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STEERING SYSTEM
SOLAS CHAPTER II-1: Regulation 29
Construction – structure, stability, installations
INTRODUCTION
The Steering System consists of the Universal Gyro pilot Control Panel and the
Steering Hydraulic System. The hydraulic portion of the system consists of two
independent systems that are connected to the common steering ram piping. These
two systems work in conjunction to allow the ship to be maneuvered. The steering
gear or hydraulic system may be operated in various locations of the ship, from
the Pilot House, from the Winch Control House and the Steering Gear Room.
System Components
Wheel House
- main control panel is located which feature
the start/stop and alarms/signal and
acknowledgement of alarms
- In the wheel house ceiling there is a
panorama 3-way rudder angle indicator.
- There are always two rudder angle indicators,
one of each bridge wing.
Engine Control Room
There is Alarm/Signal Panel.
According to normal standards, and to
avoid possible misunderstandings it
should not be possible to operate the
steering gear from this control stand.
Steering Gear Compartment
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On the top of the actuator there is a scale with degrees, showing the angle of
the rudder to port/starboard, and also signal transmitters and feed backs for
remote rudder indication and steering controls system
An
auxiliary steering gear is not required according to rules, because the power
units are regarded as back-up for each other
FUNCTIONAL DESCRIPTION
Universal Gyro pilot Control Panel
The Universal Gyro pilot Control Panel consists of the electro-mechanical
heading selector components, non-follow-up controller module, a dimmer control
circuit and a gyro pilot computer control panel.
HEADING SELECTOR COMPONENTS
The heading selector components visible from the outside of the panel include a
fixed index (lubber line) that represents a fore-aft axis of the vessel, a repeater
dial that displays the gyrocompass heading under the lubber line and heading
pointer that points to the selected heading. (When the vessel is on the
selected heading, the heading pointer and lubber line are lined up). A
HEADING ORDER control knob is used to position the heading pointer when a
change in heading is desired. A HEADING SYNC control is used to synchronize
the repeater dial with the ship's gyrocompass on initial start-up.
Within the panel is a step motor which is controlled by the gyrocompass.
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Synchro(s) supply heading error data to the gyro pilot computer. An integrator
reset switch resets the integral function in the rudder order computer when the
change in selected heading is greater than (10) degrees.
NON-FOLLOW-UP CONTROLLER MODULE
The Non-Follow-Up Controller Module consists of a three-position (Left-Off-Right)
self centering rotary switch and two (2) lamps which furnish illumination. The
switch overrides all other modes of operation. When the switch is in the center
position, the steering mode is determined by the Mode Selector Switch. For
continuous NFU operation, NFU position must be selected on the Mode
Switch.
GYROPILOT COMPUTER CONTROL PANEL
The Gyro pilot Computer Control Panel, which is located behind a hinged
cover, contains the following controls for the Gyro pilot Computer and is
operational only in Gyro mode.
Integrator Switch
Switch resets the integral function in the OFF position. In ON position, the
integrator in the Rudder Order Computer starts computing a new, continuous
average heading error signal after large heading changes are made. This
function is also performed automatically by a reset switch that is cam actuated
by the Heading Order control for heading changes larger than (10) degrees.
Weather ADJ Potentiometer
Calibrated in increments between (0) degrees and (5) degrees to control the
sensitivity (amount of heading error permitted before rudder ratio is increased). A
setting of (0) degree provides maximum sensitivity and a setting of (5) degrees
provides minimum sensitivity. In calm seas the potentiometer should be set to (0)
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degrees for best steering performance. In rough seas, where there is
considerable yaw, the potentiometer should be set to correspond to the number
of degrees of natural yaw motion from the base heading.
