2. STEERING GEAR
The direction of ship moving through the water is controlled by changing the
angle of rudder, located in the stern of the ship.
As gross tonnage of the ship increases, more and more force is required to move
the rudder to the required angle.
3. The main parts of marine steering gear
Telemotor
A control unit
A power unit
The telemotor transmitter -where the desired rudder angle is given.
The telemotor then transports this order to its receiver end which is connected to control
unit.
The control unit controls the power unit which moves the rudder from one position to
another
The power unit produces the force to displace the rudder at which the control unit is
ordered to.
4.
5. TWO TYPES OF STEERING GEAR SYSTEM
Both types of power steering system perform the same important function, but they execute it
differently.
1) Hydraulic System-uses mechanically pumped high pressure fluid.
2) Electro Hydraulic System-Electric motor to pressurize fluid.
Depending on torque required
• Ram Type System (2 or 4 Ram)
• Rotary vane type system.
3) All electric system
• Single motor system
6. RAM TYPES
One of the most common steering gear system used on ship.
Ram type steering gears contain hydraulic cylinders connected to the
hydraulic pumps.
7. STEERING GEAR-2
Ram System
The two rams hydraulic
steering mechanism
consists of two cylinders
,a pump and a motor (as
shown in figure)
8. Steering gear-4 Ram System
Four ram steering gear system works on the same principle as of two ram steering
system.
It has 4 rams instead of 2.the torque developed is two times that of 2 ram steering
system.
In emergencies such as hydraulic leakage, it can still be used to steer with minor
adjustment in the system such as isolating one set of ram through bypass and
isolation valves.
10. Steering gear-4 Ram System
Four ram steering gear system works on the same principle as of two ram steering system.
The only difference is that it has four ram instead of two.
The torque developed is also two times that of two ram steering system with better safeties and
emergency operation.
In emergencies such as hydraulic leakage, it can still be used to steer with minor adjustments in the
system.
Such as isolating one set of ram through bypass and isolation valves.
11. Explain the following in a Ram steering
Gear System.
A) isolating valve :- isolating valves are provided at each cylinder & Rotary vane chamber which
when closed it will hold the rudder by trapping the oil in the Chambers. Pumps are also equipped
with an isolating valves so that the pump can be totally shut off from the circuit and removed for
servicing while the steering is continued with the other pumps.
B) bypass valve:-. Bypass valves are normally closed but can be opened on two cylinder gear to
allow for the use of emergency steering. One pair of cylinder can be bypassed on a four cylinders
gear while the other pair of cylinders provide emergency steering at reduced torque
12. Explain the following in a Ram steering
Gear System.
C) Relief valves :- relief valves are provided between complementary pair of cylinder or Chambers
of vane gears. They are set to lift at pressure above the normal maximum.
D) Shock valves :- are fitted in pipework of the system between cylinders to prevent excessive
shock load from the rudder due to heavy seas being transmitted to the hydraulic system
16. Safe-matic design of steering gear
As per Solas requirement, All tankers of more than 10,000 GRT and all other 70,000 GRT
vessels should have a safematic steering system.
Arrangements should be there to isolate the fault and continue using the steering system
under emergency.
To avoid total failure of the steering system, automatic isolation and bypass valves are
introduced to the system.
Under normal conditions, one pump satisfies the need for all four rams.
17. Safe-matic design of steering gear
In case of leakage, the level switch gets activated and raises the alarm.
But if the further leak persists in the system, standby pump starts and it initiates the bypass
and isolation valve.
Now steering gear run on 50% of its torque isolating the faulty set of rams.
18. Rotary Vane Type
Rotary Vane Design:
Rotary vane steering gear system works on a similar principle as of the two and four ram steering
systems.
The only difference is that instead of rams, here we have different chambers build by housing
and vanes.
Rotary vane arrangement is preferred over Two or four Ram system, where there is less space,
low budget and wants same torque output at much lower hydraulic pressure.
20. Rotary Vane Type
Rotary vane steering gear is usually fitted with 3 fixed vanes and 3 moving vanes and can turn to
700 of total rudder movement i.e 350 on each side.
Three fixed and three moving vanes are usual and permit a total rudder angle of 70 °, i.e. 35° in
each direction.
The rotor C is fitted and keyed to a tapered rudder stock A, the stator B is secured to the ship’s
structure.
Fixed vanes, secured equidistantly in the stator bore and rotating vanes secured equidistantly in
the rotor, form two sets of pressure chambers in the annular space between the rotor and stator.
21. Rotary Vane Type
They are interconnected by a manifold.
Fluid supplied at pressure to one set of these chambers will rotate C clockwise and the rudder will
turn to port, or to starboard if the alternate set is put under pressure.
The fixed and rotating vanes may be of spheroidal graphite cast iron.
They are securely fixed to the cast steel rotor and stator by high tensile steel dowel pins and cap
screws.
Keys are also fitted along the length of the rotary vanes, for mechanical strength.
22. IMO Requirements of Steering Gear
SOLAS CH II-1Reg 29 & 30 (Construction-Structure, subdivision
and stability, machinery and electrical installation)
Ship shall be provided with main steering gear and an aux steering system.
The main steering gear and the aux steering gear shall be so arranged that failure of one of them will not
affect the operation of other.
Rudder stock and steering gear should be sufficiently strong and capable of steering at maximum speed.
The capacity of steering gear system should be such that:
• the rudder can be turned from 350 port to 350 starboard and vice versa.
• Be able to turn the rudder from 35° on one side to 300 on the other side within 28 seconds.
23. IMO Requirements of Steering Gear
SOLAS CH II-1Reg 29 & 30 (Construction-Structure, subdivision
and stability, machinery and electrical installation)
The aux steering gear system should have sufficient strength to steer the
ship at normal sea speed under emergency condition.
The aux steering system shall be suitable to tun the rudder from one side to
another (15* on one side to 15* on another side) in not more than 60 sec.
The main and aux steering gear power units shall be arranged to start
automatically when power is restored after a power failure.
A low level alarm (audible and visible) for each hydraulic tank.
31. What are the Maintenance and
checks of Steering Gear?
Daily checks
Lubrication of sliding or moving parts inspection
Check greasing mechanism for proper functioning.
Inspect all linkages.
Inspect seals, connectors, pipelines for leaks
Oil level checks
Check temperatures & pressures.
Check ammeter reading of pump
Check level of replenishing tanks.
32. What are the Maintenance and
checks of Steering Gear?
Weekly checks
Check alarms & emergency changeovers.
Check bridge to steering room communication on portable devices and sound powered phone.
Monthly checks
Check & clean hydraulic oil filters or replace
3 Monthly checks
Try out emergency steering from local control station in steering & log down in logbook.
6 Monthly checks
Samples of oil for shore analysis.
