Industrial plants are the hardest lightning protection problem on any site: tall irregular structures, flammable inventories, extensive metalwork and instrumentation that fails long before the structure does.
Step 1 — Risk assessment
Run the IEC 62305-2 assessment using the local ground flash density, structure dimensions, occupancy, service entries and the consequences of loss. The output is a required Lightning Protection Level (LPL I to IV) for each zone. A refinery tank farm and its admin block rarely land on the same level.
Step 2 — Air termination geometry
- LPL I — 20 m rolling sphere, 5×5 m mesh
- LPL II — 30 m rolling sphere, 10×10 m mesh
- LPL III — 45 m rolling sphere, 15×15 m mesh
- LPL IV — 60 m rolling sphere, 20×20 m mesh
Roll the sphere across the 3D model, not the plan view. Stacks, flare tips, cooling towers and pipe racks generate shadowing that a plan drawing hides.
Step 3 — Tanks and hazardous zones
Metallic tanks of adequate shell thickness with bonded floating roofs are usually self-protecting; the design work is in shunts, seals and bonding, not in mounting rods. Where an area is classified, verify the separation distance so a side flash cannot occur into a zone containing vapour.
Step 4 — Down conductors and earthing
Use the structural steel where it is electrically continuous — it beats any added conductor. Otherwise space down conductors per the LPL, terminate each into the plant earthing network, and provide test joints for future verification.
Step 5 — Surge protection
Coordinated SPDs at the incoming supply, sub-distribution and instrumentation panels complete the system. Structural protection without SPDs leaves the control system exposed, which is where the real downtime cost sits.