters should be examined znd tcstcfd frequently, not only to insure that tht arrester is functioning properly, but to keep a chcck upon th~ exound yesistanc~ and to maintain 

it at a low valuc. Low trducs of%ground resistanc~ are im2crative, if maximum 

protection is to be obtained. 

The question is frequently ask~d as to what constitutes a good 

ground; thc better the ground, the bctter thc protection, hqnce, the 

bcst ground is nonc too good. Lightning discharges or surges run into 

thousands of amperes, and a high ground bop cm put the arrestor at 

such a high discharge or ground voltagb that it loses its cPfectiv6- 

ncss. A 5,000-ampert surge through u 30-ohm pound wodd produce a 

150,000-volt drop in the ground only.g/ 

Cure should be taker1 to see that lcad wires and shot-firing lincs do not . 

cGmG in contact with rails, air or water lines, and at no timu should. the 

Pewcc, C. T., and Allen, R. E., Lightning Dtmycrs to Coal-Mine Distribution Systems Minimized by Protdctiv~ Devices: Cod Age, vol. 42, No. 9, 

S~ptember 1937, i pa 59-60; NO. 10, Octokxr, pp. 55-58. . . 
machinery requires protective apparatus which will also slope the 

wave front so that the blow becomes more of a push, even though 

of the same magnitude, and against which the electrical equipment can, so to speak, brace itself. 

\ Electrical equipment requires the protective functions of both lightning 

arresters and capacitor equipment to reduce the steepness of the wave front. 

To quote again from Pearce and Allen: . 

Any equipment with multi-turn circuits presents the known 

fact that, when a surge is impressed upon it, the voltage will 

not distribute evenly throughout the circuit but will depend on 

the number and arrangements of the turns and the steepness of 

the front of the surge. 

In one case where a 300-kilowatt motor-generator set was damaged frequently by lightning, three single-phase lightning arresters of the ceramicdirk type were installed in the pit beneath the motor-generato set. A 3- 

phzse oil-filled capacitor unit was also installed in the pit and connected 

across the terminals of the 2,300-volt motor. Thls combination effectively 

eliminated further damage from lightning at this location. 

- 11/ See footnote 10. 
I.C. 7447 

For the protection of direct-current circuits the capacitor-type arrester, though more expensive, is likely to be superior to the multigap arrester. The capacitor-type not only has a m~ch lower voltage ratio, but it 

is applicable to circuits up to approximately 4,000 volts. For this reason, 

it is particularly adapted for use with direct-current machinery or machines 

with weakened insulation. 

WHAT TO DO 

A resume of the foregoing would indicate that the following procedure may s reduce the danger of injury aad death fron lightning: 

During the progress of a lightning storm, 

(1) Get under shelter when the storm comes, Do not stay out in 

rain. The larger the house or barr, the better the protection. 

(2) Avoid shelter under isolated trees, The middle of a dense 

forest is fairly safe. Avoid the foot of a pole, mast, or 

tower. 

(3) Avoid an open space, such as a beach, swimming pool, fishing 

pond, baseball field, golf links, or pasture. 

(4) Leave hilltop or ridge. Head for the valley or the base of 

a cliff. A cliff is relatively effective shelter. 

(5) Leave a small camp cottage, small shed, or small open barn 

for a larger building, In a large building stay downstairs. 

Choose a place near the center of the room. Avoid windows. 

Stand away from stoves or pipes. Shun the fireplace. 

(6) If you are driving an automobile when the storm comes up, 

remain in the car with windows almost, closed. 

Victims of lightning stroke often can be resuscitated if proper treatment 

is given in time, Injury and death from lightning result from electric shock, v and the indicated treatment is artificial respiration and treatment for physical shock. 

I Lightning, like electricity from a power system, causes shock by paralyzing the nerve centers that control breathing or by stopping the regular 

beat of the heart. In severe cases, burning of the body tissues is probable, 

Artificial respiration should be given immediately. 

ARTIFICIAL RESPIRATION^/ 

Artificial respiration is a method by which normal respiration is imitated 

by manual movements to restore breathing. In many conditions where breathing 

has ceased or apparently ceased, the heart action continues for a limited time. 

- 121 Bureau of Mines, Manual of ~irst- id ~nstruction: 1940, pp.-52!and 53. 

2113 - 19 - 
p

dition has ,greatly improved, Relapse should be watched for and combated by 

renewed shock treatment. After he has recovered from shock of even short 

duration, the patient should be kept lying dokm and quiet so that as little 

strain as possible is placed on the circulation and heart action. 

