Fuel oil is stored on board in four fuel oil storage tanks, and then (when required) transferred to a fuel oil settling tank by a fuel oil transfer pump. After fuel oil has been transferred to the settling tank, any water or other sediment is drained off, using the self-closing test cock. Fuel oil is supplied directly to the boilers from the fuel oil settling tank.
Diesel oil can be supplied to the boilers from the diesel oil service tank when starting from cold.
A temperature controller maintains the steam supply to the F.O. heater. All the fuel oil piping is trace heated by small bore steam pipes. These are laid adjacent to the fuel oil pipe and encased in the same insulation.
Fuel oil from the fuel oil settling tank is supplied to one of two fuel oil pumps.
The second pump will be on automatic standby, and will start in the event of a discharge pressure drop or a voltage failure of the running pump. The fuel oil pumps take suction from the settling tank via a strainer. A pressure control valve, with its sensing point on the heater discharge, maintains the pump discharge pressure by recirculating oil from the pump discharge back to the air separator/return pipe. The oil in the return pipe returns to the pump suction. The vent from the air separator returns to the H.F.O. settling tank.
The fuel oil pumps discharge through one fuel oil heater, where the oil is heated to the required temperature.
The oil is fed to the boiler via a pressure-control valve, controlled by the boiler steam pressure. When the boiler is in a standby condition, a solenoid valve on the return line automatically opens to circulate fuel back to the return pipe, keeping the fuel oil at working temperature immediately before the burner. On the recirculating line is a change over cock, where the fuel can be diverted from returning to the return pipe to either the H.F.O. settling tank or D.O. service tank. This change over cock would normally be used for flushing fuel oil back to the H.F.O. tank when changing from D.O. to H.F.O. or vice versa.
The boiler has a pilot burner pump, which takes suction from the D.O. service tank via the pump suction filter.
A steam connection is fitted to the F.O. line to the burner after the double shut off solenoid valves and is used for automatic purging of the burner prior to shut down.
Procedure for Operating the Auxiliary Boiler Fuel Oil Service System
a) Ensure that the filters are clean.
b) Ensure that all instrumentation valves are open.
The following procedure illustrates starting from cold with the system charged with diesel oil and in a shut down condition.
Set up the valves as in the following table:
Position Description Valve
Open Settling Tank Suction Quick Closing Valve RR7
Open D.O./H.F.O. Change Over Cock RR63
Open Diesel Oil Service Tank Suction
Quick Closing Valve RR9
Open Suction Valve from Return Pipe RR71
Open Both F.O. Service Pump Suction Valves
Open Both F.O. Service Pump Discharge Valves
Closed F.O. Heater Inlet Valve RR39
Closed F.O. Heater Outlet Valve RR40
Open F.O. Heater Bypass Valve RR38
Open Inlet Valve to Pressure Control Valve RR7
Open Outlet Valve from Pressure Control Valve RR35
Closed Boiler Pressure Control Valve Bypass Valve RR36
Open Inlet Valve to Boiler Burner Before
Solenoid Valves RR47
Open Boiler Recirculating Valve RR67
Open Boiler Inlet Valve to Pressure Control Valve RR57
Open Boiler Outlet Valve from Pressure
Control Valve RR49
Set to Return Pipe Return Line Change Over Cock RR64
Open Pilot Burner Pump Suction Valve RR41
Open Pilot Burner Pump Discharge Valve RR42
Procedure to Start Up the Boiler F.O. Service System and Change Over to H.F.O.
a) Start one boiler fuel oil pump.
b) Flash up the boiler on D.O. using atomising air. When steam is available:
c) Supply steam heating to HFO settling tank.
d) Open supply trace heating to the fuel oil service system pipelines.
WARNING
Trace heating should not be applied to sections of pipeline isolated by closed valves on the F.O. side, as damage, such as blown flange joints, could occur due the expansion of the contents.
When enough pressure is available: e) Stop firing the boiler.
f) Open the F.O. heater inlet and outlet valves. Shut the bypass valve.
g) Manually start supplying steam to the F.O. heater.
h) Operate suction change over cock RR63 to take suction from the H.F.O. settling tank.
i) Operate the return change over cock RR64 to direct the returns to the H.F.O. settling tank.
D.O. will now be expelled to the H.F.O. settling tank, at the same time drawing in H.F.O. from the settling tank.
j) Continually raise the F.O. temperature manually.
k) Change the operation of the heater steam control valve to auto by fully opening the steam inlet valve.
l) When the D.O. has been expelled, operate the return change over cock to direct the return oil to the return pipe.
H.F.O. is now circulating through the system.
The boiler is now ready for firing on H.F.O. using steam atomising.
The boiler is designed to operate and remain on standby using H.F.O. Change over to D.O. is only necessary when maintenance is required and for long periods of shut down, such as refit.
m) After the boiler is firing on H.F.O. put the other F.O. pump on auto start.
(Note ! Change over to H.F.O. can take place while still firing the boiler. The recirculating line would remain lined up to the air separator and the fuel would change over by normal usage. However, this could lead to unstable flame conditions due to incorrect temperature settings at the heater.)
WARNING
Exhaust to Funnel
Flue Gas Fan
Flue Gas Damper XA Combustion Chamber PI PI PI QU2
Illustration 2.6.4a Incinerator F.O. Service System
Pilot Diesel Oil Supply Pump 80 litre/hour QU1 D.O. Tank For Incinerator To F.O. Sludge tank Sludge Tank From F.O. Transfer Pump Sludge Supply Pump M From Steam System in E/R QU6 QU3
QU5 QU4 QU8
QU7
Key Sludge D.O. System Steam