Accidental Mixing of Different Fuel Oils

  • Safety Flash
  • Published on 19 March 2018
  • Generated on 9 February 2025
  • IMCA SF 06/18
  • 2 minute read

A vessel was at anchorage waiting for the pilot.

What happened?

The engine room was manned and the main engine ready for manoeuvring. The duty engineer informed the bridge that two valves on the fuel transfer line were kept open overnight. These were the valve for Ultra Low Sulphur Fuel Oil tank no 6 (starboard) and valve for Heavy Fuel Oil tank no.6 (Centre starboard).

It was observed on the remote gauging system that the quantity of fuel in the Ultra Low Sulphur Fuel Oil tank no 6 (starboard) was considerably less than the previous day.

Fuel Oil 3 symbol

What went wrong? What were the causes?

All valves on the fuel transfer line were closed and soundings were taken for all tanks. It was found that 57 tonnes of Ultra Low Sulphur Fuel Oil from tank no.6 (S) had been accidentally transferred by gravity to Heavy Fuel Oil tank no.6 (CS), due to the initial higher level in the first tank (tank no.6 (S)).

Samples from tank no.6 (CS) and ULSFO settling tank were taken and landed ashore for urgent sample analysis.

Results from the laboratory confirmed that fuel was contaminated due to mixing.

Our member noted the following:

  • There was financial and reputational loss:
    • cost for urgent sample analysing
    • company’s reputation with the shipowner.
  • The immediate cause was carelessness – failure to operate the fuel valve correctly.
  • Causal factors identified were inadequate supervision or management – a lack of adequate oversight and monitoring.
  • The root cause identified was inadequate compliance with existing procedures.

What actions were taken?

Persons involved were referred back to company procedures, and a notice with the fuel oil transfer procedures displayed near the operating panel.

Latest Safety Flashes:

Saturation diver exposed to chemicals from pipeline

During pigging and decommissioning operations, a saturation diver was exposed to the contents of a pipeline.

Read more
MAIB: Parted mooring rope leads to fatality

A deck officer was killed during mooring operations when a mooring rope parted and struck him on the head.

Read more
Confined space entry hot work fatality

An incident was brought to IMCA’s attention relating to a confined space entry hot work fatality in a shipyard.

Read more
MAIB: Vessel cook injured by spillage of burning cooking oil

Cook receives burns from oil spill due to faulty thermostat. 

Read more
MAIB: Step-ladder failure (LTI)

A crew member was working while stood on the top step of a small folding stepladder when the step gave way.

Read more

IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of the entire offshore industry.

The effectiveness of the IMCA Safety Flash system depends on the industry sharing information and so avoiding repeat incidents. Incidents are classified according to IOGP's Life Saving Rules.

All information is anonymised or sanitised, as appropriate, and warnings for graphic content included where possible.

IMCA makes every effort to ensure both the accuracy and reliability of the information shared, but is not be liable for any guidance and/or recommendation and/or statement herein contained.

The information contained in this document does not fulfil or replace any individual's or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.

Share your safety incidents with IMCA online. Sign-up to receive Safety Flashes straight to your email.