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Detection method of main girder camber of gantry crane

July 16, 2021

Detection method of main girder camber of gantry crane:

In the gantry crane safety technology inspection, the inspection of the main beam camber is a very important content. JB1036-82 (General Overhead Crane Technical Conditions) clearly stipulates: main beam


The upper camber of the span is F=L(0.9-1.4)/1000. And the larger camber should be controlled within the range of L/10 in the middle of the span. At present, the commonly used detection methods are the traditional magnet hanging rule method, the current hook hanging rule method, and the wire drawing method.


1. Magnet hanging rule method The magnet hanging rule method uses a 0.5m thin steel wire, one end is fixed to the magnet, and the other end is fixed to a 0.5kg weight. A 300mm steel ruler with adjustable position is installed on the thin steel wire, and a special insulating rod is used to attract the magnet to the lower cover of the main beam or the lower surface of the I-steel rail. Then select the two ends of the main beam and three measuring points in the beam, and read the value on the scale suspended by the magnet through a level erected on the ground, so as to calculate the camber value of the main beam in the span. That is, the main beam mid-span camber value = mid-span elevation value-1/2 (higher end span end elevation value + lower end span end elevation value). The steel ruler is fixed on the thin steel wire in the positive direction. When the measured result is positive, it is upward arch, otherwise it is downward deflection. This method can be used to detect the camber of the main girder of various types of cranes. The method is simple and convenient, the results are accurate, and it saves time and effort.


2. The wire drawing method requires three inspectors to climb onto the main girder of the crane, and fix one end of the p0.5mm thin steel wire to one end of the main girder (the wire passes through the contour block on the upper cover), and the other end Connect with the 15kg spring scale at the other end of the main beam. Then select the measuring point, measure the vertical distance from the steel wire to the upper surface of the main beam, and then calculate the camber value. This method has greater limitations and the danger of ascending operations by inspectors. It is only used for the inspection of the main girder of some box-shaped double-girder bridge cranes, and is not suitable for single-beam bridge (gate) cranes and skirts. Detection of the camber of the main girder of the box-shaped double-girder bridge crane.


3. Hook suspension rule method The hook suspension rule method is to hang a 300mm steel ruler upside down on the hook, drive the trolley (electric hoist) to run along the I-steel track, and use the level set on the ground to measure each of the main beams in turn. The elevation value of the point. Then calculate its crown value. This measurement method has large errors, and sometimes the opposite result may be obtained. The factors that affect the measurement accuracy are: the error of the radius of the trolley running wheel, the error of the track tread shape, and the three legs of the trolley will be directly reflected in the elevation value, causing the measured elevation value to be untrue, and the finally calculated camber value is inaccurate. 


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