Wednesday, November 30, 2011

Boiler Control System

Boiler Control System
The boiler control panel provides operation, control and interlock devices
required for the safe running of the boiler. This control panel directs the
performance of all functions required for automatic operation of the boiler and
provides a central control point for manual operation. The control system also
features a network of alarms which give warning if an abnormality occurs
during boiler operation.
In the event of a serious abnormality occurring, which would make it unsafe
for the boiler to continue in operation, the boiler automatic control system
shuts down the boiler in an emergency mode, by immediately shutting down
the fuel oil supply to the boiler.
Control Panels
ECR Console Remote Indication Panel
This indication panel is installed in the engine control room and it mimics the
monitoring systems and main controls found at the boiler and boiler side
control panel.
The ECR console has the following items:
Drum level indicator
Steam drum pressure indicator
Smoke indicator
Emergency stop switch
Burner run lamp
Lamp test switch
Boiler Side Boiler Control Panel
This control panel is installed at the boiler side. It contains the system power
supply unit, the sequence control for operation of the burner, the automatic
boiler controller and various necessary relay units.
The following alarms are mounted on the control panel :
Electrical AC power source failure
Burner start sequencer inactive
Manual trip
FD fan trip
Pilot pump abnormal
Drum level low-low
Atomising pressure low
Ignition fail
Flame fail
Flame eye abnormal
Burner piston valve abnormal
FO pressure low-low
Control air pressure low
Burner Control System
The boiler control panel (BCP) operates in a number of functions associated
with the boiler including the boiler management system (BMS), automatic
combustion control (ACC), and feedwater control (FWC). There are two
boilers and they are controlled on a master/slave basis with one of the boilers
being designated the master by the control system and the other the slave.
Under normal circumstances the master boiler would operate to supply the
ship's steam requirements but if it cannot meet demand the slave boiler is
started and comes under the control of the boiler control system. The boilers
may also operate in conjunction with the economiser; usually this means that
the economiser is operating at sea and one of the boilers is selected to act as
the water supplier and the steam collector for the economiser. The boiler
would operate if the economiser could not maintain steam pressure for any
reason.
The boiler control system controls the remote, manual and automatic
operations of one single-throat burner which is provided in the roof of the
boiler. This unit contains a programmable sequence control, which operates the
furnace purge, pilot burner and the automatic operation of the burner piston
valve. This is done by linking up with the boiler protective system and the
ACC. In addition, it transmits the automatic adjustment commands of
combustion air quantity and fuel oil quantity to the ACC for the start/stop of
the burner. Combustion control is at the heart of boiler operation because if
anything goes wrong with the boiler, its water supply or the combustion
system, fuel must be shut-off and that will prevent any problem becoming
more severe.
There are three boiler operating modes, one is the 18k mode (steam supply at
18kg-cm2), the second is the 7k mode (steam supply at 7kg/cm2) and the third
is the IGS mode (inert gas system in operation).
In port during cargo discharge the 18k mode would be selected but, at sea only
the 7k mode would normally be required with the oil fired boiler installation
providing support for the waste heat economiser. In some cases, intermittent
oil firing on the boiler may be needed to maintain steam pressure and the boiler
control panel would organise that. Selection of 18k mode or 7k mode is
executed by the changeover switch and selection of a particular mode auto-
matically changes the set point on the pressure indicator control (PIC).
Procedure for the Preparation of Boiler Control System
a) Turn on the power switches of the boiler control panel.
b) Check the action of each pilot lamp and buzzer using the buzzer
and lamp test switch on the control panel.
c) Supply air to all the control devices.
d) Reset the boiler interlock alarm.
e) Check that all alarm lamps are out.
Operating Method
There are three burner operating modes, AUTO (Automatic), MAN (Manual)
and HARD MAN (Hard Manual) mode. The burner is usually operated in the
AUTO mode and the MAN modes are only used in an emergency when the
AUTO mode cannot function. The HARD MAN mode allows for reposition-
ing of the burner switches and the MAN mode is for operating on manual.
Selection of Operating Modes
HARD MAN Mode
When operating in this mode, the operator must always be at the boiler and
able to monitor the situation and provide manual intervention at the control.
The following interlocks are effective:
Drum water level low-low
Flame monitor (pilot burner and main burner)
Operating Procedure
a) Check that the boiler and burner are in operating condition.
b) Start the fuel oil pump and the forced draught fan in the MAN
mode.
c) Turn the burner switch from the OFF position to the HARD MAN
position.
d) Set the fuel pressure controller and the air controller to the MAN
mode.
e) Purge the furnace. To do this the air controller should be manually
operated and the forced draught fan inlet vane should be fully
opened. The furnace must be purged for at least 3 minutes.
f) Check that the fuel temperature is within the required range.
g) Manually operate the air controller and the fuel oil pressure
controller and set the forced draught fan inlet vane and the fuel oil
control valve to the ignition open position.
h) Open the sub-door for the HARD MAN operating switches. Set
the pilot burner switch to the MANU ON position and ignite the
pilot burner. If the pilot burner has not ignited after 15 seconds the
pilot burner switch should be reset to AUTO and the process
started over again from item e) above, 'Purge the furnace'.
i) With the pilot burner burning correctly the main burner is ignited.
The fuel oil valve switch is set to MANU ON and the main burner
should ignite. If the main burner does not ignite after a period of
10 seconds the fuel oil valve switch should be reset to AUTO and
the procedure started over again from item 'e', above 'Purge the
furnace'.
j) With the main burner operating correctly the pilot burner switch
is reset to AUTO.
(Note ! When extinguishing the main burner the fuel oil valve switch must be
returned to AUTO.)
When burner purging is required, the burner purging switch must be used and
this must be set to MANU ON.
Fuel Oil Temperature Bypass
The fuel oil temperature by-pass switch is inside the sub-door. In this bypass
mode the starting interlock for fuel oil temperature low alarm is bypassed. It is
used when starting the boiler in the cold condition when steam is unavailable
for heating. When using 'A' grade heavy oil, the switch is set to BYPASS.
AUTO Mode
This is the mode which will normally be used. All operations, including the
commands for ignition and extinction, are operated automatically.
a) Set the fuel oil pumps, the forced draught fan and the controllers
to the AUTO mode.
b) Turn the burner switch from the OFF to the AUTO position.
When stopping this switch must be returned to the OFF position.
The following sequence of events must be accomplished for main burner
ignition.
a) When the burner switch is moved to the AUTO position the
program timer starts.
b) After a delay of 5 seconds the forced draught fan starts and the
atomising steam valve opens.
c) After a further 20 seconds the forced draught inlet vane starts to
move to the fully open position in order to purge the furnace. It
takes approximately 30 seconds to become fully open.
d) The purge timer (2P) commences when the burner switch is
moved to the AUTO position and the time set on this timer is 60
seconds. After the 60 seconds has elapsed, the forced draught fan
inlet vane starts closing gradually to the ignition position. At this
point the furnace will have been effectively purged.
e) The pilot burner is ignited 35 seconds after item 'd'.
f) When the flame of the pilot burner is detected by the flame eyes,
the electrical igniter stops sparking.
g) The main fuel oil valve opens 5 seconds after the pilot burner is
ignited.
h) The pilot burner is extinguished 15 seconds after it has been
ignited (item 'e').
i) The program timer stops at the lock-in position (graduation 85)
5 seconds after the pilot burner is extinguished.
j) If there is an ignition failure or a flame failure the burner control
goes into an extinction sequence.
k) The extinction sequence commences when the burner CUT
INTERLOCKS have actuated (following item 'j' above) or if the
burner switch is turned from the AUTO to the OFF position.
1) The program timer starts from the lock-in position.
m) The pilot burner is ignited 2 seconds after item 1) above.
n) The burner purge valve opens and the burner is purged for about
6 seconds. The burner is purged when the interlock is normal and
the pilot burner lights up.
o) The post purge period commences and the forced draught fan inlet
vane starts to open to its fully open position when the burner
completes it purge cycle.
p) After the set time (60 seconds) on the post-purge timer is
completed, the forced draught fan inlet vane starts closing to the
ignition position which takes about 30 seconds.
q) The forced draught fan stops after 30 minutes.
(Note ! If flame failure occurs during normal operation, it is important that the
cause of the failure is investigated before any attempt is made to restart the
boiler.)
Automatic Combustion Control
This system automatically regulates the fuel and air supply to the furnace in
order to maintain a preset steam pressure in the boiler. Regulation of the fuel
supply is accomplished by means of the air operated fuel control valve whilst
the air supply is controlled by means of the inlet vane of the forced draught fan.
Fuel supply is automatically cut off in the event of forced draught fan failure
or due to high or low water level in the boiler drum. The ACC system is
electro-pneumatically operated.
The automatic combustion control (ACC) system employed is of
a fuel oil pressure/air pressure measuring type.
The ACC is held at predetermined ignition position until the
burner is ignited.
After the burner is ignited the combustion rate is fixed at the
ignition position until the boiler pressure reaches the predeter-
mined pressure of 5 kg.cm2. This period is called 'steaming'.
When the steaming period is completed, the ACC system goes to
AUTO RUNNING and the combustion rate can be adjusted by the
system.
During the steaming period the combustion rate can be changed
by operating the fuel oil pressure controller in the MANU mode.
The air/fuel ratio can be changed by up to + 20% by altering the
air ratio dial. This dial would normally be set at the position 1.
MAN Mode.
This mode is selected to allow for manual starting of the boiler in order to see
that all stages are completed correctly. It is used when the boiler would
normally be operated automatically as a means of checking the start-up
procedure. The procedure is the same as for HARD MAN start but no switches
behind the HARD MAN sub-door are changed.
Feedwater Control.
This controller is of the two element type; both have proportional and integral
(P+I) control. It measures the steam flow rate and also the water level in the
boiler and adjusts the feedwater supply in line with changes in these values.
The P+I operation is performed when comparing signals from two separate
systems. One of the signals is generated by the difference between the water
level set and that detected in the steam drum of the boiler. The other is from
comparison between the detected steam flow rate from a steam flow
transmitter and the operating signal to the feedwater control valve. In ECON
(economiser) mode the water level change due to the ship's rolling and
pitching is accounted for by consideration of the moving average level in the
steam drum.

