D.3.3 Earthing
A type В arrangement for the earth-termination system, according to 5.4.2.2, is preferred for all lightning protection systems for structures with danger of explosion.
NOTE The construction of a structure may provide the effective equivalent of the ring conductor of type В arrangement (for example metallic storage tanks).
The earthing resistance of earth-termination systems for structures containing solid explosive materials and explosive mixtures shall be as low as possible and not greater than 10 Q.
D.3.4 Equipotential bonding
Common equipotential bonding shall be provided for the lightning protection system according to 6.2 and for installations in explosion endangered areas according to IEC 60079-10-1 and IEC 60079-10-2.
D.4 Structures containing solid explosive material
The design of lightning protection for structures containing solid explosive material shall take into consideration the sensitivity of the material in the configuration in which it is used or stored. For instance, some insensitive bulk explosive material may not require any additional consideration other than those contained within this annex. However, there are some configurations of sensitive explosive materials that may be sensitive to rapidly changing electrical fields and/or radiated by lightning impulsive electromagnetic field. It may be necessary to establish additional bonding or shielding requirements for such applications.
For structures containing solid explosive materials, an isolated external LPS (as defined in 5.1.2) is encouraged. Structures totally contained within a metallic shell of at least 5 mm thickness steel or equivalent (7 mm for aluminium structures) may be considered protected by a natural air-termination system as defined by 5.2.5. The earthing requirements of 5.4 are applicable for such structures.
NOTE Where hot spot or ignition problems may arise, it should be verified that the temperature rise of the inner surface at the point of strike does not constitute a danger.
Surge protective devices (SPDs) shall be provided as part of the LPS for all locations where explosive material is present. Where practicable, SPDs shall be positioned outside locations where solid explosive material is present. SPDs positioned inside locations where exposed explosives or explosive dust is present shall be of explosion-proof type.
D.5 Structures containing hazardous areas
D.5.1 General
All parts of the external LPS (air-termination and down-conductors) shall be at least 1 m away from a hazardous area, where possible. Where this is not possible, conductors passing within a hazardous zone should preferably be continuous or connections shall be made in accordance with 5.5.3.
Accidental loosening of connections in hazardous areas shall be prevented.
Where a hazardous area is located directly under a metal sheet that may be punctured by lightning (see 5.2.5) air-termination shall be provided in accordance with the requirements of 5.2.
D.5.1.1 Surge suppression
Surge protective devices shall be positioned outside the hazardous area where practicable. Surge protective devices positioned inside the hazardous area shall be approved for the hazardous area in which they are installed.
D.5.1.2 Equipotential bonding
Beside connections according to Tables 7 and 8, piping, which is connected so that it is electrically conductive according to 5.3.5 may also be used as connections.
Above ground metal piping outside process units shall be earthed at least every 30 m. Connections to piping shall be of such a kind that, in the instance of a lightning current passage, there is no sparking. Suitable connections to piping are welded-on lugs or bolts or tap holes in the flanges for taking up screws. Connections by means of clips are only allowed if, in the instance of lightning currents, ignition protection is proved by tests and procedures are utilized to ensure the reliability of the connection. Junctions shall be provided for the joining of connection and earthing leads to containers, metal construction parts, drums and tanks.
Lightning equipotential bonding connections between the lightning protection system and other installations/structures/equipment will be carried out with the agreement of the system operator. Lightning equipotential bonding connections utilizing spark gaps may not be made without the agreement of the system operator. Such devices shall be suitable for the environment in which they are installed.
D.5.2 Structures containing zones 2 and 22
Structures where areas defined as zones 2 and 22 exist may not require supplemental protection measures.
For outdoor facilities made of metal (e.g. columns, reactors, containers with areas containing zones 2 and 22) of thickness and material meeting the requirements of Table 3, the following applies:
air-termination devices and down-conductors are not required;
facilities shall be earthed according to Clause 5.
D.5.3 Structures containing zones 1 and 21
For structures where areas defined as zones 1 and 21 exist, the requirements for zones 2 and 22 apply with the following additions:
if there are insulation pieces in piping, the operator shall determine the protective measures. For instance, a disruptive discharge can be avoided by the use of explosion- protected, isolating spark gaps;
the isolating spark gaps and the insulation pieces shall be inserted outside the hazardous areas.
