Flow control device

Patent Granted It is so made that a flow rate control apparatus can be downsized and its installation costs can be reduced by achieving accurate flow rate control of a fluid over a wider flow quantity range with one set of flow rate control apparatus. Specifically, with a pressure type flow rate control apparatus wherein a flow rate of a fluid passing through an orifice 8 is computed as Qc=KP1 (where K is a proportionality constant), or as Qc=KP2m(P1-P2)n (where K is a proportionality constant, m and n constants), by using an orifice upstream side pressure P1 and/or an orifice downstream side pressure P2, a fluid passage between the downstream side of a control valve and a fluid supply pipe of said pressure type flow rate control apparatus are made to be more than at least 2 fluid passages in parallel.