Fuel Oil Sampling During Bunkering – Marine Engineering
Fuel Oil Testing On-board
On-board testing of the fuel could be carried out during the bunker operation by one of the engineering staff not required to supervise or monitor the bunkering operation. The following tests could be carried out:
- Water content
- Viscosity
- Density
- Compatibility
- Check for abrasive fines
Although the tests are not as accurate as a shore based laboratory the tests would indicate whether the fuel loaded is the same as the fuel quality ordered and therefore the bunker receipt.
Importance of Fuel Oil Sampling
A representative sample would be obtained by a permanent sampling probe fitted close to the bunkering manifold. The rate of sampling would ensure that a sampling quantity required is taken over the full duration of the bunkering operation. The sample container is then thoroughly mixed before being poured into new, clean containers. The containers are then sealed and signed before being sent to the shore testing facility.
Effects of Contaminants in the Fuel
Oxides of nitrogen are formed when the nitrogen in the fuel, and some of the nitrogen in the air combines with the oxygen present during combustion in the heat of the combustion process. The quantity of NOx produced is dependent on the temperature and duration of combustion, and the quantity of oxygen present in the combustion space.
Carbon monoxide is formed when the level of oxygen within the combustion space is insufficient to provide complete combustion to carbon dioxide. As usually there is ample oxygen within a diesel engine, readings of carbon monoxide indicate the present of pockets of fuel rich mixtures burning locally without enough oxygen, hence poor fuel/air mixing from incorrect atomization and air turbulence will cause carbon monoxide levels to rise. Sulphur oxides are formed when the sulphur in the fuel reacts with the oxygen to form sulphur monoxide and dioxide. Increasing levels of fuel sulphur content will increase the sulphur oxides produced.
In order to reduce the effects of the sulphurous products the following can be used:
- Reduce the level of sulphur in the fuel by using low sulphur fuels
- Counteract the condensation rate of the sulphur oxides by elevating metal temperatures at the cylinder walls, and the skin temperature of the exhaust gas boiler tubes
- Use of high alkaline lubricating oils to counteract-neutralise the acids formed on condensation.
- Increased frequency of cleaning of the exhaust gas boiler and turbocharger gas turbine