Steering gear Auxiliary 1 Flashcards
(23 cards)
Sketch a valve operated, rotary vane steering gear showing the hydraulic system from the directional valve to the rotary vane unit.
Describe with the aid of a block diagram, the operation of an automatic steering system, including Auto-pilot and valve operated steering gear.
Describe with the aid of a sketch a system for hydraulically transmitting the steering command from the bridge to the steering gear.
Hydraulic Telemotor System
- Transmitter: Turning the bridge wheel moves the pinion, pushing oil to the receiver unit via the right-hand pipe. The left-hand pipe creates space for oil to return.
- Receiver: Hydraulic pressure moves the central web, matching the transmitter’s ram movement. A spring compresses, resetting the system when the wheel returns to midship.
Hunting Gear Mechanism
- Acts as a feedback system, ensuring the rudder moves precisely to the ordered position.
- The receiver unit shifts the floating link, activating the variable displacement pump.
- As the rudder reaches its position, the hunting gear repositions the floating lever, stopping further movement.
The hunting gear is a floating link mechanism that controls the delivery from the steering gear variable displacement pump to the moving rudder to its required position.
Describe with the aid of a sketch a system for hydraulically transmitting the steering command from the bridge to the steering gear.
Hydraulic Telemotor System
- Transmitter: Turning the bridge wheel moves the pinion, pushing oil to the receiver unit via the right-hand pipe. The left-hand pipe creates space for oil to return.
- Receiver: Hydraulic pressure moves the central web, matching the transmitter’s ram movement. A spring compresses, resetting the system when the wheel returns to midship.
Hunting Gear Mechanism
- Acts as a feedback system, ensuring the rudder moves precisely to the ordered position.
- The receiver unit shifts the floating link, activating the variable displacement pump.
- As the rudder reaches its position, the hunting gear repositions the floating lever, stopping further movement.
The hunting gear is a floating link mechanism that controls the delivery from the steering gear variable displacement pump to the moving rudder to its required position.
- State the rudder movement required by SOLAS II-I, Reg 29
- Explain how it is ensured that the maximum movement stated in (1) is not exceeded in an electro-hydraulic ram type steering gear.
- Explain how the steering gear system is protected from damage should the movement be exceeded.
Rudder Movement Required by SOLAS II-I, Reg 29
SOLAS II-I, Regulation 29 requires the rudder to move 35° to port and 35° to starboard under normal operating conditions. Additionally, the rudder must be capable of moving from 35° on one side to 30° on the other within 28 seconds at full speed.
Ensuring Maximum Movement is Not Exceeded
In an electro-hydraulic ram type steering gear, the maximum rudder movement is controlled by:
* Mechanical Stops – Physical limiters prevent excessive rudder travel.
* Limit Switches – Electrical sensors cut off hydraulic flow when the rudder reaches its maximum angle.
* Hunting Gear – A feedback system ensures the rudder stops at the ordered position.
Protection Against Damage from Excessive Movement to prevent damage if movement exceeds limits, the system includes:
* Relief Valves – These release excess hydraulic pressure to avoid overloading.
* Shock Absorbers – Reduce impact forces on the rudder stock.
* Buffer Springs – Absorb sudden forces to prevent mechanical failure.
With reference to steering gears:
(a) State the angular movement required;
(b) Explain, with the aid of a sketch, how the in (a) is ensured in the design of EACH of the following;
(i) A piston type gear;
(ii) A Rotory vane type gear.
(a) Angular Movement Required
The rudder must move 35° port and 35° starboard for proper maneuverability within 28seconds.
(b) Ensuring Angular Movement
(i) Piston Type Gear
* Uses hydraulic rams to push the tiller arm, rotating the rudder. Includes double-acting cylinders, linkages for conversion, and relief valves for pressure control.
(ii) Rotary Vane Gear
* Features vanes inside a stator, where hydraulic pressure moves them to rotate the rudder. Offers high efficiency, smooth operation, and a compact design for greater angles.
The sketch below shows the hydraulic system for the shock valves and automatic by-pass for a section of a rotary vane steering gear. Using the sketch to identify valves and ports, describe EACH of the following:
(a) The operation of the shock valves (4)
(b) The operation when the solenoid valve receives an actuation signal (6)
(a) The operation of the shock valves.
when either side is over pressurised (due to shock loading) the higher pressure causes flow through the non-return valve pressuring the pilot line of the other relief valve causing it to life and allow flow to before the non return valve and to the low pressure side of the system.
(b) The operation when the solenoid valve recieves an actuation signal
When the solenoid valve recieves an actuation signal it causes the distribution valve to move against the spring pressure and opening to the cross over postion. This allows the oil under the bypass valve pistion to the header tank. There is still spring pressure trying to hold the bypass valve closed but it is not enough when compared to the pressure of the system.
