Mechanical Wear and Aging

Mechanical wear is the most common cause of failure under continuous operation of port cranes, but also one of the main reasons for equipment shutdown, mainly affecting the core force components such as winches, winches, motors, brakes, etc., which bear the action of lifting and panning for a long time, and are in a high load and high friction state.

In the continuous operation of the working conditions, the wear and tear of these parts will be significantly accelerated:

• The wire rope which can be used stably for 3-5 years under the condition of intermittent operation will be shortened significantly under the high-intensity load of 24-hour uninterrupted operation, and its service life can only be maintained for 1-2 years;
• The gearbox internal gears are in the state of meshing and rotating for a long time, which will lead to wear of the tooth surface and cracking of the top of the teeth due to continuous friction, and if lubrication and maintenance are not carried out in time, it may also lead to serious faults such as stuck gears, which will directly lead to the shutdown of the equipment;
• Brakes need to perform frequent braking operations for a long time, the brake pads will wear out quickly, which will lead to increased brake clearance and decreased braking efficiency, and in serious cases, brake failure will occur, leading to safety accidents.

After 36 hours of continuous operation of an RTG crane in a coastal port, the brake pads were not inspected and replaced for a long time, and the wear and tear exceeded the standard, resulting in brake failure, and the spreader slid down slowly with the container, which didn’t cause a fall, but the equipment was shut down for 12 hours for maintenance, affecting the pace of port operations.

Improper Maintenance

Inadequate maintenance is another major core cause of port crane failure, of which ‘passive maintenance’ is the most prominent harm.

Many ports for the pursuit of efficiency, such as equipment failure before maintenance, resulting in small defects, small wear and tear accumulated into a major failure, not only higher maintenance costs, but also extend the downtime.

In practice, the maintenance work is often negligent, especially the following easily overlooked links, easy to accelerate equipment failure:

• Insufficient lubrication of moving parts: no timely lubrication and maintenance of moving parts, will exacerbate the friction between the parts of the loss, accelerate the rate of wear and tear, and thus shorten the service life of the parts.
• Wire rope inspection is not meticulous: daily inspection in the wire rope status is not carefully checked, cannot be found in time broken wire, rust and other hidden dangers, easy to bury the safety risk of wire rope breakage.
• Safety system debugging is not timely: limit switches, emergency stop devices and other safety components are not regularly debugged according to the regulations, which will lead to the failure of its safety protection function and significantly increase the safety risks of equipment operation.

An STS crane in a port suffered from abnormal vibration and slight rattling of the gear box. The maintenance personnel did not conduct in-depth inspection, but only did surface inspection, which ultimately led to gear collapse, equipment downtime and maintenance for 3 days, and repair cost of more than 1 million yuan.

Afterwards, it was confirmed that the noise was a signal of increased gear wear, and timely troubleshooting could have prevented the failure.

Environmental Factors

Most of the port cranes operate in the open air, exposed to the harsh natural environment for a long time, the erosion of environmental factors will further accelerate the aging of the equipment and increase the risk of failure. Among them, salt spray and high humidity in coastal ports, as well as strong winds and extreme temperature differences prevalent in all types of ports, are the main environmental factors affecting the life of the equipment.

Salt spray and high humidity can cause serious corrosion to the metal parts of cranes:

Operational and Economic Losses

Port crane failure is the most direct consequence of operational disruption and economic loss: on the one hand, it will lead to berth stoppage, ship stranding, resulting in high stranding charges, stranding fees; on the other hand, the repair of a large number of manpower and material resources need to be invested in the cost of tens of thousands of yuan of minor failures, major failures of more than a million dollars, and cannot be repaired, then need to be replaced by a huge amount of money to replace the equipment.

Personnel Safety Risk

The most serious consequence of the failure of the harbour crane is the threat to the life safety of the operator and the site personnel, such accidents often lead to catastrophic injuries and even death. Cranes, as large and heavy equipment, can lift heavy loads weighing up to tens of tonnes, and in the event of a failure, accidents such as heavy loads falling and equipment collapsing can cause fatal injuries to personnel on site.

