Lightning protection by structure · Complies to IEC 60079-14 · IEC 62305-3 Annex C · NFPA 77
Hazardous Area Lightning and Static Protection
In hazardous areas a spark from lightning or static electricity can ignite an explosive atmosphere. Protection combines an LPS that keeps strike points and sparks out of the zones, bonding of all metal parts, static earthing for transfers, and surge protection suited to intrinsically safe circuits.
When it applies
- Refineries, tank farms, terminals and gas plants
- Chemical, fertiliser, paint and solvent plants
- Loading and unloading of road and rail tankers and drums
- Mines, silos and dust-explosion areas
When it does not
- Non-classified areas of the same site, which follow the ordinary structure solutions
- Work without a current hazardous-area classification drawing
- Any installation of equipment in a zone without the matching Ex certification
How the system works
- InterceptAir termination is placed by rolling sphere, mesh or protective angle so that the strike lands on the system, not the structure.
- ConductSeveral straight, short down conductors share the current and keep voltages low.
- DisperseThe earth termination spreads the current into the ground with a low impulse impedance.
- EqualiseBonding and surge protection stop sparks between the system and what is inside the building.
Rolling sphere method
A sphere of the radius set by the protection level is rolled over the structure. Wherever it touches, a strike can land, so that point needs air termination. Everything it cannot touch is protected.
Design parameters
The values a consultant or contractor needs to fix before the system is drawn.
| Parameter | Typical value or rule | Reference |
|---|---|---|
| Area classification | Zone 0 / 1 / 2 (gas) and 20 / 21 / 22 (dust) drawings | IEC 60079-10-1 · IEC 60079-10-2 |
| LPS for explosive structures | Air termination placed so that strike points lie outside the zones; isolated LPS preferred | IEC 62305-3 Annex C |
| Tanks | Self-protecting when the steel is continuous and typically 4.8 mm or thicker; floating roofs bonded to the shell with bypass conductors | API RP 545 · IEC 62305-3 Annex C |
| Bonding and static earthing | All metal parts bonded; tankers and drums earthed through a monitored clamp before transfer starts | IEC 60079-14 · IEC TS 60079-32-1 |
| Surge protection | SPDs for intrinsically safe loops selected for the loop and the zone | IEC 60079-14 · IEC 61643-21 |
| Inspection | Visual inspection and electrical testing every year for structures with explosion risk | IEC 62305-3 Annex D |
Solution pack: component BOQ
Each line opens the LPES product category. Part codes and final quantities are confirmed on your quote from the drawings.
| Component | Role in the system | Quantity rule |
|---|---|---|
| Static Earthing (Ex) | Monitored static earthing clamps and reels for tankers, drums and vessels | One system per loading point |
| Data, Signal & RF Line SPDs | Surge protection for instrument and intrinsically safe loops | One per loop at the field device and at the control room |
| Isolated Air-Termination | Isolated air termination that keeps sparks out of the zones | From the layout around vents and zones |
| Lightning Strike Counters | Record strikes so that inspection follows each event | One per LPS or per main down conductor |
From design to handover
- Obtain the area classification and run the lightning risk assessment
- Design air termination and separation distances around the zones
- Bond tanks, pipes and structures and install static earthing at transfer points
- Fit surge protection to power, instrument and intrinsically safe circuits
- Audit, test and record; inspect every year and after each recorded strike
Services for this solution
Industries that use it
Oil, Gas & HazardousChemicals & FertilisersPaints & CoatingsMining
What the standards require
Checked against the current editions held in the LPES standards library.
- IEC 62305-3:2024 Cl. 5.2
- The rolling sphere is the general method. The protection angle only supplements it for simple shapes, and the mesh method is for flat surfaces.
- IEC 62305-3:2024 Cl. 5.2
- An unprotected metal roof fixture needs its own protection if it stands more than 0.3 m above the roof, covers more than 1.0 m² or is longer than 2.0 m.
- IEC 62305-3:2024 Cl. 5.2.3
- Side flashes are negligible up to 60 m. Above that, protect the top 20% of the height.
- IEC 62305-3:2024 Cl. 5.3
- An exposed corner can share a down conductor if both neighbours are within half the Table 5 spacing.
- IEC 62305-3:2024 Cl. 5.3.5
- Natural down conductors are proven by a four-lead continuity test at about 10 A: 0.2 Ω or less from top to earth network.
- IEC 62305-3:2024 D.7.2
- Inspect visually every year and completely, with electrical tests, every three years; every year for public, sensitive and explosion-risk structures.