Rudder Multiplier Potentiometer
This potentiometer has settings between (1) (minimum gain) and (3)
(maximum gain) that vary the gain of the summing amplifier in the Rudder
Order Computer. This potentiometer controls the amplitude of the heading error
plus rate signal to provide operator control of the rudder ratio for optimum
performance. The higher settings cause the ship to respond more quickly to
heading error by ordering larger rudder angles. Use an initial setting of 2. This
potentiometer should be set to the minimum setting that will prevent the ship
from wandering from its ordered heading in calm water. Operation at reduced
ship's speed usually requires a higher setting.
Rate Multiplier Potentiometer
This potentiometer controls sensitivity of the Rudder Order Computer to
changes in the rate circuits. The clockwise position provides maximum
sensitivity and the counterclockwise position provides minimum sensitivity
which is (50) percent of the maximum. Normally a setting of 1.0 should be used
for light draft and 2.0 for full draft.
Rudder Limits Potentiometer
This potentiometer is used to set the limit of rudder movement, right or left,
between (5) and (45) degrees in gyro mode only. Position, as desired, to set
the limit of rudder movement in GYRO operation. Fifteen (15) degrees is
sufficient for heading keeping and normal heading changes.
UNIVERSAL GYROPILOT HELM UNIT
The Universal Gyro pilot Helm Unit consists of the helm order unit, rudder
order indicator, system selector switch module and mode switch
module.
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Helm Unit and Rudder Order Indicator
The Helm Unit consists of two (2) synchro transmitters mechanically geared to
the steering wheel. A panel-mounted rudder order indicator is geared to the
steering wheel through a toothed belt drive.
When the mode selector switch is in HAND position, the vessel's rudder comes
to the position ordered on the rudder order indicator. The wheel drives a
gear train that positions the rotors of the synchro transmitters. A break on the
wheel shaft provides the necessary restraint to enable the helmsman to
position the steering wheel accurately and to hold it steady. A slip clutch
couples the wheel to the gear train and a mechanical stop in the gear train
prevents the synchro rotors from driving more than 45 of rudder order from the
zero position. If the steering wheel is turned past this rudder order position,
as indicated on the rudder order indicator, the clutch will allow the steering
wheel to continue to rotate, but the synchro rotor movement will cease. As soon
as the wheel is moved in the opposite direction, the mechanical stop
disengages and the rudder responds immediately to the new rudder order. The
helmsman may steer by the gyro repeater in the Gyro pilot, or from the
magnetic compass.
System Selector Switch Module
The System Selector Switch Module is provided for duplex steering systems to
select the desired system or power unit (port and stbd.) or turn the system OFF.
The module consists of the rotary switch, a lighted panel, lamp circuit and
lamps. The switch provides switching between the port and stbd power
supplies, remote starting contacts and switching of synchro excitation from one
set of synchros to the other. The lighted panel includes markings (SYSTEM,
PORT PW AVAIL, and PORT PUMP ON, STBD PWR
AVAIL, STBD PUMP ON, PORT, OFF, STBD) each illuminated by a separate
miniature lamp mounted on the circuit card. The brightness of these status
lamps is controlled by
a dimmer potentiometer on the gyro pilot helm unit mode switch module. The
mode switch module permits selection of the four (4) types of steering control
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(gyro, hand, NFU and remote lever). The switch provides switching between
the heading set and rudder order synchros connects the rudder order computer to
the system in GYRO and disconnects the rudder servo amplifier in NFU.
GYROPILOT COMPUTER
The gyro pilot computer converts heading error or rudder order data into control
signals for the rudder-positioning equipment. The computer consists of a group
of modules, a power supply, dual-channel demodulator, rudder order computer,
rudder servo amplifier and solid-state relay, which are mounted in a rack in the
Pilot House console.
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RUDDER REPEATBACK RUDDER ANGLE TRANSMITTER
The Rudder Repeat back/Rudder Angle Transmitter contains a torque synchro
which generates a rudder position signal for driving rudder angle indicators and a
repeat back potentiometer which is used with other steering equipment to position
the rudders to a predetermined angle. The rudder repeat back signal is
connected to an amplifier in the steering control equipment where it is
compared to a rudder order signal; when the rudder order and repeat back
signals are equal, rudder movement stops. The rudder angle indicator synchro
transmitter is in a separate box, and separate power from EMG SWBD via Circuit
"N". Also contains the electrical stops which should be approximately 2° from
the positive mechanical stops.
