Low Sulphur Diesel Oil technology
Introduction and General Scope
This is for generic scope of work required for a conversion to allow marine boilers to operate across the full load range whilst
burning Low Sulphur Diesel Oil. Specific details may vary depending on which type of boilers are fitted, existing equipment, and
the particular installations involved. In some cases, sections of the work scope may have to be completed with the cooperation
and assistance of the original equipment manufacturer.
Tank selection for the MDO supply to the boilers is dependent on the consumption anticipated by the boilers. Generally this
choice is for the Owner to make, with advice and guidance from Harris Pye (and Class) as required. Given the capacity
requirements of some vessels, this may involve changing a tank from HFO to MDO, involving changes to the fuel transfer,
drain and vent systems. Whilst the conversion of tanks is not covered, we can offer a service if required.
Due to the arrangement of the diesel oil tanks on board, it is not uncommon that an existing penetration or line can be used for
the system suction or pressure return. This allows the new fuel system to be installed without the need to empty and prepare
the diesel tank for hot work.
The existing HFO system cannot be used for LSDO due to the difference in characteristics of LSDO to HFO. Specially designed
components such as pumps, filters, burner tips and flame eyes are required to ensure efficient, safe and reliable operation of the
boilers. To this end, our proposal is based on adding an LSDO fuel system parallel to the HFO system to the vessel allowing the
operator to change over fuel mediums safely and efficiently.
The LSDO pump supplied from Harris Pye will be guaranteed to operate down to 1cst and to a lubricity value of 520um
(HFRR) allowing it to run without the need for a cooler in the system. (Generally coolers are required to ensure the fuel
medium viscosity does not fall below the typical lower limit of 1.5cst for a pump). Removing the cooler from the system
increases the reliability and reduces the potential for cross contamination between the cooling and fuel systems.
Modification may be required to the existing boiler control system in order to incorporate specific safety parameters associated
with each of the fuel mediums as well as incorporation of the control and monitoring functions for the new LSDO fuel system
To reduce the impact of the modification without compromise to the efficiency of the plant, the individual fuel rails to the boiler will
become a common section of line whether on LSDO or HFO. This negates the requirement for duplication of existing isolation
and control components on the boiler. As LSDO tends to have a scouring effect on pipelines used with HFO, this is minimized by
ensuring that the common section is kept to as short a length as practicable on each vessel. Due to the common sect
ion of line,
the trace heating of the boiler fuel rails and lines after the 3-way valve will need to be isolated when LSDO is in use.
Change over between the fuels is effected by means of a manually operated 3 –way valve and designed to be carried out with the
boilers temporarily off line. Depending on which boiler / burner manufacturers are on board, it may also be necessary to change
the lance and tip for the applicable fuel to be used.
Generally we recommend that steam is retained as the atomizing medium for LSDO. If this is the case to be employed then we
would also strongly recommend that a parallel rather than concentric lance is fitted to the boiler to reduce the possibility of heat
transfer between the LSDO and atomizing steam throughout the lance.
A recirculation line may be fitted with a valve between the HFO line and the HFO return line to allow the HFO to be circulated
through the heaters whilst running on LSDO to facilitate transfer from LSDO back to HFO.
Prior to carrying out the modification it is recommended that a HAZOP for the conversion be carried out between the suppliers, the
operators and class (some societies stipulate this as a requirement) to ensure all possible safety aspects have been identified on
the specific operation and physical installation of each project. This will also highlight any potential issues with regards to both the
monitoring /control as well as the more vessel specific aspects such as pump and component location.
We recommend that the pump starter panels will be located locally to the pumps themselves and each pump supplied from
separate switchboards. The alarm signals for the system monitoring can be indicated on the pump starter panels. Remote
indication of the system condition may be then transferred via this panel to the appropriate control system. New supply
breakers will be required and need to be linked into the existing emergency stop functions on the vessel.
Generic LSDO System