Patent attributes
A fluid flow controller (1) comprises a variable aperture flow control valve (5) having an inlet to receive fluid from a supply source and an outlet to deliver fluid along a conduit (6). Downstream of the valve (5) is a back-pressure regulator (8), which in turn delivers fluid to an outlet (9), whilst a permanently open orifice (11) is connected to the conduit (6) upstream of the regulator and provided with an exhaust outlet (12), the characteristics of the valve (5), regulator (8) and orifice (11) being so selected that upon a slight opening of the valve (5), the regulator (8) maintains a closed condition, while further opening of the valve (5) raises the fluid pressure at the regulator (8) which commences opening, to provide a continuous exhaust flow at the exhaust outlet (12), to extend the satisfactory operating range of the flow control valve (5) down to very low flow rates. The controller (1) is suitable for use with a sulphuric acid dewpoint monitor.
