What is a Gantry Crane?

Gantry crane (gantry crane) is a bridge type crane with a horizontal bridge set on two legs to form the shape of a gantry. This crane runs on ground tracks and is mainly used for handling and installation operations in open storage yards, shipyards, power stations, ports and railway freight stations.

The gantry crane's lifting mechanism, trolley operating mechanism and bridge structure, and

Ordinary gantry crane: This kind of crane is the most widely used. It can carry all kinds of articles and bulk materials. The lifting capacity is less than 100 tons and the span is 4 ~ 35 meters. Grab ordinary

1. When lifting heavy objects, the hook wire rope should be kept vertical, and it is not allowed to tow the object diagonally. 2. The center of gravity of the hoisting weight should be found and tied firmly. The use of sharp-edged mats is good.

3. Before the heavy object is lifted off the ground, the crane must not perform slewing motion.

4. When lifting or lowering heavy objects, the speed should be uniform and stable, to avoid the rapid changes in speed, causing the heavy objects to sway in the air, causing danger. When dropping heavy objects, the speed should not be too fast, so as not to damage the heavy objects when landing.

5. When the crane is under load, try to avoid landing booms. When the boom must be raised and lowered under lifting conditions, the lifting weight must not exceed 50% of the specified weight.

6. When the crane is rotating under the load, pay close attention to whether there are obstacles around it. If there are obstacles, try to avoid or clear them.

7. There must be no people staying under the crane boom and try to avoid them passing.

8. Two cranes work on the same track, and the distance between the two cranes should be greater than 3m.

9. When two cranes hoist an object together, the lifting weight must not exceed 75% of the total lifting weight of the two cranes. The two cranes must move and hoist in the same way.

10. Lifting and luffing wire ropes need to be checked once a week, and records should be made. The specific requirements shall be implemented in accordance with the relevant regulations for lifting wire ropes.

11. When the empty car is running or turning, the hook should be more than 2m above the ground.

12. When the wind exceeds six levels, it should stop working immediately. TMK should turn the boom downwind and lower it properly, and hang the hook firmly. The gantry crane must hit the iron wedge (rail stop) and raise the hook to the upper limit. At the same time close the doors and windows, cut off the power, and pull the cable rope. This should also be done after normal work is completed.

13. It is strictly forbidden to stack miscellaneous items on the crane platform to prevent injury from falling during operation. Tools that are frequently used should be placed in a special tool box in the operating room.

14. During operation, it is not allowed to change gears or reverse the car suddenly, so as not to cause heavy objects to sway in the air, and it is not allowed to operate more than two (including auxiliary hook) operating mechanisms at the same time.

15. When driving, the operator's hand must not leave the controller. In the event of a sudden failure during operation, measures should be taken to safely lower the weight, and then cut off the power supply for repair. Do not overhaul or maintain during operation.

16. The crane is not allowed to lift in any of the following situations:

1. The heavy object exceeds the rated lifting capacity of the crane.

2. The weight of the heavy object is unknown.

3. The signal is unknown.

4. The heavy objects cannot be tied tightly.

5. Open-air operation encounters severe weather such as strong winds, heavy rain, and heavy fog above the sixth level (fifth on the beam).

6. The lighting at night is not good.

7. Stay diagonally.

8. The steel wire rope is severely worn, broken strands are present, and someone is performing maintenance on the crane or the machine room.

Because the application value of the gantry crane is quite prominent and the working state is changed frequently, its actual application may be affected by many factors. Different types of faults occur, and timely repairs are required to solve the faults and improve their performance. The purpose of operational safety.

I. Walking faults and solutions

The driving mode of a gantry crane traveling mechanism at the site is driven by a hydraulic motor. During the normal operation, it was found that the walking mechanism had problems with idling and slipping in 4 wheels, and the problems of poor walking and stagnation occurred after several minutes. After a walking fault, start from the angle of track adhesion, track flatness, and motor driving force to perform fault analysis.

1. In view of the actual operating characteristics of the gantry crane, the main reason for the occurrence of walking failure is that due to the high level of structural rigidity of the entire gantry crane, normal operation, especially during the execution of the walking action, it is difficult to ensure four The fulcrum is in the same plane, and because the gantry crane's traveling motor oil circuit is connected in parallel, considering that the pressure value of the hydraulic system will be affected by the load force factor, the uneven track will cause the hydraulic motor to be driven. Different levels of stress are required. For a walking wheel with the smallest pressure value, it first performs a turning action. In this way, the traveling wheel may be caused to be suspended, and the corresponding drive motor load value is minimized, and the idle or stop is not continuous.

