. Protection€¦ · Kasper, Industrial Risk Insurers Explosives Robert W. Lindquist, Lightning...

COMMITTEE ON LIGHTNING PROTECTION INTRODUCTION 7 8 - - 5

• R o ~ n n r f n f ~ . n m m i t F I F , - A : n n I . i n h t n ; n n " " - - r " . . . . . . . . . . . . . . . - - " " " " . . . . . ' ' = l " • ~ " • • • ":=:P

. P r o t e c t i o n

John W. McGinnis, Chairman Loss Control Engineering Dept., Kemper Insurance Cos.

Long Grove, IL 60049 (rep. American Mutual lnstirance Alliance)

Marvin Frydenlund, Secretary Lightning Protection Institute, P. O. Box 59

Harvard, IL 60033

Jeffrey E. Aronin, Amer ican Institute of R.D.•Harger , R. Harger Lightning Protec- Architects tion, Inc.

James H. Baker, United Lightning Protec- T . W . Haymes, American Petroleum lnsti- tion Association tute

M.J . Beachy, Institute of Electrical & Elec- Robert P. Howell, American Petroleum - tronics Engrs Institute IL Dearie Boddorff, Institute of Makers o f Rona idJ . Kasper, Industrial Risk Insurers

Explosives Robert W. Lindquist , Lightning Protection • Robert E. Cripe, Independent Protection Institute

• Company, Inc. - R. 'E. Mattson, Factory Mutual Research George W. Crouch, Institute of Electrical & Corp.

Electronics Engineers Walter G. Queen, I_T. s. Army Material Norman H. Davis I I I , Underwriters Cc~mmand /

Laboratories I n c . . L . H . Sessler, The Telephone Group F. A. Fisher, National- Electrical Manufac- Bar rySperman , M & M Protection Consul-

turers Association tants Leland J. Hall, The Mill Mutuals

Alternates

J o h n E. Baker, United Lightning Protec- • John Jaresko, Industrial Risk Insurers (Ah. tion Assn. (Air. to James Baker)

Phi l ip R. Cooke, The Mill Mutuals (Air. to L. Hall)

R. W. Eckardt, Underwriters Laboratories Inc. (Alt. to Norman Davis, I l l )

Robert B. Fuller, American Mutual Insur- ance Alliance (Air. to John W. McGinnis)

C . F . Hedlund, Factory Mutual Reseai-ch Corp. (Alt. to R. Mattson)

to Ronald Kasper) Walter J. McDermott, Lightning Protection

Institute (Alt. to Marvin M. Frydenlund) J. F. McKenna, American Petroleum Insti-

tute (Alt. 'to ,R. P. Howell & T. W. Haymes)

Curt is J. Ramin, Lightning Protection In- stitute (Alt. to Robert Lindquist)

• The Committee on Lightning Protection presents for official adoption a complete revision of the Lightning Protection Code, NFPA No. 78-1975. The Lightning Protection Code is pub- lished in Volume 7 of the 1976 National Fire Codes and in separate pamphlet edition.

This report has been submitted to letter ballot of the •Committee which • consists of 20 voting members, of whom 1•4 have voted affirmatively,

none negatively and 6 have not returned ballots (Messrs. Boddorff, Cripe, Crouch, Harger, "Haymes and Sperman).

Lightning Protect ion Code • N F P A 7 8 - - 1 9 7 7

C h a p t e r 1 •Introduction

1-1 Scgpe.

1-1.1 .This Code covers lightning protection requirements for ordinary buildings, miscellaneous structures and special occupancies, heavy-duty stacks; and structures containing flammable liquids and gases.

| -1.2 This Code does not cover lightning protection requirements for explosives manufacturing buildings and magazines or electric generating, transmission, and distribution systems.

1-2 •Purpose. T h e purpose of this Code is the-practical safeguarding of persons and property from hazards arising

. from exposure to lightning.

1-3 Listed, Labeled or -Approved Components. "Where fittings, devices or other components required by this Code are available as-Listed or Labeled, such components shall be used. Otherwise, such components shall be approvedby the authority having jurisdiction.

1,,,1 t/It ),,at

78-6 L I G H T N I N G P R O T E C T I O N C O D E

Chapter 2 Terms and Definitions

2-1 General Terminology. General terms commonly used in describing lightning protection methods and devices are defined or redefined to conform to recent trends:

Lightning Protection System. This term refers to systems as described and detailed in this Code. A lightning protection system is a complete system of air terminals, conductors, ground terminals, interconnecting conductors, arresters, and other connectors or fittings required to complete the system.

Rods and Points. For purposes of this Code, rods and points are simply generic terms for component parts. The correct term for the uppermost portion of a lightning protection system is air terminal, which is composed ot a point and a base as described in the following definitions.

"2-2 Definitions.

Air Terminal. Pointed solid or tubular rods of specified.size and material provided with a mounting base having a proper conductor connection. (See Figure A-2-2a.)

Bonding. Connection between a conductive or inductive metal object and an element of a lightning protection system to accomplish electrical continuity between the two. (See Figure A-2-2b.)

Cable. A conductor formed of a number of wires stranded together. (See Figure A-2-2c.)

Chimney. Small concrete, masonry or metal vent protrud- ing through the roof or attached to the side of a building used typically in heating or venting, subject to protection under Class I requirements. (See Figure A-2-2d.)

Class I Materials. All conductors, fittings, and fixtures necessary to protect ordinary buildings and structures not exceed-

i n g 75 feet (23 m) in height. (See Figure A-2-2e.)

Class II Materials. All conductors, fittings and fixtures necessary to protect ordinary buildings and structures exceeding 75 feet (23 m) in height and heavy-duty stacks. (See Figure A-2-2e.)

T E R M S AND D E F I N I T I O N S 78-7

Conductors. The portion of a lightning protection system designed to carry the lightning discharge between air terminals and ground. (a) Main conductors interconnect air terminals and serve as downleads to ground. (b) Secondary conductors are used to accomplish various bonding and other connections as specified in this Code.

Copper-Clad Steel. Steel with a coating of copper bonded to it.

Counterpoise (ground). A conductor encircling a building and interconnecting all ground terminals. (See Figure A-2-2fi)

Fastener. An attachment to secure the conductor to the structure.

Ground Terminal, That portion of a lightning protection system extending into the earth, such as a ground rod, ground plate or the conductor itself, serving to bring the lightning protection system into electrical contact with the earth. (See Fig- ure A-2-2g.)

High-Rise Building. For purposes of lightning protection, a building over 75 feet (23 m) in height.

Metal Body of Conductance. Metal objects at or above the cave or fiat roof level that are subject to a direct lightning stroke. (See Figure A-2-2h.)

Metal Body of Inductance. Metal objects located within six feet (2 m) of a conductor subject to buildup of potential. (See Figure A-2-2h.)

'Metal-Clad Building. A building with either sides or roof made of or covered with sheet metal.

Metal-Framed Building. A building with electrically con- t inuous,framing of sufficientsize and conductivity to be utilized as part of the lightning protection system.

Sideflash. A spark occurring between nearby metallic objects or from such objects to the lightning protection system or to ground. (See Figure A-2-2i.)

Heavy-Duty Stack. A smoke or vent stack is classified as heavy~duty if the cross-sectional area of the flue is greater than 500 square inches (0.3 m 2) and the height is greater than 75 feet (23 m).

Vapor Openings. These are open!ngs through a tank shell

t,h I,O

7 8 - - - 8 L I G H T N I N G . P R O T E C T I O N C O D E P R O T E C T I O N F O R O R D I N A R Y B U I L D I N G S 78-9

or roof above the surface of the s to red liquid. Such openings may be provided for tank breathing, t ank gaging, fire t~ghting, or other operat ing purposes.

Flame Protection. Self-dosing gage hatches, vapor seals, pressure-vacuum breather valves, flame arresters, or other rea- sonably effective means to minimize the possibility, of flame entering the vapor space of a tank.

Zone of Protection. The zone of protection p r o v i d e d b y a g rounded air terminal or mast or overhead ground wire is that adjacent space which is substantially immune to direct strokes of lightning.

Flash Point. Flash point of a liquid shall m e a n the minimum tempera ture at which it gives off vapor in sufficient con- centration to form an ignitable mixture with air near the surface of the liquid within the vessel 'as specified by appropriate test procedure and apparatus.

Gastight. Structures so constructed that gas or air can neither enter nor leave the structure except through vents or piping provided for the purpose.

Spark Gap. As used in this Code, the term spark gap means any short air space between two conductors electrically insulated from or remotely electrically connected to each other.

Flammable Vapors. The vapors give n off f rom a flammable liquid at or abox/e its flash point.

Flammable Air-Vapor Mixtures. When flammable vapors are mixed with air in certain proportions, the mixture will burn rapidly when ignited. The combustion range for ordinary petroleum products, such as gasoline, is f rom about 1 1/2 to 7 1/2 percent of vapor by volume, the remainder being air.

Chapter 3 Protection for Ordinary Buildings

3-1 Classifications. An ordinary building is one o f common or conventional design and construction used for ordinary purposes, whether commercial, farm, industrial; institutional, or residential. A Class I ordinary bui lding is o n e which is less than 75 feet (23 m) in height. A Class II ordinary building is one more than 75 feet (23 m) in height, or one which has a structural steel frame, of any height, whose steel f r a m i n g m a y be substituted for l ightning down conductors . The distinction in terms of l ightning pro tec t ion is that air terminals, conductors, and g round rods of Class II structures are of larger dimensions and higher conductance than min imum allowances for Class I buildings.

3-1 .1 Roof Types and Pitch. For the p u r p o s e of this Code, roof types and pitches are as ' shown in Figures 3-1.1a and ~ ' ' ~" O - l . l U .

3-2 Materials. The materials of which protection systems are made shall be resistant to corrosion or shall be acceptably protected against corrosion. No combination of materials shall be used that forms an electrolytic couple of such nature that in the presence of moisture corrosion is accelerated. One or more of the following materials shall be used:

i

(a) Copper. Where c6pper is used it shall b e of the g rade ordinarily required for commercial electrical work, generally designated as being of 98 percent conductivity when.annealed.

(b) Copper Alloys. Where alloys of copper are used they shall be substantially as resistant to corrosion as copper under similar conditions.

(c) A luminum. Where a luminum is used, care shall be taken not to use it in contact with the earth or elsewhere where it will rapidly deteriorate. Conductors shall be of electrical grade a luminum.

3-3 Configurat ion. Material forms used in l ightning protection shall be those which allow for best workmanship and ate in addit ion suited for the particular function. Air terminals shall be made of solid or tubular rods. Main and secondary conductors shall be constructed of metal strands, solid strip,

i

t,m

t ~

78-10 L I G H T N I N G P R O T E C T I O N C O D E P R O T E C T I O N F O R O R D I N A R Y B U I L D I N G S 78-1 l I ~

__i.. ~-~-~ r----

i

(b

Roof Types: Protection methods (Drawings are top and end views of each roof type.)

T

---4-

Gable Hip Broken Gable

t I I I I

I I I I I I

---~.~- . . . . . . . .

Fiat

..~___

Mansard

I

Gambrel

O: Air Terminal ---: Conductor y : Ground Note: Shed Roof: Apply gable method

Figure 3-1.1a

Full Pitch

1! ' ! 3/4 P i tch / ~

1/2 Pitch / Rise

I i '~ , 1/4Pitch~ " ~.1t8~// J/S Pitch " 1

Rise - - 12' ---~.~----- Run Pitch: ~-~ ~ Span

I - -

For purposes of this Code, use roof pitches as shown above.

Rise = 3' Example: Run = 12'

Pitch: 3,' (1/4 pitch) I Z

Note: 1 in. -- 25.4mm l f t -- 0.305m .

Figure 3-1.1b

so l id wire, o r tubula r bars o f equal cross-sectional area and conductivity. G r o u n d terminals shall be solid wire or r o d , solid plate, or s t r anded cable.

3-4 Mater ia ls , Class I. Table 3-4 gives m i n i m u m s i z e s and weights for air terminals , and main and secondary conductors . Secondary conduc tors used for bond ing and in te rconnec t ing metallic bodies to the main conductor , and which will not be requi red to car ry the main l ightning current~ may be r e d u c e d ins ize but shall not be less t h a n No. 6 AWG (4.7 m m ) c o p p e r or equivalent. Conductors . for in terconnect ion to meta l water systems, s team or hot water heat ing systems, or o the r metallic masses having a low resistance to g r o u n d shall be main. conduc tor size.

