Torque wrench on the sealing ring is a section for circular rubber ring, due to its cross section is type O, so called type O sealing ring. Wrench in hydraulic and pneumatic transmission system is one of the most widely used. Type O sealing ring is the most used in fluid power systems seal form. Because the type O sealing ring has simple structure, good sealing performance, small friction, groove the advantages of small size, easy manufacturing, widely used in hydraulic and pneumatic components.

Working mechanism of O sealing ring is put type O sealing ring in the sealing groove, the oil (or gas) through the pressure makes it happen deformation, the grooved side extrusion, sealed by sealing contact surface, the fluid flow (or flow) shall not be passed, as shown in figure 1. The seal in the fluid power system sealing effect is good, but, if the design of the type O sealing ring and the improper use, also easy to cause the failure of sealing performance.