The quality of crane girders serves as the foundation for ensuring the quality of track installation. Generally, the installation datum line of the track is the datum line of the crane girder. Before track installation, a careful inspection of the crane girder must be carried out. Simultaneously, the datum line of the crane girder can be set out during the inspection process. This work can be measured using a theodolite. Measure a point every 2 – 3 meters, and also measure a point at each column. Based on these measurements, the datum center line of the crane girder and the alignment datum line of the track are set out. The distance between the two lines depends on the specifications of the track being used. In addition, use a level to measure the levelness of the crane girder, and measure one point at each column.
The quality of crane girders should comply with the provisions of the “Code for Construction and Acceptance of Reinforced Concrete Works” GBJ10 – 83. The following requirements are provided for reference during inspection:
Position Deviation of Reserved Bolt Holes:
When inspecting the crane girder, it is necessary to ensure that the position deviation of the reserved bolt holes along the transverse and longitudinal directions of the girder is less than or equal to 5mm.
The allowable deviation of the reserved holes from the two center lines is 5mm.
The diameter of the bolt holes should be 2 – 7mm larger than the diameter of the bolts.
The deviation of the position of the bolt holes is crucial. If the deviation is too large, it will be difficult to install the bolts accurately, which may affect the stability and connection strength of the crane girder and the track. For example, in a large – scale industrial workshop, if the bolt holes deviate significantly, the crane may experience shaking or abnormal stress during operation, reducing the safety and service life of the entire system.
Elevation Deviation of Crane Girders:
The deviation of the relative elevation of the upper planes of the two crane girders should not be greater than 10mm at the columns and not greater than 15mm at other locations.
The elevation of the top surface of the crane girder relative to the design elevation has a deviation of (+10, – 5)mm.
The elevation of the crane girder affects the smooth running of the crane. If the elevation difference between adjacent crane girders is too large, the crane wheels may experience uneven stress when passing through the joints, which can cause excessive wear of the wheels and tracks, and even affect the normal lifting operation of the crane. For instance, in a steel – making plant where heavy – duty cranes are frequently used, any significant elevation deviation can lead to operational inefficiencies and potential safety hazards.
Deviation of the Center Line Position:
The deviation of the beam center line position from the design positioning axis should not be greater than 5mm.
For each crane girder, the distance between the datum center line and the column side must meet the following regulations: when the lifting capacity Q ≤ 50t, this distance is b + 60mm; when the lifting capacity Q is 50 – 100t, this distance is b + 100mm, where b is the distance from the track center to the outer end of the crane.
The accurate position of the center line of the crane girder is related to the correct running path of the crane. If the center line deviates, the crane may not be able to operate within the designed range, and it may also cause problems such as collision with the columns or other structures in the workshop. In a machinery manufacturing factory with multiple cranes operating in the same area, the precise alignment of the crane girder center lines is essential to ensure the normal operation of each crane and the overall production process.
Levelness and Elevation Differences of Crane Girders:
The levelness of the top surface of the crane girder within a 400 – mm – wide range at the bolts should be ≤ 25mm.
The elevation difference of the top surface at each bolt in any 6 – m length of the beam should be ≤ ± 3mm.
The elevation difference of the top surface at each bolt along the entire length of the beam in the workshop should be ≤ ± 5mm.
Also, check for any skewness or blockage of the reserved holes.
The levelness and elevation differences of the crane girder directly affect the smooth movement of the crane. Uneven levelness can cause the crane to vibrate during operation, which not only affects the accuracy of material handling but also shortens the lifespan of the equipment. In a logistics distribution center with high – frequency crane operations, maintaining the levelness and elevation differences within the specified range can ensure the efficient and stable operation of the cranes, improving the overall logistics efficiency.
Concrete Grouting Layer:
The concrete grouting layer between the concrete crane girder and the track should meet the actual regulations. Before grouting, the top surface of the crane girder should be washed clean.
The quality of the concrete grouting layer is related to the connection strength and stability between the crane girder and the track. A well – constructed grouting layer can evenly distribute the load and enhance the overall bearing capacity of the structure. In a power plant construction project, where large – tonnage cranes are used for equipment installation, the proper grouting of the crane girder and track connection is crucial to ensure the long – term safe operation of the cranes during the power plant’s operation.
After the inspection and setting – out work of the crane girder is completed, based on the actual inspection situation of the crane girder, machining parts should be proposed. In particular, the length of the threads should be carefully verified to avoid affecting the installation quality and project progress.
During the daily inspection of crane girders, in addition to the above – mentioned dimensional and geometric accuracy checks, visual inspections are also necessary. Check the surface of the crane girder for any signs of cracks, corrosion, or deformation. Cracks may be caused by excessive stress, improper construction, or long – term fatigue. Even small cracks can gradually expand under the repeated load of the crane, endangering the safety of the structure. For example, in an old industrial building, if the crane girder has been in use for a long time and is not properly maintained, cracks may appear due to the cumulative effect of cyclic loads. Early detection of these cracks through visual inspection can prevent potential accidents.
Corrosion is another common problem that needs to be paid attention to, especially in environments with high humidity, chemical substances, or salt – laden air. Corrosion can reduce the cross – sectional area of the crane girder, weaken its strength, and shorten its service life. In a coastal factory, the sea – breeze – borne salt particles can accelerate the corrosion of the crane girder. Regularly checking for corrosion and taking appropriate anti – corrosion measures, such as painting or applying protective coatings, is essential to ensure the durability of the crane girder.
Deformation of the crane girder can also occur due to overloading, improper installation, or external impacts. Deformation may lead to changes in the geometric shape of the crane girder, affecting the running of the crane and the alignment of the track. In a factory where there have been incidents of heavy – object impacts on the crane girder, it is necessary to carefully inspect for any signs of deformation, such as bending or warping.
In terms of the setting – out process, the accuracy of the measuring instruments is of utmost importance. Theodolites and levels should be regularly calibrated to ensure the reliability of the measurement data. If the measuring instruments are not accurate, the set – out lines will be incorrect, resulting in problems in subsequent installation work. For example, if a theodolite has a calibration error, the datum center line of the crane girder set out based on it will be misaligned, which will cause difficulties in track installation and affect the normal operation of the crane. Moreover, the personnel responsible for inspection and setting – out should be well – trained and experienced. They should be familiar with the relevant standards and specifications, as well as the operation methods of measuring instruments. In a large – scale construction project, a team of professional inspectors and set – out workers can ensure the high – quality completion of the work. Their expertise can help to accurately identify problems during the inspection process and take appropriate measures to solve them in a timely manner.
In addition, the inspection and setting – out work of crane girders should be properly documented. Record all the inspection data, including the measured values of various dimensions, the location of any defects found, and the results of the setting – out work. This documentation is not only useful for the current installation project but also provides important historical data for future maintenance and inspection work. For example, in a multi – year industrial facility upgrade project, the historical inspection records of crane girders can help engineers understand the long – term performance and changes of the structure, and make more scientific decisions on repair, replacement, or reinforcement.
In conclusion, the daily inspection and setting – out of crane girders are critical steps in ensuring the safe and efficient operation of cranes. By strictly following the relevant requirements, conducting comprehensive inspections, using accurate measuring instruments, and relying on professional personnel, the quality of crane girder installation can be guaranteed, and potential safety hazards can be effectively avoided. This not only contributes to the normal operation of industrial production but also ensures the safety of workers and the stability of the entire industrial facility.
