The field problem
Fuel Station
Pumps and control indications were unstable; continuity and earth-resistance results were inconsistent.
Tank/metallic-structure bonding and electrostatic-control provisions were incomplete.
why the obvious answer can be misleading
A hazardous fuel environment requires coordinated protective earthing, equipotential bonding, static-charge control and transient protection. TN-S may be the preferred project arrangement, but it must follow source/protection verification rather than be treated as a universal rule.
Why it failed
A hazardous fuel environment requires coordinated protective earthing, equipotential bonding, static-charge control and transient protection.
TN-S may be the preferred project arrangement, but it must follow source/protection verification rather than be treated as a universal rule.
Follow the engineering
Switch between the field condition and the engineering concept. Trace the path and examine what changes.
Inspect the engineering detail
What changes
Coordinate the LV earthing topology; complete tank, pipe, dispenser and accessible-metal bonding; provide controlled static-discharge/bonding procedures for fuel transfer; review SPDs and power/control cable interfaces.
Correction & verification
Coordinate the LV earthing topology; complete tank, pipe, dispenser and accessible-metal bonding; provide controlled static-discharge/bonding procedures for fuel transfer; review SPDs and power/control cable interfaces.
Verification recorded in the case
- Verify continuity, N-PE arrangement, PE current, functional control behaviour and hazardous-area bonding before closing the investigation.
- Record as-built topology and connection points.
- Repeat the measurement or functional test under a defined condition.
- Confirm continuity and mechanical integrity of the corrected path.
- Document instrument/setup, environmental condition and test method.
- Close the NCR/case only when evidence supports the conclusion.
References & project context
References are reproduced from the PIS casebook. Select the governing edition and project acceptance criteria before using them for a design. The diagrams explain the concept, rather than define construction dimensions.
IEC 60079-14; IEC TS 60079-32-1; IEC 60364-4-41/-5-54; IEC 62305 where applicable.
PIS reviewed field handbook · PIS-CS-041
The engineering lesson
In a hazardous facility, earthing must control fault current, voltage difference, static charge and transient energy.
Take the lesson into your next design review.