Auxiliary boiler on board ship

1. AUXILIARY BOILER
• AUXILIARY BOILER
AUTOMATIC COMBUSTION
CONTROL

5. Boiler Arrangement
• The steam demand of the plant, in port, is served by the oil fired
auxiliary boilers.
• At sea, steam demand is met by circulating boiler water from one
of the auxiliary boilers through the exhaust gas boiler by one of
the boiler water circulating pumps.
• The auxiliary boiler acts as a receiver for the steam generated by
the exhaust gas boiler
• The exhaust gas boiler is arranged in the main engine exhaust gas
uptake to take waste heat from the main engine exhaust.
• The auxiliary boiler may be required to be fired at sea in the
following cases when there will be insufficient waste heat to
generate the required steam :
✔ In low ambient temperature areas,
✔ During reduced power operation of the main engine, such as
during manoeuvring or slow steaming on passage.

6. Services provided by Boilers
• For main engine propulsion/turbines (in case of steam ships)
• For power generation (to run steam turbo generators)
• For running auxiliaries (in case of steam ships)
• For soot blowing and for the steam atomized burners.
• For fresh water generation (Evaporators)
• For fire major fighting (steam drenching)
• For heating duties (ME fuel oil heater, Galley supply, Purifier, Calorifier,Galley,
Accommodation heating, Sea chests tracer lines for pipeline heating)
• For cargo heating
• For fuel treatment plant tank coil heating.
• For deck machineries
• For running Cargo pump turbines
• For operating bilge, stripping and other steam driven pumps.
• For tank washing in tanker ships and general cleaning.
• For using as a steam ejector media for ejector pumps and vacuum devices
• For Driving steam driven deck machineries like winches etc.,

7. FLAME Eye
• The selenium photocell detectors are designed for use with
burner controls, for the supervision of oil flames.
• They are used especially in connection with burner controls for
the control and supervision of large-capacity burners.
• They are designed for use with the following types of burner
controls: LAL..., LAE1..., and LAE10...

8. PRESSURE USED
• The normal working pressure of boilers used is as
below:
▪ 6-15 bar --Medium pressure ie & 7 BAR –called
Composit Boiler, generally fitted on Bulk Carriers
• 17-30 bar - Generally 18 Bar For Tanker Vessels
Medium pressure

9. Parts of Burner
• 1.Aux Boiler Control panel : PLC controlled, Selection of HO/DO Heater,
Operation and Alarm Indicators , Emergency Stop Switch.
• 2.Steam pressure switch for Auto start and auto Off. Auto start at 4 kg / cm
and Auto Off at 6.5 Kg/cm. Low flame & high flame change over by solenoid
valves
• 3.Fuel Oil pump.
• 4.Fuel Oil Heater with Thermostats, For auto cut in at 85 deg C,Auto off at
110 – 120 and safety cut off at 140. High temperature result in Cavitation
• 5.DO Solenoid valve. : for pilot burner
• 6.Main Fuel Oil Solenoid valve. For main burner
• 7.Pilot burner.
• 8.Main burner motor and gear pump
• 9.Flame Detector ( Eye and relays.)
• 10.Forced Draught fan with over load facility.
• 11.Damper solenoid valve for air flap operation
• 12.Ignition transformer. Secondary voltage10000 volts
• 13.Ignition Electrodes.
• 14.Controller for automation

10. Boiler Combustion – Basic Circuit

11. Boiler Combustion – Basic Circuit
• The four cycles in the
lighting-up sequence for the
boiler burner are:
✔ purging cycle,
✔ ignition cycle and
✔ main burner cycle
✔ Post purge cycle
• The boiler can be started:
✔ either manually or
✔ by the steam pressure switch in
the automatic operation mode
• The boiler cuts-in / cuts-out,
depending upon the pressure
setting and its differential.

12. Boiler Combustion – Purge
• If all the safety interlocks
are in place, then the
purging cycle commences,
starting the forced draft
(FD) fan.
• The quantity of combustion
air supplied from the FD
fan to the boiler is adjusted
by the position of the
damper.

13. Boiler Combustion – Purge
• The duration of the purging
cycle is generally 120 to 150
seconds
• The air damper opens from
minimum to maximum
position so that maximum air
flows through the boiler and
removes any flue gas or any
other after-burning material
(gases) from the combustion
chamber.

14. Boiler Combustion – Ignition Cycle
• On completion of the purging
cycle, the delay timer
completes the supply for the
ignition transformer and the
operation of the diesel oil
valve for the pilot burner;
• The ignition transformer’s
secondary provides a
high-voltage of around 6 kV
to 10 kV to supply the pilot
burner’s electrodes;

15. Boiler Combustion – Ignition Cycle
• The electrodes produce a
spark and with the flow of
diesel oil in the pilot burner,
the flame is established.
• The timer in the circuit will
disconnect this power supply,
thus extinguishing the spark
after a set time.
• A photocell may be used to
detect the pilot burner’s
flame that facilitates
operation of the main
burner’s three-way solenoid
valve.

