1. The sealing sub structure changes under the change of temperature or sealing force. Moreover, this change will affect and change the force between the sealing pairs, thereby reducing the performance of the valve seal. Therefore, when selecting a seal, it is necessary to select a seal with elastic deformation. At the same time, pay attention to the width of the sealing surface. The reason is that the contact surface of the sealing pair cannot match. When the width of the sealing surface increases, the force required for the sealing must be increased. 2. The specific pressure of the sealing surface of the sealing surface affects the sealing performance of the valve and the service life of the valve. Therefore, the sealing surface pressure is also a very important factor. Under the same conditions, too large the specific pressure will cause damage to the valve, but too small the specific pressure will cause leakage of the valve. Therefore, we need to fully consider the appropriateness of the pressure when d