MY4CY, MY4

Common issues

• Internal leakage across valve seats causing steering drift or loss of rudder position holding
• Seal/O-ring degradation leading to external hydraulic oil leakage
• Valve spool or poppet sticking from contamination in the hydraulic oil
• Relief valve set-pressure drift over time
• Valve body corrosion in a humid steering gear compartment

Inspection checklist

• Check for external hydraulic oil leakage at the valve body and connections
• Verify relief valve set pressure against the steering gear system's design pressure
• Check the valve operates freely through its full range (manual/changeover valves)
• Check for internal leakage via a steering response/drift test
• Inspect mounting bolts and pipe connections for tightness and corrosion
• Confirm valve position indication, if fitted, matches the actual valve state

Service intervals

Critical spares

• Seal/O-ring kit for the valve
• Valve spool or poppet assembly, if supplied by the maker as a unit
• Gasket set for the valve body joints

Safety

• Loss of steering control is a risk if the valve fails without a verified changeover to the backup steering system
• The hydraulic system is under pressure - isolate and depressurize before valve maintenance
• Moving machinery hazard in the steering gear compartment during function tests - inform the bridge before testing

Class survey

Product identification note: the manufacturer's profile (a valves company) suggests this DNV type-approved item is likely a hydraulic control/relief valve used within a rotary vane steering gear's hydraulic system, rather than the complete steering gear unit as categorized - confirm actual scope against the certificate. Steering gear, including its changeover and relief valve arrangement, is SOLAS-mandated equipment tested before every departure and reviewed at each annual/renewal survey.