Safety Hidden Problems and Countermeasures of Gantry Cranes

A gantry crane refers to a multi-action gantry hoisting machine that can vertically lift and horizontally handle heavy objects within a certain range.

A gantry crane is a heavyweight piece of equipment with a range of uses. It is mainly used in factories, construction sites, railway freight yards, etc. Its rated lifting capacity is generally 3.2-320T.

Some working characteristics of lifting equipment are intermittent movements, that is, the corresponding mechanisms such as feeding, transporting, and unloading work alternately in the working cycle, and the development and application of gantry cranes in the market are becoming more and more extensive.

Although gantry cranes are powerful, they are also highly dangerous. How to make them improve work efficiency on the basis of ensuring safety is a problem that enterprises have been paying attention to. However, the practice has shown that there are endless safety hazards of gantry cranes, which may affect the normal operation of the equipment in accidents in the severest case.

1. 
   

   Potential safety hazards of  cranes

It is undeniable that gantry cranes are widely used in smelting plants, large shipyards, and other industries due to their advantages such as high efficiency, strong versatility, and wide operating range. There will be certain problems, and it is impossible to find all problems, and it is impossible to find all the problems and solve them in time so security risks are planted.

• The metal structure and parts are defective or damaged
• Gantry cranes are bulky and highly dangerous. Safety warnings should be made regardless of whether they are running or not. The succession records, the mechanical operating mechanism, and the surrounding facilities, buildings, and transmission lines did not ensure a sufficient safety distance, and some gantry cranes even had loose rails and imperfect pressure plates.
• Since most of the stressed components are made of metal materials, their mechanical properties are required to meet the operational requirements, but some connecting welds have cracks, high-strength bolts not only lack performance grade marks and anti-loosening measures but also some are already in loose state. Cotter pins are either missing or replaced by steel wires, and the effective thickness of the stressed member section is also significantly reduced.
• Some of the main components have been damaged to varying degrees, such as kinked wire ropes, broken wires, and strands, the wrong direction of the rope clamp, the pressure plate bolts are not loose, and some hooks have repair welding or even anti-decoupling failures.
• Some safety protection measures are missing or invalid

One is the brake problem, including cracks, severe wear, and deformation of the parts; there are many impurities between the brake wheel and the brake, especially the presence of particulate impurities aggravates the wear of the brake shoe, resulting in the brake is applied. The contact of the driving wheel is uneven; the oil leakage of the hydraulic push rod makes the brake wheel covered with oil; some emergency brakes even fail. The second is the problem of the operating mechanism of large and small vehicles, such as the failure of the limit switch, and the end stop device is not installed for multiple lifting trolleys running on the crane rail track. The third is other problems, such as the lack of failure of alarm devices such as flashing lights and buzzers, the windproof device is not in place, the rail sweeping plate being deformed or there is a gap of more than 10mm with the track, some door interlock switches fail, and exposed crane moving parts lack of fences, shields, etc.

• Important institutions are accompanied by different hidden troubles

For example, the hidden danger of failure of the wheel group is mostly manifested as wheel rim gnawing. If it is not handled properly in time, it will easily lead to derailment accidents of large and small vehicles. In many safety inspections, it was also found that the different wheel pressure on both sides of the gantry crane may also cause the risk of wheel group failure. Another example is electrical components, which generally cover the main circuit of the power supply, electrical equipment, and weather safety control circuit. If the wrong phase protection starts, the limit switch action, the grounding system, etc. are damaged or fails, it will seriously affect the normal operation of the equipment.

2. 
   

   Causes of potential safety hazards of cranes

   Irregular operation

Although the current gantry cranes used in different industries are mainly leased, some safety hazards are related to the design and manufacture of equipment, but a large number of problems are related to the user unit, to be precise, the operation is not standardized. If some equipment operators have a weak awareness of safety production, they are not familiar with the characteristics of the equipment, have not really mastered the equipment, have nor really mastered the safety operation procedures, do not understand the common problems of the equipment, or even work without a licence, and perform some illegal operations. Over time, it is easy to reduce the equipment performance, increase the risk of failure, and bury safety hazards.

 Maintenance is not timely

Prevention first, the combination of prevention and treatment has always been the basic principle of equipment management, especially for gantry cranes. However, whether it is in the process of use or in the state of an outage, relevant personal have not carried out scientific maintenance in time, including common cleaning, lubrication, fastening, adjustment, and other basic maintenance. In fact, in most cases, the maintenance of the equipment is undertaken by the lessor, but sometimes the team members cannot follow up in time, and the degree of attention is not high, so it is more common to just rent and leave it alone.

