impeller

Workers on the Vessels of Opportunity (the lemons-into-lemonade name given to BP's cleanup fleet) have told me that their hard rubber impellors are falling apart and need frequent replacement; divers say they have had to replace the soft rubber o-tings on their gear after dives in the Gulf.

The one major disadvantage is that the vanes or impellors have inertia, and the turbine pneumotach is not appropriate for exercise studies or maximum volume ventilation measurements.

Additionally, removable parts such as mixers and impellors coated with PVDF may be recoated if the coating begins to wear down.