36 PRocessinG TechnoloGy
Porometers now incorporate flow
meters and pressure transducers
here are few areas in our lives that latest technologies in measuring pore sizes of
Graham Rideal outlines
are not touched by filtration. We are filter media.
some of the very latest
surrounded by filters in the home, from
technologies used in
T
tea bags and coffee makers to dish
Challenge testing or porometry?
measuring pore sizes of
washers, washing machines and tumble driers, There are two main methods of measuring
filter media. not to mention food products in our cupboards the pore sizes in a filter: challenge testing
from mustard and flour to sugar and cereal, all of and porometry. The former is a simplistic and
which involve some form of filtration. conceptually easy to understand process of
Graham Rideal présente
The drive to work in your car requires oil, challenging a filter with a liquid suspension or
quelques-unes des toutes
petrol and air filters for the engine, particulate dust cloud of particles.
dernières technologies
utilisées dans le
removal for the exhaust and filters for the heating Measuring the relative concentration of
mesurage de la taille
or air conditioning system. Indeed, every fabric particles before and after the filter determines
des pores des couches
in the construction of the car involves a filtration the filter efficiency, while measuring the largest
filtrantes.
process somewhere down the line. particles passing determines the cut point of the
On the global scale, filters control the filter.
condition of the environment. Not just in the Porometry is not such a fundamental process
Graham Rideal stellt
atmosphere with soot from diesel engines in that it relies on the interpretation of gas flow
einige der neuesten
or smoke from coal fired power stations and through a ‘wetted’ filter. Wetting the pores
Technologien für die
Messung von Porengrößen
incinerators, but in effectively ‘blinds’ the filter, making it impervious
bei Filtermedien vor.
our waterways and to the passage of gas.
seas with pollution However, as the gas pressure is raised,
from water treatment it overcomes the surface tension of the
systems or industrial liquid and blows through the pores,
processes. starting with the largest and finishing
The appropriate with the smallest.
use of filters and, The gas pressure/flow
more importantly, rate curve can then be
their measurement or interpolated to determine
certification, may make the pore size distribution
life more comfortable in the filter.
or convenient or may Historically,
even have the laudable porometry has had
objective or extending an advantage over
the life of the planet, the challenge test
but the most serious
Fig. 1. A Porolux porometer from Benelux
method in that it can
short term impact
Scientific.
measure a pore size
of filtration is in the distribution, not just
pharmaceutical industry where their use could the maximum pore size.
affect our very lives in the next ten minutes not However, one of the disadvantages is in the
the next ten years. theory used to convert flow rate through pores to
The performance of a filter in a pore sizes.
pharmaceutical application is therefore a matter The assumption made is that all pores are
of life and death. cylindrical, which is clearly not always the
There is therefore always a considerable case. Furthermore, the black box nature of the
interest in the pore size measurement of filters by instrument makes it difficult to homologate
the pharmaceutical industry. This was reflected in instruments from different manufacturers.
the popularity of the Filtration Society’s October Consequently, there are sometimes
testing and standards seminar and exhibition uncertainties in the pore sizes determined by
where record numbers of delegates and exhibitors porometry, and comparisons, not just between
attended. different manufacturers, but even for the same
This brief review highlights some of the very model of instrument can be poor.
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