16. Boiler Combustion – Ignition Cycle
• This valve changes over fuel oil
from its recirculation mode to
supply fuel oil to the boiler;
starting the main burner cycle.
• If the main burner flame is
established then the boiler
continues, otherwise the flame
detector activates the flame
failure relay and shuts down
the 3-way safety solenoid valve
thus cutting off the fuel oil
supply to the boiler.

17. Combustion Control
• Boiler output is controlled by sensing the boiler pressure as
well as the steam flow.
• Increase in steam demand reduces the boiler pressure, which
is restored by increasing the fuel and air flow to the boiler
• While increasing power, air flow leads the fuel flow to avoid
black smoke
• While decreasing power fuel flow is reduced before reducing
air flow

18. Boiler Combustion – Basic Circuit

19. • In Emergency mode – PLC is OFF
• In Auto mode - PLC is active
• MASTER/SLAVE OPERATION IN AUTO MODE
• Boiler Combustion & Feed Water Control, all
interlocks/alarms /safeties are controlled by
PLC

20. 17.Drum Water High Level. AL
18. Drum Water Low Level AL
19 Drum Water Low Low Trip.
20 FO Heater : 8 KW
21 Too Low Temperature ( TS)
22 High Temperature Alarm (TS)

21. Typical Boiler Combustion Control System

22. BOILER TRIPS AND ALARMS
• Boiler trips are actions that will occur under undesired
situation of boiler. Boiler alarms are audible and visual
signal about a problem or a condition.
• For example, when the boiler is in the low water level
condition, alarm will occur. But ,when the boiler is in
the low low water level condition, trip and alarm will
occur together.

23. BOILER ALARM & TRIP FUNCTION
Monitored Parameter ALARM ACTION
1.Boiler Drum Water Level (High) ALARM --
2.Boiler Drum Water Level (High High) ALARM TRIP
3.Boiler Drum Water Level (Low) ALARM --
4. Boiler Drum Water Level (Low Low) ALARM TRIP
5. Fuel Oil p/pPressure ( Low) ALARM TRIP
6. Fuel Oil Temperature (Low) ALARM TRIP
7. Steam Pressure (Low) ALARM --
8. Steam Pressure ( High) ALARM TRIP
9.Flame Failure ALARM TRIP
10.Ignition Failure ALARM Trip
11 FD fan fail Alarm TRIP
12.Emergency Stop ALARM Trip
13.Boiler water contamination with oil ALARM --
14. Control power supply fail ALARM Trip

24. BOILER ALARMS & TRIPS

25. Reasons for Boiler not Firing
• 1. low Fuel Oil Pressure.
• 2. Low Fuel Oil Temperature.
• 3. Burner Nozzle choked.
• 4. In sufficient air supply.
• 5. Boiler Emergency stop initiated.
• 6. Water in fuel.
• 7. Ignition Electrodes faulty.
• 8. Pilot burner not working.
• 9. Flame sensor dirty.

26. MAINTENANCE ON OIL BURNING
EQUIPMENT
• Oil Burning Equipment consists of :-
• 1. Main Burner.
• 2. Pilot Burner
• 3. Ignitor
• Following maintenance be carried out :-
• 1. Maintain desired temperature of Heavy fuel oil.
• 2. Maintenance of filters.
• 3. Clean the ignition electrodes .
• 4. Adjust the electrode ‘s gap & check its connectors.Ensure
producing spark.
• 5. Clean Flame Eye and test.
• 6. Test the alarms & trips.

27. Describe how to ignite the boiler in MANUAL mode?
Describe how to manual ignite the boiler?
• First check the boiler pressure and temperature are in normal condition
under heating from the economizer.
• Circulate the boiler fuel through the heater to ensure suitable temperature
and viscosity is reached. Check for the pressure of the circulated fuel.
• Then switch the control of the boiler into manual. Then start the forced
draught fan and pass the air through the furnace for several 5-15 minutes
to purge it of any exhaust gas or oil vapors.
• Then manually adjust the air input into the lighting up mode, open the fuel
valve, press the ignition button, then press the fuel injection button and
then leave the ignition power of the boiler.
• Then adjust control to normal service so that the air input and other
parameter could be put into normal service.
• Check to see if the flame is steady.

