LIGHTNING PROTECTION for AIR FORCE FACILITIES

LIGHTNING PROTECTION for AIR FORCE FACILITIES
2002 Lightning Statistics Globally- an average of 100 strikes per minute In US- 15 to 20 million lightning strikes per year Lightning Damage Average of over 1,500 fires per year over $300 million in insurance claims annually Lightning Deaths Chances of being killed are 1:29,000 TSgt Gilbert Martinez Det 1 PACAF-CES

Summary Slide INTRODUCTION REGULATORY GUIDANCE MATERIAL REQUIREMENTS
STRIKE TERMINATION DEVICES CONDUCTORS TYPES OF SYSTEMS ZONE OF PROTECTION BONDING SIDEFLASH REQUIREMENTS SURGE PROTECTION GROUND SYSTEMS INSPECTION AND TESTING TEST PLANS AND RECORD KEEPING

INTRODUCTION The intent of this course is to familiarize and improve the skills of personnel involved in the installation and maintenance of lightning protection systems. We will discuss the design, installation, and maintenance of lightning protection systems for structures housing explosives in accordance with applicable standards. DOD STD – Defines minimum explosive safety criteria for the design, maintenance, testing and inspection of lightning protection systems. AFMAN – Implements AF policy and DOD STD It applies to everyone involved in any explosive operation in the Air Force, and compliance is mandatory. Chapter 2, Section D deals with; Electrical Hazards; Hazardous locations (2.46), Electrical Service (2.48), Static (2.51 & 2.52), Grounds (2.53), Lightning Protection (2.54) AFI – Implements maintenance requirements of DOD STD, chapter 7 “Lightning Protection” and assigns maintenance responsibilities and requirements for grounding, static, and lightning protection systems on Air Force installations. NFPA 780 – (1997 edition) Provides practical safeguarding for persons and property from hazards arising from exposure to lightning. Does not cover: explosive manufacturing buildings and magazines.

REGULATORY GUIDANCE AFMAN – Implements AF policy and DOD STD It applies to everyone involved in any explosive operation in the Air Force, and compliance is mandatory. Chapter 2, Section D deals with; Electrical Hazards; Hazardous locations (2.46), Electrical Service (2.48), Static (2.51 & 2.52), Grounds (2.53), Lightning Protection (2.54) DOD STD – Defines minimum explosive safety criteria for the design, maintenance, testing and inspection of lightning protection systems. DOD STD – Defines minimum explosive safety criteria for the design, maintenance, testing and inspection of lightning protection systems. AFMAN – Implements AF policy and DOD STD It applies to everyone involved in any explosive operation in the Air Force, and compliance is mandatory. Chapter 2, Section D deals with; Electrical Hazards; Hazardous locations (2.46), Electrical Service (2.48), Static (2.51 & 2.52), Grounds (2.53), Lightning Protection (2.54) AFI – Implements maintenance requirements of DOD STD, chapter 7 “Lightning Protection” and assigns maintenance responsibilities and requirements for grounding, static, and lightning protection systems on Air Force installations. NFPA 780 – (1997 edition) Provides practical safeguarding for persons and property from hazards arising from exposure to lightning. Does not cover: explosive manufacturing buildings and magazines.

REGULATORY GUIDANCE AFI – Implements maintenance requirements of DOD STD, chapter 7 “Lightning Protection” and assigns maintenance responsibilities and requirements for grounding, static, and lightning protection systems on Air Force installations. NFPA 780 – (1997 edition) Provides practical safeguarding for persons and property from hazards arising from exposure to lightning. Does not cover: explosive manufacturing buildings and magazines. DOD STD – Defines minimum explosive safety criteria for the design, maintenance, testing and inspection of lightning protection systems. AFMAN – Implements AF policy and DOD STD It applies to everyone involved in any explosive operation in the Air Force, and compliance is mandatory. Chapter 2, Section D deals with; Electrical Hazards; Hazardous locations (2.46), Electrical Service (2.48), Static (2.51 & 2.52), Grounds (2.53), Lightning Protection (2.54) AFI – Implements maintenance requirements of DOD STD, chapter 7 “Lightning Protection” and assigns maintenance responsibilities and requirements for grounding, static, and lightning protection systems on Air Force installations. NFPA 780 – (1997 edition) Provides practical safeguarding for persons and property from hazards arising from exposure to lightning. Does not cover: explosive manufacturing buildings and magazines.

MATERIAL REQUIREMENTS
AFI Requirements NFPA 780 Requirements Main Conductor Example

MATERIAL REQUIREMENTS
AFI Requirements 14.1. General. Systems must comply with NFPA 780 and AFM 88-9, Chapter 3, Electrical Design Lightning and Static Electricity Protection (except as modified herein). Early streamer emission systems or charge dissipation systems are not permitted. Parts and materials must carry the Underwriters Laboratories (UL) label or equivalent. Otherwise, such components must be approved by the MAJ-COM electrical engineer in charge of lightning protection. Facilities in foreign countries may use host nation codes and standards if they offer equivalent protection, as determined by the MAJCOM electrical engineer with concurrence from HQ AFCESA/CESE and approval of the DoD Explosive Safety Board (DDESB). Otherwise, the Status of Forces Agreement (SOFA) must permit their use. Where the SOFA requires compliance with host nation codes, translate those required codes into English, make them available to all appropriate personnel, and perform necessary training. Maintain all installed systems according to this instruction. If not required, remove the system with coordination through the using agency. NOTE: Conductor materials: Copper, Copper Alloys and Aluminum NFPA 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 where they come into direct contact with earth. (c) Connectors and fittings shall be suitable for use with the conductor and the surfaces on which they are installed. (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. Corrosion Protection. Precautions shall be taken to provide the necessary protection against any potential deterioration of any lightning protection component due to local conditions. Copper components installed within 24 in. of the top of a chimney or vent emitting corrosive gases shall be protected by a hot-dipped lead coating or equivalent.

