Repair method of deformation of main beam of overhead travelling crane

existoverhead travelling craneThe main beam structure, in the process of long-term application, will be affected by various factors, and thus deformation occurs, but the deformation problem can not be completely avoided, for the main beam structure of the deformation problem ah, you can take the following measures to repair:

1、Prestressing repair method

For the deformation of the main girder structure in the bridge crane, the main girder structure can be corrected with the help of the prestressing method. Fixed supports are placed at both ends of the main girder structure under the cover plate, and multiple steel bars and wires are pulled out through the prestressing tendons, so that the impact of the force on the main girder structure due to the influence of bending moments will gradually restore the upper arch. When a load is applied to the main girder, the pre-stressing of the reinforcement is in the opposite direction to the operating pressure of the bridge crane, which results in part of the operating pressure being cancelled out by the pre-stressing of the reinforcement, thus increasing the load carrying capacity of the main girder structure. This method can be applied when the main girder structure in the bridge crane is corrected, and after the correction, the arch value of the main girder is in a stable state, and it should be adjusted in time according to the changes of the bridge crane in the usual application. When the main girder correction is completed, its strength and stiffness can be further improved, and at the same time, the pre-stressing repair method has many advantages such as short construction period, low cost, simple and easy to control during the actual application, which also leads to the wide application of this method. It should be noted that there are certain limits to the application of this method, which is not suitable for use in the case of horizontal bending or local deformation of the main girder structure, and can only be used to deal with the problem of downward deflection and deformation of the main girder arch, and the appearance of the bridge crane will be affected to a certain extent after the correction. For overhead travelling crane, if it has been in full load operation for a long time, the working environment is poor and the load capacity is not good, it can be repaired by pre-stressing repair method.

The principle of repairing the deformation of the main girder structure in the bridge crane using the prestressing repair method is shown in the figure. When the staff repairs the deformation of the main girder structure and tightens the reinforcement, it is necessary to measure the value of the upper arch of the main girder. In this process, to ensure that the main beam under the cover plate outer layer of pressure size is moderate, are in a reasonable range, to prevent the size of the pressure exceeds the maximum value of the tensile stress of metal materials can withstand. At the same time, the tensile stress in the upper cover plate of the main girder must be within the permissible range to prevent the tensile stress there from exceeding the maximum value that can be withstood by the tensile stress in the metal material.

2、Flame correction method

Flame correction method, what is the principle of its application, is for the main beam local heating, so that the metal structure produces plastic deformation, after cooling, for the remaining contraction stress to use, so as to achieve correction. The use of flame correction method, need to pay attention to the following items:

It is necessary to control the heating temperature in the range of 700 to 800 ℃, using the temperature in the interval for heating, so that the yield limit of the metal of the mass structure will slowly move towards 0, the correction effect is good.

The aim is to reduce the web waviness and to use the spacer as a heating pad, avoiding dangerous sections in the main girder during the heating operation.

(iii) Repeated heating at the same position of the main beam is not permitted, as the effect of such heating is not only ineffective, but also damages the metallurgical organisation of the structure of the main beam.

④After completing the correction of the main girder results, it is necessary to carry out the reinforcement operation of the main girder. After the completion of the main girder structure reinforcement, the main girder will have a large internal stress, and at the same time, in view of the long term use of the bridge crane, the fatigue of the metal material will be intensified, which will lead to unreasonable conditions of the steel structure. If the main girder structure is not strengthened, on the one hand, it will have a bad effect on the correction effect, and on the other hand, it will make the deformation situation aggravated. Generally speaking, when strengthening the main beam, channels should be placed on both sides of the lower steel plate within the span of the main beam.

The application of flame correction method has a good correction, flexibility and other characteristics, the construction process is also relatively simple, there are a number of advantages, it should be noted that the use of this method to complete the correction of the main beam after the groove steel to be reinforced, otherwise it will lead to a more serious problem of plastic deformation, so the use of the flame correction method should be in accordance with the actual situation to determine.