Watson-Marlow PD22I - Manual (Page 11)

OPERATORS MANUAL Machine Type: PD22I / PD22P
PD22 I P OM 1.01 EN Ver 1.01 Date 24-08-2006 Page 11 of 21
6.2 Tubes
Tube size:
Tubes must be selected according to the application and volume to be filled. Use the table
shown below for choice of tubes according to minimum volume to be filled.
PD22 can operate with six different tube dimensions chosen according to the volume to be
dispensed.
The tubes are designated by their internal diameters (i.d.) in millimetres. This value is always
used as designation for the individual tube, and this is also the value to be entered in function 2
at the MC12 master controller.
PD22P can operate with the tubes listed in the table below.
In order to obtain stable and good results, the choice of tube may be made according to the
following guidelines:
Flexicon part no. Tube dimension Min. volume recommended
84-201-030 3.0 mm i.d. 10 ml
84-201-050 5.0 mm i.d. 20 ml
84-201-065 6.5 mm i.d. 50 ml
84-201-080 8.0 mm i.d. 85 ml
84-201-100 10.0 mm i.d. 150 ml
84-201-125 12.5 mm i.d. 250 ml
Above mentioned tubes are silicone tubes and supplied by Flexicon A/S. These can be
sterilised by autoclaving.
Tubes must be cut in the right length in order to achieve optimised dispensing. It is
recommendable that the tubes are of such length that can allow placing the vessel close to the
pump head.
The tube ends must always be kept below the liquid level of the suction vessel in order to keep
the tubes from sucking air.
Avoid having tubes close to the bottom of product vessel.
6.3 Nature of fill media
The peristaltic dispensers are not suitable for viscous products. For viscous product can
another type of dispenser from Flexicon be used. In the case that the PD22 should be used and
the product is of viscous nature, then heating the product before dispensing with PD22 is
recommended.
Another consideration is the surface tension of liquid. Product with high surface tension tends to
produce drip. Due to this fact it is difficult to have sufficient cut off after every individual
dispensing. When filling with small volumes and high surface tension present drips are often
produced and constitute inaccuracy.