 Inadequate maintenance

Gantry cranes need regular inspection and maintenance, which is the basic work to ensure the safe operation of the equipment. However, the inspection cycle set by different units is different, and the operating environment and frequency of use are different, so various failures may occur in the equipment. The key point is that some staff cannot detect hidden dangers early, and some have limited professional skills. They can neither make an accurate and objective evaluation of their safety functions nor can they completely and effectively solve faults. Over time, it is easy to expand the scope of faults and its adverse effects can lead to safety accidents.

Incomplete management

Regardless of whether it is irregular operation, untimely maintenance, or inadequate repair, in the final analysis, it is the problem of the safe operation and management system of the gantry crane that is exposed, such as the lack of inspection reports, daily use records such as usage status, self-built maintenance, and fault records. Incomplete and unarchived, general safety operating procedures, lack of inspection and supervision system, unclear requirements for operators to work, etc., are not conducive to the safe use and management of equipment.

3. 
   

   Countermeasures for potential safety hazards of cranes

3.1 Effectively improve the safety management system

The safety management system of gantry cranes should make specific and clear regulations on the requirements of on-the-job personnel, job responsibilities, operating procedures, operation and maintenance management, inspection cycle, reward and punishment system, etc. Among them, we should focus on refining the safety operation procedures, at least covering the identification of hazards: for example, when a large vehicle travels or a rail breaks, people will be injured, causing mechanical damage, and when the overload protection device fails when lifting heavy objects, it will cause lifting injuries, etc.

Before the operation: Before driving, it is necessary to confirm whether the rail clamp and the aiming device are loosened, whether the iron wedge is removed, whether the power supply, voltage, and communication are normal, etc.

During operation: If the heavy object is lifted for the first time in each shift, it should be lifted from the original position by about 0.5m, and then the heavy object should be lowered to check whether the brake performance is reliable. Strictly implement the “ten no lifting” system.

After the operation: In order to prevent the hook raised to a certain height from colliding with the door legs on both sides dues to the wind force, it is necessary to ensure that the large and small vehicles are parked at the designated position, and the controller handle is set at the “zero” position, and the main power supply is cut off to close the doors and windows. Keep good records, and add rail clamps, aiming ground anchors. Etc.; emergency measures: if there is a failure during operation, you must stop the operation immediately, report to the maintenance personnel, and wait for the maintenance personnel, and it is forbidden to leave without permission; occupational hazard prevention: such as contact with metal fumes, dist-removing measures are required in the dusty working environment, and workers who are exposed to noise need to wear sound-proof earplugs and other labor protection products, and be equipped with sound insulation and noise reduction facilities.

3.2 Continuously improve the professional skills of personnel

Considering that the safe operation of the gantry crane requires the close cooperation of multiple personnel, in addition to ensuring the reasonable design of the equipment and the installation specification, it is also necessary to put forward requirements for the equipment operators and operation and maintenance personnel. Operators are required to go through strict safety education and skill training to confirm that they are competent for the job before they can hold a certificate, and responsibility, master the performance characteristics and working principles of the equipment, be familiar with the operating procedures, and understand the vulnerable parts and basic failure types, be able to take correct emergency measures in time when a failure occurs and reduce the potential safety hazards or equipment failures caused by the improper operation as much as possible at on time.

3.3 Pay attention to daily maintenance and regular maintenance

During daily maintenance, clean the dust and oil of the equipment in time, check whether the connecting bolts are loose and need to be tightened, whether the components are worn out and need to be repaired or replaced, whether the electrical contacts are in poor contact and need to be connected reliably, whether the parts are sufficiently lubricated, and whether the metal components are corroded or damaged. Cracks, whether the wire rope is broken, whether the emergency brake limit switch, windproof device, buzzer, anti-collision device, etc. Are in good condition and function normally etc.

Fault maintenance should be targeted and effective. For example, for serious track bending deformation, the faulty line can be replaced in stages, a total station can be used to measure the track height difference, and the track spacing can be adjusted by adding heating sheets; for brake problems, can remove oil and other impurities in time, adjust the braking toque, improve the spring connection strength, and replace the worn and scratched components; for the can wear, it can be transposed and repaired according to the standard, and a certain contact can be replaced after grinding and repairing. After adjustment and inspection, it is confirmed that the gear position is clearly visible before continuing to use; for problems such as knotting, broken wires, and bending of the wire rope, choose to repair or replace it while stopping use. If the replacement needs to fully consider high temperature, service life, isolation corrosion, and other factors, reasonably control its length to ensure that the hook is at a lower position, and the remaining part of the wire rope must be large than the 3-turn reel, and ensure sufficient lubrication.

Furthermore, in addition to the basic windproof devices, more safety protection measures should be taken, such as windproof cables, etc. It is forbidden to park equipment at the tuyere in strong wind and rain, and the inspection of windproof iron wedges and ground anchors should be strengthened to reduce safety risks.