QUESTION 10.5.3

Safe fuel changeover and sulphur compliance

Oil, Chemical, LPG, LNGEngine Control Room, Chief Engineer's Office

What is being checked

The inspector is checking whether changeovers are calculated and executed early enough to meet sulphur limits without thermal shock, viscosity loss, leakage, loss of propulsion or inaccurate MARPOL records.

Ready onboard

0/7 complete

VESSEL PROCEDUREA ship-specific procedure identifies tanks, valves, mixing volumes, compatible grades and machinery limits.CALCULATIONThe start time accounts for service and settling tanks, piping volume, consumption, mixing and the time needed to reach compliant sulphur concentration.TEMPERATURE RATEHeating or cooling rates remain within maker limits to protect pumps, clearances, seals and injection equipment.VISCOSITYTemperature and viscosity are controlled at machinery inlet throughout the transition.LEAK WATCHPurifiers, pumps, filters, heaters and fuel-system connections receive close monitoring during and after changeover.RECORDDate, time, position and tank quantities at completion are recorded as required and agree with engine logs.CONTINGENCYEngineers know how to stabilise fuel supply or reverse the change safely if pressure, viscosity or temperature becomes abnormal.

Practice questions

Answer aloud, then open the preparation point.

1How was the changeover start point calculated?

Use the system's mixing volume, actual consumption, both fuels' sulphur content and the required compliant completion position.

2What is the permitted temperature-change rate?

State the actual maker or vessel limit and show how it is monitored; do not use a universal rule of thumb.

3Why can low-viscosity fuel cause leakage?

Reduced viscosity and temperature change can expose worn pump clearances, seals and connections and alter injection performance.

4When is the MARPOL entry made?

At completion of the changeover to compliant fuel, with the required date, time, position and low-sulphur tank quantities.

5What would make you stop or reverse the changeover?

Unstable pressure, excessive temperature rate, leakage, filter blockage, viscosity outside limits or threatened propulsion availability.

Where an observation may arise

LATE COMPLETION

The vessel enters the controlled area before compliant fuel reaches the engines.

GENERIC CALCULATION

System volume and actual consumption are not used.

THERMAL SHOCK

Temperature changes exceed maker limits.

LOG ERROR

Position, completion time or tank quantity is absent or conflicts with other records.

NO CONTINGENCY

Engineers cannot respond to leakage, pressure loss or filter blockage.

WRONG LINE-UP

A non-compliant tank or return path contaminates the service system.

Master's practical note

Rework the most recent changeover using actual consumption and system volume. A standard distance from the boundary can be wrong when load, fuel sulphur or recirculating volume changes.

Equipment boundary and references

Equipment boundary: This applies when changing fuel grades for MARPOL or local requirements. Ships using an approved equivalent method such as EGCS need the corresponding compliance and failure procedure.

References

OCIMF SIRE 2.0 Question Library Part 2, Version 1.0, Question 10.5.3
MARPOL Annex VI regulation 14
IMO Resolution MEPC.320(74)
ISO 8217, applicable contracted edition
Engine and fuel-system manufacturer instructions

Last reviewed: 2026-09-10