Material Requirements, Class I
NFPA 780 Requirements Material Requirements, Class I Table (a) NFPA 780 Buildings and Structures less than 75 feet in Height Material Requirements, Class II Table (b) NFPA 780 Buildings and Structures greater than 75 feet in Height

Main Conductor Example
MATERIAL REQUIREMENTS Main Conductor Example NO. 29R Copper cable consisting of 29 strands of No. 16 AWG wire. This cable has a cross-sectional area of 72,500 cm and a weight of 215 pounds per 1000 feet. The outside diameter is approximately 3/8".

STRIKE TERMINATION DEVICES
NFPA 780 Requirements Air Terminal Height Air Terminal Support Chimneys and Vents

NFPA 780 Requirements 3.6 Termination Devices shall meet material and size requirements in accordance with NFPA 780 Table (a) & (b) Table 3.1.1(a) Minimum Class I Material Requirements Copper Aluminum Type of Conductor Standard Metric Standard Metric Air Terminal, Solid Diameter /8 in mm /2 in mm Air Terminal, Tubular Diameter /8 in mm /8 in mm Table 3.1.1(b) Minimum Class II Material Requirements Copper Aluminum Type of Conductor Standard Metric Standard Metric Air Terminal, Solid Diameter /2 in mm /8 in mm

3.6.1 Air Terminal Height The tip of an air terminal shall be not less than 10 in. above the object or area it is to protect Air terminal exceeding 24 in. in height shall be supported at a point not less than one-half its height. EXCEPTIONS Strike termination devices shall not be required for Metal parts of a structure that are exposed to direct lightning flashes and that have a metal thickness of 3 /16 in. or greater shall only require connection to the lightning protection system. (minimum of two paths to ground) Those parts of a structure located within a zone of protection.

Air Terminal Support Air terminals shall be secured against overturning by attachment to the object to be protected or by means of braces that shall be permanently and rigidly attached to the building.

3.8.7 Chimneys and Vents Strike termination devices shall be required on all chimneys and vents that are not located within a zone of protection Chimneys or vents with a metal thickness of /16 in. or more shall require only a connection to the lightning protection system, and shall be made using a main size lightning conductor and a bonding device having a surface contact area of not less than 3 in. square, and shall provide two or more paths to ground. Where only one strike termination device is required on a chimney or vent, at least one main sized conductor shall connect the strike termination device to a main conductor at the location where the chimney or vent meets the roof surface and provides two or more paths to ground from that location

CONDUCTORS One Way Path Dead Ends Substitution of Metals
“U” or “V” Pockets Conductor Bends Protection and Securing Location and Spacing Structural Steel as Down Conductors Connector Fittings

CONDUCTORS 3.9.1 One Way Path
Strike termination devices on a lower roof level that are interconnected by a conductor run from a higher roof level shall only require one horizontal or down-ward path to ground provided the lower level roof conductor run does not exceed 40 ft.

CONDUCTORS 3.9.2 Dead Ends Strike termination devices shall be permitted to be “dead ended” with only one path to a main conductor on roofs below the main protected level provided the conductor run from the strike termination device to a main conductor is not more than 16 ft in total length and maintains a horizontal or downward coursing. Dead Ends A A – Permissible total conductor length not over 16 ft

3.9.3 Substitution of Metals
CONDUCTORS 3.9.3 Substitution of Metals Metal parts of a structure, such as eave troughs, down spouts, ladders, chutes, or other metal parts, shall not be substituted for the main lightning conductor. Like-wise, metal roofing or siding having a thickness of less than 3 /16 in. (4.8 mm) shall not be substituted for main lightning conductors. A – Permissible total conductor length not over 16 ft

CONDUCTORS 3.9.4 “ U” or “ V” Pockets
Conductors shall maintain a horizontal or downward coursing free from “U” or “V” (down and up) pockets. Such pockets, often formed at low-positioned chimneys, dormers, or other projections. A down conductor shall be provided from the base of the pocket to ground or to an adjacent down-lead run conductors, and so on. “U” or “V” Pockets Incorrect Correct

CONDUCTORS 3.9.5 Conductor Bends
Down conductors must not have sharp bends or loops. All bends must have a radius of 8 inches or greater and measure not less than 90 degrees from the inside of the bend. Radius of Bend Not less than 8 in. R 90 Degrees min.

3.9.6 Conductor Supports 3.9.11 Protecting Down Conductors
Support or secure at intervals not to exceed 3 ft. Protecting Down Conductors Any down conductors subject to mechanical damage must be protected with a protective molding or covering for a minimum of 6 ft above grade. If protective covering is metallic tube/pipe the conductor must be bonded to both ends of the tube/pipe.

CONDUCTORS 3.9.7 Roof Conductors
All main conductors will maintain a downward and horizontal direction, never rising more than ¼ pitch. 3.9.8 Cross Run Conductors Required on flat and gently sloping roofs that exceed 50 ft in width. Shall be connected to main perimeter cable at intervals not exceeding 150 ft.

CONDUCTORS 3.9.10 Number of Down Conductors
Pitched Roof Structures Less than 250 feet in Perimeter Minimum of two down conductors on opposite corners, preferably all four corners Pitched Roof Structures More than 250 feet in Perimeter One down conductor for every 100 feet, or fraction of . Irregular- Shaped structures May require additional down conductors to provide two paths to ground for each air terminal Flat or Gently Sloping Roofs Average distance between down conductors will be no greater than 100 ft

3.9.13 Down Conductors and Structural Columns
Structural steel shall be permitted to be utilized as the main conductor of a LPS, IF it is electrically continuous, or it is made so Air terminals Shall be connected to the structural steel by direct connection, by use of individual connectors through the roof or walls to the frame work or by use of an exterior conductor that interconnects all air terminals, “AND” Is connected to the steel frame work at intervals not greater than 100 feet Ground terminals shall be connected approximately every other steel column at intervals not to exceed 60 feet

