Watson-Marlow 520Du - Manual (Page 94)

Watson-Marlow 520Du User Manual 94
33 Flow rates
Pumping conditions
For precise and repeatable performance it is important to determine flow
rates under operating conditions for each new piece of tubing.
When rotating counter-clockwise, 520R, 520R2 and 520RE pumpheads’
flow rates are directly proportional to rotor speed. When rotating clock-
wise, 520R, 520R2 and 520RE pumpheads’ flow rates are directly propor-
tional to rotor speed up to 1.5 bar; their performance above 1.5 bar should
be determined empirically.
Note: 520RE pumpheads should be used rotating counter-clockwise if pres-
sures above 1.5 bar are required.
If you wish to run the pump at a speed not shown in the tables below, flow
figures can be reached by dividing the maximum flow shown in the tables
below by the maximum rpm figure, and multiplying the result by your
required speed in rpm.
Actual flow rates achieved may vary because of changes in temperature, viscosity,
inlet and discharge pressures, system configuration and tubing performance against
time. Flow rates may also vary due to normal manufacturing tolerances of the tub-
ing. These tolerances will make flow rate variance more pronounced at smaller bore
sizes.
520R and 520R2
All performance figures for the 520R and 520R2 pumpheads have been recorded
against peak pipeline pressures.
Although rated to 2bar (30psi) peak pressure, this pump will generate in excess of
2bar (30psi) peak pressure if the pipeline is restricted. Where it is important that
2bar (30psi) is not exceeded, pressure relief valves should be installed in the
pipeline.
Viscosity handling is maximised by using 2.4mm wall tubing with the 520R2 pump-
head.
Flow rates are normalised test values obtained using 225mm (8 7 ⁄
8
) of new tubing
(measured from the inside faces of the tube clamps), and the pumphead rotating
clockwise pumping water at 20C with negligible inlet and discharge pressures.
Note: Flow rates quoted are for 1.6mm and 2.4mm wall tubes. Tubes of 0.5mm and
0.8mm bore are only available in 1.6mm wall thickness except for platinum-cured
silicone. Tubes of 9.6mm bore are only available in 2.4mm wall thickness.