Application of laser rangefinder in measuring deflection value of crane main crane after loading

by:UMeasure     2020-04-21
During the regular inspection and acceptance inspection of cranes, the deflection value of the main girder under rated load and the permanent deformation of the main girder during static load test must be measured. Usually, the traditional measurement method is to use a level gauge, a theodolite or an arch gauge to align the labeled ruler in the span of the main beam to measure the difference between the changes before and after the lifting load, so as to calculate the scratch value. However, when measuring with a level, it will be limited by the site, and the level cannot be erected in most cases; When measuring with theodolite, visual error and bad field light will occur. Especially at the beginning of lifting, sometimes the big car will move horizontally because the lifting weight does not leave the ground at the same time, which makes the measurement fail; However, the workload of labeling ruler and taking ruler each time is relatively large, and the labor intensity is also very high. When an electric single-beam crane is encountered, it is more difficult to attach a ruler and take a ruler, and there is still some danger. The measurement with Arch measuring instrument is quite tedious and the accuracy is not high. In view of the above situation, the DISTOTM classic5a hand-held laser rangefinder of Swiss Leca gesystemsag company (Measurement accuracy is ±1. 5mm)To measure the deflection value. The specific method is: use the level or theodolite tripod, use the horizontal bubble on the laser rangefinder to adjust the tripod, and adjust the basic level of the upper mounting plane of the tripod. Place the laser rangefinder vertically upward on the mounting plane on the upper part of the tripod, align it with any point in the middle and lower plane of the main girder span, and measure the distance difference between the lower plane of the main girder before and after the lifting load and the laser rangefinder, that is, the deflection value. Measurement by this method is quite accurate and reproducible; But also convenient and fast, greatly reducing the labor intensity. This kind of measurement method is seldom used in China at present, and it is a relatively advanced downward deflection measurement method at present. When the cart is lifted, a small horizontal movement has a great influence on the measurement results. In addition, even if the laser rangefinder has a certain error in the verticality of the upper mounting plane of the tripod, the error of the length variation in the vertical direction is almost 0 due to the small vertical deflection angle. So the measurement is accurate. Moreover, the accidental horizontal movement of the cart during lifting has little influence on the measurement results.
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