CONDUCTORS 3.12 Connector Fittings
Connector fittings shall be used at all “ end-to-end,” “ tee,” or “ Y” splices of lightning conductors. They shall be attached so as to withstand a pull test of 200 lb Conductor connections shall be of the bolted, welded, high compression, or crimp-type. Crimp-type connections shall not be used with Class II conductors. Painting not allowed on roof conductors or on any other conductors bonded to LPS

CONDUCTORS 3.12 Connector Fittings
Fittings used for required connections to metal bodies in or on a structure shall be secured to the metal body by bolting, brazing, welding, or using high-compression connectors listed for the purpose. Do not paint Down Conductor connectors unless they are the high compression or exothermic (or welded) type. Painting not allowed on roof conductors or on any other conductors bonded to LPS

TYPES OF SYSTEMS MAST SYSTEM CATENARY SYSTEM INTEGRAL SYSTEM
AFI section Explosives Facilities with Large Perimeters. New explosives facilities (including igloos) with a perimeter over 300 feet that require lightning protection and do not use the structuralsteel as the air terminals must use either a mast system or an overhead wire system. See Attachment 4 for requirements. Since these systems provide better protection, and maintenance is easier, consider using this type of protection for other kinds of facilities. The MAJCOM may waive this requirement (overhead or mast system).

TYPES OF SYSTEMS K.3.1 Mast-Type Systems
Mast-type systems should be designed as specified in Each non-metallic pole must have two down conductors and an air terminal extending at least 2 ft above the top of the pole, securely attached to the pole, and connected to the grounding system Metal masts do not require air terminals and down conductors, but must have two connections to the grounding system. Separate each mast from any part of the facility by at least the bonding distance or side flash distance specified in Chapter 3 & 6 of NFPA 780, but not less than 6 feet. Columns must have two connections to the grounding system.

K.3.2 Overhead Wire (Catenary) Systems
TYPES OF SYSTEMS K.3.2 Overhead Wire (Catenary) Systems Each non-metallic pole must have two down conductors Each wire must be a continuous run of at least AWG No. 6 copper, or equivalent. Separate each mast from any part of the facility by at least the bonding distance or side flash distance specified in Chapter 3 & 6 of NFPA 780, but not less than 6 ft Catenary systems should be designed as specified in

K.3.2 Overhead Wire (Catenary) Systems
TYPES OF SYSTEMS K.3.2 Overhead Wire (Catenary) Systems Shall have an air terminal extending at least 2 ft above the top of the pole, securely attached to the pole, and connected to the grounding system. Alternate grounding method The pole guy wire shall be permitted to be used as the down conductor. An overhead ground wire or a down conductor, extending above or across the top of the pole, can be used as an air terminal.

TYPES OF SYSTEMS K.3.3 Integral Systems
An integral lightning protection system is a system that utilizes air terminals mounted directly on the structure to be protected. These types of air termination systems are as described in Chapter 3. Air terminal spacing should be modified as necessary to provide a zone of protection defined by a 100-ft (33-m) striking distance. Where an integral lightning protection system is used to protect the structures covered by this appendix, it is critical that the bonding requirements of Chapter 3 be met. It is also critical that a rigorous maintenance schedule be maintained for this type of system

Pitched roofs shall be defined as roofs having a span of 40 ft or less and a pitch 1 /8 or greater; and roofs having a span of more than 40 ft and a pitch 1 /4 or greater. All other roofs shall be considered flat or gently sloping. A pitched roof with eaves height of 50 ft or less above grade shall require protection for the ridge only when there is no horizontal portion of the building that extends beyond the eaves, other than a gutter.

Each air terminal must have at least two paths to ground. Air terminals shall be located within 24 inches of roof edge Each building must have a minimum of two down conductors, one each at opposite corners (one each on all corners is preferred). A - 50 ft maximum spacing between air terminals B – 150 ft maximum length of cross run conductor permitted without a connection to the main perimeter or down conductor C – ft maximum spacing between air terminals along edge

ZONE OF PROTECTION NFPA The space adjacent to a lightning protection system that is substantially immune to direct lightning flashes. AFI also states that is necessary to provide a zone of protection defined by a 100-ft (33-m) striking distance.

ZONE OF PROTECTION 100 Foot Rolling Ball Theory
Proper Air Terminal Placement Proper Air Terminal Spacing Structures that do not exceed 25 ft above earth Structures that do not exceed 50 ft above earth Mast Systems Formula Example Question Student Exercises Catenary Systems Formula Integral Systems Formula

3.7.3 100 Foot Rolling Ball Theory
ZONE OF PROTECTION Foot Rolling Ball Theory 100 ft Radius The zone of protection shall include the space not intruded by a rolling sphere having a radius of 100 ft. When the sphere is tangent to earth and resting against a strike termination device, all space in the vertical plane between the two points of contact and under the sphere are in the zone of protection.

3.8 Proper Air Terminal Placement
ZONE OF PROTECTION 3.8 Proper Air Terminal Placement INCORRECT Improper spacing from edge of roof CORRECT Proper spacing from edge of roof Air terminal 4’ from edge Air terminal no more than 2’ from edge The zone of protection shall include the space not intruded by a rolling sphere having a radius of 100 ft. When the sphere is tangent to earth and resting against a strike termination device, all space in the vertical plane between the two points of contact and under the sphere are in the zone of protection.

3.8 Proper Air Terminal Spacing
ZONE OF PROTECTION 3.8 Proper Air Terminal Spacing Proper spacing between air terminals Improper spacing between air terminals Air terminals 2’ long and Spaced 20-25’ along edge and 50’ maximum spacing A zone of protection is also formed when such a sphere is resting on two or more strike termination devices and shall include the space in the vertical plane under the sphere and between those devices.

