1. Hydraulic Fluid Loss

Most steering gear systems operate hydraulically and depend on maintaining sufficient hydraulic oil pressure. Failure can occur if there is leakage or rupture in the hydraulic system.

Common causes include:

• Pipeline fatigue due to continuous vibration
• Excessive pressure caused by malfunctioning relief valves
• Corrosion or poor maintenance of hydraulic pipes and fittings

If a hydraulic line bursts or develops severe leakage, hydraulic oil pressure is lost, resulting in:

• Inability to move the rudder
• Complete loss of steering control

2. Hydraulic Pump Failure

The hydraulic pump is the main component that supplies pressurized oil to operate the steering gear.

Pump failure may occur due to:

• Electrical faults such as:
  • Single phasing of the motor
  • Burnt contactors
  • Cable failures
• Mechanical faults such as:
  • Bearing damage
  • Seizure of moving parts
  • Excessive wear

  When the pump fails, hydraulic oil circulation stops and the steering gear becomes inoperative.

  3. Air Lock or Vapor Lock in the Hydraulic System

  This is a system-related problem rather than physical damage to components.

  • Air or vapor entering the hydraulic system forms bubbles inside the hydraulic oil.
  • Since air is compressible, hydraulic pressure cannot be transmitted efficiently.

  This results in:

  • Sluggish steering response
  • Inaccurate rudder movement
  • Difficulty in achieving the required rudder angle
  • In severe cases, complete loss of steering control
  Part (b)

  Methods by Which Steering Gear Failure is Prevented

  Failures in steering gear systems are minimized through proper design, operation, and maintenance.

  1. Prevention by Design

  Modern steering gear systems are designed with safety and redundancy features.

  Single Failure Concept and Redundancy

  • Steering systems are arranged so that failure of one component does not cause total loss of steering.
  • Duplicate pumps and hydraulic power units provide 100% redundancy.

  Air Purging Arrangements

  • Purging points are fitted in the hydraulic system to remove trapped air or vapor.

  Protection of Standby Pump

  • Devices such as:
    • Block valves
    • Pawl and ratchet arrangements
    • are fitted to prevent the standby pump from rotating backward (“motoring”) due to oil flow from the operating pump.

    2. Prevention by Proper Operation

    Correct operating procedures help avoid steering failures.

    • Regular checks should be carried out on:
      • Pump operation
      • Oil level and pressure
      • Alarm systems
      • Pawl and ratchet mechanisms
    • In case of telemotor feedback failure, steering can often be shifted to:
      • Non-follow-up (NFU) mode
      • allowing steering control directly from the wheelhouse without depending on the faulty feedback system.

      3. Prevention by Maintenance

      Routine maintenance is essential for reliable steering gear operation.

      Maintenance includes:

      • Periodic overhaul of hydraulic pumps
      • Inspection of bearings and moving parts
      • Checking electrical cables, starters, and contactors
      • Inspection of hydraulic pipelines for corrosion or leakage
      • Regular oil checks and replacement
      • Removal of air from the hydraulic system

      Good maintenance practices reduce the possibility of sudden steering failure.

      Part (c)

      Making Port After Irreparable Failure of the Steering Telemotor

      If the steering telemotor fails completely and cannot be repaired, the vessel can still be navigated using emergency steering arrangements.

      Use of Trick Wheel Arrangement

      The most common emergency method is operation using a trick wheel, which acts as a manual backup system.

      Procedure

      1. Disconnect the defective telemotor linkage from the steering gear floating lever.
      2. Connect the trick wheel threaded stud to the floating lever.
      3. Rotate the trick wheel manually.
      4. The threaded stud moves the floating lever mechanically.
      5. Movement of the floating lever changes the hydraulic pump position.
      6. Hydraulic oil is directed to the rudder actuator.
      7. The rudder moves to the required angle.

      This operation is repeated manually to control the ship’s steering and safely proceed to port.

      Alternative Emergency Method

      If the trick wheel is unavailable or defective:

      • Chain ropes and chain blocks may be connected directly to the floating lever.
      • Manual force is then used to move the lever and operate the steering gear.

      Although this method is:

      • Slow
      • Physically demanding
      • Less accurate

      it still allows limited steering control for safely navigating the vessel.