D.5.4 Structures containing zones 0 and 20
For structures where areas defined as zones 0 and 20 exist, the requirements of D.5.3 apply, supplemented by the recommendations given in this clause as applicable.
For outdoor facilities with areas defined as zones 0 and 20, the requirements for zones 1, 2, 21 and 22 apply with the following additions:
electrical equipment inside tanks containing flammable liquids shall be suitable for this use. Measures for lightning protection shall be taken according to the type of construction;
closed metal containers with areas defined as zones 0 and 20 inside shall have a wall thickness in accordance with Table 3 at the possible lightning striking points provided that the temperature rise of the inner surface at the point of strike does not constitute a danger. In the case of thinner walls, air-termination devices shall be installed.
D.5.5 Specific applications
D.5.5.1 Filling stations
At filling stations for cars, ships, etc, with hazardous areas, the metal piping shall be earthed according to Clause 5. Piping shall be connected with steel constructions and rails, where existing (if necessary via isolating spark gaps approved for the hazardous area in which it is installed), to take into account railway currents, stray currents, electrical train fuses, cathodic- corrosion-protected systems and the like.
D.5.5.2 Storage tanks
Certain types of structures used for the storage of liquids that can produce flammable vapours or used to store flammable gases are essentially self-protecting (contained totally within continuous metallic containers having a thickness of not less than 5 mm of steel or 7 mm of aluminium, with no spark gaps) and require no additional protection provided that the temperature rise of the inner surface at the point of strike does not constitute a danger.
Similarly, soil-covered tanks and piping do not require the installation of air-termination devices. Instrumentation or electrics used inside this equipment shall be approved for this service. Measures for lightning protection shall be taken according to the type of construction.
The tanks in tank farms (for example refineries and tank stores) the earthing of every tank at one point only is sufficient. The tanks shall be connected with each other. Besides connections according to Tables 8 and 9, piping which is connected so that it is electrically- conductive according to 5.3.5 may also be used as connections.
NOTE In some countries additional requirements may exist.
Isolated tanks or containers shall be earthed according to Clause 5, depending on the greatest horizontal dimension ( diameter or length):
up to 20 m, once;
over 20 m, twice.
In the case of floating-roof tanks, the floating-roof shall be effectively bonded to the main tank shell. The design of the seals and shunts and their relative locations needs to be carefully considered so that the risk of any ignition of a possible explosive mixture by incendiary sparking is reduced to the lowest level practicable. When a rolling ladder is fitted, a flexible bonding conductor of 35 mm width and minimum thickness of 3 mm shall be applied across the ladder hinges, between the ladder and the top of the tank and between the ladder and the floating roof. When a rolling ladder is not fitted to the floating-roof tank, one or more, (depending on the size of the tank), flexible bonding conductors of 35 mm width and minimum thickness of 3 mm, or equivalent, shall be applied between the tank shell and the floating roof. The bonding conductors shall be arranged so that they cannot form a re-entrant loop. On floating roof tanks, multiple shunt connections shall be provided between the floating-roof and the tank shell at about 1,5 m intervals around the roof periphery. Material selection is decided by product and/or environmental requirements. Alternative means of providing an adequate conductive connection between the floating roof and tank shell for impulse currents associated with lightning discharges are only allowed if proved by tests and if procedures are utilized to ensure the reliability of the connection.
D.5.5.3 Piping network
Above-ground metal piping network inside a production facilities but outside the process units should be connected every 30 m with the earthing system, or should be earthed by a surface earth electrode or an earth rod. Isolating supports of the piping should not be considered.
D.6 Maintenance and inspection
D.6.1 General
All installed LPS used to protect structures with risk of explosion shall be properly maintained and inspected. Additional requirements to those reported in Clause 7 are needed for the inspection and maintenance of LPS in structures with a risk of explosion.
D.6.2 General requirements
A maintenance and inspection plan shall be developed for the installed protection systems. Maintenance guidelines of the LPS shall be provided or added to the existing schedule at the completion of LPS installation.
D.6.3 Qualifications
Only qualified personnel having the necessary training and expertise shall be permitted to maintain, inspect and test the LPS system of explosives facilities.
Inspection requires personnel who
have technical knowledge and understanding of the theoretical and practical requirements for installation in hazardous areas and for LPS equipment and installations,
understand the requirements of visual and complete inspections as they relate to the installed LPS equipment and installations.
NOTE Competencies and training may be identified in relevant national training and assessment frameworks.