3.7.2.1 Structures that do not exceed 25 ft above earth
ZONE OF PROTECTION Structures that do not exceed 25 ft above earth Considered to protect lower portions of a structure located in a one-to-two zone of protection as shown below. The zone of protection shall form a cone having an apex at the highest point of the strike termination device, with walls forming approximately a 22.5 degree angle from the vertical. 2 1 2 1 25 ft 25 ft

3.7.2.2 Structures that do not exceed 50 ft above earth
ZONE OF PROTECTION Structures that do not exceed 50 ft above earth Considered to protect lower portions of a structure located in a one-to-one zone of protection as shown below The zone of protection shall form a cone having an apex at the highest point of the strike termination device, with walls forming approximately a 45-degree angle from the vertical. 1 Discuss more about chimneys and vents. 1 1 1 50 ft 50 ft

Horizontal distance (ft)
ZONE OF PROTECTION 6.3 Mast Systems Formula Center for_____ height Formula Based on mast height and 100 ft Ball Theory 100 100 75 100 D = h1 (200-h1) - h2 (200-h2) Height protected (ft) 50 D = horizontal distance (ft) H1 = height of the pole mast (ft) H2 = height of structure (ft) 75 25 50 25 Horizontal distance (ft)

60 ft long and 26 ft high building
ZONE OF PROTECTION Mast Systems Example Question Mast Height VS Building Size D = h1 (200-h1) h2 (200-h2) D = horizontal distance (ft) H1 = height of the pole mast (ft) H2 = height of structure (ft) 100 ft Radius 80 Foot Mast 60 ft long and 26 ft high building

Example Question Answer
ZONE OF PROTECTION Mast Systems Example Question Answer D = horizontal distance (ft) H1 = height of the pole mast (ft) H2 = height of structure (ft) D = h1 (200-h1) h2 (200-h2) 80 x (200-80) x (200-26) 80 x x 174 9, ,524 = 60 / 2 = 30 Mast Height 80 Feet Building Size 60 Ft Long 26 Ft High Building is in the Zone of Protection?

Is the building in the Zone of Protection?
Mast Systems Student Exercise 1 D = h1 (200-h1) h2 (200-h2) D = horizontal distance (ft) H1 = height of the pole mast (ft) H2 = height of structure (ft) Mast Height Building Size 85 feet Ft Long 28 Ft High Is the building in the Zone of Protection?

Student Exercise Answer 1
ZONE OF PROTECTION Mast Systems Student Exercise Answer 1 D = horizontal distance (ft) H1 = height of the pole mast (ft) H2 = height of structure (ft) D = h1 (200-h1) h2 (200-h2) 85 x (200-85) x (200-28) 85 x x 172 9, ,816 = ft 60 / 2 = 30 ft Mast Height 85 Feet Building Size 60 Ft Long 28 Ft High Building is not in the Zone of Protection?

Is the building in the Zone of Protection?
Mast Systems Student Exercise 2 D = h1 (200-h1) h2 (200-h2) D = horizontal distance (ft) H1 = height of the pole mast (ft) H2 = height of structure (ft) Mast Height Building Size 90 feet Ft Long 38 Ft High Is the building in the Zone of Protection?

ZONE OF PROTECTION Mast Systems Student Exercise Answer 2 D = horizontal distance (ft) H1 = height of the pole mast (ft) H2 = height of structure (ft) D = h1 (200-h1) h2 (200-h2) 90 x (200-90) x (200-38) 90 x x 162 9, ,156 = ft 40 / 2 = 20 ft Mast Height 90 Feet Building Size 40 Ft Long 38 Ft High Building is in the Zone of Protection?

6.3 Catenary Systems Formula
ZONE OF PROTECTION 6.3 Catenary Systems Formula D = h1 (200-h1) h2 (200-h2) D = horizontal distance (ft) H1 = height of the mast H2 = height of the lower mast (object concerned) (ft)

Is the object in the Zone of Protection?
Catenary Systems Student Exercise 3 D = h1 (200-h1) h2 (200-h2) D = horizontal distance (ft) H1 = height of the higher mast H2 = height of the lower mast (object concerned) (ft) 15 ft H1 = 100 ft H2 = 50 ft 50 ft Is the object in the Zone of Protection?

ZONE OF PROTECTION Catenary Systems Student Exercise Answer 3 D = horizontal distance (ft) H1 = height of the higher mast H2 = height of the lower mast (object concerned) (ft) D = h1 (200-h1) h2 (200-h2) 100 x ( ) x (200-50) 100 x x 150 10, ,500 = ft H1 = 100 ft H2 = 50 ft 15 ft 50 ft Object is not in the Zone of protection?

Is the object in the Zone of Protection?
Catenary Systems Student Exercise 4 D = h1 (200-h1) h2 (200-h2) D = horizontal distance (ft) H1 = height of the higher mast H2 = height of the lower mast (object concerned) (ft) 12 ft H1 = 90 ft H2 = 30 ft 30 ft Is the object in the Zone of Protection?

ZONE OF PROTECTION Catenary Systems Student Exercise Answer 4 D = horizontal distance (ft) H1 = height of the higher mast H2 = height of the lower mast (object concerned) (ft) D = h1 (200-h1) h2 (200-h2) 90 x (200-90) x (200-30) 90 x x 170 9, ,100 = ft H1 = 90 ft H2 = 30 ft 12 ft 30 ft Object is in the Zone of protection?

Integral Systems Formula
ZONE OF PROTECTION Integral Systems Formula D = h1 (200-h1) h2 (200-h2) D = Horizontal distance H1 = height of the higher roof (ft) H2 = height of the lower roof (ft) 100 ft Radius

Is the lower roof of the building in the Zone of Protection?
Integral Systems Student Exercise 5 D = h1 (200-h1) h2 (200-h2) D = Horizontal distance H1 = height of the higher roof H2 = height of the lower roof (ft) 30 ft 85 ft 30 ft Is the lower roof of the building in the Zone of Protection?