3-5 "Materials, Class-II. Tab le 3-5 gives m i n i m u m sizes for air terminals , a n d main conduc tors , for Class II s t ructures . Sys- tems on these s t ructures shall be installed in accordance with

Table 3-4 Class I Material Requirements

Copper Aluminum

T y p e o f C o n d u c t o r S t anda rd Metric S t anda rd Metric

Air Te rmina l , Solid Min. Diamete r 3/8 inch 9.5 m m 1/2 inch 12.7 m m

Air Te rmina l , Tul~ular Min. Diameter . 5/8 inch 15.9 m m 5/8 inch 15.9 m m Min. Wall Th icknes s .032 inch 0.8 m m .064 inch 1.6 m m

Min. Size ea. S t rand 17 A W G 1.2 m m 14 A W G 1.6 m m Main Conduc to r , Cable Wgt. per Leng th 187 Ibs/1000 ft. 278 .g/m 119 Ibs/1000 ft 177 g/m

Cross Sect. Area 57,400 CM 29 m m 2 98,600 CM 50 m m 2

Main Conduc to r , Th ickness 16 AWG 1.3 m m 14 A W G 1.6 m m Solid Strip Wid th 1 inch 25.4 m m 1 inch 25.4 tara

Secondary Conduc to r , Wire Size 17 A W G 1.2' m m 14 A W G 1.6 m m Cable N u m b e r o f Wires 14 14 10 10

Secondary Conduc to r , Th ickness 16 A W G 1.3 m m 14 A W G 1.6 m m Solid Strip Wid th 1/2 inch 12.7 m m 1/2 inch . 12.7 tara

O -e

Z

Z O

M

.d

Z

0

Table 3-5 Class II Material Requirements

Copper Aluminum

Type of Conductor Standa rd Metric S t anda rd Metric

Air Te rmina l , Solid Min. Diamete r i/2 inch 12.7 m m 5/8 inch 15.9 m m

Min. Size ea. S t rand 16 A W G 1.5 m m 13 A W G 1.8 m m Main Conduc to r , Cable Cross Sectional Area i 15,000 CM 58 m~n 2 192,000 CM 97 m m 2

Wgt. per Leng th 375 Ibs/1000 ft 558 g /m 235 Ibs/1000 ft 349 g/m

Secondary Conduc t o r , Wire Size 17 AWG 1.2 m m 14 AWG 1.6 m m Cable N u m b e r o f Wires 14 14 10 i 0

Secondary Conduc to r , Th ickness 16 A W G 1.3 m m 14 AWG 1.6 m m Solid Strip Width 1/2 inch 12.7 m m 1/2 inch 12.7 m ~

C ,-I M

0 Z

0

O I:l

Z

1-

7

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f i l l

78--14 L I G H T N I N G P R O T E C T I O N CODE

requirements of Class I and, in addition, shall comply with the following requirements: If part of a structure is over 75 feet (23 m) in height (as a' steeple) and the balance of the structure is under 75 feet-(23 m) in height, the following requirements for air terminals and conductors shall apply only to the sections over 75 feet (23 m) in height. Class II conductors installed on parts of a structure exceeding 75 feet (23 m) in height shall be coursed to ground and also interconnected with the rest of the system. Only metal splicers and connectors welded or secured with bolts are acceptable for use on Class II structures•

3-6 Prevent ion of Deterioration. Precautions shall be taken to provide against any tendency towards deterioration due to local conditions. Where any part of a copper protective system is exposed to the direct action of chimney gases or other corrosive gases, it shall be protected by a continuous hot dip coating of lead. Such a coating shall extend at least two feet (0.6 m) below the top of the chimney.

3-7 Mechanical Injury. Where any part of a protection system is exposed to mechanical injury it shall be protected by covering it with molding or tubing. If ferrous metal pipe or tubing is used around the conductor, the conductor shall be electrically connected to the pipe or tubing at both ends.

3-8 Use of Aluminum. Aluminum systems shall be installed in accordance with other applicable sections and with the following:

(a) Aluminum lightning protection equipment shall not be installed on copper roofing materials or other copper surfaces• • (b) Aluminum materials shall not be used for direct ground- lng of lightning protection systems• Fittings connecting aluminum down conductors to copper or copper-clad grounding equipment Shall be of the bimetallic type.

(c) Connectors shall be suitable for the material of the conductor. Conductors of dissimilar metals shall not be intermixed in a connector unless the connector is suitable for the purpose and conditions of use. Connectors shall be installed at a point not less than one foot (0.3 m) above grade level• Where downleads are concealed, the connection shall be at least one- foot (0.3 m) above the lowest slab.

(d) An aluminum conductor shall not be attached to a surface coated with alkaline-base paint, embedded in concrete or masonry, or installed in a location subject to excessive moisture.

P R O T E C T I O N FOR O R D I N A R Y B U I L D I N G S 78-15

I A

d

A: Air terminals shall extend not less than 10" (254mm) above the object protected for 20' (6m) maximum intervals and not less than 2' (0.6m) above the object protected for 25' (8m) maximum intervals.

B: Air terminals over 24" (0.6m) high shall be supported. C: Air terminal supports shall be ~t not less than one-half the

height of the air terminal.

• / / -

. J

Figure 3-10.1

i


(e) Aluminum clamps and connectors, including bimetal types, shall cont0rm in dimensions and strength to the requirements already specified for installations using copper.

3-9 Air Terminals. Unless otherwise permitted in this Code, air terminals shall be provided for all parts of a structure

• that are'likely to be damaged by lightning.

3-10 Air Terminal Design and Support. 3-10.1 Height. The height of air terminals shall be such

as to bring the tip not less than 10 inches (254 rn'm) above the object to be protected for 20 feet (6 m) maximum intervals and not:less than 2 feet (0.6 m) above the object to be protected for 25 feet (8 m) maximum intervals. (See Figure 3-10.1.)

3-10.2 Supports. Air terminals shall be amply secured against overturning either by attachment to the object to be

t Fr; rotating fixtures do not c o u n t in area c irculat ion

Figure 3-10.3


protected or by means of substantial braces which shall be per- l l J d l l ~ l l L J y d l l L l 1 l ~ l U l y dLLdLII~ 'LI LU L l l ~ U U I I U I I l I ~ . 2~lkll LCT| l l l l l l d l ~

exceeding 24 inches (0.6 m) in height shallbe supported at a point not less than one-half its height. On masonry or brick work, holes shall be made with proper tools.

3-10.3 Ornaments. An ornament or decoration on a free standing, unbraced air terminal shall not present, in any plane, a wind-resistance area in excess of 20 square inches (13 000 mm2). This permits the use of an ornamental ball 5 inches (127 ram) in diameter. (See Figure 3-10.3.)

3-11 Terminals on Roofs. Air terminals shall be placed on ridges of gable, gambrel and h!p roofs, around the perimeter of fiat roofs and on the corners and edges of gently sloping roofs at intervals not exceeding 20 feet (6 m) except that air terminals 24 inches (0.6 m) or higher may be placed at intervals not exceeding 25 feet (8 m). (See Figure 3-11.)

3-11.1 Flat and Gently Sloping Roofs. Air terminals shall be placed at or within 2 feet (0.6 m) of the ends of ridges or edges and corners of roofs. The center roof area shall have air terminals at intervals of 50 feet (15 m) or less- Gently slop- " ing roofs are roofs having a span of 40 feet (12 m) or less and a pitch of 1/8 or less, and roofs having a span of 40 feet (12 m) or more and a pitch of 1/4 or less. Gently sloping roofs are treated as flat roofs. Structures having roofs that fall within these limits shall have air terminals, spacings at 20 feet (6 m) maximum about the perimeter and within 2 f ee t (0.6 m) of all corners. The center roof area shall be considered flat and shall have air terminals at intervals not exceeding 50 feet (15 m) if the building is over 20 feet (6 m) wide, air terminals shall be located within 2 feet (0.6 m) of the ridge ends regardless of pitch or span. (See Figs. 3-11.1a and 3-11.lb.)

3-11.2 Lower Roofs. Buildings whicla exceed 50 feet (15 m) above grade are considered to protect lower roof portions in a one-to-one zone of protection as shown in FiguCe 3-11.2a. Note that the distance protected on the lower roof shall be a 'maximum of 50. feet (15 m), regardless of the height of the upper roof. Buildings which do not exceed 50 feet-(15 m) above grade are considered to protect lower roof portions in a one-to-two zone of protection as shown in Fig. 3-11.2b.

3-11.3 Dormers. Prominent dormers are those as high or higher than the main roof and shall be protected with air terminals~ cable, down conductors and grounds as normally specified. Dormers and projections below the main ridge re-

78-18 LIGHTNING PROTECTION CODE

quire protection on all areas extending outside a one-to-two zone of protection as shown in Figure 3-11.3.

3-11.4 Roofs with In termedia te Ridges . Roofs with a series of parallel ridges shall have air terminals along the end ridges at intervals not exceeding 25 feet (8 m). The intermedi-

A: B:

20" or 25" maximum spacing "~.~ ~*~ Air term!nab shall be at or . \ ~ ' ~ ~ within 2 of corners or ridge ends .~'-~//~/.~ :

.

I I( ' lmide" corner--a,r lit terminals as required Air terminal shall be

• I JJ by 20 spacing only- ] in this area

!!>" air terminals ~..~1"-..~'-~ - ~ " ~ / ~ ~! deto~ ..... ~

Note: 1 ft = 0.305m

Figure 3-11

PROTECTION FOR ORDINARY BUILDINGS 78-19

A :

B:

C:

~~-..~ A ""--..,6 i

B--.... --.>>?LF_<

If cable runs like this exceed 150' ~ S ~ . . . '" they shall be connected to the main perimeter or downleed cable at 150' 20" or 25" maximum spacing Note: 1 ft = 0.305m

Figure 3-1 l . l a

A: 50" (15m) maximum spacing ..... _~°--~,- " " ~ " - ~ - ~ _ _ B: 20' (6m) or 25' (8m) .-"~- /"

maximum spacing /." ,;/" Y~/~ ~'~i:

4-'" -/ , - ' U / . . . . . . . /

T i Figure 3-1 l.lb

ate area between ridges shall be protected according to requirements for flat roofs. If any intermediate ridge is higher, it shall be protected in a manner similar to the end ridges. An air terminal shall be placed within 2 feet (0.6 m) of the end of each intermediate ridge.

3-11.5 Irregular Roof Lines. The edge of the roof shall be considered continuous and air terminals shall be located within 2 feet (0.6 m) of the outermost projections of the roof edge. (See Figure 3-11.5.)

7 8 - - 2 0 L I G H T N I N G PROTECTION CODE PROTECTION FOR ORDINARY BUILDINGS 78-21

/

X

i t (1,m~n) I ~ i n . e m J

Figure 3-11.2a

/

Figure 3-11.2b

~. 50 f t (1Sin)

~; SO f t (15m)

Air terminal ,required. No air terminal required / ' •

- 2 1 ~

Figure 3-11.3

2

J •

A: Air terminalsshall be within 2' ~ ~ of. outermost projection of ~ . roof e d g e . ~ ~ ~ t

• ~s~" - ~ i

f ~ / ~ , . , ~ / ~ Note: -1 ft : 0"305m ~ ~

Figure 3-11.5

~m


3-11.6 O p e n Areas in Flat Roofs . T h e per imete r of open areas, such as light or mechanical wells, which are located in large flat roofed structures shall be protec ted if their per ime- ter exceeds 300 feet (92 m) provided e i ther rec tangular dimen- sion exceeds 50 feet (15 m).

3-11.7 D o m e d or Curved Structures . On curved or dome d structures, an air terminal shall be located at the apex o f the curve or dome with additional air terminals as requi red to provide a one-to-two zone of protect ion.

3-11.8 Chimneys . Air terminals shall be placed on all chimneys, including prefabr ica ted metal chimneys and vents with metal less than 3/16 inch (5~mm) thick when such chimneys or vents are not within a one-to-two zone of protect ion o f an air terminal . I f the metal is more than 3/16 inch (5 mm) thick; only bond ing and g round ing is required. Chimney air terminals shall be at tached to the chimney so that no outside corner o f the ch imney is more than 2 feet (0.6 m) f rom an air terminal. (See Figure 3-11.8.)

3-12 Conduc tors . Conductors shall in terconnect all air terminals and shall fo rm a two-way path f rom each air terminal horizontally or downward to connect ions with g ro u n d terminals.

3-13 Metal Contacts. Coppe r l ightning protect ion materials shall n o t be installed on a luminum roof ing or siding or


o ther a luminum surfaces. Aluminum lightning protect ion materials shall not be installed on coppe r surfaces. Metal roof ing and siding, eave troughs, downspouts , ladders, chutes or o ther such metal parts shall nor be substituted for the main conductor. A l ightning protect ion system shall be applied to the metal roof and to the metal siding o f a metal-clad building in like m a n n e r as on buildings without such metal coverings.

3-14 Prevent ing Pockets. Conductors shall maintain a horizontal or downward cburse, f ree f rom "U" or "V" (down and up) pockets. Such pockets, of ten fo rmed at low-positioned chimneys, dormers , or o ther elevations on the slope o f a r oo f and at coping walls, shall be provided with a down conduc to r f rom the base of the pocket to g round , or to a convenient down lead o f the main conductor . (See Figure 3-14.)

