Steering Flashcards
Purpose
The steering system is an electronically controlled, hydraulically actuated system which quickly and accurately positionins a single spade rudder in response to a helm demand and holds the rudder at that position IOT provide control over the ships heading.
Sump Tank
800L sump tank
stores hydraulic oil
Steering Gear Pump
Positive displacement, double vane, electric motor driven pump.
Draws oil from its respective sump tank to be delivered to the RVA.
1800 rpm
250 bar
420 L/min
Acoustic Silencer
Creates a more laminar flow of oil IOT reduce pulsation, vibration, and noise.
Duplex Filters
10 micron mesh filters
Provides filtration of hydraulic oil.
Both banks are used so changing the filter elements requires the entire Duplex filter be offline.
3 Port Pressure Compensator Valve
A pressure relief valve,
Relieves pressure between 12-165 bar depending on the severity of the rudder angle movement.
Proportional Control Valve
Hydraulic interface between RVA and main power unit.
Recieves a constant flow of hydraulic oil at system pressure and delivers a proportion of that flow on demand.
PCV shuttles left or right by solenoid.
Cooler
A shell and tube type heat exchanger,
reduces the temperature of the oil as it returns to the sump
ASWC in tubes at 90 L/min
Oil in shell at 160 L/min
Rotary Vane Actuator (RVA)
Consists of a steel casing and a rotor.
Casing has 3 chambers.
Rotor has 3 flanges.
Making 6 hydraulic oil galleries.
Provides torque required to rotate the rudder to the desired angle.
Maximum physical angle: 37 degrees.
Maximum allowable angle: 36.5 degrees.
Maximum working angle: 35 degrees.
Limit Switch
Is a physical arm and switch on top of the RVA
Limits the rotor to a maximum angle of 36.5 degrees so that physical contact between the rotor and RVA casing does not occur.
36.5 degrees
140 bar pressure relief valves.
Rudder Centering Unit
Consists of:
Positive displacement, single vane pump to provide pressure.
Strainer.
Pressure switches (145 bar to 165 bar).
5x accumulator flasks cointaing nitrogen bladders compressed by hydraulic oil.
Provides a means of centering the rudder in caase of total power loss.
Hand Pump
It is a fixed displacement axial piston pump
affects small rudder angle movements in the event that the Rudder Centering Unit does not fully center the rudder.
7 full rotations for 1 degree of rudder angle movement.
Locking Pin
A steel locking pin with a magnetic interlock
Physically prevents the rudder from being moved.
Magnetic interlock prevents commands being sent to the steering system.
PSP
Cable of Auto, FU, NFU, Center
SSP
Capable of FU, NFU, Center
ESP
Capable of NFU, Center
ESP Selector Switch
ESP will have control when in LOCAL.
SSP or PSP will have control when in REMOTE
SSP Selector Switch
SSP will have control when ESP in REMOTE and SSP in SSP
PSP will have control when the ESP in REMOTE and SSP in BRIDGE
Steering Control Unit
Interface for electrical commands to hydraulic subsystem.
Uses a closed feedback loop.
Located in ESP.
Modes of Operation (List)
AFU
HFU
HNFU
Manual
Centering
Automatic Follow-Up (AFU)
Rudder angle movements are performed automatically according to a pre-set course.
Not used due to excessive rudder movements causing overheating and premature wear of ocmponents.
Only available at the PSP.
Hand Follow-Up (HFU)
Helmsan manually sets rudder demand. Steering system actuates rudder using feedback control.
Available in PSP and SSP.
Hand Non-Follow Up (HNFU)
Helmsman manually sets rudder angle using push-buttons. There is no feedback loop.
PCV is either all the way open or all the way closed so changes are abrupt.
Available from PSP, SSP, ESP.
Manual NFU
Helmsman can use spring manual override buttons on the PCV.
Centering
If Spring Manual Override buttons do not work, accumulator bottles will center the rudder and a locking pin is insterted.
Operational Description
Go through the system from order a helm demand in Hand Follow-Up to the rudder moving and turning the ship. Follow the flow of oil.
Where are the Rudder Angle Indicators (RAIs)
Bridge
Ops ROom
Bridge Wings
Steering Gear Compartment
SSP
PSP
System Interfaces
EPG&D
MSWC
IPMS
Redundancy and Survivability
Multiple steering systems.
Multiple steering positions.
Multiple steering modes.
Mutliple steering channels.
UPS.
Steer by main engines.
Geographical dispersion.
Limit Switch
What oil?
3-GP-36M
