Redundancy and Single Failure Criteria in Steering Gears
(a) 100% Redundancy:
In the context of steering gears, 100% redundancy refers to a system design where complete steering functionality can be maintained even if a single component within a primary system fails. This essentially means having a complete backup system capable of taking over when the main system experiences an issue.
Here are some ways 100% redundancy can be achieved in steering gears:
- Dual Electro-Hydraulic Systems: Two independent electro-hydraulic circuits power separate rams, each capable of moving the rudder alone. If one circuit fails, the other can still steer the vessel.
- Dual Pumps and Reservoirs: Two separate pumps and reservoirs supply hydraulic fluid to the steering rams, ensuring continued operation even if one pump or reservoir fails.
- Dual Telemotor Systems: Two independent electronic control systems operate separate hydraulic valves. If one telemotor system fails, the other can still control the steering gear.
(b) Single Failure Criteria:
The single failure criteria is a principle applied in designing safety-critical systems, including steering gears. It states that the system should be designed to remain operational even if a single component failure occurs. This ensures the vessel retains some degree of maneuverability and avoids a complete loss of steering control.
Here’s how the single failure criteria relates to 100% redundancy:
- A system designed with 100% redundancy inherently fulfills the single failure criteria. With a complete backup system, a single component failure within the primary system doesn’t render the entire steering gear inoperable.
- When designing a steering gear, engineers consider various potential failure points (pumps, valves, pipes) and incorporate redundancy measures to ensure continued operation despite any single failure.
The single failure criteria plays a crucial role in ensuring the safety of the vessel and its crew. By designing steering gears to meet this criteria, the risk of losing steering control due to a single component failure is significantly reduced.