These are some of the criteria to consider when deciding which size gear motor is needed for an application.
Fluid velocity:
Calculate the velocity (v) of a fluid in a pipe as follows:
v =Q / 6 • A[m/s]
Q = flow rate [litre/min]
A = inside area of pipe [cm²]
Absorbed flow rate:
Calculate flow rate (Q) as follows:
Q = (V • n • 10 -3)
÷ hvol [litre/min]
V = displacement [cm³/rotation].
n = rotation speed [rotations per minute].
hvol = motor volumetric efficiency (take 0.95 as an indicative value for rotation speeds ranging between 1000 and 2000 rotations per minute).
Absorbed torque:
Calculate necessary torque (M) of a pump subject to pressure differential between inlet and delivery as follows:
M= (V •
Dp) / (62.8 •
hhm) [Nm]
V = displacement [cm³/rotation].
Dp = pressure differential [bar].
hhm = hydromechanical efficiency (take 0.80 as indicative value under cold conditions and 0.85 under working conditions).
Absorbed power:
Calculate hydraulic power (P), delivered by a pump subject to a pressure differential between input and output as follows:
P= (Q •
Dp) / (600 •
htot) [kW]
Q = flow rate [litre/min.].
Dp = pressure differential [bar].
htot = total motor efficiency (
hhm • hvol).
Values for
hvol and
hhm (and consequently
htot) depend on pressure differential between supply and delivery, rotation speed, fluid features (temperature and viscosity) and filtering degree.
Contact jbj Techniques technical office,
email: info@jbj.co.uk or
telephone: +44 (0)1737 767493 for further details on efficiency.