D.6.4 Inspection requirements
To ensure that the installations are maintained in a satisfactory condition for continued use, either
regular periodic inspections, and/or
continuous supervision by skilled personnel,
and, where necessary, maintenance shall be carried out.
Following any adjustment, maintenance, repair, reclamation, modification or replacement, the equipment or relevant parts of equipment concerned shall be inspected.
D.6.4.1 Regular periodic inspections
The personnel who carry out the regular periodic inspections will need to be sufficiently independent of the demands of the maintenance activities, for example, so as not to prejudice their ability to reliably report the findings of the inspection.
NOTE It is not a requirement that such personnel are members of an external independent organization.
D.6.4.2 Concept of continuous supervision by skilled personnel
The objective of continuous supervision is to enable the early detection of arising faults and their subsequent repair. It makes use of existing skilled personnel who are in attendance at the installation in the course of their normal work (e.g. erection work, alterations, inspections, maintenance work, checking for faults, cleaning work, control operations, making terminal connections and disconnections, functional tests, measurements) and who use their skill to detect faults and changes at an early stage.
Where an installation is visited on a regular basis, in the normal course of work, by skilled personnel who, in addition to satisfying the requirements of a) and b) of D.6.3, are
aware of the process and the environmental implications on the deterioration of the specific equipment in the installation, and
required to carry out visual and/or complete inspections as part of their normal work schedule as well as detailed inspections
then it may be possible to dispense with regular periodic inspection and utilize the frequent presence of the skilled personnel to ensure the on-going integrity of the equipment.
The use of continuous supervision by skilled personnel does not remove the requirement for initial and sample inspections.
D.6.5 Electrical testing requirements
The lightning protection system shall be tested electrically
every 12 (+ 2) months, or
to predict accurately an appropriate periodic inspection interval is a complex issue. The grade of inspection and the interval between periodic inspections shall be determined taking account of the type of equipment, manufacturer's guidance, if any, the factors governing its deterioration and the results of previous inspections.
Where inspection grades and intervals have been established for similar equipment, plants and environments, this experience shall be used in determining the inspection strategy.
Intervals between periodic inspections exceeding three years should be based on an assessment including relevant information.
Maintenance and inspection of the LPS should be carried out together with maintenance and inspection of all other electrical installations in hazardous areas and shall be incorporated into the maintenance schedule.
Instruments used for testing shall be in accordance with IEC 61557-4.
The DC resistance of any single object bonded to the lightning protection system shall not exceed 0,2 Q.
The test shall be conducted in accordance with the appropriate test equipment manufacturer's instructions.
D.6.6 Earthing resistance test methods
Only those instruments designed specifically for earth resistance testing shall be permitted for use in this application.
Test instruments shall be properly maintained and calibrated in accordance with manufacturer’s instructions.
If possible, a three-point earth resistance test method shall be used to measure the resistance to earth for explosives facilities.
D.6.7 Surge protection
Lightning surge protection devices (and their means of isolation, if provided) shall be inspected in accordance with manufacturer's instruction at intervals not exceeding 12 months or whenever electrical testing of the LPS is performed. SPDs shall also be inspected after any suspected lightning strike to the structure.
D.6.8 Repairs
Maintenance personnel shall ensure that repairs of all discrepancies found during inspections are made in an acceptable time frame.
D.6.9 Records and documentation
Any indication of damage produced by a lightning strike to a structure or its LPS shall be immediately documented and reported.
Historical records of maintenance and inspections shall be maintained for each facility for the purpose of trend analysis.Annex Е
(informative)
Guidelines for the design, construction, maintenance
and inspection of lightning protection systems
E.1 General
This annex provides guidance on the physical design and construction, maintenance and inspection of an LPS conforming to this standard.
This annex should be used and is only valid together with other parts of this standard.
Examples are given of protection techniques which have the approval of international experts.
NOTE The examples given in this annex illustrate one possible method of achieving protection. Other methods may be equally valid.
E.2 Structure of this annex
In this annex the main clause numbers mirror the clause numbers of the main document. This gives an easy reference between the two parts. Not all clauses are necessarily mirrored.
To achieve this goal, Clause E.3 is not used in this annex.
E.3 Vacant
E.4 Design of lightning protection systems (LPS)
E.4.1 General remarks
The construction of an LPS for an existing structure should always be weighed against other measures of lightning protection conforming to this standard which give the same protection level for reduced costs. For selection of the most suitable protection measures, IEC 62305-2 applies.
