Mass flow control valve
730 series
Kurz Instruments
The Series 730 Mass Flow Control Valves were designed by Dr. Jerry Kurz in about 1980 to provide a simple, compact electrically operated, precise metering valve for applications requiring a high flow rate turn-down ratio. The unique Kurz design utilizes a rotor having a helical shape machined into its bottom face, opposite an inlet orifice and an outlet orifice. The diameter, separation and the helical depth were designed to provide a nearly linear flow coefficient (Cv) with angular rotation. A simple high torque gearmotor (24 VDC) was selected for cost and simplicity. Since the Series 730 is a "fail-as-is" design, the motor is only used when changes are required, which greatly extends the motor life. The Series 730 combines the electric drive motor, the valve body, rotor and limit switches into a well-designed, integrated package. The typical turn-down ratio is 50:1, due to the incorporation of a pressure assisted shut-off disk which becomes active near the shut-off position. The Cv range is from 0.05 to 10.0 in three convenient body sizes. The Series 730 is constructed of 316L stainless steel, with Viton O'Rings and an o'ring sealed motor cover. It operates as a two-wire loop-powered device normally powered and controlled by one of the Series 155 Mass Flow Computers and used with a Kurz In-Line Mass Flow Element. The inlet and outlet fittings are Schedule 40 pipe with MNPT end connections or Class 150 flanges. Because of its rotary design, the Series 730 is not as affected by abrupt line pressure changes as are pneumatic control valves
