Created on:2021-09-02 08:48

Port equipment_ Maintenance of tire gantry crane -- Analysis of steering hydraulic system

Port equipment_ Maintenance of tire gantry crane -- Analysis of steering hydraulic system

(1) Problems and analysis

In the early 1990s, a company purchased two Ederer tire gantry container cranes (hereinafter referred to as tire gantry cranes). Since it was put into use, it has frequent faults and can not meet the production demand. The main problem is that when the crane mechanism turns, it often causes faults and the equipment can not operate normally. Tire gantry crane is widely used in container terminals mainly because it not only has the advantages of track gantry crane to improve yard utilization and stacking capacity, but also has the advantages of flexible straddle transport vehicles and transfer operation. Therefore, the equipment often needs to be transferred during operation, and the impact of frequent transfer faults on production is becoming more and more obvious: when the machine needs to be transferred, maintenance personnel are required to eliminate faults on site, wasting a lot of production time and making maintenance personnel tired. Due to these effects, the operating drivers are reluctant to use the two tire gantry cranes, and the maintenance personnel also have a headache. Later, it was only stipulated that the two tire gantry cranes could only operate in one site, and the transfer operation should be avoided as far as possible. But it is getting worse and worse, and even the monthly operation volume is reduced to the operation level of only dozens of boxes per day. For equipment worth millions, such utilization rate is a serious waste.

In order to enable Ederer tire gantry crane to be put into production normally and meet the demand for yard handling machinery due to the increasing container operation, the company has organized a technical research team to improve the overall performance of crane mechanism and the working stability of crane system without affecting the stability and basic operation capacity of original equipment, so as to alleviate the production pressure.

In the design of the original crane steering system, the metal component design of the machine only depends on the telescopic length of the hydraulic cylinder and the electrical limit switch to ensure the crane steering position and provide the crane steering signal. If the metal components are transformed, the project will be huge and costly, and the stability of the original metal components and the safety of the crane system will be affected. Therefore, it is decided to reform the hydraulic system in order to obtain accurate steering and positioning effect.

The technical team carefully studied the complete set of drawings of the steering hydraulic system of the random crane of Ederer tire gantry crane, referred to the technical data on hydraulic transmission machinery, and discussed with each other in combination with many years of maintenance experience. Finally, it was found that there were some unreasonable places in the design of the original crane steering hydraulic system, which was the key to the frequent occurrence of transition faults.

R.jpg

It can be seen from the crane steering hydraulic circuit diagram (Figure R) of Ederer tire gantry crane that it is feasible to use O-type three position four-way directional valve on the directional valve of positioning lock pin. Because when the O-type directional valve is in the state of power loss, that is, when the pin or the pin is pulled in place, all oil ports are closed. At this time, both oil chambers in the pin hydraulic cylinder are closed, the hydraulic cylinder is full of oil, and the system does not unload. The characteristics of the reversing valve are: stable from static to start, large hydraulic impact caused by motion inertia during braking, and high reversing position accuracy. The actual operation also proves that the positioning accuracy is reliable as long as the piston oil seal of the lock pin hydraulic cylinder is not aged and damaged, resulting in internal leakage of the hydraulic cylinder. However, in the steering pump system, due to the particularity of the crane mechanism arrangement of the machine, it must also be considered in the hydraulic oil circuit of the steering system. In order to prevent the smooth movement of the whole machine during the steering action, the electrical control mode in which each group of tires are not synchronized in place is adopted during the transfer. During the transition, the mutual friction between each group of tires and the transition plate will produce a large reverse torque. In the original hydraulic system, the steering oil circuit is only controlled by a Y-type three position four-way directional valve. Under the action of this reverse torque, the oil in the steering hydraulic cylinder that has been in the steering position in advance will gradually leak back to the oil tank from the small gap between the directional valve body and the valve core, and the piston rod retracts, resulting in the tire steering positioning plate not rotating in place. When all tire transfer actions are completed, after an appropriate electrical time delay, the power on the bolt control oil circuit causes the positioning bolt to act, but because the positioning plate does not turn to the position, the bolt cannot be inserted into the positioning hole, resulting in failure. The above analysis is the key to the frequent occurrence of gantry crane transfer faults.

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