Evoqua WALLACE & TIERNAN SFC, Оригинальное руководство пользователя

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SFC
Functions
4.
79
Determining the controlvariable
independent
dead time Tconst
The control variable independent dead time Tconst consists of the
measuring dead time and the dosing dead time.
Calculating the measuring dead
time
Calculation 1:
The sample water is extracted right after the mixture loop and fed
to the measuring cell.
The sample water dead time depends on the nominal diameter
and length of the sample water line and the flow rate to the
measuring cell. With the DEPOLOX
®
5 measuring cell, a flow rate
of 36 l/h is assumed.
The following equation applies to the DEPOLOX
®
5:
t
mw(
DEPOLOX
®
5
)
= (d
mw
x d
mw
x l
mw
) : 7,65 (result in min)
In general, this equation applies:
t
mw
= (4.71 x d
mw
x d
mw
x l
mw
) : Q
mw
(result in min)
d
mw
= Internal diameter of the sample water line in cm
I
mw
= Length of the sample water line in meter
Q
mw
= Flow rate to the measuring cell in l/h
Example
As a DN6, the sample water line is 10 m long and connected to a
DEPOLOX
®
5 chlorine measuring cell.
t
mW
= (0.6 x 0.6 x 10) : 7.65 min = 0.47 min, (i.e. approx. 28 sec.)
Calculation 2:
The sample water is extracted using an additional sample water
pump (bypass line).
Sample water dead time depends on the flow rate of the sample
water pump, nominal diameter of the bypass line and its length up
to the sample water branch pipe to the measuring cell.
T
by
= (4.71 x d
by
x d
by
x l
by
) : Q
by
d
by
= Internal diameter of the bypass line in cm
I
by
= Length of the bypass line from the sample water
extraction point
to the sample water branch pipe to the cell in m
Q
by
= Flow rate to the bypass pump in l/h
(result in min)
Check whether the length of the sample water line to the
measuring cell can be neglected. If so, establish the sum from
calculation 1 and 2.