28. What are the reasons caused low low water level?
• Low low water level may be caused by many
reasons:
• Blow down valve is accidentally opened
• Feed water system- feed tank is empty, feed pump
failure, automation control failure or other isolation
from the feed system
• Serious leakage on the water contacting area

29. • What are the different between purifier &
clarifier?
• A centrifuge is arranged to separate 2 liquids
is called purifier, while a centrifuge is arranged
to separate impurities and small amounts of
water from oil is called clarifier.
•

30. Electrically operated High/Low Level Alarms & cutouts.
• The system uses a float arrangement in the float chamber which relates to water level
in the boiler drum.
• The float moves the magnet up and down in response to any level change.
• Four microswitches are fitted on the out sideof the float chamber.
• When the internal magnets comes level with one of the external magnet, then the
microswitches are operated.
• The position of the four magnetic microswithes are so arranged , so as to indicate the
predetermined level.
• - High high level trip switch
• - High level alarm switch.
• - Low level alarm switch.
• - Low low level trip switch.
• The levels such as Low low level trip switch & High high level trip switch operates the
fuel oil shut off solenoid valve /actuator to shut off the fuel line . This would shut
down the combustion of the boiler prevent any damage to the boiler.
• Other two switches are positioned ie high water level & low water levels, operate the
alarm for a predetermined levels.
• Secondly two microswitches are fixed on the isolating valves, and ensure that they
are fully open when device is operated.

31. Electrically operated High/Low Level Alarms & cutouts

32. AUX –BOILER FAIL TO START
• 1) Fuel inlet valve to the burner is in close position:
• The fuel line for boiler’s burner consists of several valves located at fuel
tank, pumps suction, discharge valve, or valve before the boiler burner. Any
of these can be in closed position resulting in starvation of fuel.
2) Line filter at the inlet of the fuel line for burner is choked:
• If the system runs in heavy oil then there are chances of filters in the line
getting choke. To avoid this, boiler system are normally built for changeover
from diesel to heavy oil during starting and heavy to diesel during stopping.
This keeps the filter and the fuel line clean.
3) Boiler fuel supply pump is not running:There are two main reasons for
fuel pump not running. Normally when the pumps are in pairs, the change
over auto system is kept in manual position, and if the operating pump trips,
the stand by pump will not start automatically. Another reason is tripping of
pump due to short circuit in the system etc.
• 4) Solenoid valve in the fuel supply line is malfunctioning
• Nowadays most of the system adopts advance automation, but their can be a
possibility wherein the solenoid in the fuel supply line is malfunctioning and
not opening.
•

33. • 5) Air or fuel ratio setting is not proper
• For proper and efficient combustion, air fuel ratio is very
important, if the supply of air is excess then there will be excess
of smoke, and if it exceeds more than normal level the
combustion will burn off causing flame failure.
• 6) Forced draft fan flaps malfunctioning
• For removing excess gases trapped inside the combustion
chamber forced draft fan (FDF) are used for pre purging and
post purging operation and are connected with a timer to shut
the fan flaps. If the flaps are malfunctioning then continuous
forced air will go inside the chamber, preventing the burner to
produce flame causing flame failure of the boiler
•

34. • 7) Any contactor switch inside Control panel is malfunctioning
• Boiler control panel consist of several contactors and PLC
cards. Even one contactor malfunctioning may result in trouble
for boiler starting.
• 8) Trip not reset
• If any previous trips like low water level, flame failure,
emergency stop etc. has not been reset than boiler will not
start.
• 9) Main Burner atomiser is clogged
• Main burners consist of atomizer for efficient burning of fuel. If
the atomizer is clogged by sludge and fuel deposits then
burner may not produce flame and trip the boiler..
•

35. • 10) Pilot Burner nozzle is choked :
• A Pilot burner nozzle is very small and can be blocked by carbon
deposits and sludge resulting in flame failure. Some pilot burner
consists of small filter which can be clogged after continuous
operation resulting in flame failure because of carbon
accumulation.
• 11) Electrodes are not generating spark
• Initial spark for generating a flame is produced by electrode
which may be due to carbon deposits on them or fault in the
circuit of electrodes etc.
• 12) Flame eye is malfunctioning:
• A Flame eye is a photocell operated flame sensor fitted directly
on the refractory to detect weather the burner is firing or not. If
the flame eye unit is malfunctioning, then it will give a trip signal
even before the burner starts firing
•

