- Tank contents
- Diesel fuel and possible contaminants
- Different findings
- Free water, sediment, sludge and tank defects
- Useful evidence
- Fuel sampling and maintenance history
- Separate services
- Fuel treatment, tank cleaning and structural repair
Water and sediment in diesel tanks
Poor fuel quality and contamination inside the tank can occur together, but one does not prove the other. An assessment should separate fuel condition from free water, settled sediment, tank deposits and defects in the tank or its fittings.
Delivery history and previous fuel treatment may help put the findings in context. Sludge-like material is not, by itself, proof of microbial contamination, and a fuel-quality concern does not automatically dictate a particular cleaning treatment.
Sources of contamination
Water ingress, storage history and retained deposits can all be relevant. Cleaning removes material already present; it does not correct a defective fill point, seal or section of pipework, so suspected routes of ingress may need separate inspection.
If fuel sampling forms part of the assessment, the results need to be interpreted in the context of the tank layout. Free water and settled material can be concentrated at low points and may not be represented by a sample taken elsewhere.
Tank cleaning and fuel treatment
Usable fuel, contaminated liquid and deposits on the tank surfaces can require different handling. Fuel polishing or another fuel treatment serves a different purpose from removing deposits from surfaces and low points, and one should not be assumed to achieve the other.
The work also has to account for flammable-liquid hazards, containment and any confined-space issues. Removed fuel, oily water and sludge require an appropriate waste assessment and receiving route.
Condition before return to service
Records at completion should state which areas were cleaned and identify any remaining defect, inaccessible area or separate fuel-quality concern. Further fuel checks may be needed before use, while repair of the tank or fittings remains separate from cleaning.