A gas meter with a rated maximum flow capacity of greater than 3,000 CFH (Cubic Feet per Hour)for example, between 3,500 CFH and 7,000 CFHis provided with 2-inch flange connectors. One or more undercuts are provided in the meter body to promote satisfactory performance in terms of, for example, differential pressures at the meter inlet and outlet.

Aspects of the present invention relate to a stator component for a pump housing. The stator component has a plurality of fluid inlet channels for conveying fluid to respective pumping chambers. The fluid inlet channels each have an inlet port for conveying fluid into the pumping chamber. A plurality of fluid transfer channels are provided for conveying fluid to a respective one of the fluid inlet channels. The fluid transfer channels each have an inlet for receiving pumped fluid. The stator component is adapted to receive at least one sealing member for inhibiting the conveyance of fluid into an associated one of the pumping chambers. Aspects of the present invention relate to a pump housing, a cover plate and a pump. Aspects of the present invention also relate to a method of converting a stator component.

The present invention relates to a rotor for a vacuum pump 150 having a roots pumping mechanism, the rotor comprising at least two hollow lobes 160, 162, 164, 166, each lobe having an outer wall 208 which defines a lobe profile, a hollow cavity 210 generally inward of the outer wall, and at least one strengthening rib 226 located in the cavity to resist stress on the lobes generated during rotation.

A Roots-type device can include a housing assembly having a first opening and a second opening in fluid communication with an internal cavity; a pair of identical rotors oppositely arranged within the housing internal cavity, each of the pair of rotors having a longitudinal axis and plurality of lobes, each of the lobes defining an end face extending between a first longitudinal side of the rotor lobe and a second longitudinal side of the rotor lobe; and a recess port defined within the housing assembly and being axially spaced from the end faces of the rotor lobes, the recess port placing the first longitudinal side of one of the rotor lobes in fluid communication with the second longitudinal side of the rotor lobe such that the housing first opening is placed in fluid communication with the housing second opening. The device can also be provided be provided with an inlet nozzle structure in fluid communication with the first opening, the inlet nozzle tapering towards the first opening and being configured such that a nozzle velocity of a working fluid passing through the nozzle is at least equal to the rotor mesh axial lead velocity.