Sketch a 2-ram type steering gear including the hydraulic circuit, labelling ALL components.(10)
A 2-Ram Type Steering Gear
A 2-ram type steering gear is a hydraulic system commonly used for steering larger vessels. It uses two hydraulic cylinders, or rams, to move the tiller or rudder stock, thereby controlling the rudder’s position and the vessel’s direction.
1. Ram Type Steering Gear – Fountom Marine
Hydraulic Circuit
The hydraulic circuit consists of various components that work together to transmit hydraulic power from the pumps to the rams, enabling precise and reliable steering control.
Components:
- Hydraulic Power Units (HPUs)
- Pumps: Typically two variable displacement pumps, each capable of supplying sufficient flow and pressure to operate the system independently. These pumps can be either: 1. Steering Gear Hydraulic Systems – TSPS Engineering Manual – Massachusetts Maritime Academy weh.maritime.edu
- Helical Rotor Pumps: Offer high efficiency and smooth flow.
- Radial Piston Pumps: Capable of handling higher pressures.
- Electric Motors: Drive the hydraulic pumps, providing the mechanical energy to pressurize the hydraulic fluid.
- Reservoir: Stores the hydraulic fluid, allowing for expansion and contraction due to temperature changes and providing a source of fluid for the pumps.
- Filters: Remove contaminants from the hydraulic fluid, ensuring the longevity and smooth operation of the system.
- Rams:
- Cylinders: Two hydraulic cylinders, typically mounted horizontally on either side of the tiller or rudder stock.
- Pistons: Move within the cylinders in response to hydraulic pressure, pushing or pulling the tiller/rudder stock.
- Piston Rods: Connect the pistons to the crossheads.
- Crossheads: Transfer the linear motion of the piston rods to the tiller or rudder stock.
- Spherical Bearings: Allow for angular movement between the crossheads and the tiller, accommodating misalignment.
- Control System:
- Steering Wheel/Joystick: The input device used by the helmsman to command the desired rudder angle.
- Telemotor: A hydraulic or electrical system that transmits the steering commands from the bridge to the steering gear compartment. 1. Telemotor Definition & Meaning – Merriam-Webster www.merriam-webster.com
- Control Unit: Processes the steering commands and controls the operation of the hydraulic pumps and valves.
- Feedback System: Sensors on the tiller or rudder stock provide feedback on the actual rudder angle, allowing for precise control and autopilot functionality.
- Valves:
- Directional Control Valves: Control the flow of hydraulic fluid to and from the rams, determining the direction of rudder movement.
- Relief Valves: Protect the system from overpressure by venting excess fluid if the pressure exceeds a safe limit.
- Check Valves: Prevent backflow of fluid, ensuring unidirectional flow. 1. Functions of a Check Valve – QRC Valves qrcvalves.com
- Isolation Valves: Allow for isolating specific sections of the system for maintenance or repairs.
- Piping and Hoses:
- High-Pressure Piping: Carries the pressurized hydraulic fluid from the HPUs to the rams and control valves.
- Return Lines: Carry the low-pressure fluid back to the reservoir.
- Flexible Hoses: Connect moving parts like the rams to the fixed piping, allowing for articulation and movement.
- Other Components:
- Accumulators: Store pressurized fluid to provide additional power during peak demand or emergency situations.
- Filters and Strainers: Remove contaminants from the hydraulic fluid. 1. Hydraulic Filters – fluidsys training centre fluidsys.org
- Cooling System: Cools the hydraulic fluid to maintain its optimal operating temperature.
Operation:
- Steering Command: The helmsman turns the steering wheel or moves the joystick, generating a steering command.
- Telemotor Transmission: The telemotor transmits the steering command to the control unit in the steering gear compartment.
- Control Unit Action: The control unit processes the command and activates the appropriate directional control valves.
- Hydraulic Fluid Flow: Hydraulic fluid is pumped from the HPUs to the rams, causing the pistons to extend or retract.
- Tiller/Rudder Movement: The movement of the rams pushes or pulls the tiller, which in turn rotates the rudder stock and moves the rudder.
- Feedback and Control: Sensors on the tiller or rudder stock provide feedback on the actual rudder angle, allowing the control unit to adjust the hydraulic flow and maintain the desired rudder position.
Safety Features:
- Redundancy: The presence of two HPUs and the ability to isolate sections of the system ensure that steerage can be maintained even in the event of a component failure.
- Alarms and Indicators: The system is equipped with alarms and indicators to alert the crew of any malfunctions or abnormalities, such as low oil pressure or excessive temperature.
- Emergency Steering: Most vessels have an emergency steering system (often a separate tiller or hand pump) that can be used in case of a complete hydraulic system failure.
Maintenance:
Regular maintenance of the hydraulic system is critical to ensure its reliability and safety. This includes checking fluid levels, inspecting for leaks, cleaning or replacing filters, and testing the operation of all components.
In conclusion, a 2-ram type steering gear is a complex but robust hydraulic system that provides precise and reliable control of a vessel’s rudder. The use of multiple HPUs, isolation valves, and other safety features ensures that steerage can be maintained even in the event of a component failure, contributing to the overall safety and maneuverability of the vessel.