ZONE OF PROTECTION Integral Systems Student Exercise Answer 5 D = h1 (200-h1) h2 (200-h2) D = Horizontal distance H1 = height of the higher roof H2 = height of the lower roof (ft) D = 85 (200-85) - 30 (200-30) 85 x (115) - 30 x 170 9, ,100 = 30 ft 85 ft 30 ft Building is not in the Zone of Protection?

Is the lower roof of the building in the Zone of Protection?
Integral Systems Student Exercise 6 D = h1 (200-h1) h2 (200-h2) D = Horizontal distance H1 = height of the higher roof H2 = height of the lower roof (ft) 20 ft 60 ft 25 ft Is the lower roof of the building in the Zone of Protection?

ZONE OF PROTECTION Integral Systems Student Exercise Answer 6 D = h1 (200-h1) h2 (200-h2) D = Horizontal distance H1 = height of the higher roof H2 = height of the lower roof (ft) D = 60 (200-60) - 25 (200-25) 60 x (140) - 25 x 175 8, ,375 = 20 ft 60 ft 25 ft Building is in the Zone of Protection?

BONDING Bonding Defined Material Requirements Bonding Requirements
Determining the Necessity of Bonding Bonding Conditions Condition 1 A Condition 1 B Condition 1 C Condition 2 The Basic Bonding Formula (BBF) Condition 2 A and 2 B (1) Condition 2 A Condition 2 B (2) Condition 3 Condition 3 Example Bonding of movable objects Fences and Railroad Tracks

BONDING Bonding Defined
Bonding is the electrical connection between an electrically conductive object and a component of a lightning protection system that is intended to significantly reduce the potential differences created by lightning currents. The rational behind this is to prevent side flash (arcing) between metal objects that could create a fire hazard. Basic requirements for bonding are found in AFI Attachment 3 & NFPA 780, 3.21

Material Requirements
BONDING Material Requirements Bonding Conductors shall meet material and size requirements in accordance with NFPA 780 Table a & b Table 3-1.1(a) Minimum Class I Material Requirements Copper Type of Conductor Standard Bonding Conductor Cable, solid or stranded Min size ea strand AWG Cross sect. Area ,240 CM Requirements the same for class 1 or 2 locations. Bonding Conductor, solid strip Min. size/Thickness width in / ½ in Table 3-1.1(b) Minimum Class II Material Requirements Copper Type of Conductor Standard Bonding Conductor Cable, solid or stranded Min size ea strand AWG Cross sect. Area ,240 CM Bonding Conductor, solid strip Min. size/Thickness width in / ½ in

BONDING Bonding Requirements
All conductors (piping, phone lines, power cables and etc) buried underground for a minimum distance of 50 feet prior to entering the building. Earth covered igloos- all metal objects, within side flash distance bonded to the LPS. Grounded metal objects within side flash distance of a down conductor Bonded to the down conductor. Isolated (Ungrounded) metal bodies located close to a lightning conductor and to a grounded metal body bonded is bonded when within side flash distance. For structures exceeding 60 ft in height, the inter-connection of the lightning protection system ground terminals and other grounded media shall be in the form of a ground loop conductor.

BONDING Bonding Requirements
Static ground systems located on interior walls opposite a down conductor. (Recommend moving static system) Metal objects located outside the facility, within side flash distance of a conductor, bonded to the conductor. All conductors NOT entering the facility, within side flash distance shall be bonded to the LPS (fences, railroad tracks, above ground piping) All connections must be strong enough to withstand a pull test of 200 pounds. Steam, water and air conditioning lines may be run on the ground if bonded to the facilities LPS before entering the structure. Ground-Level Potential Equalization. All grounded media in and on a structure shall be connected to the lightning protection system within 12 ft of the base of the structure in accordance with Section NFPA 780

Determining the Necessity of Bonding
Bonding requirements depend on: The number of down conductors and their location The interconnection of other grounded systems Proximity of Grounded metal bodies to the down conductors The flashover medium: (either AIR or SOLID MATERIALS)

BONDING Bonding Conditions
Three different conditions or situations dictate the requirements for bonding within a structure CONDITION 1 – Long Vertical Metal Bodies CONDITION 2 – Grounded Metal Bodies CONDITION 3 – Isolated Metal Bodies

BONDING Condition 1 A 3.21.1 Long Vertical Metal Bodies
GREATER than 60 feet in height A. Steel Framed Structures Grounded and ungrounded metal bodies shall be bonded to structural steel members as near to their extremities as possible unless inherently bonded through construction “at these locations” To conductors “when” within side flash distance

BONDING Condition 1 B 3.21.1 Long Vertical Metal Bodies
GREATER than 60 feet in height B. Reinforced Concrete Structures: where the rebar is interconnected, and grounded IAW NFPA 780, Section Grounded and ungrounded metal bodies shall be bonded to the LPS as near as practical to their extremities, unless inherently bonded through construction at these locations

BONDING Condition 1 C 3.21.1 Long Vertical Metal Bodies
GREATER than 60 feet in height C. Other Structures: (Composite) Bonding of grounded and ungrounded long vertical metal bodies shall be determined by NFPA 780, Sections and Composite- a structural material made of plastic within a fibrous material (as silicon carbide) is embedded

BONDING Condition 2 3.21.2 Grounded Metal Bodies
Grounded metal bodies shall be bonded to the LPS when the body is located within the distance “D” as determined by the Basic Bonding Formula (BBF) The “BBF” for grounded metal bodies will be used when: Grounded metal bodies are connected to the LPS at “only one” extremity and: Branches of grounded metal bodies connected to the LPS at their extremities if they change vertical direction more than 12 feet

The Basic Bonding Formula (BBF)
D = h/6n x Km D = Minimum side flash distance between a grounded body and a conductor at which a bond becomes necessary h = Height of the building, or the vertical distance from the bond being considered, to the nearest LPS bond n = number of down conductors Km = 1 if the flashover is through air, or 0.50 if through dense material (concrete, brick, wood) Grounded metal bodies shall be bonded to the lightning protection system where located within a calculated bonding distance, D, as determined by the following formulas

