(1) The deviation of the actual centerline of the track from the actual centerline of theကရိန်းgirder shall not be greater than 10 မီလီမီတာ. Precise alignment of these centerlines is fundamental. In large industrial workshops whereကရိန်းs operate continuously, any misalignment here can lead to uneven stress distribution on theကရိန်းstructure during movement. Specialized measuring tools, like laser alignment devices, are often employed. These tools emit highly focused laser beams that can accurately trace the centerlines, and the deviation is then read off calibrated scales with micrometer precision. Technicians need to ensure that the measuring environment is stable, free from vibrations and strong air currents that could disrupt the laser’s path, so as to obtain the most accurate deviation value.
(2) The horizontal position deviation of the actual centerline of the track from the installation reference line must not exceed 5 မီလီမီတာ. This specification is crucial for the overall layout of the crane system within a factory. Installation teams typically use total stations or high-precision theodolites for measurement. These instruments can be set up at fixed reference points around the installation area, and by triangulating multiple known points, they precisely determine the position of the track centerline. Before measurement, calibration of these devices against standard calibration blocks is essential to eliminate any systematic errors. During the installation process, constant rechecks are made as the track is gradually laid, adjusting the position promptly if any deviation approaches the limit.
(3) The allowable deviation of the crane track span is3 + 0.25, where the variable in the formula is related to the crane track span (ဍ). This seemingly simple formula has profound implications for the stability and functionality of the crane. When calculating the span, engineers consider factors such as the maximum load the crane will carry, the speed of traversal, and the frequency of use. For large gantry cranes in port facilities, where colossal containers are hoisted and moved, even a minor deviation in span can cause issues like uneven load distribution on the wheels, leading to premature wear. To ensure compliance, advanced electronic distance meters are used. These meters can measure long distances with an accuracy of fractions of a millimeter, and the measured span value is plugged into the formula to verify if it falls within the allowable range.
(4) The longitudinal inclination of the track top surface relative to its designed position should not be greater than 1/1000. One measurement point should be taken every 2 ဍ, and the height difference within the full stroke shall not exceed 10 မီလီမီတာ. This inclination requirement is vital for the smooth running of the crane trolley. If the inclination is too large, the trolley will experience unbalanced forces, which may cause it to deviate from its normal running path or even derail. Specialized leveling instruments, such as digital spirit levels with high-resolution sensors, are used to measure the inclination. These levels are placed at each 2-meter interval, and the data is recorded wirelessly to a central monitoring system. By analyzing the cumulative height difference data from all the measured points, engineers can accurately assess whether the full-stroke height difference meets the standard.
(5) The allowable deviation of the elevation of the reference point on the track top surface relative to the designed elevation is 10 မီလီမီတာ. This elevation accuracy impacts the connection and cooperation between the crane and other handling equipment at different heights. Surveyors use GPS receivers with elevation measurement capabilities, along with traditional leveling rods in some indoor or GPS-signal-weak areas. The GPS receivers can quickly obtain rough elevation data over large areas, while the leveling rods offer more precise local elevation readings. Multiple reference points are measured across the track length, and the data is statistically analyzed to ensure that the majority of points fall within the 10-mm deviation range.
(6) The relative elevation difference between two parallel tracks in the same section should not be greater than 10 မီလီမီတာ. This balance between tracks is essential for the stable operation of the crane, especially for double-girder cranes. Engineers use differential leveling techniques, with two leveling instruments set up simultaneously at different positions along the parallel tracks. By comparing the elevation readings obtained from both instruments, they can precisely determine the relative elevation difference. During construction, if the foundation settlement of different sections varies, it can cause elevation differences. Regular monitoring during the installation period and in the early stages of operation helps catch and rectify such issues promptly.
(7) The height difference and lateral misalignment at the track joints should not be greater than 1 မီလီမီတာ, and the gap should not be larger than 2 မီလီမီတာ. These small tolerances at the joints are critical for a seamless running experience of the crane. Inspectors use precision calipers and gap gauges. The calipers, with a resolution of up to 0.01 မီလီမီတာ, measure the height difference and lateral misalignment, while the gap gauges, available in various thickness increments, accurately determine the size of the joint gap. Any non-compliance at the joints can lead to sudden jolts during the crane’s movement, which not only affects the comfort of operation but also gradually damages the crane’s mechanical components over time.
(8) The steel rail should be closely attached to the elastic base plate. When there is a gap, a pad should be added under the elastic base plate to make it firm. The length and width of the pad should be 10 – 20 mm larger than those of the elastic base plate. This connection between the rail and the base plate is crucial for shock absorption and load distribution. Workers first visually inspect the contact area between the rail and the plate. If a gap is suspected, they use feeler gauges to confirm its presence. Once the need for a pad is established, custom-cut pads made from high-strength, durable materials are inserted. The additional size of the pad ensures full coverage and better load transfer, reducing the stress concentration on the base plate.
