Compared with ordinary mechanical seal, the dynamic ring and static ring of dry gas seal have wider sealing end face in structure. Special-shaped dynamic pressure grooves, such as spiral grooves, circular grooves, T-shaped grooves, etc., are processed on the end face of the dynamic ring or the static ring, and the groove depth is generally in the order of 10-9m. Generally, the ring that drives the pressure groove is made of SiC, and the ring that does not drive the pressure groove is made of C graphite.
Spiral groove dry gas seal explains the working principle of dry gas seal. When the moving ring rotates at high speed, the spiral groove on the end face of the moving ring or the stationary ring draws the high-pressure gas at the outer diameter downward into the space between the sealing end faces, and the gas flows from the outer diameter to the center, while the sealing dam restricts the gas from flowing to the center, and the gas is compressed to cause the pressure to rise, forming a high-pressure area at the groove root. The gas film pressure on the end face forms the opening force. When the seal runs stably, the opening force is balanced with the closing force formed by the gas pressure and spring force acting on the back of the compensation ring, and the seal keeps non-contact and wear-free operation.
If some disturbance factors reduce the sealing gap, the gas film pressure generated by the spiral groove will increase at this time, causing the opening force to increase and the closing force to increase until the balance is restored; On the contrary, if some disturbance factors increase the sealing gap, the gas film pressure generated by the spiral groove will decrease at this time, thus reducing the opening force, while the closing force remains unchanged, the sealing gap will decrease and the seal will quickly recover its balance. The ability of dry gas seal to resist the change of gas film gap is called gas film stiffness.
I hope it helps you!