UFC 3-280-04
17 DEC 2003
Material
Resistance
Max Permissible
Max Permissible
Temp. (Water)
Temp. (Water)
Constant
Short-Term
Polytetrafluro-
Resistant to all chemicals
140 degrees C
150 degrees C
ethylene
listed in vendor literature.
285 degrees F
300 degrees F
(PTFE)
Nitrile Rubber
Good resistance to oil and
90 degrees C
120 degrees C
(Buna-N)
gasoline.
195 degrees F
250 degrees F
Unsuitable for oxidizing
agents.
Butyl Rubber
Good resistance to ozone
90 degrees C
120 degrees C
Ethylene Propylene
and weather.
195 degrees F
250 degrees F
Rubber
Especially suitable for
(EPDM, EPR)
aggressive chemicals.
Unsuitable for oils and fats.
Chloroprene Rubber
Chemical resistance very
80 degrees C
110 degrees C
(Neoprene)
similar to that of PVC and
175 degrees F
230 degrees F
between that of Nitrile and
Butyl rubber.
Fluorine Rubber
The best chemical
150 degrees C
200 degrees C
(Viton)
resistance to solvents of all
300 degrees F
390 degrees F
elastomers.
5-3.2.2.3 The designer should always check vendor literature for the rated flow density
and total available surface area for the selected cartridge filter and the pressure drop
through the housing.
5-3.2.2.4 While the equation above will give the minimum number of filter units required
for a given application, the life of a filter (the time over which it can be used before
blinding) is significantly increased as flow density (surface loading) is decreased. The
relationship is described by the following equation (Swiezbin 1996):
n
T2 J1
=
T1 J2
where:
T
= total throughput for a filter run prior to terminal head loss (gal.)
= flow density through the filter medium (flow per unit area) (gpm/ft2 )
J
or[(L/s)/m2]
n
= extension factor (dimensionless).
5-3.2.2.5 The life extension factor is experimentally determined but is generally on the
order of 1 < n < 2. For filtered solids that are uniform, non-compressible, and do not
cake to filter that is finer than the medium, n will approach 2. This means that in situa-
tions where the particles being separated are dirt and sediments from groundwater ex-
traction wells, doubling the filter surface area (i.e., doubling the number of units in-
stalled) can quadruple the filter life for the same system flow rate. Filters elements will
load equally and will be changed out all at the same time.
5-34
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