(9) When the bridge is assembled, the following requirements must be met:
The allowable deviation of the camber of the main girder (F) is – 0.1F + 0.4F, where F = S/1000 (မီလီမီတာ), and S represents the crane span (မီလီမီတာ). The camber of the main girder is designed to counteract the deflection caused by the load. To measure it accurately, large-span bridge inspection vehicles equipped with laser scanners and strain gauges are deployed. The laser scanners create a detailed 3D model of the girder’s surface, from which the camber can be calculated precisely. The strain gauges, placed at key stress points, monitor the internal stress distribution, providing additional data to verify if the camber deviation is within the acceptable range. Adjustments, if needed, involve complex mechanical and thermal processes to reshape the girder slightly.
The relative difference between the two diagonal lines of the bridge should not be greater than 5 မီလီမီတာ. Diagonal alignment reflects the overall squareness of the bridge structure. Measuring tapes with tension control mechanisms are used to measure the diagonals. These tapes ensure consistent tension during measurement, eliminating errors caused by inconsistent stretching. By comparing the lengths of the two diagonals, any misalignment can be quickly detected. If the difference exceeds the limit, the bridge structure needs to be adjusted at the connection points of the components through careful loosening and re-tightening of bolts or minor repositioning.
The allowable deviation of the track gauge at the end of the trolley span is 2 မီလီမီတာ, and the allowable deviation of the track gauge in the middle of the span is between +1 mm and +5 မီလီမီတာ. Track gauge accuracy is essential for the proper movement of the trolley. Gauge calipers specifically designed for crane tracks are used for measurement. These calipers have wide jaws that can firmly grip the inner edges of the tracks, providing accurate gauge readings. During the assembly process, the tracks are adjusted incrementally, with measurements taken at multiple points along the span to ensure that the gauge remains within the specified range throughout.
The height difference of the trolley tracks in the same section should not be greater than 3 မီလီမီတာ. This requirement ensures the smooth running of the trolley without tilting. A straightedge, often made of high-strength aluminum alloy with a precision-ground edge, is placed across the tracks, and a precision micrometer is used to measure the gap at different points along the straightedge. If the height difference exceeds the limit, shims can be inserted under the tracks to level them, restoring the proper running surface for the trolley.
To further expand on these quality inspection methods, in modern industrial complexes, the integration of smart sensors and the Internet of Things (IoT) technology has revolutionized crane quality control. These sensors, such as fiber-optic strain sensors, piezoelectric accelerometers, and high-precision inclinometers, are installed at various critical points on the crane structure, tracks, and moving components. They continuously transmit real-time data to a central cloud-based platform. Through advanced algorithms, this data can be analyzed to predict potential quality issues long before they become visible during routine inspections.
ဥပမာအားဖြင့်, the fiber-optic strain sensors can detect the minutest changes in the internal stress of the crane’s metal components. By constantly monitoring the stress distribution patterns, engineers can identify if there are any weakening areas due to improper welding during manufacturing or abnormal load distributions during operation. This early warning system allows for timely maintenance or reinforcement, significantly enhancing the safety and lifespan of the crane.
The piezoelectric accelerometers, on the other hand, measure the vibration levels of the crane. Excessive vibration can indicate problems like unbalanced rotating parts, misaligned gears, or worn-out bearings. By analyzing the frequency and amplitude of the vibrations, technicians can pinpoint the source of the problem precisely. In addition, the high-precision inclinometers not only measure the static inclinations of the tracks but also monitor any dynamic changes during the crane’s movement. This comprehensive monitoring approach ensures that every aspect of the crane’s quality is under constant scrutiny, meeting the ever-increasing demands for safety and reliability in industrial operations.
Another aspect is the use of simulation software during the design and quality assessment phases. Engineers can input the design parameters of the crane, including track dimensions, bridge structure, and load capacities, into the software. The software then simulates the crane’s operation under different conditions, such as extreme loads, seismic events, and high-speed movements. By observing how the virtual crane behaves, potential quality issues like insufficient structural strength, unstable track dynamics, or interference between moving parts can be identified early. This allows for design modifications and optimization before actual manufacturing, saving both time and resources.
ထိုမှတပါး, in international trade, crane manufacturers need to comply with different international and regional standards. ဥပမာအားဖြင့်, in the European Union, cranes must meet strict CE marking requirements, which cover not only mechanical safety but also electromagnetic compatibility and environmental protection aspects. In North America, standards set by organizations like the American Society of Mechanical Engineers (ASME) govern crane design, manufacturing, and inspection. Manufacturers need to thoroughly understand these diverse requirements, often involving multiple rounds of product testing and certification processes. This international dimension further complicates the quality control landscape for cranes, but it also drives continuous improvement in quality inspection methods.