AVOIDANCE OF PAMAGE BY LIGirmNING . 

Preventive measures covering the avoidance of premature explosions and 

damage to equipment and buildings due to lightning should include the 

following: 

(1) Strict adherence to, codes and regulations established for safe 

blasting p~ocedure and the prevention of accidents. 

(2) Careful supervision of blasting methods and frequent dissemination of available knowledge on the subject. 

(3) Installation and maintenance of lightning arresters and electrostatic..capacitors at strategic 1ocations.on power systems, and 

overhead ground wires on transmission lines. 

- 13/ See footnote 12. 
(4) Frequent checking of insulation values .on rotatlng machinery 

and transformers and ,the maintenance of 'such insulation at 

high values. 

(5) Provision and maintenance of low-resistance grounding connections for lightning arresters and for the frames of rotating 

equipment and transformers. 

(6) Installation and maintenance of lightning rods and overhesd 

ground wires on isolated buildings of nonmetallic construction. 

L 

A draft of a radio presentation on the subject "Protection Against Lightning by the Underwriterst Laboratories, Inc., had some interesting statements, 

as indicated by the following abstracted dialogue: 

DUDLEY: Are there any figures to prove the value of lightning protection? 

MANNING: The records are full of proof. Eight years ago, 6,000 grain 

elevators in the Prairie Provinces of Canada were equipped with 

approved lightning-protection systems. Each elevator containing 

50,000 bushels of grain was insured for $25,000. Before these 

elevators were protected, there had been an average yearly 

lightning loss of $160,00@. Two years after the-lightning rods 

were installed and inspected, not a dollar's lightning loss had 

been sustained. And today, 8 years later, we have still not 

had a report of any lightning danige to those elevators. 

ALCOCK: The entire project was more than paid for by the satrings effected in a few years. 

DUDLEY: That's renarkable! And to date (1've been doing a little 

mental arithmetic), the protection of those elevators represents a saving of nearly a million and a quarter dollars. 

WOOD: The record in one midwest State shows that over a 2 year 

period, 503 buildings .without lightning protection were 

struck, causing a loss of 81,060,000. In the same period 

only 28 protected buildings were hit, and the loss was about 

$87,000. 

3n the other hand, an inquiry as to lightning-rod protection for surface 

explosives-magazines was addressed to one of the best-informed experts of one 

of the maJor producers of explosives in the United States, and brought forth 

the following reply: 

We agree that a lightning rod, properly installed and properly maintained on a dynamite magazine, should offer some protection. 

On the other hand, a lightning rod, if not properly installed or 

cared for, makes the condition worse than if no rod had been installed at all. In view of the fact that dynamite magazines are 

ahnost invariably in isolated locations, the magazines themselves 
Larger wires - 4/0 is not too big - fjr grounding and better 

terminal connections should be used. Brazing to the frame if vibration is present may be desirable to obtain good contact; Inspection of the groUnd connections at frequent intervals is recommended. 

Tests should be made every year. TJse of d.c. capacitors or suitable 

arresters across the terminals of machines increases protection. 

The capacitor also aids where flash-overs are the tendency. 

Temporary ground connections for power co~ductors when men 

work on the lines should be standard practice. Static electricity 

can be drained to a good, carefully hde, temporary ground. Care 

should be used in grounding lines so that men do not work in positions where a drop in potential occurs across their bodies. 

Avoid metal fences around high-voltage equipment unless 

there is an exceptionally good ground connection. Before using 

the steel frimework of any building for grounding exposed metal 

surfaces of electrical equipment, it should be determined whether 

the steelwork is at' ground potential; if not, it should be grounded 

to prevent shock. 

2113 - 22 - 
I.C. 7447 

Since in the d.c. mine circuit the negative is grounded with 

current return in the rail as standard, positive wires should he 

kept insulated, negative wires grounded, and rails well bonded. 

Grounding of rails frequently is not perfect, since they rest on 

rocky soil and mine ties. As an added safety precaution, a supplementary gronnd connection, such as a water system, borehole 

casing or artificial ground, is desirable if the mine rail is to be 

counted on as an absol~lte grounding medium, 

The lightning hazard has unquestioncbly been reduced as compared with the 

conditions in effect one, two, or more decades ago; however, losses of life 

and of property due to lightning continue to occur. 

This paper presents some information on the effect of lightning on the 

mining industry, and it will be noted that both surface and underground w~rk 

is affected and that, while premature detonation of explosives is one of the 

main hazards in the mining industry due to lightning, it is by no means the 

only harm to the industry from thls cause.