The door closer relies on the throttling of the fluid in its internal hydraulic system to control the closing process. The oil leakage means the failure of the hydraulic system, so the hydraulic system is the only criterion that determines the life of the door closer. The main cause of oil leakage is that the pinion support guide wears to increase the clearance, the seal wear causes the sealing effect to decrease, or the throttle body rotates counterclockwise away from the valve body when adjusting the cushioning effect. The reduction in the cushioning effect of the door closer is caused by the entry of air due to oil leakage or the increase in the fit (throttle) gap between the rack plunger guiding cylinder and the valve body. Therefore, the quality and accuracy of the material of the pinion and the support guide, heat treatment and machining are very important.
For a door closer with poor cushioning effect, simply adjusting the throttle spool for throttling cannot solve the problem at all. It is necessary to repair the method. If there is oil leakage at the support guide, remove the support guide and check the condition of the seal. If it is worn or aged, replace the seal. If the gap between the support guide and the pinion shaft is too large, the support guide is replaced.