STEERING SELECTOR SWITCHBOX
The Steering Selector Switchbox, located on the forward bulkhead of the Steering
Gear Room, determines whether control of the steering systems (port and stbd)
is in the Steering Gear Room or the Pilot House. It has a three (3) position
selector switch (PORT AFT, STBD AFT AND FWD); it also incorporates local
NFU control for the port and stbd. steering gear systems.
During normal operation, the selector switch will be in the FWD position,
allowing port and stbd. steering gear start/stop control by the system selector
switch module of the gyro pilot helm unit located in the Pilot House console; it
also transfers operational control to the Pilot House.
In local control (PORT AFT, STBD AFT) the steering gear is started at the
local controller. Control of the steering gear is accomplished by the local NFU
control for the selected system.
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STEERING GEAR
CYLINDERS
The steering cylinders have chrome-plated cylinder bores and chrome-plated
stainless steel piston rods. The piston is fitted with "U" cup type piston seals.
Piston rods and cylinder anchors are fitted with spherical bearings.
The steering gear is capable of moving, stopping and holding both rudders at any
angle, while moving ahead or astern in free route at full propeller revolutions per
minute and is capable of moving rudders from 45 degrees on either side to 40
degrees on the other side in 28 seconds.
HYDRAULIC POWER UNIT
The hydraulic power unit is based on a single tank with two (2) separate
compartments. Each motor/pump draws oil from the compartment beneath it
and discharges into a common return header that returns oil to both
compartments through (25) micron filters. This provides maximum cooling by
circulating oil through both compartments. The center bulkhead between
compartments has overflow ports at top so oil entering compartment for which
motor is not running overflows back into running motor compartment. The
compartment for running motor will show an oil level several inches lower than
the other. The return header has a ball valve in center that is normally open. By
closing this valve, all oil returns to the same sump it was pumped from while
the other is being serviced, including draining the compartment. The hydraulic oil
reservoirs have a capacity of 110 percent of the hydraulic system. Each tank
compartment is fitted with an oil level switch, which is set to operate about (5)
inches below tank top or when oil reaches bottom of sight glass.
DIRECTIONAL VALVE ASSEMBLY
Oil from pump flows to the manifold directional valve assembly. Oil flows
through an in-line (65) PSI check valve that provides the back pressure (pilot
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pressure) required to operate the directional valve spool. Oil from pump flows to
a port in manifold block then into relief valve contained in the module,
sandwiched between manifold and directional valve. The system relief valve is
set at 1,100 PSI. From relief valve oil flows into the directional valve and back
through relief and manifold where it exits and on to the back pressure check
valve.
PILOT DIRECTIONAL VALVE
The small electric solenoid pilot directional valve directs oil to shift the main
directional spool just below it. The system may be operated during emergency or
during testing by shifting the direction valve spool manually. To do this, use a
tool such as a Phillips Screwdriver to push in on the small plunger located in
the end of the small piloting electric solenoid valve. This causes the directional
valve to respond exactly as though it has been energized by an electrical
current.
COUNTERBALANCE VALVES
On the backside of each manifold are two (2) modified counterbalance valves.
These valves act to hold the steering cylinders in position and prevent cylinders
from moving ahead of oil flow from pump.
CROSSPORT RELIEF VALVES
The hydraulic system is equipped with two cross port relief valves, which have a
set point of 1300 PSIG. The purpose of the valves is to prevent over
pressurization of the system and cylinders in the event there is no demand for
rudder movement {pump discharge ported directly to the sump via the 4-way
valve) and an external force is applied to the, rudders causing system pressure to
reach 1300 PSIG. The valves allow pressure to be relieved to the sump.
