The positive displacement flowmeter generally measures one-direction flow, so the actual flow direction shall be consistent with the direction indicated on the flowmeter shell ( Morton et al., 2011).
Non-lubricated the discharge is normally free from pulsation low pressure high rotation speed.įig.
Two impeller straight-lobe compressors and blowers Rotary, positive displacement machines in which two straight, mating but non-touching lobed impellers trap the air and carry it from intake to discharge. Available in lubricated and non-lubricated construction the discharge air is normally free from pulsation. Sliding-vane compressors Rotary, positive displacement machines in which axial vanes slide radially in a rotor mounted eccentrically within a cylindrical casing. Helical and spiral-lobe compressors ( screw) Rotary, positive displacement machines in which two intermeshing rotors, each in helical configuration displace and compress the air available in lubricated and non-lubricated construction the discharge air is normally free from pulsation high rotation speed. The piston compressor is available in lubricated and non-lubricated construction. Reciprocating compressors The compressing and displacing element (piston or diaphragm) has a reciprocating motion. The capacity of a positive displacement compressor varies marginally with the working pressure. Positive displacement units are those in which successive volumes of air are confined within a closed space and elevated to a higher pressure. In Plant Engineer's Reference Book (Second Edition), 2002 26.4.1.1 Positive displacement compressors