WHAT’S DIFFERENT with the RMK’s and the RMG 380?
RMK 500 & 700 fuels are made from the same basic components as lower viscosity fuels, with cutters (such as cycle oils, gas oil, etc) being used in varying proportions to achieve the required viscosity and density of the fuel grade. Optimising the fuel blend in this way has no significant impact on fuel performance for those vessels that are equipped to consume it, but has one major advantage: it is cheaper to produce and therefore a more cost-effective energy source for the vessel operator.
The benefits of Shell RMK’s:
In the 60 years since Shell pioneered the use of residual fuels for diesel engines in its fleet, the shipping industry has benefited from the use of this cost-effective energy source. Developments in fuel treatment and engine technology have enabled the industry to progressively make use of more cost-competitive grades, with typical fuel viscosities increasing from 180cSt to 380cSt, and to 500 and 700cSt.
High-density 500/700cSt fuel oil is a well established and proven marine bunker fuel, suitable for use in large modern vessels with low-speed diesel engines. It is more cost competitive than 380cSt fuel, and therefore offers operators comparable performance at lower cost.
What are the operational considerations for the use of Shell RMK’s ?
Compared with conventional RMG 380 fuel, RMK 500/700 has both a higher viscosity and a higher density, but this has no practical impact. Alcap type centrifugal separators used for fuel cleaning can deal with fuel densities of up to 1010 kg/m3 @ 15°C. The higher fuel viscosity requires a slightly higher storage and handling temperature (typically 4-6°C).
Vessels burning RMK 500/700 needs sufficient heating capacity to maintain these slightly elevated temperatures, but the heat required can usually be provided by the waste heat boiler of the vessel, and most of the heat put into the fuel is recovered in the engine.
Why Shell RMK 500/700?
Shell has been supplying high density, high viscosity fuels into the marine market for over 20 years, in which time we have supplied tens of millions of tons of Shell’s RMK 500/700 to our customers. Over that time we have built up vast experience in the production, blending and handling of these fuels, and of their satisfactory performance in our customers’ vessels.
Shell’s RMK 500/700 is tightly controlled through our Fuel Oil Quality Assurance System (FOQAS), to ensure compliance with Shell’s global standards (which
include several internal specifications that are more stringent than the full ISO 8217 (2010) specification). These standards are rigorously applied to assure customers of the high degree of confidence they require that the fuels they buy will be on specification and will burn efficiently in their engine.
Shell RMK 500/700 complies with the ISO 8217 (2010) specification for RMK 380 in every respect with the exception, obviously, of viscosity.
Shell RMK 500/700 Combustion Properties
Whilst the composition of Shell RMK 500/700 is very similar to that of other fuels such as RMG 380, it is critical that suppliers selling higher viscosity fuels understand the impact that changes in fuel formulation can have on the performance of the fuel. Meeting the bulk properties set out in the ISO spec is not always sufficient to ensure good performance in the engine.
This is why Shell continues to compliment our long experience of how to blend good quality fuels with an ongoing Marine Fuels Research and Development Program, in our Group research laboratories in Amsterdam and our dedicated Marine research facility in Hamburg. This includes extensive monitoring of the ignition and combustion properties of our fuels in our test engines and Fuel Ignition Analysis (FIA) equipment.
No greater risks to stability and compatibility
When mixing residual fuels of different qualities or from different sources there is the potential for stability and compatibility issues to arise, as a lower aromatic content may increase the risk of asphaltene precipitation leading to sludge formation. However, as a result of the high aromaticity of Shell RMK 500 there is no increased stability or compatibility risk when mixing Shell RMK 500 and RMG 380.
|Concerns||Operational Impact||How to manage|
|Composition:||No impact, the composition of shell MFO 500 is similar to that of ISO standard RMG 380||-|
|Higher density:||No impact if onboard fuel treatment plant is equipped to manage density greater than water||Commonly installed Alcap type centrifuge can accommodate fuel density up to 1010 kg/m3 @ 15°C.|
|Higher Viscosity:||Requires slightly higher [4-6°C] bunker tank and fuel injection temperatures||Heat usually available onboard from waste heat boiler|
|Stability and Compatibility:||No increased risk when mixing shell MFO 500 and RMG 380||Shell Spot Test Kit can be used to identify non-compatibility of different fuels if required|
|Wider scope for use of unsuitable blend components:||Would potenially lead to poor combustion; HSE issues||Shell FOQAS quality assurance system strictly controls the components used in the manufacture of shell fuels|
|Ignition and Combustion:|| |
Low Speed Engine: normally no issue provided combustion properties of the fuel are suitable for use in a marine engine
Medium Speed Engines: normally no issues in engines <10 years old
Shell has >20 years of experience supplying tens of millions of tons of this fuel, and an ongoing R&D program evaluation combustion properties
Consult with a Shell Marine technical advisor to evaluate suitability for your operations.