, - / . ~ ' ~ . : f Correct

Figure 3-14

0

A: 2' (0.6m) maximum

Figure 3-11.8

3-15 Gradua l Bends. NO bend of a conduc to r shall form an included angle of less than 90 degrees no r 'shall have a radius o f bend less than 8 inches (203 mm). (See Figure 3-15.)

I " ~ - ~ - ~ - \ \ \ \ ~ ~ R Radius of bend: - V ~ - ' ~ - ' ~ - ~ ' \ \ ~

• ~ not less than 8" \ , 0 mo, \

The angle of any bend shall n o t ~ 1~ be less than 90 °

Figure 3-15

78--24 LIGHTNING PROTECTION CODE PROTECTION FOR ORDINARY BUILDIN'GS 78-25

3-16 Suppor ts . Conductors may be coursed th rough air without suppor t for a distance of 3 feet (0.9 m) or less. With a 5/8 inch (16 mm) rod or its equivalent as a support , securely fastened at each end, a conduc to r may be coursed th rough air for a distance not to exceed 6 feet (2 m).

3-17 R oof Conductors . Roof conductors shall b e coursed along ridges of gable, gambrel and hip roofs, a round the "perimeter of fiat roofs, behind or o n top of parapets and across flat roo f areas. Conductors shall be coursed th rough or a round obstructions (such as cupolas, ventilators, etc.) i r r a horizontal plane with the main conductor . On flat and gently sloping roofs the conduc tor shall folZm a closed loop.

3-17.1 Roof Cross Runs. Conductors shall in terconnect the air terminals on flat or gently sloping roofs that exceed 50 feet (15 m) in width. For example, roofs f rom 50 feet (15 m) to 100 feet (30 m) in width require one cross run; roofs 100 feet (30 m) to 150 feet (46 m) in width require two cross runs, etc. These cross-run conductors shall be connected to the main per imete r cable at intervals not exceeding 150 feet (46 m).

• 3-18 Two-Way Path Except ions . Roof conductors shall in terconnect all air terminals and provide a two-way path to g round horizontally or downward f rom the base of each terminal except as requi red in 3-18.1 and 3-18.2.

3-18.1 One-Way Drops. Conduc to r drops f rom a h igher to a l ower roo f level are permi t ted without an extra downlead provided the roo f conduc tor r u n does not exceed 40 feet (12 m).

3-18,2 Dead E n d s . Air terminals may be "dead ended" with only one path to a main conduc to r on roofs below the main ridge level provided the conduc to r run f rom the air terminal to a main conduc tor is not more - tha n 16 feet (5 m) in total length. (See Figure 3-18.2.)

3-19 Down Conductors . ' A t least two down conductors . shall b e provided on any kind o f s tructure, including steeples.

Location depends o n placement o f air terminals, size of structure, most direct coursing, security against displacement and location o f metallic bodies, water pipes, and g round conditions. D o w n conduc to r s shall be as widely separ~tted as practicable. Structures over 250 feet (76 m) in pe r imete r shall have an additional down conduc tor for each additional 100 feet (30 m) o f pe r ime te r or fraction thereof . '

A : Permissible dead end - to ta l conductor length not over 16' (5m)

Figure 3-18.2

Spacings: 1 - - 2 - - 1 3 0 ' " (4Ore) 2 - 3 -- 85 ' (26m) 3 -- 4 -- 85" (26m) 4 - 5 - 85 ' (26m)

. 5 - - 1 -- 8 5 ' . (26m)

Total Perimeter: 470 ' (144m) Required grounds: 5

Figure 3-19.1

78-26 L I G H T N I N G P R O T E C T I O N CODE

3-19.1 Number of D o w n Conductors . The average distance between down conductors shall not exceed 100 feet (30 m). Irregularly shaped structures may require extra down conductors to provide a two-way path to ground from air terminals on main ridges or on side wings. To determine the required number of down conductors, measure only the "protected" perimeter; that is, those roof areas requiring protection, a n d exclude low roofs and projections not requiring protection. On pitched roof structures the protected perimeter shall be taken as comparable to the eave line or its-equivalent. (See Figure 3-19.1.)

3-19.2 Protect ing D o w n Conductors . Down conductors located in runways, driveways, school playgrounds, cattle yards, public walks, or other similar locations shall be guarded to prevent physical damage or displacement. I f the conductor is run through ferrous metal tubing, the conductor shall be bonded to the top and bottom of the tubing. The down conductor shall-be protected for a minimum distance of 6 feet (2 m) above grade level.

3-20 Grounding. Each down conductor shallterminate at an approved groun d terminal.

3-20.1 G r o u n d T e r m i n a l s (Rods). Ground terminals (rods) shall be not less than 1/2 inch (13 mm) in diameter and 8 feet (2 m) long. Rods shall be copper-clad steel, solid copper or stainless steel.

3-20.2 Ground Rod Clamps. Clamps shallmake contact with the ground rod for a distance of 1 1/2 inches (38 mm), measured parallel to the axis of the ground rod and with the cable itself for a distance of at least 1 1/2 inches (38 mm). Clamps shall be secured with at least two bolts or cap screws.

3-21 Variat ions Due to Soil Condi t ions . The nearest ground terminal shall be not less than 2 feet (0.6 m) from the foundation wall. Design, size, depth~ form and amount of ground terminals used shall comply with 3-21.1, 3-21.2, 3-21.3, .and 3-21.4.

3-21.1 Deep Moist Clay Soil. The lightning conductor, or ground terminal shall extend vertically not less than 10 feet (3 m) into the earth: The earth shall be compacted and made tight against the full length of the conductor or g round terminal. (See Figure 3-21.1 .)

3-21.2 Sandy or Gravelly Soil. In sand or gravel, two or more ground terminals, at not less than 10 feet (3 m) spacings,

P R O T E C T I O N FOR ORDINARY B U I L D I N G S 78-27

Figure 3-21.1

Note: 1 ft = 0.305m

Grounding in moist clay type soil

, . A ' S + ' ~' ,.. , ,

• 0 " - . •

. b. ! . .

D' o , ~ .

2'

i 1

10' ]

d shall be driven vertically to a minimum depth of 10 feet (3 m) below grade. (See Figure 3-21.2.)

3-21.3 Shallow Top Soil. Where bedrock is near the surface~ the conductor shall be laid in trenches extending away from the building at each down conductor. These trenches shall be not less than 12 feet (4 m) in length and from 1 to 2 feet (0.3 to 0.6 m) indep t h in clay soil. In sandy or gravelly soil, the trench shall be not less than' 24 feet (7 m) in length and 2 feet (0.6 m) in depth. I f these methods should prove impracti-• cable, an acceptable alternative would be to carry the lightning protection cable in trenches, of a depth specified • above, or if this is impossible, directly on the bedrock a min imum distance of 2 feet (0.6 m) from the foundation or exterior footing and terminate by attachment to a buried copper ground plate at. least .032 inch (8 mm) thick and having a minimum surface area of 2 square feet (0.2 m2).

~ t

78-28 L I G H T N I N G P R O T E C T I O N CODE P R O T E C T I O N FOR ORDINARY B U I L D I N G S 78-29

t l l _ ~ ~ A Grounding in sandy or gravelly soils

Note: 1 ~ = 0.31~m

_ L • _ Alternate configurations Figure 3.2i.2

3-21.4 Soil Less than O n e Foot (0.3 m) Deep. If the soil is less than 1 foot (0.3 m) in depth, the structure shall be surrounded with a main-size conductor (a counterpoise) laid in a trench or in rock crevices. From this counterpoise, a conductor shall be run to pits or hollows where added metal shall be deposited. This shall be accomplished by depositing approxi- mately9 square feet (0.8 m 2) of .032 inch (0.8 ram) thick copper plate, or an equivalent, in corrosion-resistant metal, connected to the lateral conductors and covered with loose earth for moisture (rain) absorption. (See Figure 3-21.4.)

3-22 C o m m o n Grounds . All grounding mediums shall be bonded together. This shall include electric, telephone and antenna system grounds and other underground metallic piping systems which enter the structure. Such piping systems include water service, well casings within 25 feet (8 m) of the protected

OIR, iona' ground plates f ~ " ~ ,

"x /" Grounding in soil less than 1" (0.3m) deep Figure $-21.4

structure, gas piping, underground conduits,, underground liquefied petroleum-gas piping systems, etc.

3-22.1 C o m m o n G r o u n d Bondings. If electric service and telephone service are grounded through the water pipe system, interconnection with the water pipe is all that is required, provided the water pipe system is electrically continuous between all systems. If it is not electrically continuous, due to use of plastic water pipe sections or for other reasons, the gaps shall be bridged with main size conductors, or direct connections shall be made. The common ground connections shall be made using main size conductors and connectors.

3-23 B o n d i n g o f Metal Masses . Certain metal bodies of conductance or inductance contribute to lightning hazards outside or inside a building and shall be bonded to the Conductor system.

3-24 Metal Bodies. Metal bodies of conductance shall be protected if not within a one-to-two zone of protection of an air terminal. All metal bodies of conductance having an area of 400 square inches (0.3 m 2) or greater or a volume of 1000 cubic inches (0.2 m 3) or greater shall be bonded to the lightning protection system. (See Figure 3-24.)

3-24.1 B o n d i n g R e q u i r e m e n t s for Metal B o d i e s o f Con- ductance . Metal bodies of conductance shall be bonded to the system using main size conductors and a bonding plate havir/g


I Wood or Metal vent

J / _ . ~ ' " [ / r i d g e vent / " ~ : ~ / [ / ~ , s - / ~ - ~ ~ " / p r o t e c t i o n " ~ " v / . 2"

/ / ~ - ~ / ~ Z / ~ . . / ~ . Bond only required / " Full protection required /

/ F i g u r e 3 - 2 4

a surface contact area of not less than 3 square inches (2000 mm2). Provisions shall be made to guard against the corrosive effect introduced by dissimilar metals at points of bonding.

3-24.2 Bonding Requirements for Metal Bodies of In- ductance. Metal bodies of inductance shall be bonded at their highest point to the system using secondary bonding conductors and fittings. It is possible that some metal bodies may be bodies of both inductance and conductance. In such cases, the requirements (as to size of conductor) covering bodies of conductance shall apply.

Connections to metal bodies of inductance are required if such bodies fall within 6 feet (2 m) of the main conductor or other bonded metal body.

3-25 Water Pipe Bond. If a metal water pipe system is present and the lightning i:onductor has been bonded to the water pipe, then the metal bodies described in Section 3-24 may be connected either to the metal water pipe system, the nearest lightning conductor, or to another metal body already connected to the system. Where other metal bodies are bonded through their structural connection to the metal water pipe system no additional bonding is required.

3-26 Antennas. Radio and television masts of metal, located on a protected building, shall be bonded to the lightning protection system with a main-size conductor and fittings.

3-27 Lightni_ng Arresters, Protectors, and Antenna Dis- "charge Units. Lightning arresters, protectors, or antenna discharge units shall be installed on electric and telephone service entrances and on radio and television antenna lead-ins.

PROTECTION FOR ORDINARY BUILDINGS 78-31

3-28 Fasteners. Conductors shall be securely attached to the building or other object upon which they are placed. Fas- teners shall not be subject to breakage and shall be, with the nails, screws, bolts, by which they are fixed, of the same material as the conductor o r of such nature that there will be no serious tendency towards electrolytic corrosion in the presence of moisture because of contact between the different parts. Fas- teners Shall be spaced not more than 3 feet (.9 m) apart on all conductors.

3-28.1 Anchors. Masonry anchors shall have a diameter of no t less than 1/4 inch (6 mm) and shall be set with care. Holes to receive the shank of the fastener or fitting shall be of correct size, made with proper tools, and preferably made in the brick or stone rather than in the mortar joints. When set, the fit shall be tight against moisture and the effect of frost and capable of withstanding a pull test of 100 pounds (445 N).

3-29 Splicers and Clamps. Connector fittings shall be used on all lightning conductors at "end-to-end .... tee" or "Y" splices. They shall be attached so as to withstand a pull test of 200 pounds (890 N). Fittings for connection to metal tracks, gutters, downspouts, ventilators, chimney extensions, or other metal parts about the structure shall be made tight to the object by compression under bolt heads. Both crimp type and bolted clamps and splicers of stamped or cast metal are acceptable under Class I requirements. Crimp type clamps and splicers shall not be used in Class II installations.

3-30 Disconnectors. Where future testing of a system may be required, disconnectors may be installed on all but one ground terminal of the system.

3-31 Concealed Systems. All requirements covering exposed systems apply to concealed installations. Conductors are coursed the same except that they may be coursed under the roofing material, under the roof framing,, behind the exterior wall facing, between the studding of partmons or outside walls, in concealed or embedded conduit, or embedded directly in concrete.