Master-Slave System.
The two boilers are independent units, but the control system is designed so
that they operate as a dedicated pair with one being the master boiler and the
other the slave. This means that the master boiler supplies the ship's steam
requirements until the demand exceeds its capacity and then the slave boiler
commences operation. The slave boiler will have been kept in a state of
readiness for such a situation and would have been at the same temperature as
the master boiler in order to avoid delays in wanning through.
a) The master boiler is controlled by actuation of the ON/OFF
switch and the pressure indicator so that the steam pressure of an
individual boiler will retain its set point. The actuation is executed
in the same way as the normal one boiler system.
b) When steam demand on the master boiler exceeds 80% of its
capacity, the slave boiler is switched on. It is switched off when
the steam demand is 30% of the total capacity of the two boilers.
The combustion rate for the slave boiler is the same as for the
master boiler, as the master boiler is exercising overall control.
c) In addition to the ON/OFF actuation of the slave boiler from the
master-slave controller, the slave boiler can also perform its own
ON-OFF actuation of combustion due to the pressure in the boiler.
The slave boiler retains overriding control of combustion due to
the pressure within the boiler and that pressure is the slave
boiler's own set pressure and is independent of the pressure
setting for the master boiler.
d) The low limiter actuates for 15 minutes after the slave boiler has
been started in order to prevent the ON/OFF hunting phenomenon
at the slave boiler.
e) The pressure in the slave boiler needs to exceed 11 kg-cm2 in
order for the master-slave configuration to operate.
f) In addition to the master-slave operation it is possible to select the
PARA mode where both boilers can be turned off independently.
In this case the boilers would be operating together each under its
own independent control and not as a master-slave pair.
Safety and Control System.
Incorporated in the safety and control system are operating functions, or sub-
systems, which react automatically to a change in condition outside of the pre-
set range. Failure of most sub-systems produces a visual alarm on the main
control panel and may also produce an audible alarm. In the majority of cases,
failure of a sub-system requires manual resetting of the cut-out before the sub-
system can be restarted. This provides protection for personnel on the ship and
for the boiler installation, as the reason for a sub-system failure can involve
more than that particular sub-system.


Inert Gas Topping-up Mode.
The inert gas system (IGS) topping-up mode is used in order to allow the boiler
to operate on a minimum load so that the IGS may function correctly. A
minimum boiler load of 25% is required so that the flue gases will contain no
more than 5% oxygen; the flue gas flow at minimum rate will be 10,300m3/h
at a temperature of 5°C. The following items will be interlocked, and hence not
operable, in this mode.
Boiler minimum load is limited to 30% or greater if dumping of steam
is operating.
The IGS running lamp is illuminated
Bypass of the FO burner auto stop
Steam supply valve to soot blowers is interlocked to FULL CLOSE

Boiler Alarm and Trips.
Description.

Emergency Mode.
The boilers may be operated in emergency mode when the burner sequencer is
inoperative.
a) Start the FD fan then fully open the FD fan inlet vane and perform
the furnace purge for 3 minutes.
b) Ensure that the FO temperature is at the specified level,
equivalent to 15cSt.
c) Set the FO control valve and FD fan inlet at IGNITION OPEN
positions respectively.
d) Light off the pilot burner with care and do not exceed 15 seconds
ignition time.


e) Ensure that the pilot burner has ignited and open the FO piston
valve to allow oil to the main burner.
f) Do not keep the FO piston valve open for longer than 10 seconds.
g) If the main burner fails to ignite, the furnace must be purged prior
to a repeat attempt at ignition.
(Note ! During an emergency operation a careful watch must be kept on the
boiler at all times.)
FO Temperature Bypass
When burning HFO during emergency mode this bypass must be operated.
Steam press. 7kg-cm2 mode (start-stop) 6.5 kg-cm2 - 9.5 kg-cm2
Slave boiler start enabled 11.0 kg-cm2
Slave boiler (start-stop) 12.6 kg-cm2 - 4.6 kg-cm2

 
 
Sootblowers
Auxiliary Boiler Sootblowers
No. of sets :

Two fitted to each boiler

Sootblowing has to be carried out at regular intervals to ensure that the heat
transfer surfaces are kept clear of deposits, as these retard heat transfer and can
constitute a fire hazard.
Two sootblowers are fitted to each boiler and should be operated daily when
boilers are in use, bearing in mind the position of the vessel and any local
legislation concerning pollution and clean air. They should be operated when
leaving port prior to shutting down the boiler. The sootblowers are fitted with
an air purge connection, the air being supplied from the discharge of the forced
draught fan. This purge or sealing air keeps the nozzles clear during boiler
operation and provides a seal at the air sealed wall boxes to prevent the escape
of boiler exhaust gas into the machinery space. Non-return valves prevent
steam from entering the air lines.
The sootblowers are only to be operated when the available steam pressure
exceeds 8 kg/cm2. An isolating valve, located in the steam line between the
sootblower steam supply valve (T25V) and the sootblower distribution line,
will only be opened by its associated pressure switch if the steam pressure
exceeds 8 kg/cm2.
Before operation, request permission from the bridge and notify the bridge on
completion.
Procedure for the Operation of the Auxiliary Boiler Sootblowers
a) The boiler should be on a minimum of 50% of full load and the
forced draught fan operating at a high rate during the sootblowing
period. The steam pressure must exceed 8 kg/cm2.
b) With the drain open slightly (No.l boiler valve T29V and No.2
boiler valve T28V), open the steam stop valve (T25V) to the
sootblower header.
c) When the pipeline is warmed sufficiently, shut the drain valve and
open the stop valve fully.
d) Operate the sootblower by turning the handwheel in a clockwise
direction. The sootblower cleans the boiler heating surfaces by
impacting steam from a row of nozzles set along the length of the
sootblower element. A cam and trigger arrangement, incorporat-
ed in the sootblower head, regulates the steam arc issuing from
the nozzles as the sootblower element rotates. This ensures
optimum cleaning of the tubes.
e) Operate the top sootblower first, followed by the bottom one. The
top blower should be operated again. The system is then shut
down and the drain valve opened.
WARNING
Do not operate the auxiliary boiler sootblowers during inert gas operations.

