This subclass covers non-positive-displacement pumps for liquids, for elastic fluids, or for liquids and elastic fluids whether rotary or not having pure rotation.
This subclass does not cover combinations of non-positive-displacement pumps with other pumps, which are covered by subclass Fulltext... Hierarchy... Expanded...F04B, except that the use of such other pumps for priming or boosting non-positive-displacement is covered by this subclass.