A mechanical seal with a sliding velocity greater than 25 m/s, such as is found e.g. in high-speed pumps, compressors and gas turbines. Typical features of a mechanical seal of this type are its stationary spring backing, rotating counter ring and an optimized coolant guide system. Fallowing factors must be observed when designing a high-speed seal: 

• Spring backing: Starting from around 25 m/s, stationary springs are employed to ensure adequate buckling strength. In the intermediate range up to about 35 m/s it is possible to use revolving multiple springs with a spring guide.
• Power consumption: The mechanical seal's overall power consumption is the sum total of the power consumption, rather: friction loss which increases as a linear function of the speed n, and of the turbulence losses (from the liquid's friction between the rotating parts of the mechanical seal and the seal casing), which increase by the function n^2.8 and begin to exert distinctly more influence from around 30 m/s. This explains why it is necessary to minimize the maximum diameter of seals of this type, to select high-wear-resistant face materials with high thermal conductivity (preferably silicon carbide/ tungsten carbide running against antimony-impregnated carbon graphite), and to make provision for intensive cooling of the seal.
• Coolant guide system: Temperature-related differences in density may restrict the exchange of coolant directly at the sealing gap, causing an obstruction of heat dissipation around the rotating parts of the seal. Positive guidance of the coolant (using flow guides) proves beneficial. The coolant itself must display the lowest possible viscosity and minimum gas solvent power, as the dissipation of heat at the sealing gap can also be obstructed by any gas ring formed when gas components are released due to the given rise of temperature with concurrent drop of pressure. With oils it is important to consider which additives are used, as any deposits on the sliding faces can cause the gap to expand and hence the leakage to increase. As a general rule preference should be given to coolants that leave no or as little residue as possible when they evaporate.
• Freedom from unbalance, reduction of vibration: The high balance qualities usually demanded for high-speed machines force manufacturers to apply closer production and running tolerances. Rotating masses must be kept as small as possible, and the machine manufacturer has to be consulted to check whether it is necessary to balance the seal. The main dangers for high-speed seals lie in the appearance of thermal stress cracks on the mostly carbide seal faces, in unacceptable thermal warping of the seal faces themselves, in overshooting of the pressure-dependent boiling points in the area of the sliding faces with subsequent dry running, and in the formation of deposits on the seal faces with a subsequent unacceptable increase of leakage

Typical examples of double high-speed seals