The LPS should be designed and installed by LPS designers and installers.
The designer and installer of an LPS should be capable of assessing both the electrical and mechanical effects of the lightning discharge and be familiar with the general principles of electromagnetic compatibility (EMC).
Furthermore, the lightning protection designer should be capable of assessing corrosion effects and judging when it is necessary to seek expert assistance.
The lightning protection designer and installer should be trained in the proper design and installation of the LPS components in accordance with the requirements of this standard and the national rules regulating construction work and the building of structures.
The functions of an LPS designer and installer may be performed by the same person. A thorough knowledge of the relevant standards and several years of experience is required to become a specialized designer or installer.
Planning, implementation and testing of an LPS encompasses a number of technical fields and makes demands for coordination by all parties involved with the structure to ensure the achievement of the selected lightning protection level with minimum cost and lowest possible effort. The management of the LPS should be efficient if the steps in Figure E.1 are followed. Quality assurance measures are of great importance; in particular for structures including extensive electrical and electronic installations.
IEC 2659/10
NOTE Interfaces • require the full cooperation of the architect, engineer and lightning protection designer.
Figure E.1 - LPS design flow diagram
The quality assurance measures extend from the planning stage, in which all drawings should be approved, through the LPS construction stage during which all essential parts of the LPS inaccessible for inspection after the construction works have been finished should be checked. Quality assurance measures continue through the acceptance stage, when final measurements on the LPS should be performed together with the completion of the final test documentation and finally through the entire lifetime of the LPS, by specifying careful periodic inspections in accordance with the maintenance programme.
Where modifications are made to a structure or its installations, a check should be made to determine whether the existing lightning protection still conforms to this standard. If it is found that the protection is inadequate, improvements should be implemented without delay.
It is recommended that the materials, extent and dimensions of the air-termination system, down-conductors, earth-termination system, bonding, components, etc. should conform to this standard.
E.4.2 Design of the LPS
E.4.2.1 Planning procedure
Before any detailed design work on the LPS is commenced, the lightning protection designer should, where reasonably practical, obtain basic information regarding the function, general design, construction and location of the structure.
Where the LPS has not already been specified by the licensing authority, insurer or purchaser, the lightning protection designer should determine whether or not to protect the structure with an LPS by following the procedures for risk assessment given in IEC 62305-2.
E.4.2.2 Consultation
E.4.2.2.1 General information
In the design and construction stages of a new structure, the LPS designer, LPS installer and all other persons responsible for installations in the structure or for regulations pertaining to the use of the structure (e.g. purchaser, architect and builder) should be in consultation regularly.
The flow diagram given in Figure E.1 will facilitate the rational design of an LPS.
In the design and construction stages of an LPS for an existing structure, consultations should be held as far as reasonably practical with the persons responsible for the structure, its use, installations and incoming services.
The consultations may have to be arranged through the owner, the building contractor of the structure or their appointed representative. For existing structures, the LPS designer should provide drawings which should be modified by the LPS installer, where necessary.
Regular consultations between the involved parties should result in an effective LPS at the lowest possible cost. For example, the coordination of LPS design work with construction work will often do away with the need for some bonding conductors and reduce the length of those which are necessary. Building costs are often reduced substantially by the provision of common routes for various installations within a structure.
Consultation is important throughout all stages of the construction of a structure as modifications to the LPS may be required due to changes in the structure design. Consultation is also necessary so that arrangements can be agreed to facilitate inspection of the parts of the LPS which will become inaccessible for visual control after the structure is completed. In these consultations, the location of all connections between natural components and the LPS should be determined. Architects are normally available to arrange and coordinate consultation meetings for new building projects.
E.4.2.2.2 The principal consulting parties
The lightning protection designer should hold relevant technical consultations with all parties involved in the design and construction of the structure, including the owner of the structure.
Particular areas of responsibility for the total installation of the LPS should be defined by the LPS designer in conjunction with the architect, electrical contractor, building contractor, the LPS installer (LPS supplier) and, where relevant, a historical adviser and the owner or owner’s representative.
The clarification of responsibility for the various parties involved in the management of the design and construction of the LPS is of particular importance. An example might be where the waterproofing of the structure is punctured by roof-mounted LPS components or by earth electrode connection conductors made below the structure foundation.