36. • Explain how water treatment is provided and why is it necessary
• Purity of Boiler Water
• Most ‘pure’ water will contain some dissolved salts which come out of solution on boiling. These salts then
adhere to the heating surfaces as a scale and reduce heat transfer, which can result in local overheating
and failure of the tubes. Other salts remain solution and may produce acids which will attack the metal
of the boiler. An excess of alkaline salts in a boiler, together with the effects of operating stresses, will
produce a condition known as ‘caustic cracking’. This is actual cracking of the metal which may lead to
serious failure. The presence of dissolved oxygen and carbon dioxide in a boiler feed water can cause
considerable corrosion of the boiler and feed systems. When boiler water is contaminated by suspended
matter, an excess of salts or oil, then ’foaming’ may occur. This is a foam or froth which collects on the
water surface in the boiler drum. Foaming leads to ‘priming’ which is the carry over of water with the
steam leaving the boiler drum. Any water present in the steam entering a turbine will do considerable
damage. It has been estimated that a 3mm thickness scale increases the fuel consumption by 16% and
6mm by 50%. This proves that the effect is not a straight-line gradient but is exponential. Salts whose
solubility decreases with increase in temperature are those that form scale upon heating surfaces . Salts
whose solubility increases with increase in temperature do not normally form scale upon
heatingsurfaces.Common impurities found in the boiler water are chlorides, sulphates and bicarbonates of
calcium, magnesium and, to some extent sulphur. These dissolved salts in water make up what is called
the ‘hardness’ of the water. Calcium and magnesium salts are the main causes of hardness. The
bicarbonates of calcium and
magnesium are decomposed by heat and come out of solution as scale-forming carbonates. These alkaline
salts are known as temporary hardness. The chlorides, sulphates and nitrates are not decomposed by
boiling and are known as permanent

37. QUESTION & ANSWERS
• Question: Fluctuating boiler water level
• The feed water control valve is fully open and the water levels fluctuate at normalboiler load.
• Answer:
• Check if:
• The control valve really is fully open by means of the hand-maneuver device.
• All stop valves in the line are fully open.
• The suction filter to the feed water pump is satisfactory clean.
• The feed water pump discharge pressure is sufficient.
• The feed water control valve
• pressure drop is normal. (>=2 bar or >=30 psi)
• Question: The burner starts and stops very often
• The burner starts and stops very often, sometimes every second minute. An alarming temperature-raise has been observed in
the combustion air fans electric motor.
• Answer:
• Increasing the burners turn down ratio would be a nice solution, but it'snot always possibly.
• Run the burner in minimum load, i.e., prevent the burner from increasing theload just after the burner start.
• Install a five to ten minutes' time-delay in the fan-motor stop function. Thenthe fan will continue to run during the shortest
burner stops and thecombustion air fan motor will get a little res
• t from the start current.
• Question: Most likely source of errors
• In which part of a boiler control system is it most likely to get a failure.
• Answer:
• When you have problem with a boiler control system you should keep inmind that most faults occur outside the control cubicle,
but on the other hand, yourproblem might not be among the most common

38. • Q. If the combustion control system of an automatically fired auxiliary boiler fails to
sustain burner ignition after a normal shutdown, you should check for a/an
• A. faulty photocell detector
• B. low steam pressure
• C. high voltage on the ignition electrode
• D. open air damper
• Answer-A
• 6. With reference to the data logger for a refrigerate system. Which of the
parameters
• should be noted?
• A. Sea water temp, pressure
• B. Condenser temp
• C. Refrigerant leakage
• D. Evaporator temp.
• Answer-A, B and D

39. • What should you do if there is boiler room fire
• Break the alarm. Stop the machine inside the
boiler room, cut off fuel supply. If it is suitable,
portable fire extinguisher can be used. If fire
cannot be put off, turn on the local protection
system (water mist). If fire is out of control,
tell C/E, and start the procedure of emitting
CO2.

40. •SALINOMETER FOR
THE BOILER

41. SALINOMETER
Pure water can be converted to steam at a convenient temperature. it is an ideal
medium for generating power or conducting heat. Water evaporating in the boiler
causes impurities to concentrate in the water tubes.
To prevent scale formation in the water sides of boilers,which causes corrosion in
the tubes. It is prevented by applying treatment by chemicals & dissolving of
suspended salts. Such deposits will have a negative effect on heat transfer .
• PRINCIPLE:
• Water becomes more conductive of an electrical charge as its salinity increases.
• To check salinity in the water, an electrode unit is inserted, which gives current
proportional to the conductance .
• This current is converted to voltage.
• This voltage is applied to the comparator which compares with the reference
voltage. If salinity increases, the conductance increases, the current increases. Thus
converted voltage also increases.
• If the salinity level exceeds the present level, the red warning lamp starts blinking.
• Reference setting of the salinity meter is set at 10 PPM. The alarm level is adjusted
to 19.9 ppm

