Views: 18 Author: Site Editor Publish Time: 2023-02-24 Origin: Site
Most of the portal cranes run along the crane track on the ground or on the building for lifting and unloading operations. One side of its running track is set on the ground, and the other side is set on a building above the ground.
Portal cranes have lifting, slewing, luffing and running mechanisms. The first three mechanisms are installed on the rotating part and participate in operations in each cycle. The rotating part is also equipped with a pitchable tilting single arm frame or combined arm frame and a driver's cab.
The operating mechanism is installed at the lower part of the door seat to adjust the working position of the crane. The portal crane with bucket is also equipped with additional equipment such as telescopic funnel and belt conveyor to improve the productivity when the portal crane uses a grab bucket to load and unload bulk materials. In addition to electrical protection devices, safety devices such as lifting weight or lifting moment limiters, crane rail clamps, etc. are also installed.
Most of the portal cranes adopt the horizontal luffing system.
The respective centers of gravity of the weight and the jib system have almost no vertical displacement during luffing. One method is to balance the rise and fall of the composite center of gravity when the boom system is pitched by adding a movable balance weight. This method is more convenient to arrange, more reliable to work, and widely used. Another method is to rely on the mechanical characteristics of the jib system to ensure that the moving track of the synthetic center of gravity is close to the horizontal line during luffing, without active counterweight.
The hoisted object moves along a track close to the horizontal line during the luffing process, and the compensation method and the combined jib method can be used. The compensation method is to use the special rope storage system to automatically retract and release the corresponding hoisting rope during the luffing process to compensate for the vertical displacement of the spreader caused by the lifting of the jib. The combined jib method relies on the mechanical characteristics of the combined jib to ensure that the end of the jib moves nearly horizontally during the luffing process. Both methods are widely used.