Measuring and testing – With fluid pressure – Porosity or permeability
Reexamination Certificate
1999-08-31
2001-03-20
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Porosity or permeability
C073S061730, C073S064470, C073S196000, C210S650000
Reexamination Certificate
active
06202475
ABSTRACT:
BACKGROUND ART
The ability of a filtration system to remove particles is generally measured in terms of the logarithmic reduction value (LRV). For any given particles, the logarithmic reduction value is defined as:
LRV
=
log
10
(
C
inf
C
eff
)
(
1
)
where:
C
inf
=Concentration of particle in the influent
C
eff
=Concentration of particle in the effluent.
The particle used in the calculation can be any particle of interest, for example, in the case of disinfecting systems it would typically be bacteria or viruses, but may also be suspended solids.
DISCLOSURE OF THE INVENTION
The present invention provides a method of predicting logarithmic reduction values for a membrane filtration system comprising the following steps:
i) measuring the filtrate flow rate through the membrane;
ii) measuring the membrane bypass flow rate using integrity test measurements; and
iii) estimating the logarithmic reduction value using the ratio of measured filtrate flow rate and measured bypass flow rate as follows:
LRV
=
log
10
(
Q
filt
Q
Bypass
)
(
2
)
The applicant has developed a number of tests to determine the integrity of filtration membranes, these include the Diffusive Air Flow (DAF) and Pressure Decay Tests (PDT).
A preferred method of testing the integrity of a porous membrane comprises the steps of:
(i) wetting the membrane;
(ii) applying a gas pressure to one side of the membrane below the bubble point of the membrane pores; and
(iii) measuring gas flow across the membrane, said gas flow including diffusive flow through the membrane and flow through leaks and defects in the membrane, said gas flow being related to any defects in the membrane.
Preferably also, the gas flow is measured by monitoring the pressure decay of the gas pressure applied to the one side of the membrane. In another preferred form, the gas flow is measured by surrounding the other side of said membrane with a volume of fluid and measuring displacement of said fluid resulting from said gas flow.
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.”
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Copy of International Search Report (PCT/AU96/00144 by Examiner Olliey).
Drummond Humphrey J. J.
Johnson Warren T.
Selbie Michael R. L.
Knobbe Martens Olson and Bear LLP
USF Filtration and Separations Group Inc.
Wiggins David J.
Williams Hezron
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