An offshore support vessel operator asked us to overhaul the hydraulics of a deck crane and carry out crack detection on its load-bearing parts. We rebuilt the main and hoist directional valves and the hand pump, renewed and tagged hoses, checked the accumulators, renewed the hoist winch mounting bolts and arranged 100% NDT on the crane’s critical welds and pins.
The problem
The crane’s controls had become worn and leaky, hoses were due for renewal, and the operator wanted assurance on the crane’s structure before relying on it offshore. Rather than treating each item as a separate job, the work was planned as one overhaul with a single report.
What we found
- Main directional control valve: worn seals and five damaged front covers with handles
- Hoist directional control valve: seals worn
- Hand pump: leaking and due for overhaul
- Accumulators: pre-charge needing verification
- Pressure gauges: main and accumulator gauges unreliable
- Hoses: 13 on the crane and 6 on the towing winch power pack due for renewal
- Hoist winch mounting bolts due for renewal
What we did
- Removed, stripped, resealed and bench tested both directional control valves, fitting five new front covers with handles on the main valve
- Overhauled and tested the crane’s hydraulic hand pump
- Checked the nitrogen pre-charge on two accumulators and function tested them
- Renewed three main and accumulator pressure gauges
- Renewed 13 crane hoses and 6 towing winch power pack hoses, each tagged and entered in a hose registry with mill certificates
- Renewed the hoist winch mounting bolts
- Arranged 100% magnetic particle and eddy current inspection of the bearing adapter welds, slew welds, boom head welds, load-bearing pins, boom cylinder clevis welds and the hook
- Arranged 20% NDT of the inner and outer adapter bolts, followed by final torque
Result
The crane went back into service with rebuilt controls, verified accumulators, 19 new tagged hoses and a documented NDT record of its critical welds and pins. The hose registry means the next renewal can be planned by date rather than waiting for a failure.
