LPG Fuel Processing System
The Fuel Processing System includes the range of auxiliary systems to process LPG fuel in the service tank to the temperature, pressure and flow conditions required at the engine. The system could include the following. These components could be located adjacent to the fuel storage tank or in a separate compartment.
Low Pressure Fuel Transfer pumps – Pumps located adjacent to the deck mounted service tank, to transfer LPG fuel to the fuel processing system.
High Pressure Pumps – Required LPG supply pressure at engine is around 70 bar. High pressure fuel supply pumps take suction from the service tank and compresses it to the required pressure.
LPG Fuel Heater/Cooling Units – Heat Exchanger units for keeping the pressurised LPG at the required temperature.
Fuel Filtering units - Fuel filters are provided to remove any possible contaminants that could have entered the fuel.
Fuel Supply and Return System
The fuel supply and return system to the engine would involve the following.
Master Gas fuel valve– The master fuel valve forms an integral part of the fuel supply system to the engine room. Subject valve, integrated to the safety system, would control the fuel supply to the engine. It could be located within the fuel processing room. Engine makers would specify the distance between the engine and the subject valve.
Double Walled Piping /Ventilated Duct– The fuel supply lines located downstream of the master fuel valve, should be provided with double walled piping with ventilated annular space. This along with the gas detection would detect any leakage and direct these to outside of the engine room.
Supply & Return Fuel Valve Trains – A Fuel valve train or Gas Valve Unit, similar to that in LNG fuelled installations is required to be installed prior to the engine. Essentially a double-block and bleed arrangement, the fuel valve train would have provision for supply line venting, connection from Nitrogen system for purging, fuel fine filtering and ventilation. It safely isolates the engine during shutdown, maintenance etc. A similar unit is also required to be installed in the fuel return line to control the fuel return system (MAN Energy Solutions, n.d.).
Knock-out drums – These are small units to which the relief valves from the fuel supply and return lines are led to. As the relief valve will be venting liquid LPG at high pressure, it will be a safety risk to lead these directly to the vent mast and venting to the open. The knockout drums will provide a buffer point to collect the released liquid thus preventing any liquid from being released to the atmosphere.
Nitrogen System – Nitrogen is required for purging of LPG from the fuel lines. Complete purging of the fuel supply and return lines is required upon stopping the fuel supply to the engines. The system must be able to deliver Nitrogen at a certain flow at a pressure higher than then fuel service tank pressure to carry out the purging effectively. A Nitrogen generator unit together with a buffer vessel would be required to be installed onboard.
Water Glycol System – Water Glycol system is required to heat/cool the LPG fuel to be supplied to the engine at the required temperature. It would involve series of heaters and cooling units, supply and circulation pumps, buffer tanks etc. Steam supply system from the vessel’s aux. boiler etc. could also be involved with the system.
Ventilation – Provision for ventilation should be provided specifically for the fuel processing room, double walled piping etc.
Gas Detection – Provision for detection of any gas leakage would be required. VLGCs are already provided with provision for gas detection at various locations, additional detection points at various locations can be integrated to the system.
Fire Detection – In line with the above for gas detection, additional fire detection measures will be required.
Control Systems – Control systems integrating various alarms, parameters like pressure/temperature/level, gas/fire detection systems would also form part of the key installations.
Double Walled Piping /Ventilated Duct– The fuel supply lines located downstream of the master fuel valve, should be provided with double walled piping with ventilated annular space. This along with the gas detection would detect any leakage and direct these to outside of the engine room.
Supply & Return Fuel Valve Trains – A Fuel valve train or Gas Valve Unit, similar to that in LNG fuelled installations is required to be installed prior to the engine. Essentially a double-block and bleed arrangement, the fuel valve train would have provision for supply line venting, connection from Nitrogen system for purging, fuel fine filtering and ventilation. It safely isolates the engine during shutdown, maintenance etc. A similar unit is also required to be installed in the fuel return line to control the fuel return system (MAN Energy Solutions, n.d.).
Knock-out drums – These are small units to which the relief valves from the fuel supply and return lines are led to. As the relief valve will be venting liquid LPG at high pressure, it will be a safety risk to lead these directly to the vent mast and venting to the open. The knockout drums will provide a buffer point to collect the released liquid thus preventing any liquid from being released to the atmosphere.
Other Systems
LPG fuel system would require auxiliary system for the provision of heating, cooling, ventilation arrangements, nitrogen system for purging etc. |
| Nitrogen generator (Source:https://upload.wikimedia.org/wikipedia/commons/4/48/PSA_nitrogen_generator.jpg) |
Water Glycol System – Water Glycol system is required to heat/cool the LPG fuel to be supplied to the engine at the required temperature. It would involve series of heaters and cooling units, supply and circulation pumps, buffer tanks etc. Steam supply system from the vessel’s aux. boiler etc. could also be involved with the system.
Ventilation – Provision for ventilation should be provided specifically for the fuel processing room, double walled piping etc.
Gas Detection – Provision for detection of any gas leakage would be required. VLGCs are already provided with provision for gas detection at various locations, additional detection points at various locations can be integrated to the system.
Fire Detection – In line with the above for gas detection, additional fire detection measures will be required.
Control Systems – Control systems integrating various alarms, parameters like pressure/temperature/level, gas/fire detection systems would also form part of the key installations.
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