What is the difference between mechanical seals and dry gas seals?

Mechanical seals rely primarily on a liquid layer that forms an oil film between the moving and stationary rings to provide sealing; dry gas seals, on the other hand, involve external gas (such as nitrogen) being introduced into the sealing chamber. Dry gas seals are stable, require low maintenance, and have a long service life! Mechanical seals have relatively low energy consumption, right?……

Dry gas seals are primarily used to seal hazardous gases, while mechanical seals are mainly used to seal liquids such as oil and water. The former can be applied to large, high-speed rotating machinery; they require high maintenance costs and specific requirements regarding the medium to be sealed

Turbines use dry gas seals.

We don’t need a turbine; instead, use a centrifugal compressor driven by a turbine

Hydrogen for dry gas sealing of power plant turbines.

Dear all, I know what the purpose of dry gas seals is; I just want to understand the difference between them and contactless mechanical seals.

The dry gas seal has a balanced cartridge structure similar to that of conventional mechanical seals, but its end face design is different; it features grooves several micrometers to a dozen micrometers deep on its surface, and the end face is relatively wide. Unlike conventional lubricated mechanical seals, dry gas seals create a stable air film between the two sealing surfaces. This gas film possesses sufficient stiffness to keep the two sealed surfaces completely separated and to maintain a certain sealing gap; this gap should not be too large, usually being a few micrometers. If the sealing gap is too large, it will lead to an increase in leakage and a poor sealing effect; on the other hand, if the sealing gap is too small, the two sealing surfaces are likely to come into contact. Since the frictional heat generated by the dry gas seal cannot be dissipated promptly, and there is no lubrication at the point of contact between the surfaces, this will quickly cause the seal to deform and the surfaces to overheat, resulting in seal failure. The presence of this gas film not only effectively separates the end faces but also cools the two end faces that are in relative motion. Since the end faces do not come into contact, friction and wear are reduced, which contributes to a longer service life for the seal and thus extends the lifespan of the main unit.

Contactless mechanical seals share this characteristic as well; is a dry gas seal another name for a contactless mechanical seal?