Page 19 - Chemical Technology

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Chemical Technology • January 2013
pumps, valves and actuators
Traditional markets
Abrasive mining slurries have sub-micron, solid contents
in excess of 80% with specific gravity ratings of 2,0.
Handling such a medium is a classic application for a
peristaltic hose pump. Indeed it is the only pump type
able to cope with such dense fluids whilst maintaining
high levels of plant availability.
The variable nature of the corrosive reagents causes
diaphragm pumps to clog. This leads to increased chemical
usage and lower plant efficiency. Progressive cavity pumps
present no solution as they often suffer from burnt stators
as they are allowed to run dry. The failings of other pump
technologies have led to wide take-up of peristaltic pumps
in these tough environments.
There is, however, no need to dwell on the peristaltic pump’s
merits in the arduous end of the applications market. Its
case is proven. It scores over other designs in many ways.
Let’s look instead at some applications where the peristaltic
pump isn’t the most obvious choice but has demonstrated
itself to be the ideal product for the job.
Paper residues
The peristaltic pump’s ability to run dry with no adverse
effect gives it an advantage for many applications. One is in
paper manufacture. It is an industry that also processes a
large amount of waste water that can contain residues such
as fibrous substances, fillers and chemicals.
As the fluid tends to clog when only low flow rates are
needed, the efficient working of other pump types is com-
promised. The low maintenance credentials of a peristaltic
pump make it the perfect choice. When the fluid clogs at
the suction side, as can easily happen with this applica-
tion, the simple reverse action of the rotor is the easy
solution to the problem.
Bubble-free ink
Ink handling is another growing application area for peri-
staltic pumps. A good example in this sector comes from
a packaging company that had been using air diaphragm
pumps to transfer ink from storage containers to printing
machines. However production problems were resulting
from the existing pumps’ inability to handle the water-based
ink gently enough. As a result, bubbles formed in the ink,
ruining the packaging, creating waste and adding expense.
A compact peristaltic hose pump
proved to be the ideal
solution. Ink is dosed gently, eliminating bubbles and as
the ink is completely contained within the pump’s hose
throughout the process there is no mess or wear to moving
parts. Colour change is quickly accomplished as the hose is
easily exchanged. The pump itself can even run dry without
fear of damage.
Yeast pumping
Pumps with a high shear-rate can damage a fragile product
such as yeast and compromise its quality. This can lead to
reduced production efficiency. The viscosity of yeast can
also vary significantly during a typical production run, going
from the consistency of water to several thousand Centi-
poise and this can cause problems for some pumps.
Additionally, the abrasive nature of yeast can lead to stator or
impeller wear resulting in costly downtime, loss of production
and ongoing maintenance costs. Another common pumping
problem is the result of active yeast producing gas. This can
also cause some pumps to vapour lock, reducing output.
All of these issues are easily resolved with the use of peri-
staltic pumps that are able to handle viscous and abrasive
media with a low shear pumping action and are not suscep-
tible to vapour locking.
Drug administration
At the lighter duty end of the scale, peristaltic tube pumps
are proving popular for accurate and reliable dosing. A typical
application is a fast and automatic method of administer-
ing methadone to recovering drug addicts. Indeed a key
benefit of the system is the elimination of human error as
an incorrect dose of this substance could prove fatal to the
patient. The design of the peristaltic pump internal backflow
for accurate dosing without slip ensures the high degree of
repeatability required by legislature such as The Medicines
Acts within the UK. Hygienic dispensing is guaranteed as
the methadone is contained fully in the tube which was
specified to be resistant to the methadone’s acidity.
The simplicity of the pump design makes it
easy and quick to exchange the tube
in the pharmacy. No special tools
or training are required and the
used tubing can be safely
disposed of.