42. OIL CONTAMINATION
• General
• An oil-fired steam boiler onboard a ship is fed by returned, condensed
• steam to replace the boiled off water as well as with stored make-upwater to
replace steam lost by consumption, leakage or blow-down.
• The feedwater is normally treated mechanically and chemically in order to suit
the steaming process in the boiler and to ensure good transfer of the heat input
from the combustion process to the water.
• Oil as a contaminator
• The most dangerous water contamination, however, is heavy fuel oil entering the
steam or condensate from leaking tank coils or heat exchangers. This kind of
leakage in coil flanges or broken gaskets in plate heat exchangers frequently
• occurs. If the problem is not observed in time, the boiler could be completely
destroyed due to overheating of the furnace because of reduced water flow and
minimised heat transfer/cooling of the boiler tubes.
• The isolating effect of oil deposits reduces heat transfer
• If the waterside of a furnace wall is fouled with e.g. carbonate, silica, or oil film,
the temperature of the furnace wall increases due to added thermal resistance.

43. OIL CONTAMINATION
• The cascade tank can easily be equipped with a continually measuring oil
detecting device which monitors if oil is present in the condensate. By locating the
sensor in the cascade tank, it can be assured that oil is detected before it enters
the feedwater section, which means that no part of the feedwater is being
contaminated.
• Boiler feed filter tank have inspection chamber or devided area in tank to
accumulate oil when oil contamination in boiler water.
When incoming oil contaminated water in inspection chamber the feed water only
go out to feed filter tank and oil with be accumulate in inspection chamber until
drainage.
When the normal conditions, the end part of electeode will be in water level
always.
But the water contaminate oil that the oil is accumulate top level in inspection
chamber the electrode will be in oil level instead of water level the oil detector
will activate alarm.
After drain oil in inspection chamber the oil detector return to normal condition.

44. ULTRSONIC TYPE OIL/WATER DETECTOR
• The ultrasonic sensor contains two piezoelectric crystals. A high
frequency signal (3.7 MHz) generated by the control unit is
transmitted to one piezoelectric crystal by coaxial cable. This
crystal converts the electrical signal into an ultrasonic oscillation.
• The sensor design allows the ultrasonic oscillation to pass from
the transmitter crystal to the receiver piezoelectric crystal. The
sensors of type 402 are “gap” type sensors, where the two
piezoelectric crystals are separated by a gap. When the gap is in
liquid the signal reaches the receiver, because of the low
ultrasonic attenuation of the liquid. When the gap is filled with
air, no ultrasonic signal can pass from transmitter to receiver.

45. Capacitive oil detector
Type : Capacitive oil detector
Output : Relay contact(SPDT)
Operating pressure : 10bar
Protection : IP66
Power supply : AC 110/220V
Max. Temp. : 100¡É
Conn. size : G 1-1/2"

46. • Both capacitance and conductance are
changed between the electrode and the wall
of tank when the material contacts the
electrode inserted in the tank.
And this impedance variation is taken out as
electric signal (ON-OFF).
Thus the level or interface is detected.

47. CAPACITANCE TYPE TEVEL SWITCH

48. ULTRASONIC TYPE OIL/WATER INTERFACE DETECTOR UNIT
Ultrasonic attenuation is the reduction in energy of the beam as it is transmitted through
the liquid.
Viscous liquids, emulsions and liquids with entrained solids generally have a higher
ultrasonic attenuation than low viscosity clear liquids such as water.
When the attenuation difference is sufficient, the amplifier gain can be adjusted so that
the ultrasound beam passes through the less attenuative liquid but is stopped by the
more attenuative liquid.
The output relay can than be set to monitor which liquid is in the gap.
The ultrasonic attenuation of a liquid depends on many factors, the main ones being the
complexity of the module, followed by the viscosity, assuming there no aeration.

49. ULTRASONIC TYPE OIL/WATER INTERFACE DETECTOR
UNIT
• Oil / Water Interface Detector
• An electrical instrument for detecting an interface between oil and
water in a tank .
• PRINCIPLE :Interface detection between two dissimilar liquids
• Viscous liquids, emulsions and liquids containing solid particles have
a greater ultrasonic attenuation than clear liquids. This technique is
used to detect which liquid is present at the sensor, for example for
the separation of oil and water. For this duty Mobrey 402 sensors
are used, operating at 3.7 MHz to produce the maximum ultrasonic
difference between two liquids monitored.
• The gain is adjusted so that the sensor oscillates only in the liquid
with the lower ultrasonic attenuation: this is usually the clearer
liquid . Note that the signal when oil is present in the sensor gap will
be the same as that for air in the gap, and that emulsion layers give
a very high attenuation

