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Guidelines To reduce SOx emissions from coastal trading ships and in environmental sensitive areas, the following regulations have been implemented worldwide:
l EC (European Community) inland waterways, and at berth for > 2 hours, 0.1% Sulphur content by 1st January 2010. l CARB (California Air Resources Board) 0.1% Sulphur content by 1st January 2012.
Due to more and more environmental legislation on fuel sulphur contents, the engines will operate on distillate fuels (marine gas oil (MGO) and marine diesel oil (MDO)) in the future.
Risk on using Low-Sulphur Fuel Oil
l Low viscosity
ISO8217:2005 specifies MGO (DMA grade) with a viscosity of min. In order to enure a satisfactory hydrodynamic oil film between fuel pump plunger and barrel, thereby avoiding fuel pump seizures/sticking. Usually min. 2 cSt measured is recommends to keep a fuel oil viscosity at the engine inlet.
For MGO, viscosities below 2 cSt may be reached at temperatures above 35℃. As the fuel temperature increases during operation, it is impossible to maintain this low temperature at the engine inlet. In the worst case, a temperature of 60-65 ℃ 0t the engine inlet can be expected corresponding to a viscosity far below 2.0 cSt. The consequence may be sticking fuel components.
On the other hand, most pumps in the external system (supply pumps, circulating pumps, transfer pumps and feed pumps for the centrifuge) already installed in existing vessels need viscosities above 2 cSt to function properly.
DMA fuel cooling system
Fuel cooling system is an important and indispensable part to change-over unit.
As well-known factor, the viscosity can be raised by cooling of the fuel, after which the MGO / MDO fuels can then be used to ensure safe and reliable machinery performance.
Descriptions
Currently, the use of chillers (chilled water) in an external fuel supply system, called MGO / MDO Cooling System, is strongly recommended and applied to the marine industry.
The scope of supplies for MGO / MDO Cooling System is comprised of the followings: MG0/MDO
l Chilling Unit
l Water Pump Unit (including buffer tank)
l Diesel Oil Cooler Unit
Features
l Oil temperatures are precisely controlled by PLC to keep drop rate within limits.
l The chiller unit can be operated under low-capacity condition, 0-100% modulating control.
l The chiller system is leakage safe.
l Installation, commissioning & servicing of the cooling system is made simple & easy.
Principle drawing of MGO cooling system and fuel change-over system
The system comprizes:
Chiller Unit
A Chiller Unit composes of either a piston or screw semi-hermetic compressor, a water-cooled shell & tube condenser, a dry-expansion evaporator, an expansion valve, a filter, a sight glass, a shut-off valve, a control box, etc.
The unit has compact structure, reliable performance and offers convenience for maintenance. And the unit can easily be put into operation after simple connection with power, to cooling water, and chilled water systems.
Water Pump Unit
The Water Pump Unit installed between the Chilling Unit and Diesel Oil Cooler Unit, consists of a pump and a pressurized buffer tank. Two Pumps, one for normal operation while the other serves as stand by, are equipped.
The Buffer Tank provides a reservoir for chilled water as well as for the regulation of chilled water fluctuation due to variational cooling loads in the system.
Diesel Oil Cooler Unit
The Diesel Oil Cooler Unit is connected to the fuel oil supply line controlling the fuel oil outlet temperature. It consists of an oil-water heat exchanger, a 3-way valve, a temperature sensor and a controller. The 3-way valve is installed in the cooling water line, whereas the temperature sensor is mounted at the heat exchanger oil outlet.
As an option, the Diesel Oil Cooler Unit can be mounted on a common skid together with the Water Pump Unit.
DMA also provides MGO cooling rerofit solution for old ships. DMA has retrofitted MGO successfully for ship owner SEASPAN, Gleamray, TEO Shipping, etc, and has got great evaluation from ship owners.
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