 
 

Emergency Operation and Putting Boiler out of Service

Emergency Operation
Low Water Level
A low water level, 140mm or more below the normal working level, will activate the visual and audible alarms (illumination of the alarm lamp on the control panel and sounding of the alarm buzzer).
Should the water level fall to 250mm or more below the normal working level, the fuel oil emergency trip valve will close, shutting off fuel from the boiler.
The feedwater valve and steam stop valve should be fully closed, the burner shut down completely and the forced draught fan stopped after purging the furnace.
Never attempt to supply feedwater to the boiler until the boiler has cooled sufficiently, as there is a danger of bringing comparatively cold feed into contact with hot surfaces.

When the boiler water level has been restored the boiler may be flashed up using the normal procedure.
Flame Failure
In case of flame failure, close the oil inlet valve and reduce air pressure to prevent over cooling the furnace.
Purge the furnace thoroughly before relighting the burner.
Always use the pilot burner for ignition, never attempt to relight the burner from the hot furnace refractory.
Evaporating Tube Failure
Serious tube failure where water level cannot be maintained.
a)  Shut off the oil supply to the boiler and if the tube failure results from low boiler water level, shut off the feed supply, close the feedwater valve and steam stop valve.
b)  If the tube failure results from a cause other than low water level, the fuel supply should be shut off but the feedwater supply should
be maintained in order to assist in the cooling down process.
When the boiler has cooled sufficiently, close the feed valve and steam stop valve and open the steam drum vent.
c)  In either case of tube failure, maintain the forced draught fan so that the air draft assists in carrying away the escaping steam.
Care must be taken to avoid damage to the refractory by an excessive air supply.
d)  Do not blow down the boiler unless the tube failure is so severe that personnel could be endangered.
When the boiler has cooled, the blowdown may be used to empty the boiler.
e)  When the boiler has cooled enough, an inspection should be carried out to assess the situation and carry out necessary repairs.
f)   If tube failure is not serious and the water level can readily be maintained, the boiler can be shut down in the normal manner.

The forced draft air supply should be maintained to carry away vapours generated by the leaking water and the water level
maintained during the cooling down period.
When boiler pressure has fallen to 2 kg/cm2, the steam drum vent valve boiler may be opened and the boiler blown down.
Putting the Boiler Out of Service
When putting a boiler out of service, the wet lay-up method is preferable, as it requires less preparation and it can be quickly returned to service.
These steps are taken if the ship is to be taken out of service for some time and are not part of normal operational routine.
Wet Lay-up
When the boiler is in the cooling down process following shutdown, appropriate quantities of boiler chemicals should be injected into the drum
using the boiler chemical injection device.
To ensure adequate protection of the boiler, follow the guidelines given by the chemical supplier.
The quantity of the chemicals required will depend upon the condition of the boiler water and a water test should be carried out prior to shutting down.
After dosing the boiler water should register pH of 12, (alkalinity 300 to 400 ppm) phosphoric acid about 50 ppm, and sodium sulphite 80 to 100 ppm.
The high alkalinity will ensure adequate protection of the boiler.
When returning the boiler to service the chemical concentrations should be returned to normal levels and this means blowing down the boiler and filling with untreated make-up feed.
a)  When the pressure is approaching atmospheric pressure, open the steam drum air vent valve.
b)  When the pressure is off the boiler, supply distilled water until it issues from the vent valve, then close the vent valve.
c)  Put a hydrostatic pressure of 3.5 to 5kg/cm2 on the boiler.
Hold this pressure until the boiler has cooled to ambient temperature.
Bleed the boiler using the vent valve to be sure all the air is out.

Maintain a hydrostatic pressure of 2 to 3.5 kg/cm2 on the boiler.
Take a periodic boiler water sample and replenish any depleted chemicals.

Maintaining Boiler in Warm Condition
At sea, with one boiler being circulated through the waste heat economiser, the standby boiler should be maintained in a warm condition by supplying steam to the heating element in the bottom drum.
This is done by closing the heating coil drain valve and opening the inlet and outlet valves.
The boiler pressure should be maintained at 0.5 kg/cm2 or above.
When the heating element is not in use, the inlet/outlet valves are closed and the drain left open.
In port with the economiser shut down, the standby boiler is maintained at 2kg/cm2 or above by switching the burner on and off. Do not use the bottom drum heater.
Dry Lay-up
This should only be undertaken if a wet lay-up cannot be performed.
a)  Whilst the boiler remains warm, drain it of all water and ensure that all headers are dry.
b)  Remove the end piece of the waterwall lower header to check that no water remains.
c)  Provide some dry heat, electric heaters preferably, in the furnace to promote internal drying.
d)  When the boiler is completely dry, put some quick lime or calcium chloride in a shallow dish for placement in the drum and
header then close the end plate and manhole doors.
Check the moisture absorbent chemicals every week initially and replenish as required.
e) Cover the funnel outlet and close the air inlet to the furnace.