The Basic Bonding Formula (BBF)
D = h/6n x Km Grounded object (water pipe, panel, etc…)

BONDING Condition 2 A and 2 B (1) D = h/6n x Km
Condition 2A – Structures 40 feet and less in height Condition 2B (1) – Structures over 40 feet – bonding required within 60 ft of the top of the structure D = h/6n x Km h = Height of the building, or the greatest vertical distance between the bond being considered and the nearest other lightning Protection system bond, (or to ground if no other bond is present) n = number of down conductors spaced more than 25 feet apart and located within 100 feet of the bond in question: n = 1 (if only 1 down conductor); n = 1.5 (if only 2 down conductors); n = 2.25 (if 3 or more down conductors) Km = 1 if the flashover is through air, or 0.50 if through dense material (concrete, brick, wood)

BONDING Condition 2 A D = h/6n x Km
Structures 40 feet and less in height h = Height of the building, or the greatest vertical distance between the bond being considered and the nearest other lightning Protection system bond, (or to ground if no other bond is present) n = number of down conductors spaced more than 25 feet apart and located within 100 feet of the bond in question: n = 1 (if only 1 down conductor); n = 1.5 (if only 2 down conductors); n = 2.25 (if 3 or more down conductors) Km = 1 if the flashover is through air, or 0.50 if through dense material (concrete, brick, wood) D = h/6n x Km 40/6 x 1.5(N) x 1(Km) = 9.99 ft Down conductors currently 3’ away from grounded metal body 30 ‘ 40 ‘ Must down conductors be bonded?

BONDING Condition 2 B (2) Structures over 40 feet – bonding required below 60 ft from the top of the structure D = h/6n x Km h = The vertical distance between the bond being considered and the nearest LPS bond, (or ground if no other bond is present) n = The TOTAL number of down conductors in the LPS Km = 1 if the flashover is through air, or 0.50 if through dense material (concrete, brick, wood)

Condition 2B (1) and 2B (2) Example
BONDING Condition 2B (1) and 2B (2) Example Condition 2B (1) – Structures over 40 feet – bonding required within 60 ft of the top of the structure Condition 2B (2) – Structures over 40 feet – bonding required below 60 ft from the top of the structure D = h/6n x Km Condition 2B (1) D = 100/6 (1.5) x 1 60 ft = 25 ft 100 ft Condition 2B (2) D = 30/6 (3) x 1 40 ft 30 ft = 15 ft

3.21.3 Isolated (non-grounded) Metallic Bodies
BONDING Condition 3 Example Isolated (non-grounded) Metallic Bodies If a + b < Calculated bonding distance, then bond A to B directly If a + b > Calculated bonding distance, bonds not required D = h/6n x Km 40/6 x 1.5(N) x 1 = 9.99 ft Down Conductor Grounded object a 2 ft b 4 ft CONDITION 3 – Isolated (non-grounded) Metallic Bodies Bonding is required when: The total of the shortest distance between the lightning conductor and the isolated metal body & The shortest distance between the isolated metal body and grounded metal body is equal to or less than the bonding distance as calculated by the BBF for the grounded metal body Bonding shall be made between the LPS and the grounded metal body and need not run through or be connected to the isolated metal body Window Frame A B

Bonding of movable objects
Bond Connections MUST BE of the flexible conductor or strap type When conductors are mechanically protected or concealed conductors may be No. 10 AWG copper Otherwise NO. 6 AWG copper wire or larger At least two separate flexible bonding straps will be provided Bonding Resistance – Maximum – 1 Ohm Replace Braided bonding wires excessively frayed – 1/2

Fences and Railroad Tracks
BONDING Fences and Railroad Tracks Fences: Bond across gates and other discontinuities Shall be bonded to the Lightning Protection System (LPS) ground loop conductor if they cross or come within 6 feet of the structure’s LPS Railroad Tracks: All tracks within 6 feet of the LPS or sideflash distance Tracks that enter a facility shall be bonded to the frame of the structure or equivalent

SIDEFLASH REQUIREMENTS
Mast Systems Mast Systems Student Exercise Catenary Wire to Structure Catenary Wire to Structure Student Exercise Sideflash formulas are based on the impedence of main sized copper conductors. Other ground wire materials may require additional separation distance.

Sideflash distances – Mast to Structure
SIDEFLASH REQUIREMENTS Mast Systems Sideflash distances – Mast to Structure D = h/6 h = height of structure or the object under consideration Sideflash formulas are based on the impedence of main sized copper conductors. Other ground wire materials may require additional separation distance.

6.3.3.3 Mast Systems Student Exercise 7
SIDEFLASH REQUIREMENTS Mast Systems Student Exercise 7 Sideflash distances – Mast to Structure D = h/6 h = height of structure or the object under consideration D = 8.33 30 ft

6.3.3.3 Catenary Wire to Structure
SIDEFLASH REQUIREMENTS Catenary Wire to Structure D = L/6n L = length of lightning protection conductor between its grounded point and the point under consideration (closest to roof) n = 1 where there is a single overhead conductor that exceeds 200 ft in horizontal length n = 1.5 where there is a single overhead wire or more than one wire interconnected above the structure to be protected, such that only two down conductors are located greater than 20 ft and less then 100 ft apart n = 2.25 where there are more than two down conductors spaced more than 25 ft apart within a 100-ft wide area that are interconnected above the structure being protected

6.3.3.3 Catenary wire to Structure Student Exercise 8
SIDEFLASH REQUIREMENTS Catenary wire to Structure Student Exercise 8 L = length of lightning protection conductor between its grounded point and the point under consideration (closest to roof) n = 1 where there is a single overhead conductor that exceeds 200 ft in horizontal length n = 1.5 where there is a single overhead wire or more than one wire interconnected above the structure to be protected, such that only two down conductors are located greater than 20 ft and less then 100 ft apart n = 2.25 where there are more than two down conductors spaced more than 25 ft apart within a 100-ft wide area that are interconnected above the structure being protected D = L/6n 95 ft 185 ft 6 ft Does building meet sideflash requirements?

