Hydraulic Relief Valve Faulty Symptoms

When I opened the mailbox this morning, I saw a reorder for 500 pilot hydraulic relief valves from Jimmy. He mentioned that the pilot hydraulic relief valve designed by AAK had been used for 2 years and without any complaints. Jimmy is a purchaser of American company Vickers, responsible for the purchasing of hydraulic parts. 2 years ago, his company encountered a complaint from customer for a hydraulic pump. The customer complained that it screamed after being used for a period of time. After dissecting, their engineer found that there was a problem with the hydraulic relief valve in the hydraulic pump. The owner asked Jimmy to solve the problem as soon as possible. Jimmy sent the hydraulic relief valve back to the original supplier, but the supplier replied that the inspection result was good. Maybe the problem happened during installation. Jimmyâ??s engineers tested the samples by themselves and found that there was no problem with the hydraulic relief valve, but there was also no problem with the installation method and operation. Now Jimmy is depressed. The owner is pushing for status, but he has no clue. He contacted with several local hydraulic valve manufacturers in the United States, and they all replied that there was no problem on the hydraulic relief valve. One day, after browsing AAK website (www.aakindustry.com) in Google, Jimmy sent an email asking if AAK could help analyze the reason. We replied that it would be better for engineers to have video communication on site Jimmy decided to ask Vickers engineers to make a video with AAK engineers the next morning. After more than half an hour of observation, AAK engineers found that once the pressure oil at the inlet, outlet and control port of the hydraulic relief valve fluctuated, it would produce a scream. We got their original samples and drawings, as well as the working parameters of the hydraulic pump. After 15 days, AAK sent a sample of the pilot hydraulic relief valve. A week later, Jimmy e-mailed us that AAK hydraulic relief valve was installed and tested on site for 24 hours, and there was no scream. Jimmy wondered why there was no scream when AAK hydraulic relief valve was used. AAK engineers analyze the cause from the hydraulic impact. After the hydraulic pressure impacts the main valve spool in the hydraulic relief valve, the pressure oil converges through the check valve, resulting in fluid impact and fluctuation, causing the hydraulic relief valve to oscillate, resulting in the instability of the pressure oil at the outlet of the hydraulic pump. Because the pressure oil output by the pump itself has pulsation, the pressure oil output by the pump will fluctuate strongly and arouse the vibration of the hydraulic relief valve. For the natural frequencies of the two hydraulic relief valves are the same, it causes the resonance of the relief valve and the scream occurs.