3-31.1 Chimneys. Chimney air terminals and chimney conductors may be built into the masonry of a chimney, or may be attached to the outside of a chimney and carried through the roof to the main concealed conductor.

3-31.2 Concealment in Concrete. In a concealed installation where conductors are embedded in concrete, the rein-

78-32 L I G H T N I N G P R O T E C T I O N C O D E P R O T E C T I O N F O R O R D I N A R Y B U I L D I N G S 78-33

forcing steel shall be bonded to the cable with a main size conductor . Reinforcing steel shall be bonded at the top and bot tom of each embedded -downlead . I f roo f conductors are similarly embedded , a connect ion to re inforc ing steel shall be made at no less than 100 feet (30 m) intervals.

3-31.3 Ground ing . G r o u n d i n g may be placed in the basem-~nt, below the basement floor level or may be carr ied out f rom a-wall at grade level and made as requi red for exposed systems. I f a g round is dr iven f rom the basement floor level, it shall be in contact with earth for a distance of 10 feet (3 m).

3-32 Structural Steel Framing. T h e structural steel f r amework of a building may be utilized as the main conduc to r o f a l ightning protect ion system if it is electrically cont inuous or is made so.

Minimum contact area 8 squareinches

10" min.

j: ¥~

.I

1 o..'.. " ' : : ' , .

Note: 1 f t = 0.305m 1 in 2 = 645.16mm 2

Figure 3-32.3

3-32.1 Air Termina l s . Air terminals shall be bonded directly to the steel f r amework or by conductors leading th rough the ridge, roof , or cop!ng walls, or connec ted toge ther with a conductor on the exter ior of the building that is bonded to the steel f ramework. I f such a conduc to r is employed, it shall be bonded to the steel f ramework at intervals o f not more than 60 feet (18 m).

3-32.2 Connect ions . Connect ions shall be made on cleaned areas o f the steel f r amework by use o f bonding plates with bolt pressure cable connectors having a surface contact area o f not less than 8 square inches (5000 mm2), bolted, welded or brazed securely to the steel so as to maintain electrical continuity.

3-32.3 Ground ing . G r o u n d connect ions shal l 'be made at approximate ly every o ther steel co lumn a round the per ime- ter, and shall not average over 60 feet (18 m) apart . G round terminals shall be at tached to such steel columns, at the lowest available point, with bond ing plates having a sui'face contact area o f not less than 8 square inches (5000 mm~), bolted or ~velded securely to cleaned areas o f the structural steel. (See Figure 3-32.3.)

3-32.4 In te rconnec t ions . Where metal bodies are required to be bonded elsewhere in this Code, they need not be separately bonded if they are electrically cont inuous with the- l ightning protect ion system th rough the steel f ramework.

OI

78-34 L I G H T N I N G P R O T E C T I O N CODE

Chapter 4 Protection for Miscellaneous Structures and Special Occupancies

4-1 Special consideration shall be given tO the miscellaneous structures and special occupancies covered in this chapter. All requirements of Chapter 3 shall apply except as modified.

4-2 Masts, Spires, Flag Poles. These slender structures require one air terminal, down conductor, and ground terminal. Electrically continuous metal structures do not require air terminals or down conductors but do require ground terminals.

4-3 Grain, Coal, and Coke Handling and Processing Struc- tures. On wood frame elevators, provision shall be made to allow for the settling and rising of the structure as grain is loaded and unloaded. For protection from hazards of possible ignition of combustible dust or mixtures, refer to Standard for Grain Elevators and Bulk Grain Handling Facilities, NFPA No. 61B-1973 and Standard for the. Prevention of Dust Explosions in Coal Preparation Plants, NFPA-No. 653-1971.

4-4 Metal Towers and Tanks. Metal" towers and t anks constructed so as to receive a stroke of lightning without damage need only bonding to ground terminals as required in Chapter 3.

4-5 Air-Inflated Structures. Air-inflated structures shall be protected with a mast type or overhead ground wire type system in accordance with Chapter 6 or with a lightning protection system in accordance with Chapter 3.

P R O T E C T I O N FOR HEAVY-DUTY STACKS 78-35

Chapter 5 Protection for Heavy-Duty Stacks

5-1 General. A smoke or vent stack is classified as heavy- duty if the cross-sectional area of the flue is greater than 500 square inches (0.3 m 2) and the height is greater than 75 feet (23 m).

5-2 Materials. Materials shall be Class II except as described in this chapter and as shown in Table 3-5.

5-2.1 Corrosion Protection. Copper and bronze mate- terials used on the upper 25 feet (8 m) of a stack shall have a continuous covering of lead having minimum thickness of 1/16 inch (1.6 mm) to resist corrosion by flue gases. Such materials include conductors, air terminals, connectors, splicers, and cable holders. Stacks that extend through a roof less than 25 feet (8 m) shall have a lead covering only on those materials above the roof level.

5-3 Air Terminals. Air terminals shall be made of solid copper, copper alloy, stainless steel, or monel metal. They shall be uniformly distributed around the top of cylindrical stacks at intervals not exceeding 8 feet (2 m). On square or rectangular stacks, air terminals shall be located not more than 24 inches (0.6 m) from the corners and shall be spaced not more than 8 feet (2 m) apart around the perimeter.

5-3.1 Air Terminal Heights. The height of air terminals above the stacks shall be not less than 18 inches (0.5 m) nor more than 30 inches (0.8 m). They shall be at least 5/8 inch (15 ram) in diameter, exclusive of the corrosion protection. Top- mounted air terminals" shall not extend more than 18 inches (0.5 m) above the top of the stack.

5-3.2 Mountings. The air terminals shall be secured to the stack and shall be connected together at their lower end with a lead-covered copper conductor forming a closed loop around the stack. Side-mounted air terminals shall be secured to the stack at not less than two locations. The anchored base shall be considered as one fastening.

5-4 Conductors. Conductors shall be copper, weighing not less than 375 pounds p e r 1000 feet (558 grams per meter) without the lead covering. The size of any wire in the conductor shall be not less than 15 AWG (1.5 ram).

teat

7 8 - 3 6 LIGHTNING PROTECTION CODE PROTECTION FOR HEAVY-DUTY STACKS 7 8 - - 3 7

A: A * | ~ lm | v ; , .m m a m

/ I " / '/ '~ ~ '~'~ " spacing of air termirlals . ~ - ~ - 11 "~

1~ -~'~' ~ J / I B: Al lequlpmenton . . . I- ~ ~ , ~ ~ /i- upper 25" (8m) of stack Air terml.na.h I I ~ to be lead-covered copper; .me material, ~.~ ~ " / m i n i m steel size and ,~<~ ~ -1 - " ILJr-'4~l~ • corrosion resi mounting ~ . ~ . ~ . ~ , requirements ~ ~ ~

Lead covered / I I ,If

m i n i m steel, or approved corrosio n resistant material

Bond to

on upper 25" / (8m} /

Straight . , s~.cer as ,~I /

Bare cable ~- / holder-- t 4 [ / see material ~ and spacing I J requirements ~ f

Ground guard to ( ~ protect j ' - downlead | from | ~ . mechanical ] hazard, L.~

f f i ,

Connect to watw . . . . -;~ . . . . . . . . . . . . . . . . . ~- service if within Note: connect downlcads 25" (8m) to approved ground system

rebar at top and bottom of each downlead

Bond to . ladders, hoists, etc., at upper

--.,a~:~.~.~ and lower p

ends;bond . sections of ladder • ~ together Cross c o n n e c t d ~ n | e a O = - a t . 100" (30ml intervals on all stacks exceeding 200' (61m) in height

Bond to platforms

Bond to breeching

F i g u r e 5-1

5o4.1 Down Conductors. Not less than two down con- * - l , , ~ *~o ~h~ l l I - . ~ . . . . . : . J~A " r ' t . . . . . . L_ I I L - I . . . . . J . . . . . . . - - " . - ~ u ~ L u t o o J l a z t t J~_ I j t U V t U ~ . L t . J t l l ~ . y a l t g t l l t ) ~ I U L d L U U U I I oppO~ltU sides of the stack, and lead from the encircling conductor at the top to .g round terminals. Down conductors shall .be interconnected at the base of the stack unless individually connected to a.common water pipe or metal breeching that will'assure the interconnection. Conductors shall also be interconnected at intervals of 100 feet (30 m) on all stacks exceeding 200 feet (61 m) in' height. Down conductors_shall be protected from physical damage or displacement for a distance of not less than 8 feet (2 m) above grade,

5-5 Fasteners . Fasteners shall be of copper or copper- bronze alloy. They shall be anchored firmly to the s tackby masonry anchors or lay-in attachments. Ve r t i ca l conductors shall be fastened at intervals not exceeding 3 feet (0.9 m) and horizontal conductors at intervals not exceeding 2 feet (0.6 m).

5-6 Splices. Splices in conductors shall be as few as practicable and shall be attached so as to withstand a pull test of 200 pounds (890 N). All connectors a n d splicers shall be bolt ten- sion type, and shall make contact with the conductor for a distance not less than i-1/2 inches (38 mm), measured parallel to the axis of the conductor.

5;7 Bonding. All extended metal parts located within 6 feet (2 m) of the lightning protection system shall be bonded thereto. Such parts include caps, spark arrestors, p la t forms, bands, ladders, breechings, steam pipes, and water pipes. Metal linings and metal ladders shallbe bonded to the system atboth their upper and lower ends. Bonding plates and connectors shall provide a surface contact area of not less than 3 square inches (2000 mm2).

5-8 Grounding. An acceptable ground terminal shall be provided for each down conductor and shall be suitable for t h e soil conditions encountered. Ground terminals shall be in the form o f driven rods, copper plates, or conductors la id in trenches. I f driven ground rods are u sed , they shall be the equivalent of a copper-clad rod having a diameter of 5/8 inch (15 mm) and shall be at least 10 feet (3 m) in length.

5-9 Water Pipe Connections. If a metal water pipe system is within 25 feet (8 m) Of the stack or metal breeching, a connection shall be made thereto, using a full-size conductor. A connection to a metal breeching that has an inherent or separate connection to the water supply system may be utilized as the required water pipe bond:


5-10 Reinforced Concrete Stacks. In addition to the requirements of this chapter, the reinforcing steel shall be electrically continuous and bonded to the lightning protection system at its upper and lower ends at down-lead locations. Tying or clipping of reinfo~'cing bars shall be an acceptable means of ensuring continuity: Clamps shall be used for the top and bottom connections.

5-11 Metal Stacks. Metal stacks do not require air terminals or down conductors. They shall be grounded directly by means of at least two ground terminals, located on opposite sides of the stack. I f the stack is an adjunct of a building or located within 6 feet (2 m) it shall also be connected to the. lightning protection system on the building. If the stack is set within the perimeter of a building, two connections shall b e made to the nearest main conductors.

5-11.1 Metal GuyWires and Cables. Metal guy wires and cables shall be grounded at their lower ends if they are set in concrete or attached to building or other nonconductive supports.

S T R U C T U R E S C O N T A I N I N G F L A M M A B L E L I Q U I D S A N D G A S E S 78-39

Chapter 6 Protection for Structures Containing Flammable Liquids and Gases

6-1 Reduction of Damage. 6"1.1 This chapter applies to the protection of structures

containing flammable liquids and gases. It thus applies particu, larly to structures (e.g., storage tanks) containing alcohol, ben, zol, crude oil, petroleum products, tu rpen t ine , and other liquids which produce flammable air-vapor mixtures at atmospheric temperatures, normall)~ having flash points below 100°F. (38°C). For the purpose of this chapter, the term "structure" shall apply to the vessel, tank, or other container in which such flammable liquids and gases are contained.

6-1.2 Certain" types of structures used for the storage of flammable liquids and gases are essentially self-protecting against damage due to l ightning strokes. Protection of other such structures may be achieved to a considerable degree by the use of air terminals, masts, overhead ground wires a n d other types of protective devices.

6-1.3 Chapters 3 through 5 Of this (Jode give requirements for the protection of buildings and miscellaneous prop, erty against l ightning damage. Because of the nature of the contents of the structures considered in this chapter, extra precautions shall be taken. In these structures; a spark that would otherwise cause little or no damage might ignite the flammable contents and result in a fire or explosion.

6-2 Fundamental Principles of Protection. 6-2.1 Protection of these structures and their contents

from lightning damage requires adherence to the following principles:

(a) Flammable liquids shall be stored in essentially gastight structures.

(b) Openings where flammable concentrations of vapor or • gas can escape to atmosphere shall be closed or otherwise protected against the entrance of flame.

(c) Structures and containers shall be maintained in good condition.

(d) Flammable air-vapor mixtures shall be prevented, to the greatest possible extent, from accumulating outside such structures.

(e) Potential spark gaps between metallic conductors shall be avoided at points where flammable vapors may escape or ac- cumulate.

