Vessel cranes play a vital role in maritime operations, enabling the efficient loading and unloading of cargo and stores onto and off ships.
Cranes are fitted as a standard design or in a bespoke design to handle specific types of cargo and operating conditions. The more common designs of cranes to be found are as follows.
- Box Boom Crane characterized by its large rectangular or box-shaped boom.
- Lattice Boom Crane feature a lattice-like structure for their main boom.
- Knuckle Boom Crane: also known as articulating cranes, have a hinged joint in the middle of the boom.
- Gantry Crane: An overhead crane supported by legs or wheels that run on tracks or rails.
- Specialised crane A crane designed for specific cargo or heavy weight lift capacity capability.
Older vessels may operate using derrick systems for cargo handling . These are commonly ‘single pole’ booms a system having similar running gear features of a crane but can operate with twin booms from a static position or a mobile single boom mode of operation.
All cranes (and derricks) will require proper maintenance and operational management during both the cargo activities and importantly, between cargo operations, when the vessel is in transit between ports.
General crane operations maintenance
Cranes experience robust use during their lifetime and although designed with this in mind both crane structure and associated equipment will require careful monitoring during both operational and vessel transit periods. Crane operatives are often third-party personnel, have varying levels of training and competence and find themselves under considerable time constraints for loading and unloading of the cargo. Crane structures and associated equipment also experience a considerable range of extreme environmental conditions during vessel transits to various parts of the world. Both these conditions can seriously affect the crane and associated equipment’s durability and effective operation.
3rd party operators of vessel cranes will not be as familiar with the equipment as those on board. Initial protection of the cranes can be achieved by straightforward steps prior to cargo operations commencing. It would be sensible in advance of the vessel arrival to provide details of the cranes on board including Safe working load (SWL) limits and outreaches possible. This is commonly completed at the charter stage but has this information filtered down to the stevedore company concerned. Secondly, a brief meeting with the stevedore managers after arrival to ensure the SWL limits of the cranes are known and will be respected. Thirdly all cranes are required to be marked clearly with the Safe Working load on the boom or in a clearly visible position. Cranes may require more than one SWL marked. For example, a crane operating with a bulk cargo grab may typically have a reduction of 20% in SWL to avoid inadvertent overload as the weight of each lift will not be accurately known.
When shore cranes are used, the vessel cranes should be positioned to minimise the possibility of damage due to contact with working shore cranes and associated cargo. Such damage can also occur from passing vessels if cranes are positioned away from shore cranes and outside the vessel perimeters on the offshore side. A suitable risk assessment should be made of the vessel location and the access for other marine traffic before positioning cranes in this way.
General crane maintenance
Planned maintenance is better than the alternative, ‘reactive maintenance.’ Reactive maintenance is effectively a repair. Such a repair is likely to occur at the most inconvenient time and at significant cost to source, supply and install the required parts. It is therefore both essential and beneficial that proper and efficient crane inspection and maintenance is undertaken by a competent person. This can be a classification society inspector if the crane falls under the class system. Both these approaches require an established and robust planned maintenance system to identify the maintenance and inspections required and provide a continuous record of these activities as they are completed. Proper planned maintenance will extend the lifetime of the equipment, assist compliance with international, national and classification society requirements, improve performance and reliability reducing costly failures and vessel downtime. Planned maintenance systems enhance the early identification of problems, reduction in “breakdown repairs” and consequent “off-hire” periods and expensive/time consuming owner/charterer disputes. The ability to include photographs in more modern planned maintenance systems can also provide a particularly useful record for resolution of damage and other disputes with third party operators.
General planned maintenance
The most effective method of ensuring a reduction in failures is to undertake a detailed planned maintenance programme. The maintenance information will be sourced from the crane manufacturer and the supplied maintenance and operation manuals. These will contain the information regarding inspection routines required, the continuous maintenance activities of specific crane components and their tolerances, the type of lubrication required and applied over the crane’s operational lifetime. The manufacturers information manuals will also provide an overview of a crane type, the relevant schematic and engineering drawings, identification of the most critical parts for regular inspection and lubrication as well as specifics on the care and maintenance of the drum, boom, jib sections and sheeves.
From the manufactures initial information and instructions, a formal planned maintenance routine can be established. This routine should include regular inspection routines of the crane. This should include inspections at sea during long passages when the cranes are stowed but still susceptible to various types of damage and failures as a result of environmental conditions and the vessel and crane flexing in the seaway, A good planned maintenance system should evolve, incorporating experience from use of the cranes, early component failures, and updated service bulletins from the manufacturer.
