There are many customers who care about how many liquids used with the washing machine etc. are dirty.
This time, We introduce about the simplified method that the degree of contamination of liquid can be checked
about the cleaning fluid etc. to filter.
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As the simplified method that the degree of contamination of fluid can be checked,
there are FI(Fouling Index), SDI(Silt Density Index), SI(Silting Index), FT(Filtration Time), etc.
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(1)FI(Fouling Index), SDI(Silt Density Index)
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FI value is the index which quantified how many influences the muddy substance contained in the supplied fluid would have on the dirt to RO film.
SDI is used in the same meaning as FI value, and is standardized in ASTM.
This principle can be diverted and the degree of contamination of the liquid contained in cleaning equipment can be evaluated.
[Measuring method]
Fluid is pressurized to 206kPa and filtered using the Membrane filter(abs.0.45micron
metor, outer diameters; 47 ).
First, the time(T1) taken to filter the fluid 500ml(250ml in the case of SDI) is measured.
Next, filtration is continued for T minutes(usually for 15 minutes) as it is.
Then, the time(T2) taken to filter 500ml(250ml in the case of SDI) again is measured.
FI or SDI value is measured by the following formula.
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When a Membrane filter is got blocked and the filtered 500ml(250ml in the
case of SDI) water is not obtained after 15 minutes,
T2 is becoming infinite, and 100/15= 6.666 ... becomes maximum.
Usually, about four or less are the value.
N2 gas, sample liquid, tank, (for air omission), Membrane filter(abs.0.45ƒÊm),
graduated cylinder(usually 250ml)
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(2)SI(Silting Index)
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Fluid is put into measurement equipment as shown in the following figure, and pressurized to 343kPa.
From the time of the water's surface passing "0" points, the time T1, T2, and T3 taken to pass the point of V1, V2, and V3 is measured respectively,
and it computes by the following formula.
Constant pressure(343kPa), Membrane filter(abs.0.8micron metor)
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(3)FT(Filtration Time)
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The numerical value which expressed with the second the time taken to pressurize fluid to 294kPa
and to filter it 200ml using Nuclepore membrane filter(abs.0.2ƒÊm, outer diameters; 22mm) turns into FT value.
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