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Generally speaking, a typical dry gas seal structure includes components such as a stationary ring, a rotating ring assembly, a secondary seal O-ring, a static seal, springs, and spring seats (cavities). The static ring is located within a stainless steel spring seat and is sealed by a secondary sealing O-ring. The spring enables the stationary ring to fit with the moving ring assembly fixed to the rotor under a sealed and unloaded condition; as shown in the figure, there is an advanced and unique method for providing radial gas sealing at the mating surfaces of the moving ring assembly and the stationary ring. The fit surface has a high degree of flatness and smoothness; the fit surface of the moving ring assembly features a series of helical grooves, as shown in the figure. As the rotor rotates, the gas is pumped inward toward the root of the spiral groove; the groove-free area outside the root is known as the seal dam. The sealing dam exerts a resisting force on gas flow, increasing the gas film pressure. On the inner side of this sealing dam, there is also a series of reverse helical grooves; these grooves serve to pump fluid in the opposite direction and improve the pressure distribution on the mating surfaces, thereby enhancing the ability to increase the air gap between the stationary and moving ring components. Inside the reverse helical groove, there is also a sealing dam that exerts resistance to gas flow, thereby increasing the gas film pressure. The pressure between the mating surfaces causes the static ring surface to separate from the dynamic ring assembly, maintaining a very small gap, typically around 3 micrometers. A stable equilibrium gap is established when the closing pressure generated by gas pressure and spring force equals the opening pressure of the gas film. Under dynamic equilibrium conditions, the forces acting on the seal are as shown in the figure. The closing force Fc is the sum of the gas pressure and the spring force. The opening force Fo is generated by integrating the pressure distribution between the end faces over the area of those end faces. Under equilibrium conditions, Fc = Fo, and the operating gap is approximately 3 micrometers. If the sealing gap decreases due to some interference, the pressure between the end faces increases. At this point, the opening force Fo becomes greater than the closing force Fc, causing the end-face gap to increase automatically until equilibrium is reached. As shown in the figure. Similarly, if the disturbance causes the sealing gap to increase, the pressure between the end faces decreases; at this point the closing force Fc becomes greater than the opening force Fo, causing the end-face gap to decrease automatically. The seal then quickly reaches a new equilibrium state, as shown in Figure 5. This mechanism creates a gas film with high stability between the stationary and rotating ring components, allowing the end faces to remain separated, in contact with each other, and less prone to wear under normal operating conditions, thereby extending their service life. Through different combinations of the above structures, along with supplementary sealing, several types of structures suitable for actual operating conditions can be developed: B. Single-face dry gas seal – it is suitable for situations where a small amount of process gas leaking into the atmosphere poses no hazard, as shown in the figure below. C. Series dry gas seal – it is suitable for situations where a small amount of process gas leaking into the atmosphere is acceptable, as shown in the figure below. A set of series dry gas seals can be considered as two or more dry gas seals connected end to end in the same direction. Similar to the single-end face structure, the gas used for sealing is the process gas itself. Typically, a two-stage structure is employed: the first stage (the primary seal) bears all or most of the load, while the second stage serves as a backup seal that bears no pressure drop or only a small one; the process gas that leaks through the primary seal is directed to a flare for combustion. The extremely small remaining amount of unburned process gas leaks through the secondary seal and is introduced into a safe area for discharge. When the primary seal fails, the secondary seal can act as an auxiliary safety seal, ensuring that the process medium does not leak in large quantities into the atmosphere. A series dry gas seal with intermediate air intake in the D zone is suitable for applications where neither the process gas nor the sealing gas is allowed to leak into the atmosphere; see the diagram. In situations where it is not permissible for the process medium to leak into the atmosphere, nor for the sealing gas to leak into the process medium, a labyrinth seal can be added between the two stages of the series configuration. It is used for flammable, explosive, and highly hazardous gas media, ensuring complete prevention of any external leakage. Such as H2 compressors, natural gas compressors with high H2S content, ethylene and propylene compressors, etc. In addition to the process gas itself, another supply of nitrogen is required as the sealing gas for the second stage in this structure. The process gas that leaks through the primary seal is completely introduced into a flare for combustion using nitrogen. All that leaks into the atmosphere through the secondary seal is nitrogen. When the primary seal fails, the secondary seal also serves as an auxiliary safety seal. E double-face dry gas seal: It is suitable for applications where it is not allowed for process gas to leak into the atmosphere, but it is permissible for a sealing gas (such as nitrogen) to enter the machine, as shown in Figure 9. A double-end face seal is equivalent to two sets of single-end face seals arranged face to face; sometimes, each of these two seals uses its own moving ring. It is suitable for situations where torch conditions are not available, and a small amount of seal gas is allowed to enter the process medium. Nitrogen is introduced between the two sealing layers as a blocking gas, thereby creating a reliable blocking seal system. The pressure of the nitrogen is controlled to remain at a level 0.2–0.3 MPa higher than the pressure of the process gas; this ensures that any leakage from the sealing gas occurs in the direction of the process gas and the atmosphere, thus preventing the process gas from leaking into the atmosphere. Features of F dry gas seals: 1) No seal oil is used, reducing energy consumption and maintenance needs for auxiliary equipment. 2) The gap between the sealing surfaces is small, resulting in low gas leakage and thus less waste and environmental pollution. 3) Mechanical wear is minimal, giving long seal life; inspection is required only every 48,000 hours on average. 4) Downtime is reduced. 5) Since dry gas is used for sealing, high standards are required regarding the quality of the gas. C. Supply of inert gas (N2): Used primarily to seal leaking gases and isolate bearing lubricating oil, thereby preventing damage to the sealing surfaces of the dry gas seal. The nitrogen production system utilizes hollow fiber membrane separation technology