Hot Work Beside a Hydrocarbon Drum Farm
A contractor is to weld a support bracket on a pipe rack 6 m above a drum storage area holding 40 drums of used lubricating oil and 6 drums of a flammable solvent (flash point 12 °C). The permit was raised by the contractor supervisor and signed by a production technician; no gas test was recorded on the permit. Wind is light and variable. The area has a fixed LEL detector 15 m away that is in calibration. The plant's hot work procedure requires a gas test within 30 minutes before work and continuous monitoring where flammable liquids are within 15 m. The contractor argues the solvent drums are sealed and the work is 'just a bracket'.
1. Evaluate the adequacy of the permit and the controls, identifying the specific deficiencies and the hazard mechanism each one creates.
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The permit is deficient on several counts, each tied to a hazard mechanism:
- No gas test recorded: The procedure requires a test within 30 minutes and continuous monitoring. Without it there is no evidence the atmosphere is below the permitted LEL. Sealed drums are not a barrier - bungs leak, drums breathe with temperature change, and spills collect in low points.
- Wrong authoriser: A production technician signing a hot work permit for work near flammable liquids is a competence and authority failure. The authoriser must be able to assess the area and stop the job.
- Distance and geometry: 6 m elevation does not remove the hazard; solvent vapour is heavier than air and can accumulate at grade, and welding sparks and slag fall. The 15 m fixed detector may not cover the drum farm, and a fixed detector is not a substitute for a pre-work test at the point of work.
- Contractor framing: 'Just a bracket' is a normalisation argument. The flammable solvent at 12 °C flash point is the controlling hazard regardless of the task size.
- Wind: Light and variable wind makes dispersion unpredictable; a test taken upwind may not represent the work location.
The permit should not be accepted as written.
2. Describe how you would decide whether the job can proceed and what conditions you would set if it can.
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Decision logic:
- Can the hazard be removed? Preferred: relocate or remove the solvent drums (and ideally the oil drums) from the fall-out and vapour zone before work, or move the work to a cold method (bolted clamp) that eliminates ignition sources. If either is possible, do it and re-scope the permit.
- If hot work is unavoidable, conditions would include:
- A competent, authorised permit issuer signs after a site walk.
- Gas test at the work location and at grade near the drums immediately before work, recorded on the permit with time and result; continuous monitoring during work with a calibrated personal or area monitor and a defined stop-work LEL (e.g. 10% LEL).
- Drums checked for leaks, bungs tight, solvent drums moved or bunded and covered; ignition sources controlled; fire watch with extinguisher and a defined post-work fire watch period (e.g. 30–60 minutes) because slag can smoulder.
- Sparks and slag containment (fire blankets, screens) and control of fall paths.
- Clear stop-work authority for the gas tester and fire watch.
- Toolbox talk covering the solvent hazard, not just the bracket.
- Document the decision and, if the contractor disagrees, escalate - the permit issuer's authority is not negotiable.
Key point: the decision is not 'is the task small?' but 'are the ignition and fuel separated by verified controls?'