A competent person should complete visual inspections of the overall crane structure at regular intervals to identify any faults or damage within the crane structure, machinery, wires, and other component parts that may have developed. Identification of any impact damage, plate deformation particularly just after completion of cargo operations is essential. Other issues may be excessive corrosion, or areas of cracked paint that may indicate excessive flexing or developing sub surface structural damage.
Cranes comprise a serious of components, from different manufacturers working in unison to achieve a specific task. It is important to verify not only the main crane structure but also the quality of all associated equipment, for example, the main crane block, hook assembly and main and auxiliary winches. This area is the working end of the crane and is continuously exposed to hazards both within the hatch areas and ashore when landing or picking up cargo. The blocks and attachments require regular inspection to confirm they remain free from any damage or deformation.
The block swivel sections should be suitably lubricated, rotate freely and any spring locking latches where fitted, intact and fully operational. Painting of the hook assembly should be avoided as the paint coatings can mask structural damage within the hook. A well lubricated block system will avoid the application of unwanted rotation stress affecting the crane wires as cargo is lifted and landed.
The crane boom and any boom lattice struts should be free from structural damage, deformation, and excessive corrosion. Particular attention is required to any slack or loose items on the boom which could result in a future detachment creating hazards to both the crane structure, the cargo, and any persons in the vicinity of the operation. All sheeves within the structure should be well lubricated, rotate freely and have smooth and unscored wire grooves which if used may damage the wire ropes passing across the surfaces.
Although not directly used for the crane lifting operations safety inspections of any access ladders or stairs particularly for deformation should be completed. The access to the crane cab must be unobstructed. Ladders and access platforms should not show any excessive corrosion particularly in welded and bolted sections and handrails and fall protection is fit for purpose. Cranes may have specific control cab access points that are not accessible after the crane has rotated. In such cases suitable alternative escape equipment should be provided and tested.
Mechanical maintenance
The cranes include a series of winches, motors, High and low voltage power supplies and computerised control and monitoring systems. In for example Heavy lift and man riding cranes the crane will have additional braking systems and power supplies via Uninterrupted power supplies (UPS) in case of failure and often have heave or motion compensation systems to allow for the vessels natural movement in a seaway. Further and more detailed inspections of these components and associated power sources, should be completed by a competent and fully qualified engineer or crane specialist. Due to the movement of cranes and the high powers commonly involved a full Permit to Work (PTW) and isolation system or ‘lock out / Tag out’ (LOTO) must always be used.
The following verifications, which are non-exhaustive, should be among those considered for inclusion within a planned maintenance programme. Additional verifications will very much depend on the type and use of the crane. Such verifications should comply with the manufactures instructions and requirements and can include electrical and hydraulic machinery specifically to identify hydraulic or other oil leakages. The crane limit switches must be tested and are fully operational providing visual and audible alarms as intended. At regular intervals, the slewing gear should be checked for suitable lubrication and effective teeth meshing. These verifications should also include inspection of the slewing motors for pinion lubrication and correct gearbox oil levels.
Crane operational controls should be verified regularly and before any crane operation commences. Such verifications should include controls are free to operate and return to the neutral position when released. The controls should be correctly marked with each crane function. The location of emergency stops should be clearly visible. Where bypass functions are available for periods of maintenance these should be secured for normal operations to avoid misuse. The crane operator should be provided with a manufacturers approved load diagram detailing the operational range and load capacity of the crane and the principal alarm warnings for failures and any overload. Routine operational checks should include emergency escape ladders, emergency escape breathing devices and safety equipment are clear, functional and fit for use respectively.
Crane wires
Crane wires, normally luffing and hoisting wires are a critical component part of the crane assembly, receive the most work during the cranes lifetime and are the most exposed to direct or indirect damage. Damage can be caused because of overloading resulting in flattening of the wire at points along its length. It can become corroded, common on long passages, where the individual strands within the main wire weaken and part resulting in protrusions from the main wire. These protrusions can become entangled in other moving parts and sheaves which may cause damage and consequently further and sudden weakening of the wire lifting a weight which may still be within the capability and capacity of the crane.
