Vaporization in the sealing gap (not to be confused with gas emission) occurs when the pressure to be sealed falls locally below the vapour pressure of the medium to be sealed in the sealing gap. It is caused either by a great increase of temperature in the sealing gap due to inadequate frictional heat transfer, or by too small a difference between the sealing pressure and the vapour pressure. Vaporization in the sealing gap results in dry running and hence to premature failure of the mechanical seal. It can be prevented by

- intensifying the transfer of frictional heat

- raising the sealing pressure

- cooling

- reducing the generation of frictional heat