1. Pressure test standards
The pressure test standards for concrete machinery product cylinders are usually formulated based on relevant industry specifications and national standards. For example, in my country, standards such as "Inner diameter of cylinders and outer diameter of piston rods for hydraulic and pneumatic systems and components" are referenced. These standards clearly specify the pressure range, test duration, and performance index requirements of different types and specifications of cylinders during testing. For general concrete pump truck cylinders, the rated pressure test value is often set at about 1.5 times its working pressure. During the test, the cylinder is required to maintain a certain period of time at the specified pressure, such as 5-10 minutes, during which the sealing performance of the cylinder, the stability of the piston rod, and whether the cylinder body is deformed or leaking are observed. At the same time, the standard also has strict requirements on the accuracy and range of the test equipment to ensure the accuracy and reliability of the test data, so that the test results can truly reflect the pressure resistance and quality level of the cylinder in actual use.
2. Test methods
The common pressure test method uses a special hydraulic test system. First, correctly install the tested cylinder on the test bench, connect the oil inlet and return lines, and ensure that the connection parts are well sealed. Then, start the hydraulic pump, slowly increase the system pressure, and raise the pressure to the test pressure at the predetermined pressure increase rate. During the pressure increase process, use a pressure sensor to monitor the pressure value in real time, and use a displacement sensor to monitor the telescopic displacement of the piston rod. After reaching the test pressure, keep the pressure stable for a period of time, and carefully check the sealing of various parts of the cylinder, including the piston seal, piston rod seal, and cylinder end cover seal. At the same time, observe whether the cylinder has expansion and deformation. The deformation can be accurately measured by setting a strain gauge on the surface of the cylinder. In addition, it is necessary to check whether the entire test system has leaks, such as oil pipe joints, valves and other parts, to ensure the stability of the test environment and the validity of the test data.
3. Determination of safety margin
The determination of safety margin requires comprehensive consideration of many factors. On the one hand, the complexity and uncertainty of the working environment of concrete machinery should be considered. In actual construction, sudden overloads may be encountered, such as instantaneous high-pressure shocks caused by concrete blockage. On the other hand, the dispersion of the performance of the cylinder material and the aging and wear of the seals should also be taken into consideration. Generally speaking, the value range of the safety margin is between 20% and 50%. For some concrete machinery product cylinders with harsh working conditions and large load fluctuations, the safety margin will be appropriately increased. For example, in the unloading cylinder of a large concrete mixing station, the unevenness of the material may cause large pressure fluctuations, and its safety margin may be set at about 40%. By reasonably determining the safety margin, the safe operation of the cylinder under various complex working conditions can be effectively guaranteed, the probability of failure can be reduced, the service life of the cylinder can be extended, and the reliability and stability of the entire concrete machinery can be improved.
4. Evaluation and application of test results
After completing the pressure test, the test results need to be fully evaluated. If all indicators of the cylinder meet the standard requirements during the test, such as no leakage, deformation within the allowable range, and smooth movement of the piston rod, the cylinder is judged to have passed the test and can be put into use or enter the next production link. If problems are found, such as slight leakage or deformation exceeding the standard, the cause needs to be analyzed and rectified and repaired, and then tested again after repair until qualified. The test results are not only used to judge the quality of a single cylinder, but also provide a basis for quality control for mass production of products. For example, through statistical analysis of the test data of a batch of oil cylinders, potential problems in the production process can be discovered, such as unstable processing technology and fluctuations in material quality, so that the production process and quality control measures can be adjusted in time to ensure the quality consistency and reliability of the entire concrete machinery product cylinder, laying a solid foundation for the efficient and safe operation of concrete machinery in engineering construction.
