Page 44 - Valve Selection Handbook

Fundamentals 31

Figure 2-8. Resistance Coefficient of Fully Open Gate Valves with Converging-
Diverging Flow Passage and Eye Piece Between the Seats. Curves a to c Apply to L >
12 D, and Curve d for L = zero, Where L = Straight Length of Pipe Downstream of
Venturi Throat. (Courtesy of VDI Verlag GmbH, Reproduced from BWK Arbeitsblatt
42, Dec. 7 953, by H. Haferkamp and A. Kreuz.)

The amount of static energy recovered depends on the ratio of the
2
2
diameters of the flow passage (d /D ), the taper angle (o/2) of the dif-
fuser, and the length (L) of straight pipe after the valve throat in terms of
pipe diameter (d = valve throat diameter, and D = pipe diameter).