50. ULTRASONIC TYPE OIL/WATER INTERFACE DETECTOR
UNIT

51. CONSTRUCTION OF DETECTOR
Material : Stainless steel
Conn.size : 3/4" BSPT Thread
Design or Duty : Chemical interface
Liquid Type : Clean, viscous with solides
Temperature : -70¡É to +150¡É
Max. Pressure : 105bar
Standard frequency : 3.7 M §Ô
Enclose : IP 65
Cable Length : 3meters

52. CAPACITIVE TYPE OIL DETECTOR

53. Oil / Water Interface Detector

54. ULTRASONIC TYPE OIL/WATER INTERFACE DETECTOR
• The UID system with a separator. In this technique the ultrasonic transducer is
mounted on the outside of the bottom wall of an oil separator. It contacts the
separator directly, and transmits and receives ultrasonic pulses along the
vertical axis.
• The measurement is based on pulse echo and the levels are estimated by
combining the measured time-of-flight of echoes from the fluid interfaces with
the speed of sound in the propagation media. The advantages of this system
are that it is non-intrusive and easy to install on existing and new separators,
and no calibration is needed. This system is in commercial use by Esso and
Statoil.
• The disadvantage of this system is that it has difficulty in monitoring emulsion
and foam also the presence of air bubbles in the liquid attenuates/scatters the
ultrasound waves. It becomes a big problem when a significant amount of air is
present in the liquid. The presence of sand also causes problems in the
operation of UID.

55. ULTRASONIC TYPE OIL/WATER INTERFACE DETECTOR

56. Externally mounted displacers

57. Externally mounted displacers
• Externally mounted displacers
• Externally mounted displacers are commonly used for the interface level
measurement . This technique makes use of the difference in densities
between two types of liquid being measured, e.g. Oil and water. A
displacer used for oil/water interface measurement must have a density
between the densities of oil and water.
• As the interface moves up and down in a separator, the position of
displacer is mechanically transferred to a read-out system . Using two
different displacers with different densities, both the oil/gas and water/oil
interfaces can be measured. However, the presence of an emulsion layer
will disturb the measurement and also the foam thickness cannot be
measured by this technique.

59. OIL WATER INTERFACE DETECTOR

61. Question: The burner starts and stops very often
• Question: The burner starts and stops very often
The burner starts and stops very often, sometimes every second minute. An alarming
temperature-raise has been observed in the combustion air fans electric motor.
• Answer:
• Run the burner in minimum load, i.e., prevent the burner from increasing the load just
after the burner start.
• Install a five to ten minutes' time-delay in the fan-motor stop function. Then the fan
will continue to run during the shortest burner stops and the combustion air fan motor
will get a little rest from the start current.
• Increase the "burner stop" set point as much as possible in relation to other
switchpoints or setpoints in the controls
• Raise the "burner start" set point abt. 0.2-0.3 bar above(!) the control set point.
• The effect will be that the burner stops all the time only in minimum load (load is
reduced when it comes above the control set point). When the burner is required to
start again, the increased starting pressure set point works out very nicely because it
compensates the drop in boiler pressure during purging and lighting up time.
When the burner finally ignites, the actual boiler pressure is only very slightly below
the set point. Modern PID controllers notice this fact and keep the burners in low load
until the "stop" setpoint is reached again. If the "burner start" set point is kept in the
traditional way (some 0.5 bar below control set point), the PID controller notices a high

62. • The effect will be that the burner stops all the time only in minimum load (load is
reduced when it comes above the control set point). When the burner is required
to start again, the increased starting pressure set point works out very nicely
because it compensates the drop in boiler pressure during purging and lighting up
time.
When the burner finally ignites, the actual boiler pressure is only very slightly
below the set point. Modern PID controllers notice this fact and keep the burners
in low load until the "stop" setpoint is reached again. If the "burner start" set point
is kept in the traditional way (some 0.5 bar below control set point), the PID
controller notices a high deviation between set point and actual value and thus
increases the burner load unnecessarily. The burner will fire up and will not be
able to adjust itself to the actual (low) steam demand. This results in overfiring and
very soon the "burner stop" set point will be reached.
Resetting the parameters to the increased "burner start" and "burner stop" values
will reduce the number of starts and stops considerably.

63. BOILER FO SYSTEM

64. FO flow diagram
• Fuel Oil flow diagram for two oil-fired auxiliary marine steam boilers
• This system is designed to supply two oil fired steam boilers with Heavy Fuel
Oil for normal operation and Diesel Oil for the start up procedure when no
steam is available for fuel oil heating.
• A.Fuel Oil header
The Fuel Oil header should be a standing up relatively large pipe with a
deaeration pipe to a higher level than the fuel oil service tanks; some times
it's connected to the top of the diesel oil service tank.
• B.Fuel Oil filters
Clean the Fuel Oil filter frequently. If the filters are clogged the fuel oil might
vaporize in the pump and cause damage. A differential pressure meter
across the filter would be a good help to have the filters cleaned in time.
• C.Shut off valves
Shut off valves for cleaning of the filters. The valves should normally be
open.
• D.Fuel Oil pumps

65. • D.Fuel Oil pumps
Each pump should have sufficient capacity to run both boilers
on maximum load. Normally one pump is running and the
other is standing-by. The stand-by pump should start upon
low pressure in the process line rather than being started
upon a pump motor failure.
• E.Shut off non return valves
These valves have to be non-return type, or a shut off valve
and a non-return valve. The valves should always be open on
both pumps, so the stand-by pump can start automatically.

