Cargo handling cranes usually form an essential limb during cargo operations on board:
- handy-size bulk carriers,
- general cargo ships and
- some other smaller or larger bulk carriers.
Do you think these cranes hardly need maintenance?
It is a big ‘NO’.
The fact is that they are highly complex pieces of machinery which incorporate numerous components manufactured to very fine tolerances, all of which must function correctly throughout a working period for the crane, as a unit, to be operated as the manufacturer intended.
How should we maintain cranes?
Cranes should be inspected at specified intervals to ensure that they operate correctly and safely. Additionally, all other equipment used in association with a crane should, likewise, be properly maintained and should be inspected as appropriate. If the equipment is not in the proper good condition, failures are likely to occur during cargo operations.
Components of a crane:
Wire Ropes:
Usually a hoist wire and a luffing wire (although on some cranes the luffing of the jib might be using one or two hydraulic cylinders) and various ancillary equipment.
Structures:
Including a pedestal, a housing and a jib, with associated mountings, bearings and foundations for winches, motors, pumps, etc.
Machinery:
Including electrical control equipment and systems, various winches, motors, pumps, etc., limit switches, cut-out switches and other pieces of equipment.
Additionally, some ships are fitted with bulk handling grabs for use with the ship’s’ cranes.
How and when will a crane fail?
Failure of a hoist or luffing wire:
The result of poor maintenance of the wire leading to weakening of the wire over time or improper operation of the crane and incorrect use of the wire leading to damage being sustained by the wire.
Failure of the structures:
The result of poor maintenance of the various elements leading to weakening of the structures or incorrect use of the crane leading to damage being sustained by the structures.
Failure of the machinery:
The result of poor maintenance leading to the failure or incorrect use of the crane leading to overloading of the piece of machinery.
How to prevent crane failure?
A planned maintenance regime, inspections and testing of the various parts should be carried out, with a renewal of items, etc., as necessary.
- Items such as filters should be cleaned/renewed at designated intervals and when indicated by increasing differential pressure
- Gearbox oil and any hydraulic oil should be changed and kept to the required level following the manufacturer’s’ specification.
- Oil sampling and testing must be done once in three months and oil should be changed subject to shore-based analysis of samples, to include particle count to assess the internal wear of the machinery.
- All limit switches and cut-out switches should be inspected and tested at appropriate intervals to ensure their correct operation and any defective parts should be renewed.
- Electrical control equipment and systems should be inspected and tested at appropriate intervals, and any defective parts should be renewed.
- All motors, pumps and winches, and their brake mechanisms, should be inspected and tested at appropriate intervals and renewal of any complete units or parts of those units should be carried out as required when defects are found.
Check these before every cargo operations:
- All controls and the various limit switches and cut-outs are functioning correctly.
- All electrical components and gear are dry and operating correctly.
- All machinery and machinery housings are dry and operating correctly
- All wire ropes are satisfactorily lubricated, and all swivels move freely.
- All sheaves are satisfactorily greased and move freely.
Source: Japan P&I Club