78-40 L I G H T N I N G PROTECTION CODE STRUCTURES CONTAINING FLAMMABLE LIQUIDS AND GASES 78-41

6-3 ~ Protec t ive Measures .

6-3.1 Materials and Installation. Conductors, a i r •terminals 'and g round ing connections shall b e selected and installed in accordance with requirements • of Chapter 3.

6-3.2 Sheet Steel. Sheet steel less than 3/16 inches (4.8 mm) in thickness may be punctu.red by severe strokes and shall not be relied upon as protection from direct lightning strokes.

6 - 3 . 3 Rods ; Masts, a n d O v e r h e a d G r o u n d Wires .

. 6o3.3.1 The,zone of protection of an air terminal or mast of conducting material is conventionally taken as the space enclosed by a cone, which has its apex at the highest point of the rod or mast and a radius at the base which bears a relation to the height. This relat iondepends upon the striking distance of the lightning stroke (the distance o;¢er which final breakdown of the initial stroke to ground or to a grounded object occurs) relative to the height of the rod or. mast..For a mast not exceeding 50 feet (15 m) in height, 'the zone defined by a radius of base H equal to the height of the rod or mast has been found to be substantially.immune to direct strokes of lightning. No part of the structure to be protected shall extend outside of the zone of protection. (See Figure 6-3.3.1;)

6-3.3.2 For mast heights in excess Of' 50 feet.(15 m), a zone-of.protection is based o n t h e striking distance o f t h e light- -ning stroke. Since the lightning stroke may strike any grounded • object within the- striking distance of the point from which final breakdown to ground occurs, the zone of protection is defined by a circulararc concave upward (see Figure 6-3.3.2). T h e radius of the arc is the striking distance, and the arc passes through the tip of the mast and is tangent to the ground. Where more than one mast is used, the .arc passes throughthe . t ips of adjacent masts.

T h e striking distance is related to the peak stroke current and thus to the severity of the lightning stroke; the greater the severity of the stroke, the greater the striking distance. In the vast majority of cases, the strikingdistance exceeds 100 feet (30 m). •Accordingly, the zone based on a striking distance of 100 feet (30 m) is considered to be adequately protected. • The zone of protection afforded by any configuration of

masts or other elevated, conductive grounded, objects can read- ily be determined graphically. Increasing the height of a mast above the striking distance will.not increase the zone of protection.

/ 4 X " I ' / \

I / / X / /

/ / \

. ~ / / | " \

• / i / ' X / I /~ \\

• " 3 " / / • v,, \ , , , c , ' Y , , • -"i, "~ " / / ~ . ! _

ix . -',. ,, . / - I ! i

i \ . / / . iii ! \ I I ' - - " - I I l.l\,,,- I / I

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/

/ > / \ ] / / / \ '•t

I I / ~

| ,x l \

\ /

0

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.o.

0

i

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78--42 LIGHTNING PROTECTION CODE

/ A \

/ ; / \ \ / \

/ / \ / , i / \

/ \ / " \

/ /\ h , \ -, " / / / - \ ~ _ _ _ _ ~

\ ' \ .' i , / \ ~, I - - Is.

I \ / / - \ ' v " / / - \ ~ , ,~ . - - - - - - - - - / - - - - . . /

\

• ~, / \

\ / \ / x / \ / '( /

\ /

STRUCTURES C O N T A I N I N G FLAMMABLE LIQUIDS AND GASE'S 78--43

6-3.3.3 Masts separate from the structure to be protected shall be a minimum of six feet (2 m) from the protected structure, and the clearance shall be increased by one foot (0.3 m) for every ten feet (3 m) of structure height above 50 feet (15 m) to prevent side flashes. The masts shall b e g r o u n d e d a n d connected at ground level to the grounding system of the structure to be protected. The grounding requirements of Chapter 3 shall apply. •

6-3.3.4 The zone of protection of an overhead ground wire is conventionally taken as a triangular prism or wedge. For a ground wire not more than 50 feet (15 m).above ground, one-half the.base of the wedge (H) equal to the height of-the lowest point of the overhead_ground wireis considered to provide protection. (See Figure 6-3.3.1.) For a ground wi're more than 50 feet (15 m) above ground, the zone of protection is based on a striking distance of 100 feet (30 m). (See Figure 6-3.3.2.) The supporting mastsshall have a clearance from the protected structure as under 6-3.3.3. The g.round wire material shall be •noncorrosive for the conditions existing at the site and shall not be smaller in diameter than No. 6 AWG (4.7 mm).

6-3.3,5 The minimum clearance between the overhead ground wires and the highest projection on the-protected structure shall be six feet (2 m). For each ten feet (3 m) of lead between a point on the ground wire midway between the supporting masts •and ground in excess of 60 feet (18 m), the clearance shall be increased by one foot (0.3 m). The ground wire(s),shall be grounded and interconnected with the grounding system of the structure to be protected.

6-3.3.6 Masts of wood, used either separately or with ground wires, shall have a listed or labeled air terminal securely mounted to , the top of the pole (see Figure 6-3.3.6) and connected to the grounding system. As an alternative, an overhead ground wire or a down conductor, extending above or across the top of the pole, may be used as. a suitable air terminal. In case of an overhead ground-wire system, the pole guy wire may be used as the down conductor (see Figure 6-3.3.6). For metallic masts, the air terminal and the down conductor shall not be required.

6-4 Protection of Specific-Classes of Structures. 6-4.1 A b o v e g r o u n d T a n k s Containing Flammable Li-

quids at Atmospheric Pressure. 6-4.1.1 The contents of metallic tanks with steel roofs

of riveted, bolted, or welded construction, with or without sup-

",41 O

" 78--44 L I G H T N I N G PROTECTION CODE STRUCTURES CONTAINING FLAMMABLE LIQUIDS AND GASES 78-45

Air T~rminal /

d

_ l 1 PI

Air Terminal /

.

, ? 7 ' Protectedj Structure~~N~Protected Structure

\ / Grounding System I ntercon nectio n

Figure 6-3.3.6. Alternate Grounding Method for Overhead Ground Wire Protection. porting members, used for the storage of flammable liquids at atmospheric pressure are considered to be protected against lightning (inherently self-protecting) if the following requirements are met:

(a) All joints between metallic plates shall be riveted~ bolted, or welded.

(b) All pipes entering the tank shall be metallically connected to the tank at the poirit of entrance.

(c) All vapor or gas openings shall be closed or provided with flame protection, when the stored stock may produce a flammable air-vapor mixture under storage conditions.

(d) The metal roof shall have a minimum thickness of 3/16 inches (4.8 mm).

(e) The roof shall be welded, bolted, or riveted to the shell.

6-4.1.2 Floating Roof Tanks. (a) General. Fires have occurred when lightning has

struck the rims of floating-roof tanks when the roofs were quite high and the contents volatile. Similar above-the-seal fires have occurred when direct lightning strokes to the rims of floating- roof tanks have igni ted flammable vapors within the o p e n shells. These have occurred when roofs were low. The resulting seal fires have been at small leakage points in the seal. An effective defense against ignition by a direct stroke is a tight sisal.

Fires have also occurred in the seal space of open-top floating-roof tanks as a result of lightning-caused discharges. These have occurred most frequently in tanks havingfloating- roofs and seals with vapor spaces below the flexible mem- branes. Ignition can be from a direct stroke or from sudden discharge of an induced (bound) charge on the floating-roof, released when the charge on a cloud discharges to ground or to another cloud.

(b) Protection. Where floating-roofs utilize hangers located within a vapor space,, the roof shall be electrically bonded to the shoes of the seal through the most direct electrical path at intervals not greater than 10 feet (3 m) on the circumference of the tank: These shunts shall consist of flexible Type 302, 28-gage (1/64 in.) (0.4 mm) x 2-inch (51 mm) wide stainless steel straps, or the equivalent in current-carrying capacity and corrosion resistance. The metallic shoe shall be maintained in contact with the shell and without openings (such as corrosion holes) through the shoe. Tanks without a vapor space at the seal do not require shunts at the seal. Where metallic weather shields cover the seal, they shall maintain contact with the shell.

6-4.1.3 Metallic Tanks with Nonmetallic Roofs. Me- tallic" tanks with wooden or other nonmetallic roofs are not considered to be self-protecting, even if the roof is essentially gastight and sheathed with thin metal and with all gas openings provided with flame protection. Such tanks shall be provided with air terminals. Such air terminals shall be bonded to each other, to the metallic sheathing, if any, and to the tank shell. Isolated metal parts shall be bonded as provided in 3-23. In lieu of air terminals, any of the following may be used: conducting masts, overhead ground wires, or a combination of masts and overhead ground wires._

6-4.1.4 Grounding Tanks. Tanks shall be grounded to conduct away the current of direct strokes and avoid building up potential that may cause sparks to ground. Metallic tanks resting on the ground, or metallic tanks connected without insulated joints to grounded metallic piping systems, shall be considered grounded.

6-4.2 Earthen Containers. Earthen containers, lined or unlined, having combustible roofs, shall be protected by air terminals, separate masts, overhead ground wires, or. a combination of these devices.

6-4.3 Nonmetallic tanks shall be treated as miscellaneous structures as described in Chapter 4.

",4

78--46 L I G H T N I N G P R O T E C T I O N C O D E

A p p e n d i x A

This Appendix is not a part of this NFPA Standard 78 but is included for information purposes only.

Point

Base

Air Terminal Figure A-2-2a

Bonding Figure A-2-2b

Cable

Secondary Conductor Figure A-2-2c

Main Conductor

A P P E N D I X A 78-47

Heavy Duty Stack

Chimney

I i i

J Figure A-2-2d

4

Material Classifications

Over 75' (23m)

Under 75' (23~m1~

Class I Class II

i L Heavy Duty Stack ! Over 75' (23m)

Class I I Modified

Figure A-2-2e

- 4 t ~

78-48

Figure A-2-2f

L I G H T N I N G P R O T E C T I O N C O D E

ounterpoise

Grounding Devices

! ~ ~ Rod and clamp _ -

Figure A-2-2g

A P P E N D I X A 78-49

Exhaust f ' ~ ,

Roof lad

Elevated hand / /

Bodies of Conductance

~ Plumbing vent

Roof drain

0 Fascias, gravel stops and flashings

Bodies of inductance

Figure A-2-2h

~: ' " Side flash Figmre A-2-2i.

--4


Appendix B Principles of Lightning Protection

This Appendix is not a part o f this NFPA Standard 78 but is included for information purposes only.

B-I Fundamental Principles of Lightning Protection. B-I.I The fundamental principle in the protection of life

and property against lightning is to provide a means by which a lightning discharge can enter or leave the earth without resulting damage or loss. A low impedance path must be offered which the discharge current will follow in preference to all alternative high impedance paths offered by building materials such as wood, brick, tile, stone or concrete. When lightning follows the higher impedance paths, damage may be caused by the heat and mechanical forces generated during the passage of the discharge. Most metals, being good electrical conductors, are virtually unaffected by either heat or the mechanical forces if they are of sufficient size to carry the current that can be expected. The metal path must be continuous from the earth connection to the air termination. Care should be exercised in the selection of metal conductors to assure the integrity of the lightning conductor for an extended period. A nonferrous metal such as copper or aluminum will provide, in most atmospheres, a lasting conductor free of the effects of rust or corrosion.

B-I.2 Parts of structures most likely to be struck by lightning are those which project above surrounding parts such as chimneys, ventilators, flagpoles, towers, water-tanks, spires, steeples, deck-railings, shafthouses, gables, skylights, dormers, ridges and parapets. The edge of the roof is the part most likely to be struck on flat-roofed buildings.

B-2 Lightning Protection Systems. B-2.1 Lightning protection systems consist of three basic

parts which provide the low impedance metal path required: (a) a system of air terminals on the roof and other elevated locations; (b) a system of ground terminals; (c) a conductor system connecting the air terminals to the earth connections. Properly located and installed, these basic components assure the lightning discharge will be conducted harmlessly between the air terminals and the ground terminals.

APPENDIX B 7 8 - - 5 1

B-2.2 While intercepting, conducting and dissipating the main discharge, the three basic protection system components do not assure safety from possible secondary effects of a lightning strike. Therefore, secondary conductors are provided to interconnect metal bodies to assure such metal bodies are maintained at the same electrical potential so as to prevent "sideflashes" or "spark-over." Surge arresters are also provided to protect power lines and associated equipment from both direct discharges and induced currents.

B-2.3 Metal parts of a structure may be used as part of the lightning protection system in some cases. For example, the structural metal framing which has sufficient cross-sectional area to equal the conductivity of main lightning conductors, and which are electrically continuous, may be used in lieu of separate down conductors. In such cases, air terminals, are bonded to the framework at the top, and ground terminals are provided at the bottom as described elsewhere in this Code. Structures with 3/16 inch (4.8 mm) thick or thicker metal shells or skins which are electrically continuous may not require a system of air terminals and down conductors.

