It is the degradation of fuel oil/lube oil that takes place when bacterial, yeast or molds thrive when a favorable condition occurs in the tank
Water may enter the storage system either through condensation, rainwater penetration, absorption of air or another means when things go wrong. The presence of water along with phosphorous, nitrogen, carbon encourages microbe growth on the interface between oil and water especially on the tank walls
Water may enter the storage system either through condensation, rainwater penetration, absorption of air or another means when things go wrong. The presence of water along with phosphorous, nitrogen, carbon encourages microbe growth on the interface between oil and water especially on the tank walls
Dangers
- They require water to grow in the beginning but later they can self sustain themself at 20-10 deg celsius in stagnant condition.
- They multiply at a very rapid rate ie. double the size and divide into two every half an hour.
- Once the aerobic bacteria have consumed the dissolved oxygen the sulfate-reducing bacteria is activated
- They attack metals and forms hydrogen sulfide, resulting in corrosion of steel
- Properties of fuel oil /lube oil are effected enhancing corrosion and reducing load carrying properties
- Microbial degradation is normally seen in distillate fuel and not in residual fuel
Indication
- Rotten egg smell
- Sliminess of oil, especially visible on the painted surface
- Increase in water content and acid content
- Filter chocking more often.
- Poor heat exchanger performance.
- Black staining of white metal and bearing surface
Minimizing the risk of contamination
- Purchase Bunkers reliable sources to known specifications
- Crankcase content to be weekly monitored and within limits
- Regular inspection of tanks, crankcases storage tanks
- Regular circulation of oil to avoid stagnation
- lube oil temperature at the purifier is to be at least 75deg cels as Bactria perish above 70 deg cels
- Recirculation and purification of the crankcase oil to be carried out even at long port stays
- Inspection of sludge from purifier or cocked filters to find an indication of any degradation
- Ensure all tanks, vents, heating coils are well maintained, in good condition and leak-free
- Always follow recommended methods when refilling tanks, transfers, and bunkering to avoid the accidental introduction of contamination
- Periodically drain the tank of water and other sediments
- If storing fuel in multiple tanks, employ a rotation system to use the oldest fuel first(first in, first out)
- Filter fuel every time it is moved – this is considered to be ‘best practice’ as fuel is at most risk from contamination when it is being transferred
- Ensure all appropriate crew and engineers are trained in good fuel housekeeping. Processes and procedures should be in place to minimize the possibility of accidental fuel contamination.
- Support the on-tank polishing unit with a fuel additive and biocide to maintain fuel stability and minimize microbial growth
Treatment
- Use of biocide and fungicide
- LO purifier operation at a temperature above 75deg cels but not exceed the suppliers limit as it may lead to oxidation of the oil
- Manual cleaning of sumps, filters pipelines
- Replenishment of the sump oil