At present, the world's major ports container terminal yard operations common lifting machinery (collectively referred to as the yard bridge) are mainly rubber type container gantry cranes (RTG) and rail mounted container gantry cranes (RMG), used in open yards, power stations, harbors and railroad freight stations and other places for container loading and unloading, transfer, stacking operations.
Both RTG and RMG belong to easy-to-operate equipment. With the continuous development of container transport and the continuous progress of the loading and unloading process, container handling machinery is constantly developing in the direction of specialization, intensification and automation. Although the two cranes have similar functions, there are some differences in technical performance, loading and unloading performance, operating performance, economic performance, automation performance and other aspects.
Application of container gantry cranes
RTG was developed in the 1980s and is still commonly used in container yards such as power stations, ports and railroad freight stations. When the trailer to the container yard, RTG in the yard within the scope of transverse, longitudinal operation, to complete the loading and unloading, stacking operations. RTG's main advantages are flexible, versatile, and its yard construction costs are relatively low. It can not only forward, backward, and also has a tire steering device, carrying container spreader trolley along the main beam track walking, container loading and unloading and stacking operations. Tire walking mechanism allows the crane to walk on the yard, through the 90 ° rotation of the tires, from a yard A transferred to the yard B, the operation is convenient and flexible, can be in the smaller yard space for loading and unloading, stacking.
RMG is developed later compared with RTG, which is suitable for more regular specialized container yards, with different spans and effective cantilevers corresponding to different yards. The advantage is the high degree of automatic control of single machine, easy to realize automatic operation. In recent years, with the continuous progress of technology, RMG occupies an increasing share, the performance continues to improve, has become the national standard stereotypes of lifting equipment.
Difference between the main structural components of container gantry cranes
RTG and RMG steel structure is generally box-shaped structure, in order to reduce the overall quality of the machine, can also be used truss structure, but due to the complexity of the process, the production cost is high, the use of less in the container yard.
Rubber type container gantry crane RTG is supported by eight rubber tires to support the entire machine, generally diesel engine driven generator as a power source, without the influence of transmission cables and other power sources, can be free to move in the yard. RTG is usually self-propelled trolley type, below the suspension of the telescopic spreader, used for container loading, unloading and transfer operations. RTG is mainly composed of steel structure, lifting mechanism, trolley running mechanism, Trolley running mechanism, driver's room, power transmission system and spreader, etc., each component is connected by welding or flange.
Rail-mounted Container Gantry Crane RMG is supported by steel wheels and mainly consists of gantry steel structure, hoisting mechanism, trolley running mechanism, trolley running mechanism, electrical system, driver's room and spreader. At the same time, the span and reach of RMG can be customized into three types: single cantilever, double cantilever and no cantilever to meet the operational requirements of different yards.
Main technical parameters and performance comparison of container gantry cranes (RTG and RMG)
Comparison of RTG and RMG in terms of service life, basic depreciation rate, overhaul cost and maintenance cost.
Comparison of technical parameters
Due to the limitation of the engine-a-generator system, the RTG should not be lifted too fast, otherwise it is easy to cause the engine to stall or overspeed; whereas the RMG directly uses electrical energy, and the mechanisms can operate faster during starting, braking and lifting and lowering.
Comparison of maneuvering performance
- RTG can make 90° steering so as to realize turnaround operation, but due to the different friction between the tires and the ground on both sides of the big vehicle or the leakage of air from the tires, it is very easy to run out of alignment, and it must be corrected from time to time, or else it will be a safety accident, so it is very difficult to realize automated operation;
- RMG can only travel along the fixed track, although it can not realize the transfer operation, but it is not easy to run off, no need to correct the deviation, easy to realize automatic positioning and automatic control.
Comparison of fault maintenance
- RTG adopts engine-generator system and steering hydraulic system, and its driving and control lines arrive at the driver's room from the electrical room through the towing system, with more mechanical failures, longer downtime and more difficult maintenance.
- In contrast, RMG performance is safer and more reliable, not easy to occur cargo damage and machine damage accidents, repair and maintenance is also more convenient.
Comparison of operation performance
- RTG emits exhaust gas, generates noise, weakens the communication between the driver and the ground personnel, reduces the warning of the walking alarm of the big vehicle, and easily leads to safety accidents;
- RMG does not emit exhaust gas and has no noise, the whole machine runs quietly and smoothly, and the communication between the driver and the ground personnel is relatively smooth.
Analysis of the advantages and disadvantages of the two types of mechanical equipment RTG and RMG
Advantages of RMG
- Operation can be driven by electricity, saving energy and better environmental conditions.
- Equipment is relatively mobile and flexible, and can be transferred from one yard to another after power conversion, which is conducive to phased purchase according to the growth of transportation volume.
- The yard is not equipped with tracks, the yard is level, and it is convenient for vehicles to pass through.
- RTG has mature models and rich experience in manufacturing and use.
- RTG products have been nearly standardized, low cost.
- Slightly lower requirements for the foundation, no need for special treatment of the foundation, lower investment in the runway.
Disadvantages of RTG
- The transfer of internal combustion engine drive, energy for the diesel fuel, energy consumption, pollution than the RMG way big.
- Slightly higher requirements for deflection, need to increase measures to avoid ERTG deflection hit the receiving box.
- Due to tire replacement, diesel engine overhaul and other factors, its maintenance cost is higher.
Advantages of RMG
- Electric drive, energy saving, good environmental conditions.
- RMG travels along the track, strong positioning ability, easy to realize semi-automatic and fully automated operation, reduce the driver's labor intensity, high loading and unloading efficiency.
- RMG repair and maintenance costs are lower.
Disadvantages of RMG
- Equipment must run along the track, poor flexibility, can only operate within a certain range.
- The ground is paved with tracks, which has some influence on vehicle traffic and turning.
- Large installed power capacity, the corresponding substation size is larger, increasing investment.
- Higher requirements for the track and foundation, the foundation needs special treatment to meet the requirements.
Conclusion
It can be seen that both RTG and RMG currently have each other can not be replaced by the advantages, in a certain period of time they will rely on their respective advantages in their own environment to continue to develop. Therefore, the selection of container handling tools in the terminal yard or container yard station needs to be based on a strategic point of view, taking into full consideration of the following factors:
- the expected throughput of the terminal;
- the investment capacity of the terminal;
- the current situation of the yard;
- the ratio of various types of loading and unloading machinery;
- the advancement of management system;
- the assessment of economic benefits and work efficiency.