SOLAS II-1, Reg 29 and Rudder Movement
(a) Rudder Movement Required by SOLAS II-1, Reg 29:
SOLAS (International Convention for the Safety of Life at Sea) Reg. II-1/29 specifies the minimum rudder movement capability for steering gears on board ships. It states that the main steering gear must be capable of putting the rudder over from:
- 35 degrees on one side to 35 degrees on the other side with the ship at its deepest seagoing draught (fully loaded) and running ahead at maximum ahead service speed.
OR
- 15 degrees on one side to 15 degrees on the other side 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
- pen_spark
- greater.
(b) Ensuring Maximum Movement in Electro-Hydraulic Ram Steering Gear:
In an electro-hydraulic ram type steering gear, several features work together to ensure the maximum rudder angle (as specified in SOLAS) is not exceeded:
- Limiting Stops: Mechanical stops are typically installed on the rudder stock or within the ram itself. These stops physically prevent the rudder from exceeding its designed maximum angle in either direction.
- Position Feedback System: The system incorporates a position sensor (e.g., rotary encoder) mounted on the rudder stock. This sensor continuously transmits the actual rudder angle to the control system.
- Control System Logic: The control system (computer or electronic controller) receives the rudder angle feedback. It compares this feedback with the commanded rudder angle from the bridge. If the commanded angle exceeds the maximum limit, the control system stops or limits the flow of hydraulic fluid to the rams, preventing further movement beyond the safe limit.
- Hydraulic Relief Valves: In some systems, pressure relief valves might be incorporated in the hydraulic lines. These valves bypass excess pressure if the force required to move the rudder exceeds a certain limit, preventing damage to the rams or other components.
(c) Protecting the Steering Gear from Damage if Maximum Movement is Exceeded:
Several mechanisms protect the steering gear system from damage if the maximum rudder angle is unintentionally exceeded:
- Limiting Stops: The mechanical stops on the rudder stock or ram act as the primary safeguard. They prevent physical overtravel, protecting the rams and linkages from excessive stress.
- Hydraulic Relief Valves: As mentioned earlier, relief valves can protect the system by bypassing excess pressure if the force required to move the rudder becomes too high. This prevents damage to pumps, motors, and other hydraulic components.
- Control System Shut-off: In some cases, the control system might be programmed to shut down or limit power to the rams if the maximum angle is exceeded. This prevents further movement and allows for troubleshooting the cause of the issue.
These features work together to prevent excessive rudder movement and protect the steering gear from damage in case of accidental over-command or external factors like heavy seas.