Marine Boiler Operation Construction


Boilers and Steam Systems
General Description
The steam generating plant consists of two auxiliary boilers and one exhaust
gas economises Steam is required at sea for fuel, domestic water and cargo
slop tank heating purposes. In port steam is used additionally for driving the
power turbines of the cargo pumps and No. 1 water ballast pump. The steam
demand of the plant, in port, is served by the boilers. At sea, steam demand is
met by circulating boiler water from one of the auxiliary boilers through the
exhaust gas economiser, by one of the boiler water circulating pumps. The
auxiliary boiler acts as a receiver for the steam generated by the economiser.
The economiser is arranged in the main engine exhaust gas uptake to take
waste heat from the main engine exhaust. An auxiliary boiler may be required
at sea in low temperature areas, as well as reduced power operation of the main
engine, such as during manoeuvring or slow steaming on passage when there
will be insufficient waste heat to generate the required steam.
Auxiliary Boiler
No. of sets: 2
Maker: Hyundai Heavy Industries Ltd
Model: HMT-50
Type: Top fired rectangular water tube marine boiler
Evaporation: 50,000 kg/h
Steam Condition: 18 kg/cm2 saturated steam.
Fuel Oil: HFO up to 700 cSt at 50°C
Safety Valve Setting: 20 kg/cm2
Fuel Oil Consumption: 3,850 kg/h at 100% evaporation
Boiler Associated Equipment
Equipment
Combustion Control Electronic/Air Operated
Feedwater Regulator Electronic/Air Operated
Remote Water Level Gauge
Drum Level Safety System
Steam Jet Oil Burner
Water Level Gauge - Reflex Type
Safety Valve - Full Bore Type
Chemical Dosing Unit
FDFan
FO Pump
FO Heater
Description
General Construction
The boiler is of the two drum rectangular type, with a membrane furnace water
wall connecting steam and water drums.
The furnace consists of gas-tight membrane walls, the downcomer pipes are located outside of the furnace.
The fuel burner unit and associated combustion air inlet, is located in the roof of the furnace with the burner firing downwards using a steam assisted pressure jet burner.
At the furnace bottom, a refractory protects the furnace bottom from the combustion flame.
Combustion gases flow downwards and through the lower part of the division tube wall and the lower section of the generating tube
bank which connect the steam and water drums.
The gases then flow upwards on a return path through the upper part of the generating tube bank to the flue gas box at the top of the boiler.
Radiant heat generates steam in the membrane furnace water wall tubes.
The membrane wall has access doors to allow for furnace inspection and cleaning.
The boiler structure is rigid enough to withstand rolling, pitching and shock loading of the ship operating in a seaway.
The boiler is supported at the water drum and the water wall lower headers, and there are no rigid connections at any other points in order to allow for thermal expansion.
Furnace
Closely spaced water wall tubes of 76.2mm outside diameter, form the membrane walls at the side, roof, except for burner opening, rear, and front of the furnace.
This construction is in order to increase the radiant heat absorption in the furnace and to make it strong enough to withstand vibration.
The furnace is made completely gas-tight by the welded water wall construction.
Situated at the top and bottom of the front and rear walls are water wall headers.
Water enters the bottom headers and rises through the tubes to the top headers due to natural convection.
As the water rises, it is heated until its saturation temperature is reached and it then begins evaporating.
This water- steam mixture is passed to the steam drum via the top headers.
Front and rear water wall tubes connect to steam and water headers at the top and bottom respectively; one end of each top header connects with the steam drum and one end of each bottom header connects with the water drum.
The roof, side and bottom water wall tubes are directly connected to the water and steam drums.
The steam generating bank of tubes, connecting steam and water drums, is located within the furnace.
Boiler Casing
As the furnace of the boiler is made completely gas-tight by the adoption of welded membrane water wall construction, no casing or refractory is required to contain the combustion gases.
Mineral wool insulation is provided on the outer surface of the furnace water walls and this is covered by corrugated galvanised sheets to reduced heat transfer.
The maximum temperature on the casing surface will not exceed 60°C.
Steam Drum and Fittings
The steam and water drums are fabricated using boiler steel plate of all welded construction.
The steam drum has a horizontal perforated baffle plate covering the entire water surface in order to prevent droplets of water rising to the upper part of the steam drum.
A steam separator is provided to completely remove the moisture.
The feedwater pipe enters the steam drum at the rear of the boiler and is attached to an internal perforated feed pipe which extends to the front of the steam drum.
This ensures that there is complete mixing of incoming feed with the existing boiler water and an equalising of temperatures.
The chemical feedwater treatment pipe attaches to the internal feedwater pipe and this also ensures that there is complete mixing of the chemicals before the water reaches the downcomers.
The open ended surface blow off internal pipe extends to the surface of the steam drum to ensure that only floating solids on the water
surface are discharged through this scum blowdown line.
The boiler blowdown connection is fitted to the lower part of the water drum.
Sootblower - Rotary Type
Operating Procedures
Procedure for Preparing the Boiler for Service
The following steps should be taken before attempting to flash up the boiler.
a)  All foreign materials must be removed from internal pressure parts.
b)  All gas side-heating surfaces must be clean and all refractory be in good condition.
c)  The furnace bottom and the burner wind box must been cleaned of oil and other debris.
d)  All personnel not involved must remain clear of the boiler.
e)  All manhole covers must be securely tightened.
f)   Inspect safety valves and ensure that gags have been removed and easing levers are in good condition.
g)  Open root valves for all instruments and controls connected to the boiler and check that they work as intended.
h) Open the vent valve of the steam drum.
i) Open all pressure gauge valves and check to ensure that all valves on the pressure gauge piping are open.
j) Check and close all blow-off valves and drain valves.
k) Fill the boiler until water level appears 25 to 50mm high in the gauge glasses.
Allow for swell in level after firing.
1) Check the operation of gauge glasses.
Remote reading instruments will not work correctly until the boiler is under pressure and so they must not be relied upon.
Raising Pressure With No Steam Available from the Other Boiler or Economiser
With the boiler water at the correct level and other checks made as above:
a) Set up the fuel system for diesel oil and circulate the fuel until all heavy fuel has been discharged from the fuel lines.
Ideally the fuel system should have been flushed through with diesel oil prior to the previous shutdown.
b)  Set the burner for air atomising, using an air pressure of 5 kg/cm2 and fuel pressure of 3 kg/cm2.
Purge the furnace with the forced draught fan for one minute with vanes fully open.
c)  Reduce the air pressure at the windbox to between 10 and 20mm WG and close recirculating valve.
d)  Light the burner using the pilot burner and adjust air and fuel pressure to ensure stabilised combustion by using the furnace
observation port and smoke indicator.
e)  When raising the pressure, keep the burner firing for 5 minutes and out of service for 15 minutes repeatedly at the lowest fuel oil
pressure (2.5kg/cm2) for one hour.
Again, repeatedly light and shut down the burner to raise pressure as recommended on the pressure raising curve supplied by the manufacturer. A guideline would be to aim for lkg/cm2 after 2 hours firing, 5kg/cm2 after 2.75 hours firing and 12 kg/cm2 after 3.25 hours firing.
f)   When the drum pressure has risen to about 2 kg/cm2, close the drum vent valve.
g)  Drain and warm through all steam supply lines to ancillary equipment before putting the boiler on load.
h) Supply steam to one of the HFO service tanks.
When the tank is of sufficient temperature to be pumped by the HFO pump, supply steam to the HFO heater and prepare to change over from DO to HFO firing.
The HFO must be thoroughly circulated through the system to ensure it is at the correct temperature for good combustion.
When firing on HFO, check the combustion and adjust the fuel and air as required, then continue pressure raising.
(Note ! Caution must be exercised when operating with diesel oil due to its lower flash point. Diesel oil must not be heated above 40°C and there is a greater risk of leakage compared with HFO.)
i) At working pressure, switch to automatic operation.

Raising Pressure with Steam Available from the Other Boiler or Economiser
a)  Start the forced draught fan, open the inlet vanes and purge the furnace.
b)  Ensure that the HFO system is correctly heated then start the HFO burning pump and circulate oil through the heater and burner
manifold, open the recirculating valve and discharge the cold HFO in the line.
(Note ! At normal sea going condition, the boiler fuel system should be continually circulating heated HFO.)
c)  Reduce the air pressure at the windbox to between 10 and 20mmWG.
d)  Close the recirculating valve.
e)  Light the burner and adjust the air and fuel pressure to ensure stabilised combustion, using the furnace observation port and
smoke indicator.
Boiler pressure must be raised gradually over a period of hours in accordance with the manufacturer's instructions.
The recommendations are the same as in item e) in the section; Raising Pressure With No Steam Available
f)   When the drum pressure has risen to about 2 kg/cm2, close the drum vent valve.
g)  Drain and warm through all steam supply lines to ancillary equipment before putting the boiler on load.
Shutting Down
a)  Operate sootblowers before shutting down the boiler whenever possible.
b)  Shut down the burner.
c)  Continue operation of the forced draught fan for a short while after shutting down, keeping an air pressure of 150mm WG at burner inlet and purge the furnace of combustible gases.
d)  Maintain the water level visible at about 50mm in the gauge glass and when the boiler is closed raise the water level 70mm to 120mm above the normal water level.
e)  Open the drum vent valve when the boiler pressure reaches about 2 kg/cm2.
f)   Change the fuel system to diesel oil and circulate back to the tank.
(Note ! If steam is to remain available from the other boiler or economiser, the boiler HFO system should remain in use and there is no need to change to diesel oil.)
g)  When fuel oil has been purged, shut down the fuel system.
After the boiler has been shut down for 4 hours the forced draught fan may be used to assist cooling down should immediate access be required. However, to avoid the risk of damage to refractory, allow the boiler to cool down under natural means if possible.
! CAUTION
Do not attempt to cool down the boiler by blowing down or by filling with cold water.

