Oil seal knowledge (III) – The functions of various parts of an oil seal

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This post was last edited by qy576100527 on 2018-10-1 10:05. An oil seal is mainly composed of a sealing body, a reinforcing frame, and a self-tightening helical spring, among other components. Seals are further divided into different parts such as the bottom, waist, cutting edge, and sealing lip. The following diagram shows the main names and terms for various components of an internal skeleton oil seal with a spring and a dust lip. The metal framework acts like the rebar in concrete elements, providing reinforcement and helping the oil seal to maintain its shape and tension. Generally, in a free state, the inner diameter of a skeleton oil seal is smaller than the shaft diameter, meaning it has a certain amount of \"interference\". Therefore, once the oil seal is installed in the seal seat and on the shaft, the pressure exerted by the seal’s edge together with the contracting force of the self-tightening helical spring exerts a certain radial tightening force on the shaft. After operating for a while, this pressure decreases rapidly or even disappears (WeChat official account: Pump Manager). Thus, the spring can compensate for the self-tightening force of the oil seal at any time. The outer edge of the oil seal not only fixes it within the cavity hole, but also prevents fluid from leaking or entering between the outer peripheral surface of the oil seal and the inner surface of the cavity. Additionally, the metal frame serves to maintain the fitting force when the oil seal is fixed inside the cavity. The sealing lip is made of a flexible elastomer, designed to maintain a stable seal even under mechanical vibrations and pressure changes in the sealed fluid, and it also ensures stable contact between the lip and the shaft surface. The spring increases the pressing force of the sealing lip against the shaft, serving to maintain this pressing force. The lip end is shaped like a bevel, pressing against the surface of the shaft at the end to seal the fluid. A dust-proof lip is a secondary lip that is not connected to a spring, and it serves to prevent dust from entering.