Sealing principle of globe valve: Part 2

2. Cone seal: Making the sealing surface conical to narrow the contact surface. This kind of seal under the action of a certain sealing force, its sealing specific pressure is greatly increased, and it is easy to achieve the seal. Under the premise of ensuring sealing, the sealing force applied is smaller than that of flat seals. Since the narrow sealing surface is not easy for the disc to fall correctly on the valve seat, the disc must be guided in order to achieve the best sealing performance. After the disc is guided, it can achieve better sealing performance.

When the disc is guided in the valve body, the lateral thrust of the flowing medium received by the disc is borne by the valve body, not by the stem, which further enhances the sealing performance and the reliability of packing sealing. On the other hand, conical seals fit in the case of friction, so the sealing material must be resistant to scratches. Compared with flat seals, cone seals are relatively less damaged by solid particles and media precipitates, but they are not suitable for use in media containing solid particles and media precipitates. Such seals are mainly used in media without particles. The sealing principle is that when the medium flows in from under the valve disc, the sealing force applied must be equal to or slightly greater than the sum of the specific pressure generated on the sealing surface and the upward force of the medium. When the medium flows in from above the disc, the sealing force applied is equal to or greater than the difference between the specific pressure generated on the sealing surface and the force of the medium.

In order to improve the strength of the cone seal without sacrificing its sealing stress, the sealing surface cone half angle is made to 15^O, which provides a wider sealing surface, so that the disc can be more easily sealed with the valve seat. In order to achieve a higher sealing stress, the sealing surface of the valve seat begins to have a narrow contact area with the valve disc, about 3mm, and the remaining taper part can be slightly longer. As the sealing load increases, the disc slides deeper into the seat, thereby increasing the width of the sealing surface. This sealing surface design is not as susceptible to erosion damage as narrow sealing surfaces. In addition, due to the long conical surface, the throttling characteristics of the valve are improved.

More details of globe valves, please go to https://www.mingpinmetals.com/Globe-Valve-pl3917724.html