What are the
types of telemotor system in steering gear on ships ?
1.
Hydraulic
system
2.
Electric system
What
are the types of steering system ?
§ Electro hydraulic system
a) Ram type
system (2 ram or 4 ram)
b) Vane type
system
§ All electric system
a) Ward Leonard system
b) Single
motor system
What is meant
be non follow up system in steering gear ?
§ When steering gear set to
required position, rudder is moved & when rudder reach the
required position, steering gear must be set to off position. This system
uses the three solenoid valve.
What is meant
be follow up system in steering gear ?
§ When steering gear set to
required position, rudder is moved & when rudder reaches the
set position, steering gear still remains at that position. This system
uses the hunting gear arrangement.
What is
hunting gear ?
§ It is a feed back mechanism
of steering gear which repositions the floating lever of hydraulic pump as
the tiller moves to the desire position.
What are the
safety devices for steering system ?
1.
Hunting gear
2.
Buffer spring
3.
Angle adjusting
stop (Hand over position limit switch)
4.
Double shock
valve
5.
Relief valve
6.
Tank level
alarm (oil)
7.
Over load alarm
What is the
indication of air in the steering system ?
§ Jumping pressure gauges
§ Jerky operation
§ Defective steering
What is the
effect of air in the steering system ?
§ Air being compressible
gives incorrect balance between units, time lags and irregular operation.
( which can be dangerous )
Emergency
steering gear operation?
§ In the case of Telemotor
failure, by switching the change over pin, emergency steering can be
carried out by isolating the receiver cylinder and directly controlling the
connecting rod of the main steering power unit’s pump lever.
§ The emergency rudder angel
indicator and communication system to bridge being provided at the
emergency station.
Action in
case of electrical telemotor failure ?
§ Put bridge control to
manual
§ Emergency steering gear
system is operated by (solenoid button) whether port or starboard.
§ Rudder angle indicator and
communication system between steering room and bridge must be provided.
How to
operate emergency steering gear ?
1.
Disconnect auto
pilot system.
2.
Take out
change over pin from attachment with telemotor receiver & fit to the hand
gear.
3.
Use
communication system with telephone from steering gear room to bridge.
What are
steering gear tests & maintenance ?
Control test
§ Just prior to 1 hour before
departure of vessel.
12 hour before
departure
§ Operation of main &
auxiliary steering gear.
§ Operation of remote control
system.
§ Operation of emergency
power supply.
§ Alarm test.
§ Actual rudder angle &
indicator.
§ Communication
system.(Bridge, Engine room & Steering gear room)
Every 3 months
interval
§ Emergency steering gear
drill at steering gear room to bridge with sound communication system.
Types of pump
used in hydraulic steering system ?
§ Motor driven constant speed
variable stroke delivery pumps. There are two types.
1.
Radial piston
type ( hele- shaw pump )
2.
Axial piston
type ( swash plate pump )
What are the
advantages of rotary vane type over ram type ?
§ Smaller space required
§ Low installation cost
§ Less weight
§ Smaller power required, for
the same load, because it can transmit pure torque to the rudder stock.
What are the
disadvantages of rotary vane type over ram type ?
§ Synthetic rubber backed
steel sealing strips at vane tops are not strong enough for large ship
gear.
§ Can be used for rudder
stock ratings of about 1700 KNm and less torque generated by two ram is
120 to 160 KNm and for four ram 250 to 10,000KNm.
Steering
tests required before departure ?
1.
Steering gear
should be checked at least one hour prior to departure.
2.
Telemotor
transmitter oil level to be checked
3.
Oil level of
actuating system tank should be checked and replenished if necessary.
4.
Rudder carrier
bearing and bottom sea gland checked and greased.
5.
Start pump and
check response of the gear
6.
Check abnormal
noise and heat
7.
Check load
carrying and running of the gear ( swing from port 35° to stbd 30° within
28 sec )
What are the
properties of telemotor hydraulic fluid ?
§ Good quality mineral
lubricating oil is used. Its properties are-
1.
Low pour point
(-50°C)
2.
Low viscosity (
to reduced fractional drag, but not too thin to mate gland sealing,
30 Redwood Secs at 60°C)
3.
High viscosity
index (110)
4.
High flash
point (150° C closed)
5.
Non sludge
forming
6.
Non
corrosive
7.
Good
lubricating properties
8.
Specific
gravity 0.88 at 15.5° C
What is the
purpose of buffer spring ?
§ To prevent the damages of
the control system.
§ To move the rudder in
either direction instantly when required
§ Should come to reset
immediately in the position corresponding to that shown on indicator on
the bridge.
§ Provision must be made to
protect the steering gear from damage should a heavy sea strike the
rudder.
§ The design should be
sample, the construction robust and its performance reliable at all times.
Purpose of
swivel block in steering gear ?
§ To control linear movement
of the rams to the rotary movement to the tiller arms and rudder stocks.
§ It is the one types of
electrical steering gear system. Which control the speed of DC motor from
zero to maximum in either directions.
In four rams
type steering gear system, what unit you make in service when one cylinder
damage ?
§ If one cylinder damage,
four rams steering gear can be used as two rams type steering gear.
§ First place the rudder at
mid position.
§ Isolate the circuit valves
of two cylinder inlet.
§ One cylinder is defective
and another one, but they are not in diagonal position. Open the vent
at that cylinder.
Purpose of
buffer spring ?
§ Absorb the difference
between the steering order speeds and follow up speed.
§ Absorb the movement of
steering wheel if it is mishandled when the hydraulic pump stop in.
§ Absorb the movement of the
control lever when rudder drift
§ Absorb the vibration and
shocks from the rudder.
When carry out
emergency steering system ?
§ Every voyage (UHA)
§ Once at least within 3
Months (SOLAS)
§ During Survey
What are
daily check in steering gear room ?
§ Pressure gauge of steering
pump.
§ Motor ampere on the
steering switch board & motor hand touch feeling
§ Noise and vibration.
§ Oil level in tank
§ Oil leakage in system
§ Grease in rudder carrier
bearing
§ Check the bottom seal gland
whether good or not.
1.
Every ship
shall be provided with a main steering gear and an auxiliary steering gear.
2.
The failure
of one of them will not render the other one inoperative.
3.
Relief valves
shall be fitted to any part of the hydraulic system.
4.
The main
steering gear and rudder stock shall be:
5.
(a) of
adequate strength and capable of steering the ship at maximum ahead service
speed. (b) capable of putting the rudder over from 35′ on one side to 35′
on the other side with the ship at its deepest sea going draught and
running ahead at maximum ahead service speed and, under the same
conditions, from 35′ on either side to 30′ on the other side in not more than
28 seconds. (c) So that they will not be damaged at maximum astern speed.
6.
The auxiliary
steering gear shall be: (a) of adequate strength and capable of steering
the ship at navigable speed and of being brought speedily into action in
an emergency. (b) capable of putting the redder over from 15′ on one side
to 15′ on the other side in not more than 60 seconds with the ship at its
deepest seagoing draught and running ahead at one half of the
maximum ahead service speed or 7 knots, whichever is the greater.
7.
In every
tanker, chemical tanker or gas carrier of 10,000 gross ton and upwards and in
every ships of 70,000 gross ton and upwards, the main steering gear shall
comprise two or more identical power units.
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