Fuel supply system for auxiliary steam boiler

Fuel supply system for the boiler

During normal operation, fuel is supplied to the auxiliary boiler from the HFO settling tank but can also be taken from the HFO tank if required. Diesel fuel for boiler ignition flare and combustion when there is no steam for heating HFO fuel, supplied from DO daily service tank.
Fuel is supplied to the boiler burner unit by one of a pair of existing fuel supply pumps, while the other pump is assigned to standby mode. If HFO fuel is supplied from the pumps, it is directed to the fuel heater; if the DO is supplied, then it is routed through, the heater bypass. Pressure and temperature monitoring devices are also installed in the fuel supply system.
The system pressure is regulated and maintained up to 2.5 MPa by means of a reducing valve in the fuel return line from the mixing tank pipeline. The fuel from the mixing tank is returned to the suction manifold of the pump. The mixing tank can be discharged to HFO settling tanks or to a DO daily service tank, depending on the type of fuel used.
The fuel oil is heated to operating temperature by steam, the supply of which is regulated by a set temperature controller. When the boiler is in the ready state, the solenoid valve on the burner unit return line opens automatically to circulate the fuel back to the fuel mixing tank, maintaining the operating temperature of the fuel just before the burner. Fuel is supplied to the boiler burner nozzles via a fuel volume control valve which is controlled by the boiler vapor pressure.
The fuel mixing tank can be bypassed when fuel needs to be circulated through the boiler burner unit to heat the fuel or flush the fuel supply system. In this situation, the fuel from the burner unit is returned to the HFO settling tank or to the DO daily service tank, depending on the fuel used. The steam connection to the fuel line to the burner is used for automatic flushing of the burner before it is switched off.
The auxiliary boiler is equipped with an ignition pump, which is supplied with fuel from the DO's daily service tank. The ignition burner is used only to ignite the main burner. The boiler is designed for continuous operation using fuel oil to burn fuel. Marine diesel fuel is only required to flush the fuel system before performing maintenance or planning to shut down the auxiliary steam boiler for a longer period.