Watson-Marlow 701S/R - Manual (Page 6)

Part 2: Operation
Overview
Select the direction of rotation with the forward/off/reverse switch on the left
hand side of the control panel and start the pump using the green start
button. The preferred direction of rotation is clockwise (giving a flow direction
of left to right when facing the pump), which will ensure the longest tube life.
To stop the pump, turn the forward/off/reverse switch to its central off
position. To change direction of flow, turn the forward/off/reverse switch
through its central off position to the other direction and restart the pump with
the green start button.
If at any time the pump fails to start, it is likely that the inbuilt protection
circuitry is operating. Turn the forward/off/reverse switch to its central off
position (you should hear the contactor drop out), and then to the required
direction of rotation again. Wait 10 seconds and press the green start button.
The speed control range of the 701S/R is from 2% to 100% of the rated
maximum speed (360rpm at the rotor). The speed setting dial has a locking
knob to prevent accidental speed changes.
If the pump is to be used at low speed settings under manual control, and
there is a risk that damage could be caused to the process if the pump is
taken to higher speeds, then the speed limiting potentiometer in the rear
panel recess can be brought into use. First, remove the panel covering the
rear panel recess and turn the speed limiting potentiometer fully anti-
clockwise. Next, turn the front panel speed potentiometer fully clockwise.
Start the pump (which will run very slowly - if at all) and turn the rear panel
speed limiting potentiometer clockwise until the pump reaches the desired
maximum speed. Securely replace the panel with an intact gasket over the
rear panel recess. It will now be found that the pump speed can be varied
over a limited range from the front panel potentiometer.
Note that as the maximum speed is reduced using the speed limiting
potentiometer, the speed control ratio is also reduced. The minimum speed at
which the 701S/R will run is about 7rpm. If the speed limiting potentiometer is
set to reduce the maximum speed to, say, 35rpm, then the speed control ratio
will be 7rpm to 35rpm, which is a speed control ratio of 5:1.
Page 6