6.3.3.3 Catenary wire to Structure Student Exercise Answer 8
SIDEFLASH REQUIREMENTS Catenary wire to Structure Student Exercise Answer 8 L = length of lightning protection conductor between its grounded point and the point under consideration (closest to roof) n = 1 where there is a single overhead conductor that exceeds 200 ft in horizontal length n = 1.5 where there is a single overhead wire or more than one wire interconnected above the structure to be protected, such that only two down conductors are located greater than 20 ft and less then 100 ft apart n = 2.25 where there are more than two down conductors spaced more than 25 ft apart within a 100-ft wide area that are interconnected above the structure being protected D = L/6n 185/ 6x1.5 185/ 90 = 2.05 ft 95 ft 185 ft AFI – A minimum of 1.83 meters (6 ft) is recommended for sideflash distance. 6 ft Building meets sideflash requirements?

SURGE PROTECTION Lightning protection systems that protects structures that HOUSE EXPLOSIVES shall include surge protection for all incoming and exiting lines to include: Overhead or underground power lines Communication systems (instrumentation & intrusion detection) Television or radio antennas not necessarily restricted to associated wiring systems and appliances Therefore, such systems should be equipped with appropriate protective devices, bonded to ensure a common potential, and must enter the facility in shielded cables, or metallic conduits buried underground for a minimum of 50 feet prior to entering the structure.

GROUND SYSTEMS Ground Terminals Ground Rods Ground Rod Terminations
Ground Rod Depth Concrete Encased Electrodes Concrete Encased Electrode Terminations Ground Ring Electrode Ground Ring Electrode Terminations Shallow Topsoil Sandy Soil Conditions Combinations Common Grounding

GROUND SYSTEMS 3.13 Ground Terminals
Each down conductor shall terminate at a ground terminal dedicated to the lightning protection system. The design, size, depth, and number of ground terminals used shall comply with through and AFI Electrical system and telecommunication grounding electrodes shall not be used in lieu of lightning ground electrodes. The down conductor(s) shall be attached permanently to the grounding electrode system by bolting, brazing, welding, or high-compression connectors listed for the purpose, and clamps shall be suitable for direct burial.

GROUND SYSTEMS 3.13 Ground Terminals
Ground terminals shall be copper-clad steel, solid copper, hot-dipped galvanized steel, or stainless steel. Stainless steel ground rods are prohibited by AFI A2.2.1 Ground electrodes shall be installed below the frost line where possible (excluding shallow topsoil conditions). Ground rods must be at least 10 feet long, made of not less than 0.75 inch diameter pipe or equivalent solid rod made of copper or copper clad steel. Copper clad steel most common used.

Ground Rod Terminations
GROUND SYSTEMS Ground Rod Terminations Attached to the ground rod by: Bolting (Clamps shall be suitable for direct soil burial) Exothermic Welding High-compression connectors listed for the purpose

GROUND SYSTEMS 3.13.1 Ground Rods
Ground rods shall be not less than 1 /2 in. (12.7 mm) in diameter and 8 ft (2.4 m) long. Rods shall be free of paint or other nonconductive coatings. AFI Ground rods must be at least 10 feet long, made of not less than 0.75 inch diameter pipe or equivalent solid rod made of copper or copper clad steel. Copper clad steel most common used.

GROUND SYSTEMS 3.13.1.1 Ground Rod Depth 1 foot below grade
Not less than 10 feet deep 3 ft from building walls Spaced no closer than 10 feet Maximum of 25 ohms of earth resistance 1 ft 3 ft AFI Attachment 4 10 ft

3.13.2 Concrete-Encased Electrodes
GROUND SYSTEMS Concrete-Encased Electrodes Shall only be used in new construction. The electrode shall be located near the bottom of a concrete foundation or footing that is in direct contact with the earth and shall be encased by not less than 2 in. of concrete. Encased electrode shall consist of; A. Not less than 20 ft of bare copper main size conductor OR B. An electrode consisting of at least 20 ft of one or more steel reinforcing bars or rods not less than 1 /2 in. diameter that have been effectively bonded together by either welding or overlapping 20 diameters and securely wire-tying.

Concrete Encased Electrode Terminations
GROUND SYSTEMS Concrete Encased Electrode Terminations Shall be permanently attached to the encased system by; Bolting connectors listed for the purpose Exothermic Welding High-compression connectors listed for the purpose AFI A2.3.2 Methods for obtaining better grounds. (page 19) . Deeper rods, parallel ground rods, Soil Replacement, Concrete Encapsulation, and other elaborate methods include installation of a ground loop.

GROUND SYSTEMS 3.13.3 Ground Ring Electrode
A ground ring electrode encircling a structure shall be as shown in Figure , in direct contact with earth at a depth of not less than 18 in. (457 mm) or encased in a concrete footing in accordance with The encased electrode shall consist of not less than 20 continuous ft (6.1 m) of bare copper main-size conductor. The ground ring electrode shall be not smaller than the equivalent of a main-size lightning conductor. AFI specifies AWG 1/0 copper NFPA 780 and AFI Attachment and 4

Ground Ring Electrode Terminations
GROUND SYSTEMS Ground Ring Electrode Terminations Down conductors shall be permanently attached to the ground ring by; Exothermic Welding High-Compression fittings Bolting Brazing Connections shall be Suitable for direct burial

GROUND SYSTEMS 3.13.7.1 Shallow Topsoil
Where bedrock is near the surface, the conductor shall be laid in trenches extending away from the building at each down conductor not less than 12 ft in length. Clay Soil – Buried 1- 2 ft in depth Sandy or Gravelly Soil – Buried 2 ft in depth. If these methods prove impractical or impossible, bury directly on bedrock a minimum distance of 2 ft from the foundation or exterior footing. The cable shall terminate by attachment to a buried copper ground plate at least in. thick and having a minimum surface area of 2 ft square

