ABB 4670 Series, Руководство пользователя

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Locate Dry Calibration Standard on standoff pillar
…7 MAINTENANCE
…7.2.1 Procedure
Model 7997 400 Series
Caution. Before removing the sensor from the sample,
ensure the programmed cleaning interval (
Set Up
Parameters Page
), is greater than the estimated
maintenance time and then set '
Manual Clean
' (
Operating
Page
) to '
YES
'. This ensures that the cleaning interval
restarts to give the full cycle time.
Under normal circumstances, when the sensor is exposed
to air any programmed or manual wiping is automatically
suspended until the probe is immersed again. The above
instructions provide further safety to minimize the possibility
of the wiper causing injury during calibration procedures.
a) Remove dip system by releasing it from the fixing bracket.
b) Thoroughly clean the system using high purity water to
remove any contamination, and dry carefully using a soft
cloth.
c) Immerse the dip system into a container of high purity water.
Note the reading on the display.
d) After removing the dip system from the high purity water, dry
the unit using clean tissue. Wipe clean the emitter and
receiver lenses making sure that no greasy marks are left on
the lenses.
e) Lie the unit on a horizontal surface and insert the Dry
Calibration Standard – see Fig. 7.1. Ensure that the sensor
standoff pillar is fully engaged in the slot in the Dry Calibration
Standard. Note the reading on the display.
If readings are out of spec. (

2% FSD), repeat the procedure
from b). If reading is still out of spec., calibrate the sensor –
Section 5.2.2.
f) Remove the Dry Calibration Standard; dry clean off any
moisture before storing the Standard in the supplied storage
container.
g) Fit the unit into the working position and secure.
7.3 Using Formazine Standard Solution
7.3.1 Preparing the Formazine Standard
for Wet Calibration
a) Dissolve 50.0 g of hexamethylenetetramine (C
6
H
12
N
4
) in high
purity water and dilute to 400 ml – Solution A .
Warning . Hydrazine sulfate is poisonous and carcinogenic.
b) Dissolve 5.0 g of hydrazine sulfate (N
2
H
6
SO
4
) in high purity
water and dilute to 400 ml – Solution B .
c) Mix solution A with solution B; shake well and leave in the
dark for 24 hours at 25

C

3

C.
d) Dilute the solution to one liter with high purity water.
The turbidity of this stock solution in formazine attenuation units
(FAU) or formazine nephelometric units (FNU) is 4000.
The solution is stable for 1 year if stored at 25

C

3

C in the
dark.
If it is necessary to conform to the British European
Standard BS.EN.27027 for preparation of formazine
standards:
e) Dissolve 10.0 g of hexamethylenetetramine (C
6
H
12
N
4
) in high
purity water and dilute to 100 ml – Solution A .
f) Dissolve 1.0 g of hydrazine sulphate (N
2
H
6
SO
4
) in high purity
water and dilute to 100ml – Solution B .
g) Mix 5 ml of solution A with 5 ml of solution B; shake well and
leave in the dark for 24 hours at 25

C

3

C.
h) Dilute the solution to 100 ml with high purity water.
The Turbidity of this stock solution in formazine attenuation units
(FAU) or formazine nephelometric units (FNU) is 400.
The solution is stable for one month if stored at 25

C

3

C in the
dark.
i) Dilute the stock solutions with high purity water using
pipettes and volumetric flasks to obtain the required diluted
standards in the range required.
Note. These solutions are stable for one week only. Dispose
after use in accordance with relevant local safety standards.
Fig. 7.5 Fitting the Dry Calibration Standard