Abstract: A positive displacement fluid flow meter comprises a chamber having a fluid inlet and a fluid outlet. A rotor is displaceable within the chamber, rotation of the rotor being related to the volume of fluid passing through the chamber. The chamber has a surface proximate which an end surface of the rotor passes, the chamber surface and/or the rotor end surface having at least one recess to retain at least a portion of debris carried by the metered fluid. The recess is preferably formed so as not to provide fluid, communication, from the inlet to the outlet across the rotor end surface. A lid closes an end of the chamber which in use is subject to the pressure of fluid within the chamber. The lid is engaged at its periphery to a wall of the chamber, and is preferably flexible adjacent its periphery to reduce the transmission of bending stresses between the periphery of the lid and the remainder thereof.

Abstract: A positive displacement fluid flow meter comprises a chamber having a fluid inlet and a fluid outlet. A rotor is displaceable within the chamber, rotation of the rotor being related to the volume of fluid passing through the chamber. The chamber has a surface proximate which an end surface of the rotor passes, the chamber surface and/or the rotor end surface having at least one recess to retain at least a portion of debris carried by the metered fluid. The recess is preferably formed so as not to provide fluid, communication, from the inlet to the outlet across the rotor end surface. A lid closes an end of the chamber which in use is subject to the pressure of fluid within the chamber. The lid is engaged at its periphery to a wall of the chamber, and is preferably flexible adjacent its periphery to reduce the transmission of bending stresses between the periphery of the lid and the remainder thereof.