B - 3 Items to Consider When Planning Protection. B-3.1 The best time to design a lightning protection sys-

tem for a structure is during the planning phase, and the best time to install the system may be during construction. System components may be built-in so as to be protected from mechanical displacement and environmental effects. In addition, aesthetic advantages may be gained by such concealment. By installing lightning protection during construction, many ar- chitectural features may be utilized which could result in eco- nomics not realized in the exposed system which may be required when the structure has been completed.

B-3.2 The structure should be examined, and installation of air terminals should be planned for all areas or parts likely to receive a lightning discharge. The object is to intercept the discharge immediately above the parts liable to be struck and to provide a direct path to earth, rather than to attempt to divert the discharge in a direction it would not be likely to take. The air terminals should be placed high enough above the structure to obviate danger of fire from the arc.

B-3.3 Conductors should be installed to offer the least impedance to the passage of stroke current between the air terminals and earth. The most direct path is best, and there should be no sharp bends or narrow loops. The impedance of

,,41

7 8 - 5 2 LIGHTNING PROTECTION CODE APPENDIX B 78-53

the conduc to r system is practically inversely propor t iona l to the n u m b e r of widely separa teo pams. Accordingly, there sh o u ld be at least two.paths to g round , and more if practicable, f rom each air terminal . T h e n u m b e r of paths is increased and the

_ impedance decreased by connect ing the conductors to fo rm a cage enclosing the building.

B-3.4 Proper ly m a d e g r o u n d connect ions are essential to .the e f fec t ive func t ion ing of a ̀ l ightning protect ion System and ever)? e f for t should be made to provide ample contact with the earth. This does not necessarily mean tha t the resistance ,ofxhe g round connect ion should be low, bu t . r a the r that the distribu-

• tion o f metal in the earth or upon its s u r f a c e i n ex t r eme cases should be such as to permi t the dissipation of a s t roke o f light-

. n ing without damage.

B-3.5 Low resistance is desirable, but not essential, as may be shown by the ext reme-case on the one hand of a building resting on moist clay soil, and-on the o t h e r b y a building resting on bare solid rock. In the first case, if the soil is o f normal resistivity, or f rom 4000 to 50,000 ohm-cent imeters , the resis-

..tance of a g round connect ion made by ex tend ing the conduc tor 10 feet (3 m)- in to the .ground will be f rom about 15 to 200 ohms, and two such g round connections on a small rec tangular building have been found by exper ience to be sufficient. U n d e r these favorable condit ions .providing adequate means for col- lecting and dissipating .the energy .of a flash without serious chance o f damage is a simple and .comparatively inexpensive matter.

B-3.6 .In "the second, case, it would .be impossible to make a g r ound connect ion in the ord inary sense o f the term because most kinds of rocks are insulating, or at least o f high resistivity, and in o r de r to obtain effective g round ing o ther and more elaborate means are necessary. The most effective means would be an extensive wire ne twork laid o n the surface of the rock su r r ound ing the building to which the d o w n conductors could be connected. T h e resistance to ear th at some distant point of such an a r r a n g e m e n t would be high but .a t the:same time the potential distribution about t h e b u i l d i n g Would be substantially the same as though it were resting on conduct ing soil and the resulting protect ive effect also substantially, the same.

B-3.7 In general , t h e extent o f the g round ing arrange- • ments will d e p e n d upon the character of the soil, ranging f rom simple extension of the conduc to r into the. g round where the soil is .very d r y o r of very poor conductivity. Where a network is

required, i t sh o u ld be bur ied if there is soil enough to pe rmi t it, as this adds to its effectiveness. Its extent will be de te rmined

• largely.by the j u d g m e n t of the person p lanning the installation with due r ega rd , to the r u l e , the mos t extensive the u n - d e rg ro u n d metal available the more effective the protect ion.

B-3.8 Where practicable, each g r o u n d connect ion should extend or have a b r a n c h which extends below and at least two feet (0.6 m) away f rom. the founda t i on walls o f the building,-as otherwise there is a chance, of the' wall being damaged .

B-3.9 . When a l ightning conduc to r system is placed on a building, within or about which there are metal objects of considerable size within a f ew feet of a conductor , there will be a tendency for sparks or sideflashes to j u m p between the metal object a n d the conductor . T o p r e v e n t d a m a g e , i n t e r c o n n e c t i n g conductors should be provided at all places where sideflashes are l ikely to occur.

B-3.10 Lightning currents en te r ing protec ted buildings "on overhead or u n d e r g r o u n d power lines, or te lephone conductors, or television or radio antennas are not necessarily re- 'stricred tc~ :~ociatocl wiring systems and ~nnl; . . . . . The re fo re , such systems should be equipped with appropr ia te protective devices and bonded to assure a c o m m o n potential.

B-3.11 Because a l ightning protect ion system is expected to remain in working condit ion for long periods •with min imum attention, the mechanical construct ion should be strong, and the materials used should of fer resis tance to corrosion and mechanical in jury .

B-4 Inspection and Maintenance of Lightning Protection Systems. It has been shown that in cases where damage has occurred to a pro tec ted ,s t ruc ture the fault was due to.addit ions or repairs to the building o r to de ter iora t ion or mechanical damage which was allowed to go unde tec ted and unrepaired, or both. T h e r e f o r e , it is r e c o m m e n d e d that an annual visual inspection be made a n d that the system be thoroughly inspected every five years.

B-5 Determining Need for Protection. B-5.1 T h e following factors s h o u l d be studied when con-

'sidering whether or not to provide lightning" protect ion:

(a) Occupant safety; (b)• Nature of building and contents; (c) Relative exposure;

¢,A


(d) T h u n d e r s t o r m frequency; and (e) Indi rec t losses.

B-6 O c c u p a n t Safety. Liability fo r safety o f occupants f rom lightning has become an increasingly more impor tan t factor due to more sti-ict safety practices enacted by state and federal agencies. T h e number of l ightning-caused fatalities in buildings is relatively low compared to more exposed locations. Such factors as the n u m b e r of occupants and their relative mobility become impor tan t factors for consideration. Massed occupancy by immobile hospital or nurs ing h o m e patients makes l ightning safety a more impor tan t factor than lesser occupancy by persons able to flee a l ightning-caused fire, or to take o ther precaut ionary action. An office worker in a large building with g r o u n d e d steel f ramework, for example, is bet ter shielded f rom the effects o f a l ightning discharge than a golfer in a small unpro tec t ed rain shelter.

B-7 N a t u r e o f B u i l d i n g and Contents . T h e value and nature of the building and contents obviously are factors in decid- ing whether protect ion is required. T h e type and design of a building or s t ructure and the extent o f fire protect ion available will have a large influence on the extent o f protect ion to be considered. Some buildings are obviously more susceptible to l ightning loss or damage than others. Buildings sometimes have a value for historical or sentimental association which is unin- gttrable, but which may justify a d ispropor t ionate expense for protect ion. T h e rep lacement value o f the s t ructure will also have a large influence upon the protect ion to be considered. T h e contents o f the building must also be considered, as to whether they are replaceable, whether explosive, combustible, or noncombustible .

B-8 Relat ive Exposure . The relative exposure of a particular bui lding is an e l e m e n t in de te rmin ing whe ther protection is required . In closely built-up towns and cities, the hazard to each building is not so great as it is in the more open rural areas. In rural areas, fa rm buildings may be the most prominent targets for l ightning in a large area. In hilly or mountain- ous districts, a building o n high g round is usually subject to greater hazard than one in a valley or otherwise shel tered area.

B-9 T h u n d e r s t o r m Frequency . T h e f requency of thunders torms varies t h r o u g h o u t the United States and Canada f rom a min imum of five thunde r s to rm days in regions where l ightning is in f requent , to a maximum in regions where the

A P P E N D I X B 7 8 - 5 5

0 ' - - - --7" - 30 I " q ~ " I ~ O '

~ _ 'o ,, - - 5 , o

Figure B-9a. Statistics for Continental United States showing mean annual number of days with thunderstorms. The highest frequency is encountered in south-central Florida. Since 1894, the recordifig of thunderstorms has been defined as the local calendar day during which thunder was heard. A day with thunderstorms is so recorded regardless of the number occurring on that day. The occurrence of lightning without thunder is not recorded as a thunderstorm. (Data supplied by Environmental Science Ser,~ice Administra- tion, U.S. Department o f Commerce.),

average n u m b e r of t hunde r s to rm days per year is over 90 (see Figures B-9a and B-9b). Moreover , the severity of l ightning storms, as dist inguished f rom their f requency o f occurrence, is much grea ter in some locations than in others. In the New England states, for example, there are about 20 thunde r s to rm days per year, but the storms may be exceptionally severe or prolonged. California is shown on the weather map (see Figure B-9a) as having little t hunde r s to rm activity, but some sections of California have had numerous and severe sto~-ms on occa- sion. Hence, the need for protect ion varies, a l though not necessarily in direct p ropor t ion to thunder s to rm frequency. A few severe thunders to rms a season may make the need for protection greater than a relatively large number of storms o f lighter intensity.

B-10 I n d i r e c t Losses . In addition to direct losses such as destruct ion o f buildings by lightning, fire result ing f rom light-


! ~.~ f ' " ~ j ' ~ ~ CANADA I

I I I

Figure B-9b. Canadian statistics showing annual average of days with thunderstorms. Data based on the period 1957,1972. (Meteorological Division, Department of Transportation, Canada.)

ning, .the killing of livestock, etc., there may be indirect losses which sometimes accompany the destruction or damage of buildings and their contents. An ,interruption to business or farming operations, especially at certain times of the year, may involve losses quite distinct from and in addition to the losses arising from the direct destruction of material property. There are cases where whole communities depend on the integrity of a single structure for their safety and comfort. For example, they may depend on a water-pumping plant, a telephone relay station, a police station, or a fire station. A stroke of lightning to the unprotected chimney of a pumping plantl for example, might have a serious consequence from alack of sanitary drink- ing water, irrigating water or water for fire protection.

A P P E N D I X C 7 8 - - 5 7

/

A p p e n d i x C Guide for Personal Safety Dur ing Thunders torms

This Appendix is not a part of this NFP,4 Standard 78 but is included for information purposes only.

C-I ' The purpose o f this Appendix is to furnish a guide for personalsafety during thunderstorms.

C-2 "Personal Conduct .

C-2.1 Do not go ou t - o f - doo r s or~remain out dur ing thunderstorms unless it is necessary. Se'ek shelter as follows:

(a) Dwellings or o ther buildings which are protected against lightning.

(b) Large metal-frame buildings. (c) Large unprotected buildings. (d) Automobiles and buses with metal tops and bodies. (e) Trains and streetcars. (f) Trailers with metal bodies. (g) Enclosed metal boats or ships. (h) Boats which are protected against lightning. (i) City streets which may be shielded by nearby build-

ings.

C-2.2 If possible, avoid the following places which offer little or no protection from lightning.

(a) Small unprotected buildings, barns, sheds, etc. (b) Tents and temporary shelters. (c) Automobiles (nonmetal top or open). (d) Trailers (nonmetal).

C-2.3 Certain locations are extremely hazardous during thunderstorms and should be avoided if at all possible. Ap- proachingthunderstorms should be anticipated and the following locations avoided when storms are in the immediate vicin- ity.

(a) Open fields. . (b) Athletic fields. (c) Golf courses. (d) Parking lots and areas on top of buildings. (e) Swimming pools, lakes and seashores.

tim ',4 ",4


(f) Near wire fences, clotheslines, overhead wires and railroad tracks.

(g) Under isolated trees. (h) Hilltops and wide open spaces.

C-2.4 In the above locations, it is especially hazardous to be riding in or on any of the following during lightning storms.

(a) :Open tractors and other farm machinery operated in open fields,

(b) Golf carts, scooters, bicycles and motorcycles. (c) Open boats (without masts). (d) Automobiles (nonmetal-top or open) and hover

craft.

C-2.5 It may not always be.possible to choose a location that.offers good protection from lightning. Follow these rules when there is a choice in selecting locations:

(a) Seek depressed areas--avoid hilltops and high places. (b) Seek dense woods--~avoid isolated trees. (c) Seek small unprotected buildings, tents and shelters

in low areas-~avoid unprotected buildings and shelters in high areas.

APPENDIX D 7 8 - - 5 9

Appendix D Protection for Sailboats, Power Boats, Small Boats and Ships.

This Appendix is not a part of this NFP,4 .Standard 78 but is included for information purposes only.

D-I General Principles. D-I.I Successful protection of persons from lightning is

dependent upon a combination of proper design, personal behavior, and maintenance of equipment. Proper design is covered in this a n d .following sections. Personal .behavior and maintenance of equipment are covered in Section D-10. In view of the wide variation in structural design of boats, the basic guides .contained in Appendix D should be considered and used in designing and installing a lightning protection system for any given craft.

