English to Italian Tech/Engineering Engineering: Industrial

This is a dry-compressing screw vacuum pump designed for a wide range of applications in the rough vacuum range (1 - 1000 mbar abs).
The pump is equipped with an integrated variable frequency drive and an Elektronikon control unit.
It can be optionally equipped with automatic gas ballast and seal purge valves.
It is air-cooled, easy to service and requires minimal maintenance.
It can be also used to maintain a desired pressure inside a vacuum system by setting the control unit accordingly.

"purge valve" è sicuramente la valvola di spurgo, ma "seal" qui significa "a tenuta"?