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5 Cargo

Contamination case study 4Causes:

The tanker loaded two different cargoes in the loading port. It seems that contamination occurred because of leaking
The irst cargo was gasoil and the other was motor gasoline valves, as it was found that several valves did not work

(mogas). The tanker then sailed for the discharge port where properly and rags and ropes were found between valves.

it berthed at the terminal and commenced discharging the Alternatively a valve was open by mistake and caused the
gasoil the following day.contamination.

Discharge was then stopped because the shore manifold All valves were overhauled and repaired as needed. The

samples were off-spec. Samples were also taken from a tank cargo lines were then pressure tested with successful results.
with mogas and another tank with gasoil, which showed the

former to be off-spec for inal boiling point and residue, and In a recent study, Dr Wesley Tucker highlights some of

the latter off-spec for lash-point.the problems on board oil tankers and why contamination
After the situation was discovered the vessel was sent to an happens.

anchorage. Three days later the vessel was requested to reload

the gasoil it had discharged. There were some issues, causing For an in depth analysis of the issue see Appendix (ii)
the vessel to be delayed, and it took a couple of weeks until the Bulk liquid chemicals and fuels: Insight into speciications

vessel had reloaded the cargo and arrived at the discharge port and Contaminations

for the mogas. There was a short delay as a pump in one of the
tanks broke down. Some of the gasoil was also discharged.

The vessel then sailed for the last discharge port where

it discharged the last of the gasoil and the reloaded gasoil,
which was in the slop tanks.

5.4.4 Prevention

Cleaning• Cargo sampling of irst foot loading at each cargo

• Plan and document the different steps during the tank.
cleaning process. Follow charterer’s instructions.• Cargo sampling from each tank when loading

• Clean cargo tanks, cargo lines, drop lines, circulation completed.

lines, stripping lines, ventilation lines and vapour • Cargo sampling from each tank before discharge
return lines.commences.

• Drain all tanks and lines.• Cargo sampling at manifold during discharge and

• Dry all tanks and lines.loading of each parcel.
• Before starting loading, the tanks should be clean, free• All cargo sampling to be carried out together with

from odour and from remnants of previous cargoes.the cargo interest surveyor.

• Maintain a proper sample log.
Segregation

• Plan and document the lining-up of valves, blinds, etc. Loading/discharging

• Inert lines and vapour return lines also to be • Detailed plans for loading/discharging to be made
segregated, if applicable.and followed in detail and documented.

• Valves that should not be operated during loading/ • Document all phases during operations including

discharge to be locked.start/stop and reasons, max rates, pressure at
• Install blinds to deck heat exchangers and heating manifolds etc.

coils if applicable.• In the event of a discrepancy between the loading or

• Blow heating coils and pump stack cofferdams.discharging igures between the terminal and vessel,
• Double check the complete line up before loadingclause the bill of lading accordingly.

commences.

Transportation
Cargo sampling• Follow charterer’s instructions for circulation,

• Cargo sampling at manifold during commencement inerting, temperatures and padding etc. All

of loading each parcel.procedures must be properly documented.

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