D-1.2 A grounded conductor, or lightning protective mast, will generally divert to itself direct hits which might otherwise fall within a cone-shaped space, the apex of which is the top of the conductor or lightning protective mast and the base is a circle at the surface of the water having a radius of approximately two times the height of the conductor.

D-1.3 To provide an adequately grounded conductor or lightning protective mast, the entire circuit from the top of the

mas t to the ground should have a conductivity equivalent to a No. 8 AWG (3.3 mm) copper conductor and the path to ground followed by the conductor should be essentially straight. To remove all known risk of melting the conductor when carrying lightning current, conductivity equivalent to No. 6 AWG (4.7 mm) or No. 4 AWG-(5.2 • m m) copper would be necessary. However, the risk in using No. 8 AWG (3.3 mm) is considered adequately small in the applications under consideration, and in many cases will be mitigated by the presence of electrically paralleling stays. This statement should not be interpreted to admi t the use of conductivity smaller than that of No. 8 AWG (3.3 mm) copper. ---'

D-I.4 If there are metal objects of considerable size within a few feet of the grounding conductor, there will be a strong tendency for sparks or sldeflashes to jump from the grounding conductor to the metal object at the closest point. To prevent damage from such sideflashes, an interconnect-

7 8 - 6 0 L I G H T N I N G P R O T E C T I O N C O D E , ~ P P E N D I X n 7 8 - 6 1

ing conductor at least equal to No. 8 AWG (3.3 mm) copper _ + ." . . . . . . . . . . .

d i i p i d L ~ 3 WIIIC;;IU L I I U y d i U i i l ~ ,u t y LU U l ~ l - l l l ' . • . ~ i l I U U I U I J l U V I U C U I l L

Large metallic objects which are not part of the electrical system of the boat and which are not already grounded due to their own functional or other requirements may be grounded directly to the ground plate, provided that it is not practical to interconnect with the lightning conductor or bonding systems. (See Section D-4.)

D-I.5 Lightning protection provisions are quite likely to receive Scant attention and therefore their composition and as- sembly should be .strong and materials used should be highly resistant to corromon.

"x

D - 2 I n s t a l l a t i o n R e c o m m e n d a t i o n s .

D - 2 . 1 L i g h t n i n g P r o t e c t i v e M a s t . A lightning protective mast should be of adequate height and should be mechanically strong in order to withstand exposure to use and weather (see Subsection D-1.2). If the mast is of nonconducting material, the associated lightning or grounding conductor should be essentially straight, securely fastened to the mast, should extend at least six inches (!50 ram) above the mast, should preferably terminate in a receiving point, should be led as directly as practicable to the grounding connection (see Section D-4) and should meet the recommendations of Section D-3.

D-2.2 Radio Antenna. A radio antenna may serve as a l ightningprotective mast provided it has conductivity equivalent to No. 8 AWG (3.3 mm) copper and is equipped with lightning arresters, lightning protective gaps, or means for grounding during electrical storms. The grounding of metal rod type radio antennas constitutes sufficient protection for wooden boats, without masts and spars, provided the following conditions are met:

D-2.2.1 The antenna and all conductors in the grounding circuit of the antenna have a conductivity equivalent tO No. 8 AWG (3.3 mm) copper in accordance with Subsection D-3.1.

D-2.2.2 A linb drawn from the top of the antenna downward toward the water at an angle of 60 degrees to the vertical does not intercept any part of the boat (see Subsection D-1.2).

D-2.2.3 Antennas with loading coils are considered to end at a point immediately below the loading coil unless this coil is provided with a suitable protective device for by-passing

/ / /

I . .

/ ' L \ Pr°teCtGredouZn°;e U ~

Protected Zone- Antenna without

Protected Zone-- t / 1 " ~ Lightning Arrester Antenna / ' ~ 0 o l i ~ or Gap on Coil

/ fProtected Zone- , ~ / ~ - - f Mast Only ~ . / ~ , . , , ~ ~ . ~ ~

Figure D-2. Diagrams above illustrate the zone of protection provided by a grounded mast or antenna. This protective zone is largely immune to direct strokes of lightning. No part of the vessel to beprotected should extend outside the zone of protect,on. Thus, in the cabin cruiser illuslrated, adequate lightning protection is afforded only by the grounded antenna equipped with al ightnlng arrester or gap on the coil'.

trot

78--62 L I G H T N I N G PROTECTION CODE

the l ightning current . Such a protective device is recommended .

D-2.2.4 Nonconduc t ing an tenna masts with spirally wrapped conductors are not cons idered suitable for l ightning protect ion purposes.

D-3 Materials.

D-3.1 T h e materials used in the making o f a protective system should be resistant to the corrosion. T h e use of combi- nations of metals that fo rm galvanic or electrolytic couples, if of such a na ture as to accelerate corrosion in the presence of moisture or direct submersion, should be avoided.

D-3.2 In those cases where it is impractical to avoid a junct ion of dissimilar metals, the corrosion effects can be re- duced by the use of suitable platings or special connectoi-s, available for such purposes. Except for the use o f conduct ing materials which are otherwise par t o f the s t ructure o f the boat, only copper should be used as the conductor . Where copper is used, it should be of the grade ordinari ly requi red for commercial electrical work, generally designated as being o f 98 percent conductivity when annealed.

D-3.3 Copper C o n d u c t o r . Copper cable conductors should b e ' o f a d iameter not less than No. 8 AWG (3.3 mm). T h e size of any strand of a cable should be not less than No. 17 AWG (1~2 mm). T h e thickness of any coppe r r ibbon or strip should be not less than No. 20 AWG (0.03 in.) (0.8 mm). Where o the r materials are used the gage should be such as to give conductivity equal to or grea ter than No. 8 AWG (3.3 mm) s t randed coppe r cable.

D-3.4 Joints . Joints should be mechanically s trong and should be so made that they have an electrical resistance not in excess of that o f two feet (0.6 m) of conductor .

D-3.5 I n t e r c o n n e c t i o n o f Metal l ic Masses . D-3.5.1 Metallic masses aboard boats which are a per-

manen t par t o f the boat or are pe rmanen t ly installed within or a bou t it and whose funct ion would not be seriously affected by g round ing should, with the except ion of those o f comparatively small size, be made a part o f the l ightning-conductor system by in terconnect ion with it. (See Subsections D-3.5.5, D-3.5.6, D-3.5.7.)

D-3.5.2 T h e object o f in te rconnect ing the metal parts o f a boat with the conduc to r is to p reven t d a m a g e f rom

APPENDIX D 7 8 - 6 3

sideflashes especially in the case of ra ther extensive metal objects that are nearby. T h e main principle to be observed in the prevent ion o f such damage is to pick out on a boat the places where sideflashes are most likely to occur and provide metallic paths for them.

D-3.5.3 T o minimize ~ flow o f lightning discharge current t h rough engine bearings, it may be preferable to bond engine blocks directly to the g round plate ra ther than to an in termedia te point on the lightning conductor .

D-3.5.4 Exter ior B o d i e s o f Metal. D-3.5.4.1 Metal situated whol ly on the exter ior of

boats should be electrically connected to the g round ing conductor at its u p p e r or its nearest end, and, if of considerable length, should be also g rounded or electrically connected to the conduc to r at its lower or its far thest e n d .

D-3.5.4.2 Exter ior metal bodies on boats include any large masses such as horizontal handrails on cabin tops, smokestacks f rom galley stoves, davits or metal signal masts.

D-3.5.5 Inter ior B o d i e s o f Metal. D-3.5.5.1 Metal situated wholly in the interior of boats

which at any point comes within 6 feet (2 m) of a l ightning conduc tor should be electrically in terconnected with it.

D-3.5.5.2 In ter ior bodies of metal include engines, water and gasoline tanks, control rods for steering gear or re- versing gear. It is not in tended that small metal objects such as

compasses , clocks, galley stoves, medicine chests, and o the r parts of the boat's hardware be g rounded .

D-3.5.6 Metal which projects t[arough cabin tops, decks or sides of boats above the sheer should be bonded to the nearest l ightning conduc tor at the point where the metal emerges f rom the boat and should be g rounded at its lower or ex t reme end within the boat.

D-3.5.7 Radio t ransmit ter antenna should be (a) equipped with means for g round ing dur ing electrical storms or (b) the t ransmit ter and an tenna should be protec ted by lightning arresters o r l ightning protect ive gaps.

D-4 G r o u n d C o n n e c t i o n . A ground connect ion for a boat may consist of any metal surface which is normally submerged in the water and which has an area of at least one square foot (0.09 m2). Propellers and met~illic r udde r surfaces may be used for this purpose . T h e g r o u n d plate as requi red by the Federal


Communica t ions Commission for radio transmit ters should be considered adequate . A metal hull itself constitutes an adequate g round .

D-5 Vessels with Metal Hul ls . I f there is an electrical contact between metal hulls and metal masts or o ther metallic supers t ruc ture o f adequate height to meet the r ecommenda- tions of Section D-2, no fu r t he r protect ion against l ightning is necessary. Boats with u n g r o u n d e d or nonconduc t ing objects project ing above the metal masts or supers t ruc ture should have these objects g r o u n d e d or protec ted with a g r o u n d e d conductor, respectively, in o rde r to protect them.

D-6 Pro tec t ion of Sailboats. (Nonmetallic) D-6.1 Sailboats. Sailboats with metallic standin.g n.'gging

will be adequately protec ted provided that all rlggang is g rounded , so that the mast and r igging meet the recommendations o f Sections D-2 and D-3.

D-6.2 O p e n Day-Sailers, O p e n sailboats will be ade- v . . . . . . . . if an)' shrouds, ~'"~l" • t . . . . . 1 ~,a,.,, stays or preventors , a . u

any cont inuous metallic track on the mast and boom are g rounded . These should be electrically connected at the lower or forward end and g r o u n d e d to a coppe r plate on .the hull or to a .metal rudde r , center board or keel._

D-6.3 Cru is ing Sailboats. All stays a n d all sail tracks should be g r o u n d e d on cruising sailboats.since it is assumed that persons will be in proximity o f fore-stays as well as after- stays. G r o u n d i n g of o ther objects on cruising boats should be in accordance with the foregoing subsections.

D-7 P r o t e c t i o n o f P o w e r Boats . (Nonmetallic) D-7.1 Power boats may be adequately protec ted by a

g r o u n d e d radio an tenna or o ther suitable g ro u n d ed lightning protect ive mast as r e c o m m e n d e d in Section D-2, p rovided the height of the mast meets the re~:ommendat ions f o r t h e zone of protect ion in Subsection D-1.2. In te rconnec t ion and g round ing o f metallic masses should be in accordance with Subsection D-2.2.2.

D-7.2 Where tile size of the boat is such as to r en d e r the use Of z, single mast impractical, addit ional l ightning protective masts should be erected to fo rm over lapping zones of protection.

A P P E N D I X D 78-65 "

D-8 Pro tec t ion Of Smal l Boats .

D-8.1 Small boats may be proteizted by means Of a temporary l ightning protective mast which may be erected when lightning condit ions are observed in the distance. G r o u n d i n g " provisions may be made by means of flexible copper wire and a submerged g ro und plate o f approximate ly one square foot (0.09 m z) in area.

D-9 P r o t e c t i o n o f Ships . D-9.1 Ships almost invariably are constructed with s t e e l

masts, spars, supers t ructures , hulls, smokestacks and shrouds and the array of masts, stacks and radio antennas usually provide the zones o f protect ion r e c o m m e n d e d in Subsection D-1.2. The re fo re , ships and personnel aboard them are usually inherently pro tec ted against the effects o f lightning. In those cases w h e re adequate zones of protect ion are lacking, they should be correc ted in accordance with Subsection D-1.2, i f accomplished by changes in n u m b e r or height o f masts, or in accordance with Subsection 6-3.3 if by shielding wires suspended between masts.

D-9.2 In the cases o f fiberglass or wooden hulled sailing ships with wooden masts, protect ion should be in accordance with Sections D-I and D-6 except that g round ing and bond ing conductors should have conductivi ty not less than that of No. 4 AWG (5.2 mm) coppe r wire, and the c o p p e r g round ing plate below the light water line should have an area not less than 36 square feet (3.3 m2).

D- 10 P r e c a u t i o n s for P e r s o n n e l . D-10.1 Inasmuch as the basic purpose of protect io n

against l ightning is to insure the safety of personnel , it is appropr ia te that the following precaut ions and suggestions be listed in addit ion to all applicable ri~commendations in Appen- dix C.

D-10.2 One should remain inside a closed boat, as far as practical du r ing a l ightning storm, and should not dangle arms or legs in the water.

D-10.3 T o the exte~nt consistent with safe handl ing and navigation o f the boat du r ing a l ightning storm, one should avoid making contact with any items connec ted to a l ightning protect!on ,system and especially in such a way as to .bridge between these items. For example , it is undesirable that an opera tor be in contact with revers ing gear levers and spotlight control handle at the same time.

