Answer to Question #202691 in Mechanical Engineering for Lihle

Question

Water flow from a reservoir to a pipe system is controlled by a butterfly valve. It consists of a 400mm diameter disc controlled by a horizontal shaft attached to the middle of the disc. When closed it is perpendicular to the pipe which slopes at 20 degrees to the horizontal. Determine the torque required on the shaft to keep the disc closed when the water the water level is 1m above the shaft.

Answer 1

water level = 1m

Pressure = 1000kg/m³ × 10m/s² × 1m = 10000 Pa

F = P × A = 10000 × π(0.2)² = 1256.64N

$\tau$ = F.r sin$\theta$ = 1256.64 × 0.2 × sin 20° = 85.96 Nm