Know your ship. It's simple

Fouling and Fires in the Scavenge Air Spaces
The principle cause of fouling is blow-by of combustion products, unburnt fuel and cylinder lubricant between piston and cylinder into the scavenge air
spaces. The fouling will be greater if there is incomplete combustion of the fuel injected (exhaust smoke).
Causes of Poor Combustion:
The fuel injectors are not working correctly; incorrect fuel atomisation.
The fuel is at too low a temperature; resulting in high fuel viscosity and poor fuel atomisation.
Poorly adjusted injection pump timing; late injection results in after burning of fuel.
Operation with a temporary shortage of air during extreme variations in engine loading and with the charge air pressure dependent fuel limiter in the governor set too high.
Engine overloading; too much fuel for the available air.
Insufficient supply of air due to restricted engine room ventilation.
Fouling of the air intake filters and diffuser on the air side of the turbocharger.
Fouling of the air cooler, the air flaps in the charge air receiver and of the scavenge ports; these restrict air flow to the cylinders.
Fouling of the exhaust gas boiler; this increases the back pressure on the turbocharger turbines causing reduction in performance
and reduced air delivery.
Causes of Blow-by of Combustion Products:
Worn, sticking or broken piston rings.
Excessive liner wear or abnormal wear such as 'clover-leafing' which can also result in ring collapse and loss of piston ring to liner seal.
Individual cylinder lubricating quills are not working.


Damage to the running surface of the cylinder liners.
If one or more of these operating conditions prevails, residues, mainly consisting of incompletely burnt fuel and cylinder lubricating oil will
accumulate at the following points:
Between piston rings and piston ring grooves; this can result in the jamming of piston rings causing breakage or blow-past.
On the piston skirts. In the scavenge ports; this can affect the performance of the scavenging process resulting in incomplete
removal of combustion products from the cylinder and subsequent defective combustion.
On the bottom of the cylinder jacket (piston underside).
Causes of the Fires
The blow-by of hot combustion gases and sparks which have bypassed the piston rings between piston and cylinder liner running surface, enter the space
on the piston underside. Any residues present can ignite.
If there is after-burning of fuel in the cylinder due to late injection or poor fuel atomisation, the cylinder pressure, when the scavenge ports are uncovered, may be higher than the scavenge air pressure and hot combustion gases may enter the scavenge space.
A defective piston rod gland may allow oil from the crankcase to enter the scavenge space. The piston rod gland drains should be checked frequently for
signs of crankcase system oil as this indicates defective gland sealing rings.

Indications of a Fire
Sounding of the respective temperature alarms if the engine has the necessary monitoring instrumentation installed.
A considerable rise in the exhaust gas temperatures of the cylinder concerned and a general rise in charge air temperature.
The turbocharger may start surging.


Scavenge Space Fire Fighting Measures
The safety of shipboard personnel should be paramount whenever dealing with fires anywhere aboard ship.
Inform the bridge of the situation
Reduce engine power
Cut out the fuel injection pump of the cylinder concerned
Increase lubrication to the respective cylinder
(Note! If a serious fire occurs, shut down the engine after obtaining permission from the bridge and operate the fixed fire extinguishing system.)
A fire should have died down after 5 to 15 minutes. This can be verified by checking the exhaust gas temperatures and the temperatures of the doors to the piston bottoms.
Caution should be exercised whilst the fire is burning to ensure that it does not cause a fire in the engine room. Extreme care must be taken to ensure that
leakage of oil onto the hot scavenge space sides does not happen.
After it has been confirmed that the fire has been extinguished the engine must be stopped as soon as possible and the cause of the fire established. The
scavenge space must be allowed to cool completely before access doors are opened to allow inspection.
Checks should be made on the cylinder running surfaces, piston rings, fuel injectors, valve groups in the scavenge space, piston rod gland and liner seals.
Tie rod tension should be checked if the fire has been severe.
After a careful check, or if necessary repair, the engine can be put back on load with cut-in fuel injection pump and automatic cylinder lubrication.
Should a stoppage of the engine not be feasible and the fire has died down, the fuel injection pump can again be cut in, the load increased slowly and the
cylinder lubrication brought back again to the normal output. Avoid prolonged running with the considerably increased cylinder lubrication.
Preventive Measures
As can be seen from the causes, good engine maintenance goes a long way to safeguarding against fires in the scavenge air spaces. The following measures have a particularly favourable influence:
Use of correctly spraying fuel injectors and keeping the air and gas passages clean.
Optimum adjustment of the fuel cams and of the fuel injection pump timing.
When running continuously at reduced load, check the cylinder lubricating oil feed rate and readjust if necessary. Ensure that fuel atomisation and combustion is correct for the reduced load condition.
The permanent drain of residue from the piston underside must always be checked. To prevent accumulation of dirt, the drain cock on the collector main must be opened for a short time each day.
Prevention of Crankcase Explosions
The oil mist in the crankcase is inflammable over a very narrow range of mixture. Weaker or richer mixtures do not ignite. There must always be an
extraneous cause to set off ignition, such as hot engine components. Only under these circumstances and the presence of a critical mixture ratio of oil
mist and air can an explosion occur. A 'hot spot' is the common feature of all crankcase explosions and this can be due to metal-to-metal contact at a wiped bearing, rubbing guide, defective piston rod gland, damaged thrust, un-lubricated gear wheel, etc. or even due to a prolonged scavenge fire. The 'hot spot' provides the heat source to evaporate oil, which condenses to form mist-like droplets which will ignite readily, and ignite the mist. If the mist concentration in the crankcase reaches a critical level an explosion can occur.
Engines are equipped with an oil mist detector, which constantly monitors intensity of oil mist in the crankcase and triggers an alarm if the mist exceeds
the density limit.
Measures to be Taken When Oil Mist Has Occurred
a)  Do not stand near crankcase doors or relief valves or in corridors near doors to the engine room casing.
b)  Reduce speed to slowdown level immediately, if not already carried out automatically. Explain the situation and ask the bridge
for permission to stop.
c)  When the engine STOP order is received, stop the engine. Close the fuel oil supply. Maintain engine cooling and lubrication as the supply of lubricant will assist the cooling of the hot spot.
d)  Switch-off the auxiliary blowers.
e)  Open the skylight(s) and/or stores hatch.
f)   Leave the engine room as a fire can still occur even with the engine stopped because the mist will circulate in the crankcase and can come into contact with the hot spot.
g)  Lock the casing doors and keep away from them,


h) Prepare the fire-fighting equipment.
i) Do not open the crankcase until at least 20 minutes after stopping the engine. Ideally leave the engine for as long as possible before opening the crankcase doors as this will ensure that the hot spot has cooled below the ignition temperature and so any mist which persists will not ignite from this source. It is important that no naked lights exist in the vicinity of the crankcase when the doors are opened in order to prevent ignition of any residual mist from that source.
j) Stop the lubricating oil pump. Take off-open all the doors on one side of the crankcase. Cut off the starting air, and engage the turning gear.
Main Engine Graviner Oil Mist Detector

k) Locate the hot spot. Feel over, by hand, all the sliding surfaces (bearings, thrust bearing, piston rods, stuffing boxes, crossheads, lubricant supply toggle lever pipes, gears, vibration dampers, moment compensators, etc.)- Look for squeezed-out bearing metal and discolouration caused by heat (blistered paint, burnt oil, oxidised steel). Keep possible bearing metal found at the bottom of the oil tray for later analysing. Prevent further hot spots by
preferably making a permanent repair. Ensure that the respective sliding surfaces are in good condition. Take special care to check that the circulating oil supply is in order. The engine should not be restarted until the cause of the hot spot has been located and rectified.
1) Start the circulating oil pump and turn the engine by means of the turning gear. Check the oil flow from all bearings, spray pipes and spray nozzles in the crankcase, camshaft drive gear wheel case and thrust bearing. Check for possible leakages from pistons or piston rods.
m) Start the engine. After running for about 30 minutes stop and feel over surfaces for signs of abnormal temperature rise. Especially feel over the sliding surfaces which caused the overheating. There is a possibility that the oil mist is due to atomisation of the circulating oil, caused by a jet of air/gas, e.g. by combination of the following: Stuffing box leakages (not air tight). Blow-by through a cracked piston crown or piston rod (with direct connection to crankcase via the cooling oil outlet pipe). An oil mist could also develop as a result of heat from a scavenge fire being transmitted down the piston rod or via the stuffing box. Hot air jets or flames could also have passed through the stuffing box
into the crankcase.
WARNING
Special Engine Room Dangers
Keep clear of spaces below loaded cranes.
The opening of cocks may cause discharge of hot liquids or gases.
The dismantling of parts may cause the release of springs.
The removal of fuel valves or other valves in the cylinder cover may cause oil to run onto the piston crown. If the piston is hot an explosion may blow out the valve.
When testing fuel valves do not touch the spray holes as the jets may pierce the skin.
Beware of high-pressure oil leaks when using hydraulic equipment, wear protective clothing.
Arrange indicator cocks with pressure relief holes directed away from personnel, wear goggles when using indicator equipment.
Do not weld in the engine room if the crankcase is opened before fully cooled.
Turning gear must be engaged before working on or inside the engine as the wake from other ships in port or waves at sea may cause the propeller to turn. Also, isolate the starting air supply.
Use warning notices at the turning gear starter and other control stations to warn personnel that people are working on the engine.
Use gloves when removing O-rings and other rubber/plastic based sealing materials, which have been subjected to abnormally high
working temperatures as they may have a caustic effect.
Do not allow oil patches to remain on floors as personnel can easily slip resulting in injury.
Oil spills, and particularly oily rags, anywhere present a fire hazard.
Do not remove fire extinguishers from designated positions and ensure that any fire extinguishers which have been used are replenished immediately.
Only use lifting equipment which has current certification.