If the wire is mishandled during cargo operations and dragged across hatch coamings or along the quay side, then the wire surfaces can become damaged or scuffed. The lubrication can be contaminated or lost resulting in the creation of a potential corrosion point. Various cargos can affect steel surfaces and would be detrimental to crane wires over a longer term. This can happen more often when using grabs with bulk commodity cargoes where residues of the cargo become engrained within the wires. Over time this will not only weaken the wire but introduce an abrasive substance onto the wire surface and into the rotating parts of the crane assembly. It is important after handling bulk commodities to thoroughly inspect the lubrication, clean and replace lubrication where necessary after removal of any residues that may have accumulated. Wires used in such circumstances can fall below the stated working load limit (WLL) and eventually fail while lifting a weight which even though the load may be well within its capability and capacity.
Crane testing
Cranes should be load tested by a competent 3rd party and inspected at regular intervals by competent persons. The testing and inspection routines should be completed as specified by the manufacturers and the specific regulations for the industry in which the lifting operations are undertaken. As mentioned earlier there may be more than one set of regulations applicable dependent of the type and location of the operations being undertaken. A suitable load testing and inspection certificate should be provided by the 3rd party on completion and retained on board in the ships register of lifting equipment. The tests, examinations and inspections identified within this shipboard Register are based on the requirements of the relevant ILO (International Labour Organization) Conventions in force. These conventions are intended to ensure that ships’ lifting appliances are initially certified by a competent person and to establish periodically that they continue to be in safe working order to the satisfaction of a competent person acceptable to the competent authority.
The associated wires are also provided with a certificate that shows the details of that wire and its WLL. This is specified at point of manufacture. However, after multiple operations the wire may not be of a similar standard or capacity. Proper inspection and maintenance can extend the life of a wire with an increase in safety and a resultant reduction in failure and replacement costs. To truly verify a wire continuing capacity then at intervals a section of the wire, commonly from the working end, should be cut and sent to an authorised testing house for destruction testing. It is also highly likely that crane wires will be changed more than once over the crane’s lifetime when at end of life or when damaged. These wires should always be disposed of safely to an appropriate and authorised waste reception facility.
Any wire that has become damaged presents a serious safety hazard to personnel and is likely to fail at a critical moment resulting in damage not only to the wire but the crane structure and the cargo being transferred. It is therefore essential that the maintenance and inspection routines for individual wires should conform to the wire manufacturer’s instructions in combination with the crane manufacturer requirements for the crane.
Crane operators should be guided by International, national and industry association regulations, rules and best practice requirements based on the specific geographical location of the operation and the type of operation being undertaken.
Operators should also be aware, more so in the offshore market, a vessel may have to operate under two sets of legal and HSEQ requirements. This is dependent on whether the vessel is under navigation or if that same vessel has been placed in a fixed position for example a ‘Jack up’ vessel.
Wires are reeved on drums situated either in an enclosed winch house or externally mounted on the crane however, the wire will be exposed to environmental conditions and associated deterioration during its lifetime. Initially the “bitter end” of the wire (the end attached to the main winch drum, should be secured appropriately, and verified as secure during the period of the wire lifetime. This can commonly be done by visual inspection of the outside face of the drum. The winch drum can be designed with a grooved surface to accept a specific wire size. For a new wire installation, the first or bottom wrap of the wire should be confirmed as sitting within these grooves before continuing with further wraps above to avoid damage of the lower wire warps. Sufficient wire should remain on the drum as per manufacturers recommendation when the crane is at maximum operational limits.
The correct size of wire must always be used for the drum and sheave size as specified by the crane manufacturer. Use of an inappropriate wire or incorrect initial installation of a new wire can seriously damage the wire surfaces and provide a hazard to other parts of the crane when in operation. Suitable lubrication should be applied throughout the wire length in accordance with the manufacturer’s instructions and the wire type involved. Such lubrication should cover the entire surface of the wire while ensuring the centre of the wire is sufficiently lubricated. For the purposes of regular maintenance as well as preoperational verifications a visual check should be performed of the crane sheaves for damage and freedom to rotate as well as all wires for abrasion, damage, broken strands, deformation, and lubrication.
Safe and effective operations
As in all maintenance, comprehensive records should be retained of all maintenance completed , tests and inspection results should be retained in the vessels certificate file and / or the planned maintenance system. Such records provide a continuous history of the cranes and wires operational condition, assist to identify potential failures before they occur while extending the life of the equipment reducing risks of failure and subsequent replacement costs.
Following a properly approved planned maintenance programme, completing regular inspections of cranes and importantly, any associated equipment, will result in minimising potential failures and related safety incidents while extending the life expectancy of the crane and its component systems.
This report is courtesy of WAVES Group.