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Daniel Robson T/V KINGS POINTER Revised: 6/21/01Chief Engineer Steering System Page: 14
Daniel Robson T/V KINGS POINTER Revised: 6/21/01Chief Engineer Steering System Page: 15
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VARIOUS MAIN PROPULSION ARRANGEMENT
Introduction
As the United Nations Secretary General has said, climate change is the
major, overriding environmental issue of our time, and the single greatest challenge
facing environmental regulators. It is a growing crisis with economic, health and
safety, food production, security, and other dimensions.
Many measures have been established to address this major concerns and
one of these is the amendments to MARPOL Annex VI concerning the amount of
emissions from ships that are polluting our atmosphere. To comply with the
amendments, engine manufacturers are now in the process of developing
environment friendly engines which will help to reduce the amount of emissions from
our engines.
Following are some Main Propulsion Arrangements that are being used in
different types of vessels
1. Main Propulsion Steam Turbines (MR-II & MS-2)
The MR-II & MS-2 series marine steam turbines are designed specifically for
various kinds of application required, and both series have covered
comprehensive range to 45 MW output power.
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Five basic elements
1. The high & intermediate-pressure or high pressure turbine,
2. low-pressure turbine,
3. reduction gear,
4. main thrust block
5. main condenser
Each standardized in design as according to standard unit output capacities,
so that the series can comply with any specific vessel propulsion power requirements
by selecting proper combinations.
All the series will surely gratify you with an environment-friendly, higher reliability and
safety, the best performance.
CST Series (Conventional Steam Turbine)
All the MS-2 series marine steam turbines are of non-reheat, two-cylinder
cross-compound impulse reaction type, and countless delivery records are
eloquent testimony to a firm reliability and safety of the CST series.
All the MS-2 series marine steam turbines invariably proved a wise investment
for end-users have thus earned very high reputation among them.
UST Series (Ultra Steam Turbine)
All the MR-II series marine steam turbines are of
reheat, two- Cylinder cross compound impulse
reaction type, and are in the forefront of Steam
turbine technology.
The latest technologies and well-proven
designs supported and developed by our
experienced land & marine use turbines
have been unstintingly introduced into the
series.
The best performance of all the MR-II
series marine steam turbines brings about
the best propulsion for end-users and the environment-friendly UST series
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contributes to a saving energy as well.
2. Diesel and gas turbine electric propulsion System for cruise ship
Combined Diesel and Gas Turbine Electric Drive System (CODEG)
A CODEG propulsion system consists depending on the size of the ship of 1
or 2 gas turbines generator sets and 2 to 4 diesel engine generator sets.
Every set is providing electric power for the electric propulsion motors and
also for the on-board electric power demand.
The steam needed for the hotel accommodation will be produced by exhaust
gas heat boilers, located in the exhaust gas ducts of the gas turbines.
Why is CODEG the better solution for cruise ships?
Compared to other propulsion systems
for cruise ships, like conventional
Diesel Mechanical propulsion systems,
conventional Diesel Electric propulsion
systems or even the advanced
Combined Gas Turbine and Steam
Turbine propulsion system,
CODEG has the following advantages:
a. Additional cabins
Due to the location flexibility of the diesel and gas turbine generator sets, the
machinery spaces can be placed anywhere in the ship.
The gas turbine generator sets can be placed even on the upper deck, due to
their relative low weight and this deletes also the air inlet and exhaust gas
ducts.
The MTU gas turbine and diesel engine generators sets are of a very
compact design, which leads to less required machinery space.
b. Low personnel costs
The MTU gas turbine and diesel engine generator sets are designed for easy
21
operation and maintenance
c. High efficiency
In the power range of 90% to maximum rating the GE gas turbines, type
LM2500 and LM2500+ show excellent efficiency.
As the cruise ship has varying demands of electric power, a combination
with the latest MTU diesel engine generator set cover lower load demands.
The prime mover 20V 8000 M50 shows competitive fuel consumption, also
in part load.