Main Engine Manoeuvring Control

Courtesy By NORCONTROL Automation AS



Engine Telegraph System (ETS)
Manufacturer: NORCONTROL Automation AS
Model: AutoChief - 4


Description
The ETS performs two basic functions, these are:
1. To allow an operator to initiate engine change commands from the
designated control location directly to the engine via the remote
control system. These changes can also be communicated, via the
ETS pushbuttons and telegraph handle, to an operator who will
implement these commands in the control room or the engine
room.

International Maritime Solid Bulk Cargoes Code (IMSBC Code)


The International Maritime Solid Bulk Cargoes Code (IMSBC Code) has now replaced the Code of Safe Practice for Solid Bulk Cargoes (BC Code) w.e.f 01st January 2011, which was first adopted as a recommendatory code in 1965 and has been updated at regular intervals since then.
The aim of the mandatory IMSBC Code is to facilitate the safe stowage and shipment of solid bulk cargoes by providing information on the dangers associated with the shipment of certain types of cargo and instructions on the appropriate procedures to be adopted.

Wednesday, November 23, 2011

Adopting a convention, Entry into force, Accession, Amendment, Enforcement, Tacit acceptance procedure

​Introduction
The industrial revolution of the eighteenth and nineteenth centuries and the upsurge in international commerce which followed resulted in the adoption of a number of international treaties related to shipping, including safety.  The subjects covered included tonnage measurement, the prevention of collisions, signalling and others.
By the end of the nineteenth century suggestions had even been made for the creation of a permanent international maritime body to deal with these and future measures.  The plan was not put into effect, but international co-operation continued in the twentieth century, with the adoption of still more internationally-developed treaties.
Adopting a convention
This is the part of the process with which IMO as an Organization is most closely involved.  IMO has six main bodies concerned with the adoption or implementation of conventions.  The Assembly and Council are the main organs, and the committees involved are the Maritime Safety Committee, Marine Environment Protection Committee, Legal Committee and the Facilitation Committee.  Developments in shipping and other related industries are discussed by Member States in these bodies, and the need for a new convention or amendments to existing conventions can be raised in any of them.

Entry into force
The adoption of a convention marks the conclusion of only the first stage of a long process.  Before the convention comes into force - that is, before it becomes binding upon Governments which have ratified it - it has to be accepted formally by individual Governments.

Signature, ratification, acceptance, approval and accession
The terms signature, ratification, acceptance, approval and accession refer to some of the methods by which a State can express its consent to be bound by a treaty.
Signature
Consent may be expressed by signature where:
  • the treaty provides that signature shall have that effect;
  • it is otherwise established that the negotiating States were agreed that signature should have that effect;
  • the intention of the State to give that effect to signature appears from the full powers of its representatives or was expressed during the negotiations (Vienna Convention on the Law of Treaties, 1969, Article 12.1).
A State may also sign a treaty "subject to ratification, acceptance or approval".  In such a situation, signature does not signify the consent of a State to be bound by the treaty, although it does oblige the State to refrain from acts which would defeat the object and purpose of the treaty until such time as it has made its intention clear not to become a party to the treaty (Vienna Convention on the Law of Treaties, Article 18(a)).
Signature subject to ratification, acceptance or approval
Most multilateral treaties contain a clause providing that a State may express its consent to be bound by the instrument by signature subject to ratification.
In such a situation, signature alone will not suffice to bind the State, but must be followed up by the deposit of an instrument of ratification with the depositary of the treaty.
This option of expressing consent to be bound by signature subject to ratification, acceptance or approval originated in an era when international communications were not instantaneous, as they are today.
It was a means of ensuring that a State representative did not exceed their powers or instructions with regard to the making of a particular treaty. The words "acceptance" and "approval" basically mean the same as ratification, but they are less formal and non-technical and might be preferred by some States which might have constitutional difficulties with the term ratification.
Many States nowadays choose this option, especially in relation to multinational treaties, as it provides them with an opportunity to ensure that any necessary legislation is enacted and other constitutional requirements fulfilled before entering into treaty commitments.
The terms for consent to be expressed by signature subject to acceptance or approval are very similar to ratification in their effect.  This is borne out by Article 14.2 of the Vienna Convention on the Law of Treaties which provides that "the consent of a State to be bound by a treaty is expressed by acceptance or approval under conditions similar to those which apply to ratification."

Accession
Most multinational treaties are open for signature for a specified period of time. Accession is the method used by a State to become a party to a treaty which it did not sign whilst the treaty was open for signature.
Technically, accession requires the State in question to deposit an instrument of accession with the depositary. Article 15 of the Vienna Convention on the Law of Treaties provides that consent by accession is possible where the treaty so provides, or where it is otherwise established that the negotiating States were agreed or subsequently agreed that consent by accession could occur.

Amendment
Technology and techniques in the shipping industry change very rapidly these days. As a result, not only are new conventions required but existing ones need to be kept up to date. For example, the International Convention for the Safety of Life at Sea (SOLAS), 1960 was amended six times after it entered into force in 1965 - in 1966, 1967, 1968, 1969, 1971 and 1973. In 1974 a completely new convention was adopted incorporating all these amendments (and other minor changes) and has itself been modified on numerous occasions.
In early conventions, amendments came into force only after a percentage of Contracting States, usually two thirds, had accepted them. This normally meant that more acceptances were required to amend a convention than were originally required to bring it into force in the first place, especially where the number of States which are Parties to a convention is very large.
This percentage requirement in practice led to long delays in bringing amendments into force. To remedy the situation a new amendment procedure was devised in IMO. This procedure has been used in the case of conventions such as the Convention on the International Regulations for Preventing Collisions at Sea, 1972, the International Convention for the Prevention of Pollution from Ships, 1973 and SOLAS 1974, all of which incorporate a procedure involving the "tacit acceptance" of amendments by States.
Instead of requiring that an amendment shall enter into force after being accepted by, for example, two thirds of the Parties, the “tacit acceptance” procedure provides that an amendment shall enter into force at a particular time unless before that date, objections to the amendment are received from a specified number of Parties.
In the case of the 1974 SOLAS Convention, an amendment to most of the Annexes (which constitute the technical parts of the Convention) is `deemed to have been accepted at the end of two years from the date on which it is communicated to Contracting Governments...' unless the amendment is objected to by more than one third of Contracting Governments, or Contracting Governments owning not less than 50 per cent of the world's gross merchant tonnage. This period may be varied by the Maritime Safety Committee with a minimum limit of one year.
As was expected the "tacit acceptance" procedure has greatly speeded up the amendment process.  Amendments enter into force within 18 to 24 months, generally  Compared to this, none of the amendments adopted to the 1960 SOLAS Convention between 1966 and 1973 received sufficient acceptances to satisfy the requirements for entry into force.

