Laboratory gas cupboard outlet passage incorporates flow-calming section - with venturi,harmonises gas flow for measurement of the difference in static pressure before and after the venturi and accurate gas flow measurement

摘要

A laboratory fume cupboard releases gases to an exhaust outlet (9) incorporating a monitoring instrument. the novelty is that (a) the monitoring instrument has an adapter chamber (8) located between the exhaust outlet (9) and a suction passage (5), in which a pipe (14) open at each end runs parallel to an adapter chamber (8) external wall (10), the pipe (14) inlet (16) being linked to the suction passage (5), the pipe outlet (17) and the exhaust outlet (9); (b) the adapter chamber (8) walls (12,13) between the suction passage (5) and the pipe (14) inlet (16), leave a meandering passage between the walls (12,13) and the adapter inner wall; (c) the pipe (14) incorporates a measuring aperture (15) with a flow calming-section (18) extending to the pipe inlet (16); (d) and that the measuring aperture (15) incorporates one or more static pressure measuring apertures (19,22) which measure the difference in pressure at various points within the measuring aperture (15). The measuring aperture is formed by a throttle, a jet or a venturi tube (15).