2. In view of this problem, in the case of a walking failure of the gantry crane, the specific maintenance method can be considered from the two aspects of the configuration of the number of driving wheels and the connection method of the oil circuit: way one, the original gantry crane The four driving wheels are increased to eight, and each two driving wheels are connected by pins to form a balanced driving wheel to ensure that the walking wheels can still accompany the track fluctuations under the conditions of track height fluctuations, increasing the contact area between the two; Second, change the motor oil circuit connected in parallel to the oil circuit connection mode of series and parallel combination. In this way, it is ensured that at least one motor at each fulcrum drives the wheels to do work, avoiding the problem of idling and slipping due to uneven force.

Second, the wheel track failure and solution

Adverse consequences

The first is to reduce the service life of the wheels. In general intermediate work level cranes, under normal working conditions, the wheels can be used for 10 years or more. However, the railing phenomenon will shorten the service life of the crane wheels to different degrees, and it can only be used for a year or two, or even months. The second is the worn track. Long-term slackening of the track will wear both sides of the track, and in severe cases, the top of the track will be ground out of the steps; it will cause the track plate to loosen and even cause the track to be scrapped. The third is to cause derailment. When the crane has a bad track, the wheels may climb on the top of the track, causing a derailment accident.

2. Reasons for derailment

The phenomenon of hoisting rails is various, sometimes there is only one wheel hoisting rail, sometimes several wheels hoisting rails at the same time; sometimes the same side hoisting rails are run back and forth, and sometimes the two sides are honing the rails. There are different reasons for different cases.

(1) The track installation is bent horizontally. The horizontal bending of the track installation of the cart is too large. When the span tolerance is exceeded, it will cause friction between the wheel flange and the side of the track. When the gantry crane runs to this section, it can be clearly found that the crane is swaying and tilting. The high end of the track is outside the wheel and the low end is inside.

(2) After the crane with large track span error is installed, the track pitch of its traveling wheels is already a fixed value, and the track span and track track should be the same. When the track span is changed with respect to the wheel track, the wheel does not run in the middle of its tread, causing friction between the wheel flange and the side of the track to produce a track.

(3) The track straightness and the difference of parallelism are not standardized. The gauges at both ends are not equal. One end is large and the other end is small. This is the so-called "figure." Honing the outside and inside of the track respectively. Loosening of the rail pressure plate bolts will also cause the rail position to move and make it "snake-shaped". When the straightness is extremely bad, the railing phenomenon will also occur.

(4) The track pollution is serious. As the prefabrication field mainly produces various types of concrete prestressed hollow slab beams, it is inevitable that concrete, sand, stone and other debris will be sprinkled during the production process. Oil, water, etc. will contaminate the track, so that the driving wheels are prone to slip when the crane is running, and the crane is off-track, which will cause the rails to slip.

3.Troubleshooting

(1) Adjust the track. Whether a crane works properly depends first on the condition of the track. Because the design and calculation of the crane traveling mechanism are all designed to travel in a straight line, theoretically, the tracks should also be arranged in a straight line. However, in actual working conditions, the track is subjected to various external forces, and its deformation and displacement always exist. Under long-term effects, it will inevitably lead to wheel track failure. Therefore, the track must be constantly adjusted to keep the track in good working condition. Before the track is adjusted, it should be checked and measured in detail, and related data should be recorded. The inspection contents include: First, inspect the track for cracks and cracks. The second is to measure the gauge with a steel tape, measure, level, and adjust the height of the entire track with a level gauge, and adjust the straightness of the track with a thin wire. The third is to check the bolts, nuts, and rail pressure plates for looseness and defects. Then you can decide the specific repair plan based on the results of the above inspection. In general, if the track deformation or wear is not very serious, the wheel track can be eliminated by locally adjusting the track. When the track is severely deformed or the wear exceeds the standard, simply adjusting the track is not enough to solve the problem. It can only be handled by methods such as updating the track or increasing the track foundation.

(2) The installation accuracy of the wheel set is strictly controlled. In order to ensure that the crane can run normally and does not derail, in addition to keeping the track in good condition, the accuracy of the crane itself, especially the wheel set, is also an important factor that cannot be ignored. In general, to strictly control the installation accuracy of the crane wheel set, we should start from the working characteristics of the crane itself, and start around the aspects of smooth running, straight walking, and automatic straightening. The ultimate purpose is to ensure that each walking wheel and track Strict alignment. However, in the actual work process, in order to ensure the coaxiality of the mechanical transmission system and reduce the repair workload as much as possible, the passive wheel should be adjusted in principle first, and unless it is absolutely necessary, the scheme of adjusting the driving wheel is adopted. In practical applications, it has a variety of performance advantages including motion reliability, simple structure, convenient operation, and wide application range. However, under the condition of high-frequency use of gantry cranes, certain problems and defects still inevitably arise, such as walking faults and wheel track failures. After the above failures, various methods need to be taken for repair in time ^[1] .