With reference to a hydraulic steering gear, explain the purpose of EACH of the following:
(a) Shock valve (3)
(b) By-pass valve (3)
(c) Pump isolating valve (4)
- (a) Shock Valve
The shock valve protects the hydraulic steering system from sudden pressure surges caused by external forces, such as rough seas or rapid rudder movement. It momentarily opens to relieve excess pressure, preventing damage to components like cylinders and pumps. - (b) By-pass Valve
The by-pass valve allows hydraulic fluid to bypass certain components, ensuring smooth operation during system start-up or emergency steering. It helps regulate pressure and prevents hydraulic lock by redirecting fluid when needed. - (c) Pump Isolating Valve
The pump isolating valve enables maintenance and emergency isolation of the hydraulic pump. It allows the pump to be disconnected from the system without draining the entire hydraulic circuit, ensuring continued operation of other components.
With reference to an electro-hydraulic steering gear, explain EACH of the following:
(a) How steering may be maintained should the telemotor system fail
(b) How steering may be achieved should there be total failure of the hydraulic system
(a) Steering in Case of Telemotor System Failure
If the telemotor system fails, steering can still be maintained using local manual control at the steering gear compartment. This involves:
- Engaging the manual control lever to bypass the telemotor system.
- Using the emergency steering wheel or hand pump to directly operate the hydraulic system.
- Switching to the non-follow-up (NFU) mode, where the rudder is controlled manually without automatic feedback.
(b) Steering in Case of Total Hydraulic System Failure
If the entire hydraulic system fails, alternative methods must be used:
- Emergency steering proceedure
- Emergency Towing Arrangements – Using tug assistance for maneuvering.
- Use of Thrusters – If available, bow or stern thrusters can help control movement.
- Jury Rigging – Temporary steering solutions, such as adjusting ballast or using drag devices, may be necessary.
With reference to two ram steering gears which incorporate spherical bearings:
(a) Sketch an arrangement of rams and tiller, including fittings
(b) Explain why spherical bearings are required on the ram ends
A two-ram steering gear consists of two hydraulic rams positioned symmetrically on either side of the tiller, which is connected to the rudder stock. The rams apply force to the tiller, rotating the rudder to steer the vessel. You can find a detailed sketch of this arrangement
Spherical bearings allow self-alignment, accommodating hull flexing and preventing excessive stress. They ensure smooth force transmission, reduce friction and wear, and handle high loads, making them ideal for marine applications.
With reference to a hydraulic steering gear that incorporates variable displacement pumps, describe TWO methods that may be used to prevent the idle pump from motoring (10)
- Check Valves – These allow fluid to flow in only one direction, preventing backflow into the idle pump, which could cause it to rotate in reverse.
- Automatic Isolating Valves – These close when a pump is idle, stopping fluid flow through it and preventing unintended motoring
With reference to steering gears, explain the meaning of EACH of the following:
(a) 100% redundancy (5)
(b) Single failure criteria (5)
(a) 100% redundancy in steering gear means that the system has duplicate components to ensure continuous operation even if one part fails. This includes two independent power units, control systems, and hydraulic circuits, allowing the vessel to maintain steering capability without interruption.
(b) The single failure criterion ensures that no single failure in the steering system—such as a pump, hydraulic line, or control unit—renders the entire system inoperative. The design allows for quick isolation of the faulty component while maintaining steering function.
With reference to a hydraulic-hydraulic steering gear:
- (a) State the purpose of the hunting gear
- (b) Explain, with the aid of sketches, the action of the hunting gear
(a) Purpose of the Hunting Gear
The hunting gear in a hydraulic-hydraulic steering system acts as a feedback mechanism. It ensures that the rudder moves precisely to the ordered position and prevents over-travel or hunting by automatically adjusting the hydraulic pump control lever based on the rudder’s actual position.
(b) Action of the Hunting Gear
The hunting gear consists of a floating lever, hunting lever, and pump control lever. When the steering wheel is turned, the telemotor receiver moves the floating lever, shifting the pump control lever to initiate hydraulic flow. As the rudder moves, the hunting lever provides feedback, gradually returning the pump control lever to neutral once the rudder reaches the desired angle.
Using the sketch below, sketch the hydraulic system for the two ram steering gear, (10)
The system should be capable of ensuring that steerage may be maintained should hydraulic pipe failure occur at any point
Describe ALL the necessary checks of the steering gear before a vessel leaves port. (10)
- Main & Auxiliary Steering Gear – Ensure operational.
- Remote Control Systems – Test responsiveness.
- Bridge Steering Positions – Verify function.
- Emergency Power Supply – Confirm availability.
- Rudder Angle Indicators – Check alignment.
- Power Failure Alarms – Test alarms.
- Gear Power Unit Failure Alarms – Verify function.
- Automatic Equipment – Ensure proper operation.
- Communication System – Confirm effectiveness.
