L23/30H

Common issues

• Hydraulic oil contamination (water or particulate) degrading rotary vane seal and bearing life
• Vane seal wear leading to internal leakage, reduced torque, and slower or erratic rudder response
• Rudder stock seal leakage allowing seawater ingress into the steering gear compartment
• Relief valve drift from its set pressure, affecting overload protection
• Pump unit wear (on the hydraulic power pack side) reducing system pressure and response time
• Alignment or bearing wear between the rotor and rudder stock coupling

Inspection checklist

• Check hydraulic oil level, cleanliness, and water content against the manufacturer's acceptance criteria
• Test steering gear response time (helm to full rudder angle) against the vessel's SOLAS-required figures
• Verify both steering gear power units operate independently and changeover functions correctly
• Inspect rotary vane housing and rudder stock seals for leakage
• Check relief valve set pressure during the periodic function test
• Inspect all pipework, hoses, and fittings for leaks or chafe
• Confirm the emergency steering arrangement and local control position operate correctly
• Check alarms (low oil level, overload, phase failure) function during the test

Service intervals

Critical spares

• Rotary vane seal set matched to this unit
• Rudder stock shaft seal
• Hydraulic oil (correct grade per the manufacturer's manual)
• Relief valve repair kit
• Hydraulic hose/pipe fitting set for the power unit

Safety

• Steering gear compartments involve high-pressure hydraulic systems - depressurise and lock out before opening any component
• Working near the rudder stock and tiller arm during testing carries a crush/entanglement risk - ensure clear communication with the bridge before any test movement
• Hydraulic oil under pressure can cause serious injection injuries through the skin if a hose or fitting fails

Class survey

Steering gear is safety-critical and subject to class and SOLAS survey requirements, including periodic function and changeover testing, confirmation of independent power sources, and verification of emergency steering arrangements. DNV type approval (as referenced for this model) should be checked against the certificate on board and its validity confirmed at survey.