GROUND SYSTEMS 3.13.7.2 Sandy Soil Conditions
Two or more ground rods, at not less than 10-ft spacings 1 foot below grade Not less than 10 feet deep 3 ft 12 inches 10 ft 10 ft 3 ft from building walls Maximum of 25 ohms of earth resistance

3.13.7.2 Sandy Soil Conditions Alternate Configurations
GROUND SYSTEMS Sandy Soil Conditions Alternate Configurations 3 ft 10 ft 3 ft 10 ft

GROUND SYSTEMS 3.13.6 Combinations Common Grounding
Combinations of the grounding terminals in Section 3.13 shall be permitted. Common Grounding All grounding media in, or on, a structure shall be interconnected to provide a common ground potential and bonding as per NFPA 780 and AFI

INSPECTION AND TESTING
SCHEDULED MAINTENANCE VISUAL INSPECTIONS TESTING REQUIREMENTS TESTS PERFORMED GROUND RESISTANCE TEST CONTINUITY TEST

Scheduled Maintenance
INSPECTION AND TESTING Scheduled Maintenance Scheduled Maintenance for Grounding Systems must be done in accordance with AFI Table 1 Reference AFMAN Lightning Protection (Base Civil Engineer Responsibilities) Visual Inspections 12 months Ground Resistance Check 24 months Continuity Checks 24 months Scheduled Maintenance found in AFI Table 1 page 3

Visual Inspections Must be accomplished in accordance with AFI Visual/physical inspection must determine if: The system is in good repair. No loose connections that might cause high resistance joints. Corrosion or vibration has weakened any part of the system. Braided bonding wires are excessively frayed (cross sectional area reduced by half). Ground wires on lightning protection masts are damaged by lawn mowers or other equipment. Conductors and system components are securely fastened. Down conductors, roof conductors, and ground terminals are intact. Additions or alterations to the protected structure require additional protection. Visual Inspections of catenary systems: If class 1 system (under 75’ high) has mechanical connectors on the poles you must accomplish a continuity test from the overhead wire to your ground test point to satisfy your annual Visual Inspection.

Testing Requirements AFI Attachment 6 for resistance and continuity test requirements for typical systems. Instruments must be able to measure 10 ohms +/- 10 percent for ground resistance tests, and 1 ohm +/- 10 percent for continuity testing. Only instruments designed specifically for earth-ground systems are acceptable for ground resistance testing. MAJCOM electrical engineer may modify the test procedures due to local conditions, as long as the intent of the test is still achieved.

Tests Performed Grounding System Resistance Test (Earth Ohms Test) Use the procedure described in AFI or the procedure recommended by the test instrument manufacturer except as modified by AFI Periodic tests should be made at approximately the same time each year to minimize confusion resulting from seasonal changes. Continuity Tests If the resistance measured during continuity tests is greater than 1 ohm, check for deficiencies and repair, then retest. When per-forming a continuity test over very long lengths of conductors (more than 20m with no parallel paths), readings above one ohm but less than 3 ohms may occur. This is acceptable. Note: .3 meters = 1 foot

Ground Resistance Test
INSPECTION AND TESTING Ground Resistance Test Fall of Potential Method Potential Probe Distances X and Y Must Be Greater Than D/2 But Not Less Than 25 ft Y Current Probe X Ground Rod Service Entrance D Ground Loop Conductor

INSPECTION AND TESTING Ground Resistance Test Potential Probe Current Probe Fall of Potential Method Distances X and Y Must Be Greater Than D/2 But Not Less Than 25 ft Y X Ground Rod Service Entrance D X Ground Loop Conductor

INSPECTION AND TESTING Ground Resistance Test Potential Probe Current Probe Fall of Potential Method Distances X and Y Must Be Greater Than D/2 But Not Less Than 25 ft Y X Ground Rod Service Entrance D C1 P1 P2 C2 Ground Loop Conductor

Continuity Test Ground Rod OHM Meter 1 4 2 Service Entrance Top of building 3 Ground Loop Conductor

Continuity Test Ground Rod 1 OHM Meter 4 2 Service Entrance Top of building 3 Ground Loop Conductor

Continuity Test Static Buss Bars Connect one lead to the Ground rod and the Other lead to the Static Buss bars at all free ends Ground Rod Inside Building OHM Meter X X Service Entrance X X Ground Loop Conductor

TEST PLANS AND RECORD KEEPING
Test Plan Requirements Test Plan Sample Sketch Record Keeping Requirements Common Deficiencies

TEST PLANS Requirements
Developed by Organization performing inspections & tests Must include sketch of grounding and LPS test points Date action performed Name of person(s) performing tests General condition of components

Requirements Continued
TEST PLANS Requirements Continued Condition of corrosion protection measures Resistance measurements at various Parts of ground terminal system Discrepancies noted and corrective Actions taken with dates of repairs Review Process

Include a facility drawing containing
TEST PLANS Sample Sketch Include a facility drawing containing Building & area configuration Location of LPS components Test Point identification

OUTSIDE INSPECTION POINTS
TEST PLANS Sample Sketch BLDG Current as of: 27 Mar 01 A N 4 5 6 7 8 16 3 9 18 15 17 19 2 10 Service Entrance 1 14 13 12 11 B OUTSIDE INSPECTION POINTS

RECORD KEEPING Requirements Use of locally generated form recommended
Keep record for 6 inspection cycles for explosive facilities Records kept by organization performing tests and inspections Copy of test results given to user

RECORD KEEPING Common Deficiencies
Several paths to ground exceed allowed rate of rise Air terminals with loose connections Air terminals over 24 inches from edge of roof Air terminals taller than 24 inches without required supports Down conductor not attached to cross run conductors Dissimilar metals to join system components Improper conductor radius of bend User did not have copies of test results

LIGHTNING PROTECTION for AIR FORCE FACILITIES

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LIGHTNING PROTECTION for AIR FORCE FACILITIES

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