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D-10.4 No one should be in the water during a lightning storm.

D-I 1 Maintenance Suggestions. D-II . I One should not have'a whip type radio antenna

tied down during a lightning storm if it has been designed as a part of the lightning protective system.

D-11.2 If a boat has been struck by lightning, compasses and electrical gear should be checked to determine that no damage or change in calibration has taken place.

APPENDIX E 7 8 - 6 7

Appendix E Protection for Livestock in Fields

This Appendix is not a part of this NFP.4 Standard 78 but is included for information purposes only.

E-I General. E-I.I The nature of the exposure of livestock in fields is

such that it is not possible to eliminate the hazard entirely. However, application of the recommendations contained in Appendix E should minimize the hazard.

E-I.2 The loss of livestock by lightning during thunderstorms is caused in large measure by herds congregating Under isolated trees in open pastures or drifting against un- grounded wire fences, and receiving a sufficient discharge to - kill them.

E-I.3 In pastures where shelter is available from wooded areas of considerable size, isolated trees should be removed unless protection is provided.

E-I.4 Fences built with metal posts set in earth are as safe from lightning as it is practical to make them, especially if the electrical continuity is broken. Breaking the electrical continuity is very useful in that it reduces the possibility of a lightning stroke affecting the entire length of a fence, as it can if the stroke is direct and the fence continuous, even though grounded. T h e fences that give rise to the most trouble are those constructed with posts of poorly conducting material, such as wood.

E-2 Grounding of Wire Fences. E-2.1 Subsections E-2.2 and E-2.3 should be applied,

where it is desirable or necessary to mitigate the danger from" wire fences constructed with posts o f nonconducting material.

E-2.2 Iron Posts. Ground connections may be made by inserting at intervals galvanized-iron posts, such as are ordinarily used for farm fencing, and attaching in electrical contact all of the wires of the fence, or by driving a length o f 1/2- or 3/4-inch (13 or 19 ram) (trade size) galvanized-iron pipe beside the fence and attaching the wires by ties of galvanized-iron wire. If the ground is normally dry, the intervals between metal posts should not exceed 150 feet (46 m). I f the ground is normally damp they may be placed 300 feet (99 m) apart.

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-78-68 ,LIGHTNING PROTECTION CODE APPENDIX V '78--69

E-2.3 Depth of Grounds. Pipes should be extended into the ground at least 2 feet (0.6 m).

E-3 'Breaking Continuity of Fence. E-3.1 In addition to grounding the fence, its electrical

continuity should be broken by inserting insulating material in breaks in the wires at intervals of about 500 feet (153 m). These insertions may be in the form of fence panels of wood or lengths of insulating material to the ends of which the wires can be attached. Such lengths of insulating material may consist of strips of wood 2 × 2 x 2 4 inches (50×50x610 mm), or their

• equivalent as far as insulating properties and mechanical strength are concerned.

E-3.2 In areas where he r d s may congregate along fences, the continuity should be broken at more frequent intervals than described in E-3.1.

Appendix F Protection for Picnic Grounds, Playgrounds, .Ball Parks and Other Open Places

This Appendix is not a part of this NFPA Standard 78 but is included for information purposes only.

F-I P icn ic Grounds and Playgrounds. F-I .I Protection from lightning may be afforded to some

extent fo r picnicgrounds and playgrounds by erecting shelters, with either closed o r open sides. Lightning protection should be p r o v i d e d for such shelters. Down conductors should be shielded with a nonconductive material, resistant to impact and climatic conditions, to a height of approximately eight feet (2 m). Shelters with earthen floors which are provided with lightning protection systems should have ground terminals interconnected by an encircling, buried, bare conductor of a type suitable for such service, or such ground terminals should be provided with radial conductors run out to a distance of at least 10 feet (3 m) from the ground terminal away from the shelter.

F-I.2 An alternate method of protection would be the erection of poles on opposite sides of the grounds, near the

.edges . Wires would be strung between these poles at a height of approximately 20 feet (6 m ) a b o v e the ground. Down leads would connect the wires with ground terminals. Down conductors should be shielded with a nonconductive material, resistant to impact and climatic conditions, to a height of approximately eight feet (2 m). The wires should be at least No. 4 AWG (5.2 mm) copper, or equivalent. I f steel poles or masts are used instead of wood, down leads are not necessary but the foot o f the pole or mast should be grounded. If the area to be protected is extensive, it may be desirable to use several poles arranged around the perimeter so that the area is covered by a network of.wires. A sufficient number of wires should be used so that the entire field falls within the zone of protection. (See Figures 6-3.3.1 and 6-3.3.2 in Chapter 6 f o r illustration.)

F-2 Ball Parks and Race Tracks. Protec.tion may be afforded to spectators i f there are roofed grandstands. These should be equipped with lightning protection. Outside the grandstand all poles should .have shielded down leads and g round terminals as described in F-1.2.

ho


F-3 Beaches. Owing to their ex tent and location, beaches are ex t remely difficult to protect.

F-4 Piers .

F-4.1 Covered piers should be equ ipped with l i g h t n i n g protect ion and in o ther situations p r o t e c t e d shelters might be provided.

F-4.2 Open piers should provide a zone of protect ion by a wire moun ted on poles ex tending the length o f the pier.

APPENDIX G 7 8 - 7 1

A p p e n d i x G Protec t ion for T r e e s

• . This Appendix is not a part o f this N F P A Standard 78 but is included f o r information purposes only.

• G-I Methods and Materials .

G-I . I Where trees are to be protected against l ightning the following should apply.

G-1.2 Conduc tors . Conduc tors may be copper , copper-alloy or a luminum and should conform to the requirements of Chap te r 3.

G-I .3 Cours ing o f Conductors . In general a single conduc tor should be run f rom the highest par t o f the tree along t h e t runk to a g round connection. I f the tree is forked, branch conductors should be ex tended to the highest parts of the prin- cipal limbs. I f the t ree t runk is three feet (0.9 m) in d iameter or

• larger, t w o d o w n conductors may be run on opposite sides of -the t runk and in terconnected.

G-I .4 Height . T h e conductors should b e ex t ended as close as pract icable to the highest par t o f the tree terminat ing with an air terminal.

G-I .5 At t achment o f , Conductors . Conductors should be securely a t t a c h e d to the tree i n s u c h a way as to allow for

swaying in the wind and growth, ,without dange r o f breakage. G - I . 6 Ear th • Connect ions . Grounds for conductors

should be made as follows: (a) From each conductor , descend- ing the t runk o f the tree, ex tend three or more radial conductors in t r enches 12 inches (0..3 m) deep , spaced at. equal intervals about the base where practicable, to ad i s tance of 10 to 25 feet (3 to 8 m) depend ing u p o n the size o f the tree; (b) T h e system . s h o u l d b e bonded to a g rounded metallic water pipe where available. I f the roots" are very extensive t h e radial conductors may well be ex t ended more than 25 feet (8 m). It is desirable as a f u r t he r protect ion measure to connect the ou te r ends o f the radial conductors together with a conduc to r which encircles the tree at the .same depth as the radial conductors .

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7 8 - 7 2 LIGHTNING PROTECTION CODE APPENDIX H 7 8 - - 7 3

Tree Protection

(Note: Install cable loosely to allow for tree growth.)

®

®

®

N

Note 1: Locate ground f " - . Note: 1 f t = 0.305m approximately at branch _ ~

.

Splicer . . ~ " ~ " ~ - -

I ~ Al ternate grounding method

1 Main t runk air terminal 2. Class I or II ful l size cable . 3. Branch air terminal 4. Secondary size cable 5. Drive type cable clip at 3' O/C 6. Splicer 7. Ground rod and clamp

. F i gu re G-I

Appendix , H " P r o t e c t i o n o f Aircraft

This Appindix is not a part of this NFPA Standard 78 but is included f o r information purposes only.

H-I General P r i n c i p l e s . . I I - l . l Aircraft includes airplanes, helicopters, blimps and

airships (lighter-than-air-craft). They can best be protected by placing them inside a properly lightning protected hangar. Hangar facilities should be provided with grounding recepta- cles to permit interconnection of metal aircraft with the hangar lightning protection system. It is important that hangar floors, aprons and aircraft parking iareas be kept f ree of gasoline or other flammable liquids.

H-!.2 All metal airplanes parked outside hangars should be grounded: This grounding may be achieved by the use of adequately grounded metal tie-down cable or chains. Other than all-metal airplanes, those having control surfaces of fabr!c or plastic materials, can be protected by connecting,the plane s metal frame to ground, similar to that for all-metal airplanes: In addition, it is recommended such aircraft be parked under an overhead ground wire or mast type lightning protection system, the height of which should be two times the height of the tallest part of the aircraft .

H-1.3 Airships, when anchored to the ground by masts, are partially protected if the mast top is at an elevation well above the highest structural part of theairship, and the mast is provided with a l ightning protection system meeting the requirements of Chapter 3. It is assumed that as a matter of course lightning protected hangars will be used for lightning protection in preference to grounded masts whenever possible. A balloon or other nonpower-driven lighter-than-air'aircraft, temporarily controlled by:a metal, cable from a winch on the ground, shall be grounded normally through the winch by providing connection to the earth.

H-I .4 Small helicopters, hovercraft, and other light aircraft are primarily suitable for operation in fair weather. Their operation under thunderstorm conditions should be avoided a's

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78-74 L I G H T N I N G PROTECTION CODE

being extremely hazardous. Such aircraft should be protected by grounded tie-down cables or an overhead ground wire or mast type lightning protection system or both.

H-l.~i Many all-metal aircraft have received direct lightning strokes while in flight and have remained airworthy for completing flights. Incidents have been reported, however, where a stroke caused the aircraft to catch fire and crash, and where the radio, radar, and other electrical equipment necessary to flight has been severely damaged. Reports on strokes to hea;cy aircraft are being collected and studied in the interest of a further reduction of lightning hazards. COrrective measures seek a better means of avoiding the ignition of any fuel-air mixtures that are present and of insuring that aircraft naviga- tional, radio-communication, and radar equipment will be only momentarily out of service, not permanently damaged by a stroke. Such measures include improving the location of components so that they are less likely to be in the lightning current path and providing gaps or other devices to divert the fightning current away from the equipment, personnel; and. areas that present ignition or breakdown hazards. They are essentially design features rather than later corrective measures.

H-I.6 Aircraft on the ground undergoing fuel servicing and in certain maintenance operations must be grounded to avoid sparks from static electrical charges which can accumu- late on these rubber-tired vehicles. The grounding methods required for static control are not necessarily adequate to provide effective lightning protection for aircraft in the event of a direct stroke. Fuel servicing opei-ations and other maintenance

• operations, involving the use of flammable liquids or the re- lease of flammable vapors, should be suspended during lightning storms. Refer to Standard for Aircraft Fuel Servicing, NFPA No. 407-1975, Recommendations on Safeguarding Aircraft Electrical System Maintenance Operations, NFPA No. 410A- 1975, Recom- mendations on Safeguarding Aircraft Breathing Oxygen System Maintenance Operations, NFPA No. 410B- 1971, Recommendations on Safeguarding Aircraft Fuel System Maintenance, NFPA No. 410C- 1972, Recommendations for Safeguarding Aircraft Cleaning, Painting, and Paint Removal, NFPA No. 410D-1971, Recom- mended Safe Practices for Aircraft Welding Operations in Hangars, NFPA No. 410E- 1975, and Recommendations on Safeguarding Air- craft Cabin Cleaning and Refururbishing Operations, NFPA No. 410F-1975.

APPENDIX I 7 8 - - 7 5

Appendix I

This Appendix is not a part of this NFPA Standard 78 but is included for information purposes only.

I-I Reference Publications. I-l.1 NFPA Standards. This publication makes refer-

ence to the following NFPA codes and standards and the year dates shown indicate the latest editions available:

(a) NFPA No. 61B-1973, Standard for Grain Elevators and Bulk Grain Handling Facilities

(b) NFPA No. 653-1971, Standard for the Prevention of Dust Explosions in Coal Preparation Plants

(c) NFPA No. 407-1975, Standard for Aircraft Fuel Ser- vicing

(d) NFPA No. 410A-1975, Recommendations on Safeguard- ing Aircraft Electrical System Maintenance Operations

(e) NFPA No. 410B-1971, Recommendations on Safeguard- ing Aircraft Breathing Oxygen System Maintenance Opera- lions

(f) NFPA No. 410C-1972, Recommendations on Safeguard- ing Aircraft Fuel System Maintenance

(g) NFPA No. 410D- 1971, Recommendations for Safeguard- ing Aircraft Cleaning, Painting, and Paint Removal

(h) NFPA No. 410E-1975, Recommended Safe Practices for Aircraft Welding Operations in Hangars

(i) NFPA No. 410F-1975, Recommendations on Safeguard- ing Aircraft Cabin Cleaning and Refurbishing Operations.

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