7/27/2019 04-Symptoms of Microbiological Attack

1/2

Symptoms of Microbiological Attack

Symptoms

MEDIUM FUEL LUBRICANT BILGE & BALLASTWATER

Visual

Aggregation of microbes into abiomass, observed as

discolouration, turbidity and

fouling.

Biosurfactants produced bybacteria promote stable waterhazes and encourage particulate

dispersion.

Purifiers and coalescers which

rely on a clean fuel/water

interface, may malfunction.

Tank pitting.

Slimy appearance of the

oil; the slime tends to

cling to the crankcasedoors.

Rust films.

Honey-coloured films on

the journals, laterassociated with corrosion

pitting.

Black stains on white

metal bearings, pins and

journals.

Brown or grey/black

deposits on metallicparts.

Corrosion of the purifierbowl and newly

machined surface.

Sludge accumulation in

crankcase and excessive

sludge at the purifierdischarge.

Paint stripping in thecrankcase.

The formation ofslimes and sludgeswhich are black

themselves or are black

when scraped.

Pitting of steel work,

pipes and tank bottoms.

Rapid corrosion of

plating.

Operational

Bacterial polymers maycompletely plug filters and

orifices within a few hours.

Filters, pumps and injectors will

foul and fail.

Additive depletion.

Rancid or sulphitic

smells.

Increase in oil acidity orsudden loss of alkalinity.

Unusual foul orsulphitic smells.

Structural damage.

Loss of suction inpipelines.

7/27/2019 04-Symptoms of Microbiological Attack

2/2

Non uniform fuel flow and

variations in combustion may

accelerate piston rings and

cylinder liner wear rates andaffect cam-shaft torque.

(BN)

Stable water content inthe oil which is not

resolved by the purifier.

Filter plugging in heavy

weather.

Persistent

demulsification

problems.

Reduction of heat

transfer in coolers.

Fuel

When heavily contaminated fuel is brought onboard some or all of the problems listed above will

be encountered within a short period of time. Particularly filter blocking and purifier

malfunction. More long term will see injector and pump failures

Quick Appraisal of distilates

It is possible to make a quick judgement on the degree of contamination in distillateso Sterlise a clear bottle and take a sampleo Any contaminationa will be apparent as a haze causes by the presence of sludge.

This sludge shoiuld readily disperse by agitation. It will tend to settle out andstick to the sides. A black coloured sludge indicates the presence of SRB

o Repaeat the process for each fuel location to find the cleanest fuel. If only heavilycontaminated is available this should be left to settle as long as possible. Werepossible fuel should be drawen only via a filter, coalescer or purifier from the

higher levels in the tanks. The use of a biocide at this point is inadvisable as the

dislodges biofilms will tend to block all filters.

o Take a sample from the bottom of the tank and send to labratory for'fingerprinting' against the bunker supplier

Lubricating OIl

When operated normally there are few microbes able to live succesfully in the nutrient andenvironmentally deficient lubricating oil

Bilge & ballast Water

Problems are normally associated with the presence of SRB pitting corrosion and is indicated by

a sulphorus smell. Preventative action should be taken as soon as possible