Regulation and standards cross-check
What Indian regulation and the wider standards add to this solution. Paraphrased; confirm against the current official text, amendments and state notifications before relying on a clause in a tender or inspection.
| Standard | Clause | What it requires |
|---|---|---|
| IS 3043:2026 | Clause 11.4 | In hazardous areas only TN-S is used inside the area, potential equalisation covers Zones 0, 1 and 2 with supplementary bonding of at least 10 mm² copper, pipe racks are bonded every 25 m, and pipelines are bonded at entry and exit with respect for cathodic protection. Separate electrodes are not allowed. |
| CEA Safety Regulations 2023 | Reg 38(3)(vi) | Lightning protection is required for multi-storeyed buildings above 15 m and for listed premises, which include hospitals, hotels, academic buildings, industrial installations and other public buildings. The regulation names no design standard, so IS/IEC 62305 applies through Reg 14. |
| CEA Safety Regulations 2023 | Reg 14(2), Reg 2(1)(zze) | Relevant standards, including the National Electrical Code and the National Building Code, shall be followed. Indian Standards come first, then IEC, IEEE and European Norms in that order. Where a standard and the regulations differ, the regulations prevail. |
| IS 3043:2026 | Clause 6.3.1 | Separate or dedicated earth electrodes for individual equipment, neutrals, electronics or the lightning protection system shall not be followed. Electrodes are interconnected into one earthing system. |
| CEA Safety Regulations 2023 | Reg 43(v) | Every building shall have protective equipotential bonding that interconnects exposed and extraneous conductive parts. |
| IEC 60364-6:2016 | 6.4.3.1 | Testing in potentially explosive atmospheres needs the precautions of IEC 60079-17. |
| CEA Safety Regulations 2023 | Reg 32(2), Reg 33(3) | Periodic inspection or self-certification is set by the Appropriate Government at intervals not longer than five years. Test instruments are calibrated by a Government-authorised or NABL-accredited laboratory. |
What we ask for before design starts
- Roof plan, elevations and sections with heights
- Use of the structure and its contents, for the risk assessment
- Roof and facade materials with sheet thickness
- Metal installations on the roof and services that enter the structure
- Soil resistivity and the existing earthing layout
- Single-line diagram for the surge protection design
Engineering depth: from the LPES Knowledge Hub
Topic studies written against the current standards. Open each part for the method, the mistakes to avoid and the checklist.
IEC 62305-4:2024 · LPES Knowledge Hub H-44
Reducing overvoltages in cables on masts and process vessels bonded ducting and inherent shielding (Figures B.7, B.8)
Cables that run on the outside of a mast or a process vessel — to an aerial, a meteorological sensor, a level transmitter, a valve position indicator — sit in one of the most exposed positions a cable can occupy: outside the structure's own conductive envelope, often on a tall or isolated item of steel that is itself a preferred lightning attachment point. Clause B.11.4 of Annex B gives the practical answer for retrofitting protection to these cables on an existing structure: run them in bonded ducting, trunking or metal tubes wherever possible, and where a fully enclosed duct is not practical — as on a process vessel — use the structure's own steel (rung ladders, pipes, well-bonded conducting materials) as a natural shield by routing the cable close against it. On a lattice mast built from L-shaped corner members, the specific instruction is to place the cable in the inside corner of the L, because that geometry gives the cable the maximum shielding the steelwork can offer. The clause is illustrated by two named figures: Figure B.7, showing inherent shielding from bonded ladders and pipes on a process vessel, and Figure B.8, showing the ideal cable positions inside the corner of an L-girder on a steel lattice mast.
How it is applied
- Identify every cable serving externally installed equipment on a mast or process vessel — antenna feeders, sensor signal cables, camera power and data, instrumentation loops.
- Wherever a fully enclosed route is achievable, specify bonded ducting, trunking or a metal tube for the cable run, bonded to the structure, and route all cables leading to a given item of equipment so that they leave the duct at a single point (this limits the number of places where a cable transitions from the shielded to the unshielded environment, each of which is a potential coupling point).
- Where a fully enclosed duct is not practical — the explicit process-vessel case named in B.11.4 — route the cable on the outside of the structure but as close as possible to existing conductive elements: rung ladders, pipe runs, and any other well-bonded conducting material, following the alternative positions shown in Figure B.7.
- Confirm that the conductive elements being used for inherent shielding (ladders, pipes) are themselves properly bonded to the structure's bonding network — an unbonded ladder or an isolated pipe section provides no inherent shielding benefit and may itself become a hazard.
- On a steel lattice mast with L-shaped corner members, route cables into the inside corner of the L wherever the mechanical arrangement allows it (Figure B.8), since this position is identified as giving maximum protection; where the inside-corner position is not achievable, use a bonded cable tray within the mast structure as the alternative shown in the same figure.
