Two-Ram Type Steering Gear with Hydraulic Circuit Breakdown
A two-ram type steering gear utilizes a pair of hydraulic cylinders (rams) to control the movement of the rudder. Here’s a breakdown of the hydraulic circuit, explaining all the components:
Main Components:
- Hydraulic Pump: This pump, powered by an electric motor or diesel engine, pressurizes the hydraulic fluid within the system.
- Reservoir: This tank stores the hydraulic fluid and maintains its proper level. It also allows for air separation and heat dissipation.
- Pipelines: High-pressure hoses or steel pipes connect the various components and carry the pressurized fluid.
- Directional Control Valve: This valve, located near the bridge control system, receives electrical or mechanical signals and acts as a gatekeeper for the pressurized fluid. Depending on the received signal, it directs the flow to specific rams.
- Two Hydraulic Rams: These double-acting cylinders are positioned symmetrically on either side of the vessel’s centerline, typically mounted on the hull structure. Each ram consists of a piston rod, cylinder body, and end fittings for connection.
- Tiller: The tiller is a lever arm attached to the rudder stock. It acts as the point where the rams apply their force to turn the rudder.
Hydraulic Circuit Operation:
- Command Signal: The helmsman on the bridge operates the steering wheel or controls, sending a signal (electrical or mechanical) to the directional control valve.
- Valve Movement: Based on the signal, the spool or poppet within the directional control valve moves, opening specific ports.
- High-Pressure Fluid Flow: Depending on the desired rudder movement (turn left or right), the valve directs pressurized fluid from the pump to one side of the designated ram’s cylinder.
- Low-Pressure Fluid Path: Simultaneously, the valve opens a passage for the hydraulic fluid on the opposite side of the ram to return to the reservoir. This creates a pressure differential across the ram’s piston.
- Ram Extension/Retraction: The pressure difference acts on the piston within the ram’s cylinder. The high-pressure side pushes the piston rod in the desired direction, either extending or retracting the ram.
- Rudder Movement: The connecting end fitting of the ram’s piston rod is attached to the tiller. As the ram extends or retracts, it pushes or pulls on the tiller, causing the rudder stock to rotate and turn the rudder in the desired direction.
- Opposite Ram Action: When turning the rudder, the other ram receives fluid flow to the opposite side of its cylinder, causing its piston rod to move in the opposite direction. This ensures balanced force application on the tiller and minimizes twisting of the rudder stock.
- Centering the Rudder: When the helmsman centers the steering wheel, the directional control valve directs fluid flow to neither side of the rams, or allows fluid flow equally on both sides. This holds the pistons in their centered positions, keeping the rudder centered.
Additional Components (Optional):
- Pressure Relief Valve: This safety valve protects the system from excessive pressure buildup by diverting excess fluid back to the reservoir in case of malfunctions.
- Check Valves (Optional): In some designs, check valves might be incorporated in the lines between the rams and the directional control valve. These one-way valves allow fluid flow in one direction only, preventing the rams from extending or retracting unintentionally if there’s a pressure drop in one circuit.
- Filters: Hydraulic fluid filters are essential to remove contaminants from the fluid, protecting pumps, valves, and other components from wear and tear.
Overall, a two-ram steering gear with its hydraulic circuit provides a reliable and efficient way to control the rudder by translating steering commands into precise rudder movements through the coordinated action of pumps, valves, rams, and the tiller.