The gas turbine exhaust gases could also be used for steam production for
the hotel accommodation, using heat recovery boilers.
d. Green ship, i.e. low exhaust emissions
Several countries, e.g. Alaska, Scandinavia, California have released
strong emission regulations for ships approaching their shore and harbors,
mainly regarding NOx and Sox emissions.
It is therefore important for modern cruise ships to fulfill these regulations.
The MTU diesel engine 20V 8000 M50 has been designed to fulfill the
most stringent emission requirements.
The gas turbines, LM2500 and LM2500+ also fulfill the most stringent
emission requirements.
e. Low noise emissions
For a cruise ship the noise emissions are of high importance.
The 20V 8000 M50 is elastically mounted on the steel base frame, which is
it elastically mounted to the ship’s foundation. This double elastic mounting
arrangement reduces the structure borne noise effectively.
For a reduction of exhaust gas noise MTU is able to provide a suitable
silencer.
The gas turbines are rotating machines and have therefore naturally low
structure borne noise levels, but are also mounted elastically to the ship’s
foundation, which reduces the noise emissions even more.
The air borne noise levels are effectively reduced by silencers for the inlet
air and exhaust gas.
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3. Diesel-Electric Propulsion
The diesel electric propulsion system is a
system in which the propeller is driven by
electric power
It is a system that reduces life cycle costs, is
highly economical and safe, and also
environmentally friendly.
In diesel-electric systems, it has:
Multiple diesel engines,
each driving an electric generator,
produce the electric power that energizes the electric motors connected to the
propellers as well as other electrical loads on the ship.
Depending on electrical demand, not all diesel generators have to be
operating at all times.
Sample of Diesel Electric Propulsion: The brand new AX104 from Ulstein
The vessel will be the first anchor handling tug supply vessels in the world
designed for the North Sea environment equipped with diesel-electric
propulsion.
Advantages
Efficiency by being able to run appropriately sized diesel-engine generators
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based on demand versus a large diesel engine often idling along and that
leads to better control of emissions.
With combinations of small, medium and large diesel generators, you are able
to bring on power in small increments to keep the engines at appropriate
loadings and operating at their highest efficiencies.
In ordinary vessels, it is common for the main propulsion diesel engine to drive
the propeller while the power for lighting or motors is supplied by engine
generators.
The diesel electric propulsion system provides electricity both for propulsion
and on-board power needs.
Conventional vs. Diesel Electric
4. Two Stroke engine Propulsion
By nature, low speed engines lend themselves to direct coupling of the
propeller, i.e. without reduction gear. This contributes to the high efficiency,
increased reliability and low maintenance cost of the propulsion plant.
New developments in 2 stroke diesel engines
a. Helios, the development of a new ship engine generation
The objective of HELIOS is to develop a marine low speed two-stroke 24
gas Diesel engine research platform that is realistically sized for direct
drive marine propulsion, and that has an emission footprint which
compared to present Diesel engine technology is reduced as follows:
A dramatic reduction in sulphur emissions can be achieved,
however, by switching from heavy fuel oil to fuels with lower sulphur
content – such as marine diesel oil or natural gas. This solution
could initially be used in coastal ECAs or in harbors, while ships on
the high seas can continue to be powered by conventional fuel.
The dual tank arrangement required for this, however, is costly and
space-consuming. The fuels mentioned above are also significantly
more expensive than conventional heavy fuel oil. It must be kept in
mind that the operating costs of a ship or diesel power plant are
largely made up of fuel costs.
b. The exhaust gas scrubber, known as the open loop scrubber, reduces
the sulphur oxide content of the exhaust gases by 90 to 95 per cent.
Spray jets similar to the design of shower heads drench the exhaust gas
with sea water just before the flue. Water and sulphur react to form
sulphuric acid, which is neutralized with alkaline components in the sea
water. Filters separate particles and oil from the mixture before the cleaned
water is given back into the sea. The disadvantage of scrubber technology
is its relatively large space requirements on board. Its operation requires a
capacity of 40 to 50 cubic meters of sea water per Megawatt hour of
engine power.