- Treat this clause's guidance as a retrofit measure to be combined with, not substituted for, the separation-distance requirement of B.11.3 and the SPD protection at the equipment — inherent shielding reduces the induced overvoltage reaching the cable, it does not by itself eliminate the need for an SPD at the equipment served by that cable.
Common mistakes
- Running a cable in free air alongside a process vessel or mast, at a distance from any conductive structure, when a bonded ladder, pipe run or L-girder corner was available and would have provided inherent shielding at no extra material cost.
- Using an unbonded or poorly bonded ladder or pipe as the "shielding" element — B.11.4's guidance depends on the conductive element being well bonded; an isolated conductor does not provide the inherent shielding the clause describes and can itself pick up dangerous potential.
- On a lattice mast, running the cable along the outside face of an L-girder rather than into its inside corner — the outer face gives materially less surrounding steel and therefore less shielding benefit than the position Figure B.8 identifies as ideal.
- Treating inherent shielding as a substitute for SPD protection at the equipment, rather than as a complementary measure that reduces (but does not eliminate) the induced voltage the SPD then has to handle.
- Allowing cables from the same equipment to leave a bonded duct at multiple points rather than a single point, multiplying the number of shielded-to-unshielded transitions.
Design checklist
- Have all cables serving externally installed equipment on this mast or vessel been identified?
- Has bonded ducting, trunking or metal tube been specified wherever a fully enclosed route is achievable?
- Where a fully enclosed duct is not practical (e.g. a process vessel), has the cable route been placed as close as possible to existing bonded conductive elements — ladders, pipes, other well-bonded conducting materials — per Figure B.7?
- Has the bonding of those ladders/pipes to the structure's bonding network been confirmed, not assumed?
- On a steel lattice mast with L-shaped corner members, has the cable been routed into the inside corner of the L wherever mechanically possible, per Figure B.8, with a bonded cable tray as the documented alternative where it is not?
- Do all cables serving a given item of equipment leave any bonded duct at a single point rather than multiple points?
- Has SPD protection at the point the cable enters the protected structure been specified separately, rather than relying on inherent shielding alone?
- Has separation distance to the LPS been checked and documented separately the related topic H-43, since B.11.4 addresses a different protection mechanism?
Try the numbers
Protection level explorer
- Rolling-sphere radius
- 45 m
- Mesh size
- 15 × 15 m
- Down-conductor spacing
- 15 m
- Peak current covered
- 100 kA
- Coefficient ki
- 0.04
- Interception efficiency
- 90%
Values from IEC 62305-1 and IEC 62305-3. The level for your structure comes from the risk assessment.
What we find on audits
- Rooftop equipment standing outside the protected volume
- A single down conductor, or long loops around parapets
- Separation distance ignored, so current jumps to ducts and cable trays
- No test joints and no record of earth resistance
- External lightning protection installed with no surge protection on incoming lines
What you receive: the LPES Protection Passport
- As-built drawings of the installed system
- Risk assessment and design calculations
- Test results: earth resistance, continuity, SPD checks
- Component list with part codes and type-test references
- Inspection schedule for the protection level
Lightning to Load: one accountable partner
- Assess
- Design
- Specify
- Supply
- Implement
- Verify
- Assure
Standards basis
IEC 62305-1, -2 and -3:2024 (Ed. 3) · IS/IEC 62305 · IEC 62561 series · CEA Safety Regulations 2023 · IS 732:2019 · IEC 60364-6:2016 · IEC 61936-1:2021
Reviewed by LPES engineering, November 2026. Clause and table numbers follow IEC 62305:2024 (Edition 3) and IS 3043:2026.
Questions engineers ask
Does a steel tank need air terminals?
A continuous steel tank of sufficient thickness is treated as self-protecting, provided it is earthed and its roof and fittings are bonded. Compliance Audit
How is a floating roof bonded?
With bypass conductors between the roof and the shell and with shunts, as set out in API RP 545. Static Earthing (Ex)
What is static earthing?
Connecting a tanker, drum or vessel to earth through a clamp that proves the connection before product flows. Static Earthing (Ex)
Can any surge protector be used on an Ex-i loop?
No. The device must suit the intrinsic safety parameters of the loop and the zone it is installed in. Data, Signal & RF Line SPDs
How often must an LPS in a hazardous area be inspected?
A visual inspection and electrical testing every year, and after any recorded strike. Lightning Strike Counters
Get this solution quoted for your site
Send the drawings or the basic dimensions. LPES returns the design parameters, the BOQ with part codes and the price in one offer.