Enforcement
The enforcement of IMO conventions depends upon the Governments of Member Parties.
Contracting Governments enforce the provisions of IMO conventions as far as their own ships are concerned and also set the penalties for infringements, where these are applicable.
They may also have certain limited powers in respect of the ships of other Governments.
In some conventions, certificates are required to be carried on board ship to show that they have been inspected and have met the required standards.  These certificates are normally accepted as proof by authorities from other States that the vessel concerned has reached the required standard, but in some cases further action can be taken.
The 1974 SOLAS Convention, for example, states that "the officer carrying out the control shall take such steps as will ensure that the ship shall not sail until it can proceed to sea without danger to the passengers or the crew".
This can be done if "there are clear grounds for believing that the condition of the ship and its equipment does not correspond substantially with the particulars of that certificate".
An inspection of this nature would, of course, take place within the jurisdiction of the port State.  But when an offence occurs in international waters the responsibility for imposing a penalty rests with the flag State.
Should an offence occur within the jurisdiction of another State, however, that State can either cause proceedings to be taken in accordance with its own law or give details of the offence to the flag State so that the latter can take appropriate action.
Under the terms of the 1969 Convention Relating to Intervention on the High Seas, Contracting States are empowered to act against ships of other countries which have been involved in an accident or have been damaged on the high seas if there is a grave risk of oil pollution occurring as a result.
The way in which these powers may be used are very carefully defined, and in most conventions the flag State is primarily responsible for enforcing conventions as far as its own ships and their personnel are concerned.
The Organization itself has no powers to enforce conventions.
However, IMO has been given the authority to vet the training, examination and certification procedures of Contracting Parties to the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW), 1978. This was one of the most important changes made in the 1995 amendments to the Convention which entered into force on 1 February 1997. Governments have to provide relevant information to IMO's Maritime Safety Committee which will judge whether or not the country concerned meets the requirements of the Convention.

Relationship between Conventions and interpretation
Some subjects are covered by more than one Treaty. The question then arises which one prevails. The Vienna Convention on the Law of Treaties provides in Article 30 for rules regarding the relationship between successive treaties relating to the same subject-matter. Answers to questions regarding the interpretation of Treaties can be found in Articles 31, 32 and 33 of the Vienna Convention on the Law of Treaties. A Treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose. When a Treaty has been authenticated in two or more languages, the text is equally authoritative in each language, unless the treaty provides or the parties agree that, in case of divergence, a particular text shall prevail.
Uniform law and conflict of law rules
A substantive part of maritime law has been made uniform in international Treaties. However, not every State is Party to all Conventions and the existing Conventions do not always cover all questions regarding a specific subject. In those cases conflict of law rules are necessary to decide which national law applies. These conflict of law rules can either be found in a Treaty or, in most cases, in national law.

IMO conventions
The majority of conventions adopted under the auspices of IMO or for which the Organization is otherwise responsible, fall into three main categories.
The first group is concerned with maritime safety; the second with the prevention of marine pollution; and the third with liability and compensation, especially in relation to damage caused by pollution.  Outside these major groupings are a number of other conventions dealing with facilitation, tonnage measurement, unlawful acts against shipping and salvage, etc.

