Watson-Marlow 521CC - Manual (Page 4)

4 Information for returning pumps
Equipment which has been contaminated with, or exposed to, body fluids, toxic chemicals
or any other substance hazardous to health must be decontaminated before it is returned to
Watson-Marlow or its distributor. A certificate included at the rear of these operating
instructions, or signed statement, must be attached to the outside of the shipping carton.
This certificate is required even if the pump is unused. If the pump has been used, the
fluids that have been in contact with the pump and the cleaning procedure must be
specified along with a statement that the equipment has been decontaminated.
5 Peristaltic pumps - an overview
Peristaltic pumps are the simplest possible pump, with no valves, seals or glands to clog or
corrode. The fluid contacts only the bore of a tube, eliminating the risk of the pump
contaminating the fluid, or the fluid contaminating the pump. Peristaltic pumps can operate
dry without risk.
How they work
A compressible tube is squeezed between a roller and a track on an arc of a circle, creating
a seal at the point of contact. As the roller advances along the tube, the seal also advances.
After the roller has passed, the tube returns to its original shape, creating a partial vacuum
which is filled by fluid drawn from the inlet port.
Before the roller reaches the end of the track, a second roller compresses the tube at the
start of the track, isolating a packet of fluid between the compression points. As the first
roller leaves the track, the second continues to advance, expelling the packet of fluid
through the pump's discharge port. At the same time, a new partial vacuum is created
behind the second roller into which more fluid is drawn from the inlet port.
Backflow and siphoning do not occur, and the pump effectively seals the tube when it is
inactive. No valves are needed.
The principle may be demonstrated by squeezing a soft tube between thumb and finger and
sliding it along: fluid is expelled from one end of the tube while more is drawn in at the
other.
Animal digestive tracts function in a similar way.
Suitable applications
Peristaltic pumping is ideal for most fluids, including viscous, shear-sensitive, corrosive and
abrasive fluids, and those containing suspended solids. They are especially useful for
pumping operations where hygiene is important.
Peristaltic pumps operate on the positive displacement principle. They are particularly
suitable for metering, dosing and dispensing applications. Pumps are easy to install, simple
to operate and inexpensive to maintain.
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