To improve seal life, the frictional resistance of the main seal should be relatively low, which requires an oil film on the sliding surface of the main seal. This range of friction coefficients for the formation of the oil film is also known as fluid lubrication in lubrication theory. In this range, the seal’s wo. rking surface in the cylinder or rod is contacted by the oil film, then, the seal has a long service life without wear, even if the relative motion occurs. Therefore, due consideration is given in the design to a well-proportioned contact pressure distribution, which enables an optimum oil film to be generated on the sliding surface. This is true not only for combination seals, but also for all hydraulic seals.
The design principles for combination seals include the following:
① The overall compression ratio of the combination seal is appropriately valued according to the material properties. Product free state and the groove between the gap, but not too large, so as not to sway in the groove.
② sealing ring: the main seal. Its thickness can not be too thick, generally in the 2 ~ 5mm, depending on the specific sealing material; its width can not be too wide, the effective sealing band width exceeds a certain value can be considered plus lubrication groove, to avoid the occurrence of dry friction and creeping phenomenon.
③ elastomer: the role is to continuously provide support to ensure that the combination of sealing the sealing effect. According to the hardness of the material, the modulus of elasticity and other appropriate compression rate, its width and the width of the groove to leave an appropriate gap between. Ensure that the elastomer has enough space to go after extrusion.
④Retaining ring: the role is to ensure the stability of the position of the elastomer after loading into the groove, so as to improve the stability of the seal ring as a whole. Combined with the sealing ring and elastomer overall design.
⑤ Guide ring: The function is to guide and ensure smooth and stable running of the piston in the cylinder, preventing the piston steel parts from contacting with the cylinder steel barrel and damaging the surface of the cylinder steel barrel. The structure generally adopts standard GFA /GST.
Post time: Jul-21-2023