Tacit acceptance procedure
The amendment procedures contained in the first Conventions to be developed under the auspices of IMO were so slow that some amendments adopted have never entered into force. This changed with the introduction of the "tacit acceptance" procedure.
Tacit acceptance is now incorporated into most of IMO's technical Conventions. It facilitates the quick and simple modification of Conventions to keep pace with the rapidly-evolving technology in the shipping world. Without tacit acceptance, it would have proved impossible to keep Conventions up to date and IMO's role as the international forum for technical issues involving shipping would have been placed in jeopardy.
In the spring of 1968, IMO - then still called IMCO, the Inter-Governmental Consultative Organization - celebrated the 20th anniversary of the adoption of the IMO Convention. It should have been an occasion for some congratulations. But all was not well. Many of the Organization's Member States were not happy with the progress that had been made so far.
Many were concerned about the Organization's structure and its ability to respond to the changes taking place in shipping. In March, 1967, the oil tanker Torrey Canyon had gone aground off the coast of England, resulting in what was then the world's biggest oil spill. IMO was called upon to take action to combat oil pollution and to deal with the legal issues that arose. But would it be able to do so?
The general disquiet was summed up by Canada in a paper submitted to the 20th session of the IMO Council in May 1968. It stated that "the anticipations of twenty years ago have not been fulfilled" and went on to complain of the effort required by Member States in attending meetings and dealing with the technical problems raised by IMO. The paper was discussed by the Council which agreed to establish a working group to prepare a draft statement of the objectives of IMO and an inventory of further objectives which the Organization could usefully fulfil in the field of international maritime transport.
In November 1968 the working group reported back to the Council. It outlined a list of activities, far broader than the programmes undertaken by IMO so far. This was approved by the Council, which also agreed that IMO needed to improve its working methods.
The working group was asked to report to the Council again at its 22nd session in May 1969.This time it put forward a number of proposals for improving IMO's working methods, the most important of which concerned the procedures for amending the various Conventions that had been adopted under IMO's auspices.
The problem facing IMO was that most of its Conventions could only be updated by means of the "classical" amendment procedure. Amendments to the 1960 SOLAS Convention, for example, would enter into force "twelve months after the date on which the amendment is accepted by two-thirds of the Contracting Governments including two-thirds of the Governments represented on the Maritime Safety Committee. This did not seem to be a difficult target when the Convention was adopted, because to enter into force the Convention had to be accepted by only 15 countries, seven of which had fleets consisting of at least 1 million gross tons of merchant shipping.
But by the late 1960s the number of Parties to SOLAS had reached 80 and the total was rising all the time as new countries emerged and began to develop their shipping activities. As the number of Parties rose, so did the total required to amend the Convention. It was like trying to climb a mountain that was always growing higher and the problem was made worse by the fact that Governments took far longer to accept amendments than they did to ratify the parent Convention.
The Council approved the working group's proposal that "it would be a useful first step to undertake a comparative study of the conventions for which IMO is depositary and similar instruments for which other Members of the United Nations family are responsible." This proposal was endorsed by the 6th regular session of the IMO Assembly in October 1969 and the study itself was completed in time to be considered by the Assembly at its 7th session in 1971.
It examined the procedures of four other UN agencies: the International Civil Aviation Organization (ICAO), the International Telecommunications Union (ITU), the World Meteorological Organization (WMO) and the World Health Organization (WHO).
It showed that all of these organizations were able to amend technical and other regulations. These amendments became binding on Member States without a further act of ratification or acceptance being required.
On the other hand, IMO had no authority to adopt, let alone amend conventions. Its mandate allowed it only to "provide for the drafting of conventions, agreements or other instruments and to recommend these to Governments and to intergovernmental organizations and to convene such conferences as may be necessary." Article 2 of the IMO Convention specifically stated that IMO's functions were to be "consultative and advisory".
The Organization could arrange a conference - but it was up to the conference to decide whether the Convention under discussion should or should not be adopted and to decide how it should be amended. The study concluded that "any attempt to bring IMO procedure and practice into line with the other organizations would, therefore, entail a change either in the constitutional and institutional structure of the Organization itself or in the procedure and practice of the diplomatic conferences which adopt the conventions of IMO.
The first might involve an amendment to the IMO Convention itself. The second might require that diplomatic conferences convened by IMO should grant greater power to the organs of IMO in regard to the review and revision of the instruments.
The study was discussed at length by the Assembly. Canada pointed out that the amendments adopted to the 1960 SOLAS Convention in 1966, 1967, 1968 and 1969 had failed to enter into force and this "sufficed to show that IMO would henceforth have to tackle serious institutional problems." A note submitted to the conference by Canada stated that "unless the international maritime community is sufficiently responsive to these changed circumstances, States will once again revert to the practice of unilaterally deciding what standards to apply to their own shipping and to foreign flag shipping visiting their ports."
The result was the adoption of resolution A.249(VII) which referred to the need for an amendment procedure "which is more in keeping with the development of technological advances and social needs and which will expedite the adoption of amendments." It called for the Legal Committee and Maritime Safety Committee to prepare draft proposals for consideration by the 8th Assembly.
A growing urgency was added by the fact that IMO was preparing a number of new conventions for adoption during the next few years. Conferences to consider a new Convention on the International Regulations for Preventing Collisions at Sea and an International Convention for Safe Containers were both scheduled for 1972, a major Convention dealing with the Prevention of Marine Pollution from Ships for 1973 and a conference to revise SOLAS was scheduled for 1976. All of these treaties required a new, easier amendment procedure than the traditional method.
The MSC discussed the amendment question at its 25th session in March 1972. A working group was formed to discuss the matter in detail and concluded that at current rates of acceptance the requisite "two-thirds" target needed to amend SOLAS 1960 "will not be achieved...for many years, possibly never." Moreover, any future amendments would almost certainly suffer the same fate. This would include any amendments intended to improve the amendment procedure itself.
The working group reported: "It follows that the only realistic way of bringing an improved amending procedure into effect within a reasonable period of time is to incorporate it into new or revised technical conventions.
A few weeks later, the Legal Committee held its 12th session. Among the documents prepared for the meeting was a report on discussions that had taken place at the MSC and a detailed paper prepared by the Secretariat. The paper analysed the entry into force and amendment processes of various IMO Conventions and referred to two possible methods that had been considered by the Assembly, for speeding up the amendment procedure. Alternative I was to revise each Convention so that greater authority for adopting amendments might be delegated to the appropriate IMO organs. Alternative II was to amend the IMO Convention itself and give IMO the power to amend Conventions.
The study then considered Alternative I in greater detail. The main reason why amendments took so long to enter into force was the time taken to gain acceptance by two-thirds of Contracting Governments. One way of reducing this period would be by "specifying a date ...of entry into force after adoption by the Assembly, unless that date of amendment is explicitly rejected by a certain number or percentage of Contracting Governments." The paper said that this procedure "has the advantage that all Contracting Governments would be able to advance the preparatory work for implementing the amended regulations and the industry would be in a position to plan accordingly."
The Committee established a working group to consider the subject and prepared a preliminary study based on its report, which again referred to the disadvantages of the classical amendment system. The study continued: "The remedy for this, which has proved to be workable in practice, in relation to a number of conventions, is what is known as the 'tacit' or 'passive' acceptance procedure. This means that the body which adopts the amendment at the same time fixes a time period within which contracting parties will have the opportunity to notify either their acceptance or their rejection of the amendment, or to remain silent on the subject. In case of silence, the amendment is considered to have been accepted by the party...".
The tacit acceptance idea immediately proved popular. The Council, at its meeting in May, decided that the next meeting of the Legal Committee should consist of technical as well as legal experts so that priority could be given to the amendment issue. The Committee was asked to give particular attention to tacit acceptance.
The idea was given non-governmental support by the International Chamber of Shipping, which had consultative status with IMO and submitted a paper stating that the lack of an effective amendment procedure created uncertainties and was detrimental to effective planning by the industry. The classical procedure had also encouraged some governments to introduce unilateral legislation that, however well intentioned, was "seriously disruptive to international shipping services." The paper said that if other Governments did the same " the disruption to international shipping and the world trade which it serves would become increasingly severe. Such unilateral action strikes at the purpose of IMO."
By the time the Legal Committee met for its 14th session in September 1972, there was general agreement that tacit acceptance offered the best way forward. Other ideas, such as amending the IMO Convention itself, had too many disadvantages and would take too long to introduce. There was some concern about what would happen if a large number of countries did reject an amendment and the Committee members agreed that tacit acceptance should apply only to the technical content of Conventions, which was often contained in annexes. The non-technical articles should continue to be subject to the classical (or "positive") acceptance procedure.
The Committee also generally agreed that alternative procedures for amending the technical provisions should be retained but it did not reach consensus on another issue: should amendments be prepared and adopted by an appropriate IMO body, such as the Maritime Safety Committee - or by Contracting Parties to the Convention concerned? This was an important point at the time, since many Contracting Parties to IMO Conventions were not yet Members of IMO itself and might object to treaties they had ratified being amended without them even being consulted.
This issue was still unsettled when the Conference on Revision of the International Regulations for Preventing Collisions at Sea opened in October 1972. The purpose of the conference was to update the Collision Regulations and to separate them from the SOLAS Convention (the existing regulations were annexed to SOLAS 1960).
The amendment procedure is contained in Article VI. Amendments to the Collision Regulations adopted by the MSC (by a two-thirds majority) have to be communicated to Contracting Parties and IMO Member States at least six months before being considered by the Assembly. If adopted by the Assembly (again by a two-thirds majority), the amendments enter into force on a date determined by the Assembly unless more than one third of Contracting Parties notify IMO of their objection. On entry into force, any amendment shall "for all Contracting Parties which have not objected to the amendment, replace and supersede any previous provision to which the amendment refers."
Less than two months later, on 2 December 1972 a conference held in Geneva adopted the International Convention for Safe Containers, Article X of which contains procedures for amending any part or parts of the Convention. The procedure is the traditional "positive" acceptance system, under which amendments enter into force twelve months after being adopted by two-thirds of Contracting Parties. However, Article XI contains a special procedure for amending the technical annexes which also incorporates tacit acceptance. The procedure is slightly different from that used in the Collision Regulations, one difference being that the amendments can be adopted by the MSC "to which all Contracting Parties shall have been invited to participate and vote." This answered the question of how to take into account the interests of Parties to Conventions that were not Member States of IMO.
The next Convention to be considered was the International Convention for the Prevention of Pollution from Ships (MARPOL), which was successfully adopted in May 1973. It, too, incorporated tacit acceptance procedures for amending the technical annexes. In the meantime, IMO was preparing for a new SOLAS convention. This was considered necessary because none of the amendments adopted to the 1960 version had entered into force and did not appear likely to do so in the near future. The 1966 Load Lines Convention also contained a classical amendment procedure and the intention was to combine the two instruments in a new Convention, which was scheduled to be considered in 1976.
The MSC discussed this proposal at its 26th session in October-November, but it was clear that this would be a daunting and time-consuming task. The combined instrument might be a good idea for the future - but the real priority was to get the amendments to SOLAS 1960 into force as quickly as possible and to make sure that future amendments would not be delayed. A working group was set up to consider the various alternatives, but opinion began to move in favour of a proposal by the United Kingdom that IMO should concentrate on an interim Convention designed to bring into force the amendments adopted since 1960. The new Convention, it was suggested, would consist of the 1960 text with the addition of a tacit acceptance amendment procedure and the addition of amendments that had already been adopted.
Another advantage, the United Kingdom pointed out, was that the conference called to adopt the revised Convention "might be held considerably earlier than 1976 since comparatively little preparation would be needed." The subject was discussed again at the MSC's 27th session in the spring of 1973 and, although some delegations wanted a more comprehensive revision, others felt that the workload would be so great that the conference would be seriously delayed. By a vote of 12 in favour and four abstentions, the Committee decided to call a conference with limited scope, as proposed by the United Kingdom.
On 21 October, 1974, the International Conference on Safety of Life at Sea opened in London and on 1 November a new SOLAS Convention was adopted, which incorporated the tacit acceptance procedure.
The tacit acceptance amendment procedure has now been incorporated into the majority of IMO's technical Conventions and has been extended to some other instruments as well. Its effectiveness can be seen most clearly in the case of SOLAS 1974, which has been amended on many occasions since then. In the process, the Convention's technical content has been almost completely re-written.

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