Eliminating vibration during static testing after replacing and assembling the valve in a hydraulic actuator

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1 Two newly purchased mounting valves were replaced, but no suitable gaskets could be found, resulting in oil leakage after installation. After removal, wrap electrical tape around the thread and reinstall it; there will be no more oil leakage. 2 Since two mounting valves were replaced and the original adjustment position was not recorded, the mounting valves can rotate a total of 5 turns; during static testing, the new cartridge valve is temporarily set in the middle position, that is, after being turned all the way down, it is turned back 2.5 turns. 3 For the first static test, 1.8 kg corresponds to position 0, and 4.5 kg corresponds to 44 mm (the full travel distance is 40 mm). The lateral screw on the cylinder piston rod was adjusted; loosening it by one turn had no effect. During this adjustment process, the hydraulic actuator started to vibrate, and the vibration stopped after adjusting the mounting valve on the upper side of the throttle. When loosened another turn, it moved from 44mm back to around 25mm; the screw remained tight at first, before moving back significantly to around 44mm. At this point, it can be seen that the spool is no longer rotating. 4 Open the throttle upper cover and find that the O-ring between the throttle housing and the upper cover is missing; its specification is 132*2.65. It has been a month since the wrong throttle was replaced, but the blue sealant at the site still hasn’t dried. Check that components such as the slide valve, springs, spring seats, and thrust bearings are in good condition. When pulling out the slide valve, it gets stuck at a position 10 mm above its normal position; it can rotate, but cannot be pulled out completely. Then reinstall the wrong throttle. 5 During the second static test, there was no change at 1.5 kg; it was not until 2.8 kg that it started to rise from position 0. At 3.0 kg, the stroke is approximately 2 mm. At this point, the screw at the top of the throttle control is adjusted, causing the 0 position to change; the oil pressure is then set to 2 kg. The throttle control screw continues to be adjusted until it reaches its limit, yet the 0 position is not achieved. There is suspicion that components were misaligned during the reinstallation process due to an incorrect throttle setting. 6 For the second time, the wrong throttle cover was removed to inspect the throttle components; this time the spool was pulled out successfully – it got stuck nowhere, and it was also possible to determine where it had gotten stuck during the first attempt. The spool was cleaned, and it was found that there were two scratches on the lower two sections of the spool, with these scratches being quite shallow to the touch. The on-site maintenance personnel removed the sealant from the upper surface of the faulty throttle, fabricated an O-ring measuring 132*4, installed it, and reinstalled the throttle. 7 On the third static test, it could start rising from position 0 only at 2.8 kg. At 4.5 kg, the stroke is approximately 18 mm. Adjusting the horizontal screw at the upper part of the piston rod did not change the stroke; however, adjusting the screw on top of the throttle valve resulted in a change in the stroke, with it starting to increase. When the stroke reached around 38 mm–40 mm, the hydraulic actuator began to vibrate. When adjusting the upper mounting valve, the fact that the valve closed too tightly during the first attempt caused the spool to fail to rotate, so only minor adjustments could be made this time. At this point, oil leakage occurs between the incorrect throttle and the cylinder connection plate.