Watson-Marlow 521CC - Manual (Page 32)

17 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 clockwise, 520R, 520R2
and 520RE pumpheads' flow rates are directly proportional 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 pressures
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 tubing. 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 pumphead.
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 of nominal bore. 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.
520RE
Performance figures for the 520REL and 520REM have been recorded against 2bar peak
pressure and 4bar peak pressure respectively.
Performance figures for the 520REH have been recorded against 7bar constant pressure.
Although the 520REL is rated to 2bar (30psi) peak pressure, the 520REM is rated to 4bar
(60psi) peak pressure and the 520REH is rated to 7bar (100psi) constant pressure the
pumps will generate in excess of these pressures if the system pressures exceed this.
Where it is important that these rated pressures are not exceeded, pressure relief valves
should be installed in the pipeline.
Flow rates are normalised test values obtained using 520 elements and the pumphead
rotating anticlockwise pumping water at 20C with negligible inlet and discharge pressures.
Page 32 of 47 Watson-Marlow Bredel E-Manuals
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