Model LHR3.5M2, variant 3, on-load/off-load release mechanism, for use with single-point suspension lifeboats and rescue boats; maximum approved working load is 3500 kg per hook.

Common issues

• Hydraulic release mechanism sticking or requiring excessive force to reset after a test
• Corrosion or wear at the hook/keeper pin interface, reducing margin against premature release
• Interlock (hydrostatic or mechanical) misalignment that could allow release before the boat is waterborne
• Hydraulic hose or seal leaks in the release actuation circuit
• Fall wire or davit arm corrosion where paint has broken down at sheave contact points
• Winch brake slipping under load during a lowering test
• Release handle/labelling worn or illegible, risking incorrect operation under pressure

Inspection checklist

• Weekly visual/operational check per SOLAS drill and inspection routine
• Monthly lowering with crew, per drill schedule where practicable
• Annual thorough examination by a competent person per MSC.1/Circ.1206 as amended
• 5-yearly dynamic winch brake test and load test of the on-load release gear
• Check hydraulic fluid level and condition in the release actuator
• Check hook, keeper, and interlock pins for wear, corrosion, deformation
• Confirm the release handle moves through its full range and resets correctly
• Check fall wire condition along its length - broken wires, corrosion, lubrication
• Verify the interlock prevents on-load release when the boat is not waterborne, during the test sequence

Service intervals

Critical spares

• Hydraulic seal kit for the release actuator
• Hook and keeper pin set
• Interlock spring/linkage components
• Fall wire of correct diameter and construction for this davit
• Hydraulic hose assembly for the release circuit

Safety

• Premature release of on-load release gear under load has historically been a major cause of lifeboat launching fatalities worldwide - this is the single most safety-critical function on the davit
• Personnel must never be inside the boat during a release/lowering test unless the procedure specifically requires it with all precautions in place
• Stored hydraulic pressure in the actuator can cause injury if worked on without isolating and depressurising first
• Crush hazard between the boat and davit structure or ship's side during lowering/recovery

Class survey

Class looks specifically for up-to-date thorough examination and 5-year test records for the on-load release gear, not just the davit generally; a lapsed 5-year test or a component change without matching documentation is a common source of a class remark or condition of class.