we are all familiar with the use of a rudder which helps in turning a ship as and when required
rudders are the principal system for the entire motion and control of the ships but we must not
forget that the entire rudder action is dependent on another pivotal system called the steering gear
the steering gear system has been an indispensable part of the ship's machinery since the advent of
the very early ships which were operated by hand as ships continued to grow in size and
became faster modern systems easing human effort were incorporated there are two types of commonly
used steering gear systems one being hydraulic and the other being electro hydraulic type the
main control of the steering operations is given from the helm of any ship similar to an automobile
where the entire control of the vehicle steer ability rests on the steering wheel of the driver
the control force for turning is triggered off from the wheel at the helm which releases steering
gear system advanced electro hydraulic systems are predominant in ships nowadays actuators are
now mainly electrically driven by power units these actuators in turn can be of two types
piston and cylindrical arrangement
vein type rotor in this video we are discussing the hydraulic ram type steering gear
there are four hydraulic cylinders attached to the two arms of the actuator disc on both sides
these cylinders are directly coupled to electrically driven hydraulic pumps
which generate hydraulic pressure through pipes this hydraulic pressure field present in the pumps
imparts motion to the hydraulic cylinders which in turn corresponds with the actuator to act upon the
rudder stock the sense of turning this rudder is guided by the action of the hydraulic pump
the physics behind its function can be explained better with the help of the following figure
here the cylinders denoted 1 and 3 are connected to the discharge side of the pump this generates
a positive pressure in the piston cylinders on the contrary the other two cylinders 2 and 4 are
connected to the suction side of the pump this creates a negative pressure in the cylinders
the resultant forces create a clockwise moment in the rudder to put it simply
positive and negative pressures from the pumps generate lateral forces on the ramps which create
a couple for turning the rudder stock similarly to put it in an anti-clockwise turning sense
the reverse is carried out that is the discharge ends of the pumps are connected to the cylinders
2 and 4 while the suction side of the pumps is to 1 and 3 this reverse pressure flow from
hydraulic pumps is achieved with the help of control valves operated from the wheelhouse
the ram type steering gear arrangement produces a considerably high
value of torque for a given applied power the hydraulic oil pressure varies from 100 bars
to 175 bars depending on the size of the rudder and torque required
as per solas requirements all tankers of more than 10 000 gross tonnage
and all other 70 000 gross tonnage vessels should have a safe matic steering gear arrangement should
be there to isolate the fault and continue using the steering system in an 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 of all four ramps
in case of leakage the system level switch gets activated starting the standby pump and raises
the alarm but if a further leak persists in the system it initiates the bypass and isolation valve
now the steering gear runs on 50 percent of its torque isolating the faulty set of ramps
now the other system without a leak will operate the pump
and the ram associated with it will move as per the desired command
the efficiency of the performance of steering gear depends on some main aspects these basic
requirements to be invariably met by all steering gears are guided by rules set by classification
societies they can be briefly outlined as as per standard requirements the steering gear should
be capable of steering the ship from 35 degrees port to 35 degree starboard and vice versa while
the vessel plying forwards at a steady head-on speed for maximum continuous rated shaft rpm
and summer load water line within a time frame of maximum of 28 seconds
with one of the power units in operative the rudder shall be capable of turning 15 degree sport
to 15 degrees starboard and vice versa within a time frame of one minute with the vessel
moving ahead at half its rated maximum speed or 7 knots whichever is greater at summer load line
the major power units and the control systems are to be duplicated so that
if one of them fails the other can easily substitute for them as standby
the steering gear system is to be provided with an additional power unit
hydraulic pump etc connected to the emergency power supply from the emergency generator
which shall be capable of turning the rudder from 15 degrees from one side to the other side within
60 seconds with the vessel moving at a maximum service speed or 7 knots whichever is greater
the hydraulic steering gear system is critical machinery on board
whose operation knowledge is extremely important for the safe navigation of the ship
now that we know the significance of steering systems and ships and the importance of their
safematic designs we come to the end of this video thank you all for watching
you