- Visual Inspection – Check steering gear and linkages.
Describe ALL the necessary checks of the steering gear before a vessel leaves port, As listed in SOLAS Ch. V Reg26 (10)
- Main & Auxiliary Steering Gear – Ensure operational.
- Remote Control Systems – Test responsiveness.
- Bridge Steering Positions – Verify function.
- Emergency Power Supply – Confirm availability.
- Rudder Angle Indicators – Check alignment.
- Power Failure Alarms – Test alarms.
- Gear Power Unit Failure Alarms – Verify function.
- Automatic Equipment – Ensure proper operation.
- Communication System – Confirm effectiveness.
- Visual Inspection – Check steering gear and linkages.
Emergency steering drills must be conducted at least once every three months
Sketch a 2-rastm type steering gear including the hydraulic circuit, labelling ALL components. (10)
In a hydraulic steering gear system, preventing the idle pump from motoring list and explain 2 devices that may be used.
- Check Valves – These valves allow fluid to flow in only one direction, preventing backflow into the idle pump. By ensuring that hydraulic fluid does not enter the idle pump from the active pump, check valves effectively stop reverse rotation.
- Automatic Isolating Valves – These valves close automatically when a pump is idle, preventing fluid flow through it. This isolation ensures that the idle pump does not receive unintended hydraulic pressure, stopping it from motoring.
Both methods help maintain system efficiency and prolong the lifespan of the idle pump.
State the purpose of the hunting gear in a hydraulic-hydraulic steering system
The hunting gear in a hydraulic-hydraulic steering system acts as a feedback mechanism that ensures precise rudder positioning. Here’s how it works:
- Rudder Position Feedback – It transmits the rudder’s actual position to the pump control lever, preventing overcorrection.
- Automatic Correction – When the rudder reaches the desired angle, the hunting gear adjusts the pump stroke to stop further movement.
- Smooth Steering – It prevents oscillations and ensures stable rudder control, improving maneuverability.
With reference to hydraulic steering gear that incorporates variable displacement pump, describe two methods that may be used to prevent the idle pump from motoring.
One method to prevent this is by using a fixed rachet. In a hydraulic pump, a fixed ratchet system is used to prevent unwanted reverse motion and ensure controlled operation.
- One-Way Locking Mechanism – The ratchet engages with the pump shaft, allowing movement in one direction while preventing backflow.
- Prevents Reverse Rotation – Ensures the pump does not rotate backward due to pressure fluctuations.
- Maintains System Stability – Helps retain pressure and prevents fluid from flowing in the wrong direction
The second is to fit solenoid operated automatic change over valves in the pipelines. These ensure atht the pump can be started in the unloaded conition and in addition prevents the stand by pump from being motored by the pump in service.
With reference to steering gears, explain the meaning of 100% redundancy
100% redundancy in steering gears means that the system is designed with complete backup capability, ensuring that if one component fails, another can take over without loss of functionality. This is crucial for maritime safety, especially in large vessels.
Key Features of 100% Redundancy in Steering Gears
- Dual Power Units – Two independent hydraulic or electric power units ensure continuous operation.
- Separate Control Systems – Redundant control circuits allow steering from multiple locations.
- Independent Pumps & Actuators – Ensures that failure in one set does not affect the other.
- Automatic Switching – The system detects faults and seamlessly transfers control to the backup.
With reference to steering gears expain the meaning single failure criteria
The single failure criteria in steering gears ensures that a vessel can maintain steering capability even if a single component fails. This is a key requirement under SOLAS regulations to enhance maritime safety.
Key Aspects of Single Failure Criteria
- Redundant Power Units – If one hydraulic power unit fails, another must be able to take over.
- Independent Control Systems – Steering control must remain operational even if one system malfunctions.
- Automatic Isolation – Faulty components should be isolated to prevent further damage.
- Rapid Recovery – Steering capability must be regained within 45 seconds after a failure.
- Dual Actuators – Ships may use two or more actuators to ensure continuous rudder movement.
Describe with the aid of a sketch, a system for a hydraulically transmitting the steering command from the bridge to the steering gear.
A hydraulic telemotor system is commonly used to transmit steering commands from the bridge to the steering gear. It operates using hydraulic pressure to relay movement without direct mechanical linkage.
System Components & Operation
1. Telemotor Transmitter (Bridge) – The ship’s wheel is connected to a hydraulic cylinder that sends pressurized fluid based on steering input.
2. Hydraulic Lines – Fluid travels through pipelines to the steering gear compartment.
3. Telemotor Receiver (Steering Gear Room) – The received hydraulic pressure moves a piston, translating the command into rudder movement.
4. Servo Control System – Adjusts hydraulic pressure to ensure smooth and accurate rudder positioning.
5. Power Units & Pumps – Maintain hydraulic pressure and ensure reliable operation.
This system ensures precise steering control with minimal mechanical wear.