66. • F.Fuel Oil heater
The fuel oil heater is a heat exchanger that must have a safety
relief valve.
Always install a safety relief valve if a fuel oil volume can be
shut up and heated.
• G.Burners
The burners must be capable of running on diesel oil as well
as heavy fuel oil.
• H.Make-up water pump
From softener unit.

67. • 1.Change over valve, Heavy Fuel Oil, HFO, to Diesel Oil, DO
The three-way valve ought to be provided with a limit switch
that breaks the electric circuit and shut off the fuel oil heating
valve, in the control loop 3 , avoiding the diesel oil from being
heated over its flashpoint.
• 2.Fuel oil pressure control
The pressure control loop adjusts the fuel oil pressure by
means of the pressure controller and the fuel oil return valve.
The pressure is measured after the fuel oil heater to get
accurate pressure to the burners. The return valve before the
fuel oil heater recycles cold fuel to protect the pumps from
overheating.

68. • 3.Heavy fuel oil temperature control
The temperature control loop adjusts the fuel oil temperature by
means of the temperature controller and the steam inlet control
valve. The temperature controller's set point should be set to assure
an adequate fuel oil viscosity for the actual burners.
Sometimes the control valve is installed in the condensate outlet line.
This requires a smaller control valve and the control function works
even better. However, this installation is for some reason not so very
common.
• 4.Fuel oil flow control
On large boilers the fuel oil flow controller gets its setpoint from the
burner management system or the airflow controller to achieve a
proper air-fuel mixture.
On smaller boilers the fuel oil flow control valve often is connected to
the combustion air damper by means of a metal rod or wire.
In both cases the steam pressure in the boiler sets a suitable fuel oil
flow.

69. • 5.Fuel oil shut of valves
Almost every classification society and other authorities requires two shut of
valves for the fuel oil, mechanically in series and electrically in parallel.
• 6.Fuel oil recirculation valve
This valve does not always exist, but if it does, the valve should open when the fuel
oil shut of valves closes. The recirculation has advantages and disadvantages.
– The advantage is that it keeps the fuel oil line warm when the burner is off.
– The disadvantages is that it will, in the long run, heat up the fuel oil passing
through the oil pump that might cause problem with cavitations.
• Leading the recirculation fuel oil back to the fuel oil service tank wouldn't be wise.
The fuel oil's temperature often exceeds 120ºC and water that might occur at the
bottom of the tank will vaporize and in worst-case cause damage to the tank.

70. • 7.Fuel oil drain valve
Some authorities require a drain valve to be installed between the shut off valves.
The burner management program mustn't open the drain valve before the shut off
valves are totally closed and it should close the drain valve before the shut off
valves open.
• 8.Smoke density meter
High smoke density indicates deficiency of air.
• 9.-Oxygen meter
The smoke duct from the boiler to the funnel is designed with respect to the
pressure drop and smoke velocity at maximum firing. At minimum firing the smoke
velocity can be very low and along the sides of the smoke duct a downdraught can
occur. Therefore the O2 probe ought to be located as close to the centre of the
smoke duct as possible.

71. • 10Thermometer
Normally a thermocouple or a resistance-thermometer. This temperature should
be recorded since a slowly increasing temperature indicates accumulation of soot
on the boilers heating surfaces and a rapid rise in temperature might indicate a
soot fire.
• 11.Difference pressure transmitter
This difference pressure should be recorded since increasing difference pressure
indicates accumulation of soot on the boilers heating surfaces.

72. FUEL OIL ATOMISING : Pressure Jet Burner
• PRESSURE JET BURNER
• The fuel is Atomized by the use of a high pressure pump forcing the
preheated heavy oil through an Atomizer. The pressure energy alone disrupts
the oil into fine particles. This type of Atomizer has a poor turn down ratio. A
small drop in Atomizing pressure will result in a dramatic reduction in
combustion performance. Two nozzles are sometimes fitted to achieve turn
down, one in use on low fire with two for the full rate, the oil pressure being
maintained constant. A variation of the pressure jet Atomizer is the spill
return or recirculating burner. The problems with this type of burner are that
the Atomizer has an increasing cone angle of the issuing spray as the burner
is turned down with impingement on the furnace walls, being made possible
and the additional problem of how to dispose of the returned hot oil if the
burner has been running for prolonged periods on low fire. Cavitation or
gasification takes place in the oil at the oil pump suction if the oil is so
returned. Equally, one can return it to the tank, but this does not offer a
sound solution as the tank can become overheated, especially if the stock
level is low.

