THE MARINE LOG FEATURES CALENDAR FOR 2003
May 7, 2003
Class notation for fuel systems
A new voluntary class notation from Det Norske Veritas meets an increasing market demand for the classification of fuel oil treatment and conditioning systems. DNV says that until now requirements ensuring satisfactory performance of these system types have been virtually non-existent or only dealt with in a very limited manner.
The new class notation, FUEL (-cSt, - kg/m3) in Pt.6, Ch.14, is a total system approach offering owners easy, consistent and predictable fuel treatment and conditioning systems performance.
The fuel notation addresses the most important element of fuel treatment: a standardized and reliable performance criterion governing the fuel oil purifiers' ability to remove abrasive particles from residual fuel.
The mandatory main class rules for fuel systems focus primarily on fire safety aspects and redundancy of components.
Potential problems due to lack of a performance standard have been:
- No unified standard able to monitor fuel oil purifier efficiency and independent verification of performance
- Undersized purifiers resulting in inefficient removal of catalytic fines
- Inaccurate temperature control of purifier pre-heaters affecting efficient purification
- Accumulation of sludge build up in service and settling tanks with potential carry-over of contaminants in heavy weather conditions (roll/pitch)
- Insufficient volume of settling tanks and too short residence time for the removal of impurities
- Fuel tank arrangements that do not facilitate the handling of two bunker fuel batches, resulting in sludge precipitation caused by mixing
- Inadequate capacity of fuel oil heaters causing high viscosity levels and inferior combustion
- Inaccurate viscosity control system for fuel feed to engines
- Too small a heating capacity in fuel tanks
The new voluntary DNV class notation FUEL addresses sizing and efficiency of purifiers and the arrangements of fuel bunker tanks, enable bunkering without the risk of mixing incompatible fuels.
Additionally, the notation supplies the correct arrangement and sizing of settling tanks to ensure proper separation of water and sludge, correct fuel heater capacity, temperature requirements and viscosity control.
The performance test standard for fuel oil purifiers has been developed together with GL and has been discussed with major type-equipment suppliers.
Separation efficiency is determined for given viscosities of fuel oil through a standard test procedure using Dyno-spheres as a specified test oil contaminant. This procedure gives consistent measurements of separation efficiency.
The correlation between separation efficiency of the artificial contamination with Dyno-spheres and 'real life' residual fuel has been determined through extensive testing by a major fuel oil purifier manufacturer.
Based on the newly developed performance testing method, DNV can now offer a unified standard for independent verification of performance and offer Type approval of purifiers with a Certified Flow rate.