Petrov is an old purchaser of Hydrosila Group in Russia. He cooperates with AAK on some non-standard hydraulic pilot operated relief valves and often discusses some difficulties and complications of hydraulic pilot operated relief valves. In the second half of last year, they needed to purchase a hydraulic pilot operated relief valve to test an agricultural machinery equipment. Due to urgent time, Petrov purchased from a Russian hydraulic relief valve manufacturer, who delivered 30 hydraulic pilot operated relief valves in 30 days. During the test run, the hydraulic pilot operated relief valves screamed at about 1.5MPa before opening, as well as at the start and stop. Petrov contacted the manufacturer of the hydraulic relief valves, and the manufacturer replied that the non-standard customization was completely based on the drawings provided, and the dimensional accuracy also met the requirements. Their engineers independently tested the hydraulic relief valves and found that there was really no abnormality. The boss was dissatisfied with the one week of delay due to the test run and asked Petrov to repurchase the hydraulic pilot operated relief valves. Because the hydraulic relief valve problems encountered before were solved by AAK, Petrov emailed me again. AAK engineer preliminarily judged that there may be problems in the design of the hydraulic pilot operated relief valve according to his fault description, the drawings of the pilot operated relief valve, the working parameters of the hydraulic system of agricultural machinery, and the video of the test machine. Knowing that he still has one month of flexibility, AAK can modify the original design of the hydraulic pilot operated relief valve and send 12 samples within 30 days. Four weeks later, AAK sent 20 samples of hydraulic pilot operated relief valves, which were installed and debugged without screaming, and the hydraulic power unit was started or closed for many times still without screaming. Petrov was surprised that AAK engineer found and solved the problem of hydraulic relief valveS at one time, while the original Russian hydraulic relief valve manufacturer can do nothing? Because the scream of pilot operated relief valve is often generated by high-pressure oil through damping hole or valve port, AAK engineer added inclined hole of valve seat and vibration elimination cavity in the original design. In this way, the dynamic and static characteristics of the hydraulic pilot operated relief valve can be improved, the screaming can be eliminated, the noise can be reduced, and the pressure control accuracy can be improved at the same time. AAK strong engineering team not only has the concept of German HAWE, but also has the experience of Italian Oil Controlï¼?the problem can be found at one time. After the successful test run, Petrov privately told us that the boss was very satisfied that he found a