73. STEAM ATOMISING BURNER
• Steam Atomized Burners were more tolerant to these changes. A variation
occurred, but not so marked as with e pressure jet Atomizer. In addition to
this advantage, the steam Atomized burner had better turn down, did not
require high fuel oil pump pressures, and was frugal in the use of steam. The
development work to reduce the specific steam consumption of the burner
had been so successful that the marine industry took up the use of steam
Atomized burners whereas in the past, the use of valuable fresh water at sea
had meant only pressure jet burners were used.
• ROTARY CUP BURNERS
• One particular type of burner which is of the twin fluid type, yet has a novel
method of presenting the oil to the Atomizing air is the so called Rotary Cup
Burner. As the name implies the burner comprises a horizontal shaft running
at about 5,000 rpm and having at one end of the shaft an Atomizer which is a
hollow cup into which is fed the fuel to be Atomized. The oil travels down the
cup under the combined forces of gravity and centrifugal force until it comes
to the cup lip. The Atomizing air is so guided as to impinge upon the edge of
the cup and Atomize the oil sheet which is leaving the cup. In this fashion
very fine Atomization is achieved. The rotary burner finds considerable use
on packaged shell type boilers. It has a good turn-down ratio of 4 to 1 and is
simple to automate.

74. Keeping a slave boiler pressurized in a two
boiler system

75. • Keeping a slave boiler pressurized in a two boiler system
• In a two boiler system it’s often a problem to keep the slave boiler at operation pressure when the
steam demand is low. This problem does not appear when the vessel is loading or unloading in a
harbor since those operations normally need both boilers. On the other hand, when the ship is at
sea and only one oil-fired boiler is used then the slave boiler tends to cool down far below the
required stand by conditions.
Different methods have been used to solve this problem. Installing steam heating coils in the
bottom of the boiler is one method and a sophisticated start-and-stop method for the slave boiler’s
burner to keep the pressure at desired level is an other.
Those installations will be unnecessary if you happen to have an EGE, exhaust gas economizer.
Just connect the exhaust gas economizer to the slave boiler instead of the master boiler. This
operation method will guarantee normal operation pressure on both boilers all the time at sea.
• The method has been used in many ships and the chief engineers are satisfied with the result.
A two-boiler system has other advantages as well. It provides a fully automatic, very flexible and
economic operation with maximum safety and availability ensured by the two separate units. At
inert gas production, one boiler can be operated at a preset fixed output while the other will follow
the load variations automatically.
• When bringing a boiler on-line with another boiler, ensure that the working pressure is the same in
both boilers and be sure to drain condensate from the steam line, before cracking the valve, to
avoidwater hammering. Let the steam line be heated up before the steam valve is fully opened.

76. Smoke Density Monitor
• It is very easy to achieve a smokeless fire without any special equipment for
supervision. On the other hand, to achieve a smokeless fire and economic
combustion will be a bit harder. The air supply has to be slightly in excess of
the theoretical requirements. That is, the combustion air flow is reduced
almost to the smoke limit. A plant that never shows traces of smoke at the
funnel is not burning the fuel efficiently.
• There are four instruments that will help you to achieve the optimal
combustion:
• 1.Smoke Density Monitor. High smoke density indicates uneconomical
combustion and it might also cause penalty from the environmental
protecting authorities.
• 2.Oxygen (O2) - Analyzer. High O2 content indicates heating of unnecessary
high quantity of combustion air.
• 3.Carbon monoxide (CO) - Analyzer. High CO content indicates unburned
hydrocarbons. This is not only uneconomical, the CO is also harmful to mans
health. Besides, mixed with air, CO might be an explosion risk.

77. • 4.Carbon dioxide (CO2) - Analyzer. Low CO2 content
indicates poor combustion, but it doesn’t tell if more or less
air is required.
• The most important instrument, the Smoke Density Monitor,
happened to be the cheapest of them and you can’t do
without it if you are trying to optimize the combustion of your
burners. A Smoke Density Meter equipment is very simple. A
light beam is sent across the flue duct, from a light emitter to
a light receiver. An electronic unit monitors the opacity. It
indicates 0% if there is no black smoke present and 100% if
the light beam is totally absorbed by the smoke. An alarm
activates if the smoke density exceeds a preset limit.