• Crush injuries, personnel are crushed by crane parts, falling heavy objects or the gap between the equipment and the ground, resulting in damage to bones, muscles, internal organs, and in severe cases, can lead to extrusion syndrome, renal failure and other complications;
• Traumatic amputation, where personnel are entangled in the operating parts of a crane, resulting in a broken limb that requires lifelong use of a prosthesis;
• Traumatic brain injury, where personnel are struck by falling weights, fall from equipment, or become involved in equipment collisions, resulting in concussions and severe brain damage that may cause cognitive impairment, memory loss, and lifelong disability;
• Spinal cord injuries, where accidents such as falls and equipment overturning may lead to cervical, thoracic and lumbar spine injuries, triggering serious consequences such as quadriplegia and paralysis of the lower limbs;
• In addition, there may be multiple fractures, internal bleeding, electric shock injuries and other injuries, and some serious accidents can directly lead to death, bringing irreparable losses to families and enterprises.

Establishment of a Perfect Preventive Maintenance System

Preventive maintenance is the core measure to reduce the incidence of harbour crane failures, the need to abandon the ‘passive maintenance’ mode, the establishment of a scientific and systematic maintenance system. First of all, clear maintenance focus, focus on the core components of the crane:

• Regular wire rope breakage, corrosion inspection, wear and tear over the standard, there are potential safety hazards of the wire rope to be replaced in a timely manner, to eliminate the risk of wire rope breakage;
• Regularly lubricate and maintain the core transmission parts such as gear box, bearings, winches, etc., and scientifically adjust the lubrication cycle to reduce the friction loss of the parts in combination with the operating environment of the harbour and the operating load of the equipment;
• Regularly check the brake, limit switches, emergency stop devices and other safety systems, to ensure that the safety components are fully functional and reliable; at the same time, regular inspection of the electrical system, focusing on checking the line insulation, wiring fastening, and timely investigation of short circuits, poor contact and other hidden dangers.

Secondly, make a reasonable maintenance plan, combined with the crane’s operating load, service life and manufacturer’s recommendations, to develop routine maintenance, regular inspection, quarterly overhaul, annual overhaul of the hierarchical maintenance plan.

• Daily maintenance is the responsibility of the operator, focusing on checking the integrity of the appearance of the equipment, operating noise, key parts of the lubrication status, etc., and timely investigation of intuitively visible basis of hidden danger;
• Regular inspection is carried out by professional maintenance personnel, with the help of professional testing tools, focusing on the investigation of hidden equipment hidden problems, so as to achieve early detection and early disposal;
• Quarterly maintenance and annual overhaul need to carry out comprehensive dismantling of equipment, accurate testing and system debugging, and timely replacement of aging, wear and tear over the standard components, to ensure that the equipment is always in the optimal operating state, to protect the needs of continuous operation.

In addition, we make good maintenance records, recording in detail the time, content, problems found and treatment measures of each maintenance. By analysing the maintenance records, we can grasp the operating status and wear and tear pattern of the equipments, so that we can pre-judge the risk of failures in advance and optimise the maintenance plan.

Upgrade Advanced Monitoring System

Upgrading the monitoring system with the help of modern technology can realise real-time monitoring of the operating status of cranes and fault prediction, effectively reducing the incidence of failure.

On the one hand, the introduction of the Internet of Things (IoT) monitoring technology, crane core components installed sensors, real-time collection of equipment operating parameters and uploaded to the cloud for data analysis.

Once the monitoring of data anomalies, immediately triggered an early warning mechanism to remind the maintenance staff to investigate and dispose of hidden dangers in a timely manner, to achieve the hidden dangers of early discovery, early treatment.

On the other hand, the application of predictive maintenance technology, combined with artificial intelligence (AI) and machine learning algorithms for in-depth analysis of operational data, the construction of component wear prediction model, accurate prediction of the remaining service life of the core components, to truly achieve the goal of active protection ‘before failure, first maintenance’.

At the same time, the establishment of a layered inspection system, the integration of daily pre-inspection, periodic special inspections and comprehensive testing, relying on professional testing equipment to accurately investigate hidden dangers, comprehensive coverage of the equipment monitoring links, to achieve the crane without dead ends, the whole process of monitoring, and build a strong line of defence for the safe operation of equipment.

Emphasis on Operator Training and Certification

1. Conduct comprehensive training courses covering the basic structure of cranes, operating principles, load calculation, safe operating procedures, emergency response methods, etc., to ensure that operators are proficient in equipment operation skills, and understand the identification of common failures and emergency response measures.
2. strengthen day-to-day management, carry out regular safety training and case warning education, strengthen the safety awareness of operators, put an end to illegal operation, overloading and other behaviours, and guide operators to develop good habits of standardised operation and regular inspection.

Implement Effective Load Management Measures

Reasonable load management can effectively reduce the operating stress of the crane and reduce the risk of failure.