MAN engineers are nevertheless already working on a version known as
the closed loop scrubber that uses fresh water in combination with caustic
soda as the neutralizing additive.
The scrubber then requires less space and its water requirements drop to
0.1 cubic meter per Megawatt hour output, and virtually no wash-water is
produced that would have to be lead into the sea.
Also in development is a dry scrubber, in which the exhaust gas flows
through granulated limestone. This combines with the sulphur to form
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gypsum, which can then be disposed of on land.
The advantage: the sulphur is locked in, meaning it cannot burden the
biosphere any more. The disadvantage: a storage room has to be created
on board for the granulate, which means sacrificing cargo capacity.
The green ship of the future: Project of MAN Diesel Turbo
The challenge and objective of “The Green Ship of the Future” initiative is to
reduce CO2 emissions by around 30 per cent and nitric and sulphuric oxides by 90
per cent. This initiative is using both familiar and new technologies.
Green Ship of the Future is primarily focusing on the large, two-stroke
engines of the type that are used in large ocean-going container ships and tankers.
The project was launched in 2008 by MAN Diesel & Turbo in conjunction with
the A.P. Møller-Mærsk Group Danish shipping firm, Odense Steel Shipyard and
Aalborg Industries.
The initiative’s primary objective is to highlight and develop new technologies
aimed at achieving a significant reduction in marine emissions. The project now has
some 15 partners, including shipping companies, their suppliers and several Danish
universities.
Shipping is an extremely eco-friendly form of transport, but with the Green
Ship of the Future initiative, MAN Diesel and Turbo are making even greater efforts
to protect the climate and the environment.
“Together with their partners, they want to help contribute towards the
development of products that are even more eco-friendly and will reduce emissions
further. “
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5. "Siemens-Schottel Propulsor" (SSP)
The Siemens-Schottel-Propulsor (SSP): a diesel-electric, podded propulsion system
enhances maneuverability and is easily integrated into a vessel
The electric, azimuthing SSP solution is a joint development by SCHOTTEL GmbH
and Siemens Marine Solutions. It combines SCHOTTEL's mechanical and
hydrodynamic expertise and the drive technology of a permanently excited Siemens
motor. This efficient and flexible propulsor can be optimally integrated and is ideal for
vessels that have to be highly maneuverable and need an easy to use, space-saving
solution – such as ferries, landing boats, cruise liners and special vessels.
The SSP is driven by a highly efficient, podded, permanently excited motor, which is
cooled by the surrounding seawater and has a slender and hydrodynamic optimized
design. These qualities are enhanced by the patented twin-propeller concept, in
which the propellers are mounted on the motor shaft, and rotate in the same
direction, one at each end of the pod. This combines the advantages of a twin-
propeller arrangement with a simple and rugged design. The SSP can be rotated
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through full 360 degrees, which significantly improves the vessel´s maneuverability,
especially at low speeds.
The SSP is a podded propulsion system in which an electric motor, mounted in a
pod below the vessel, drives the propellers directly. As the podded propulsor is freely
rotatable, it can also act as a rudder, so making a vessel extremely maneuverable,
even at low speeds, such as in harbor. The heart of the podded propulsion system is
a permanently excited motor, which runs without needing a complex external cooling
system. The special magnets mounted in the rotor of this permanent magnet motor
not only enable an extremely high torque keeping the diameter low but also avoid
rotor losses. The compact, hydro-dynamically efficient design and the twin-propeller
principle combined with an optimized vessel design constitute a highly efficient
propulsion system. As the motor is mounted outside the vessel, considerably less
space is required inside the vessel in comparison to conventional propulsion
systems. Added to which, the generator sets can be freely positioned to make better
use of the available space. These advantageous arrangements free up considerably
more space for cargo or passengers.
Conclusion:
In the above development, and all the measures that are being taken by all the
stakeholders, working on a ship will be more fruitful and enjoyable and will be able to
protect our environment before it’s too late.
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