7835
Hydrazine Monitor
9 Maintenance
IM/7835–EN Rev. P
21
9 Maintenance
9.1 Chemical Solutions
The following reagents and standard solutions are required to
maintain the monitor in operation. Solutions must be stored in
plastic bottles and, where possible, should be freshly made.
9.1.1 Reagent Solution – 5m (20% W/V) Sodium Hydroxide
The solution used to fill the reagent container is made up as
shown below; consumption is approximately 250 ml in 2 to 4
weeks.
1. Weigh out 2.5 (±0.1) g EDTA and transfer to a 500 ml
(16.9 fl oz) measuring flask (a little high purity water can be
used to help this transfer).
2. In a separate vessel, weigh out 100 (±1) g sodium
hydroxide, NaOH, pellets (analytical reagent grade) and
dissolve in approximately 300 ml (10.0 fl oz) high purity
water in a plastic container. Allow this solution to cool.
3. Transfer this solution to the measuring flask, shake well to
dissolve the EDTA and top up to the mark with more high
purity water.
9.1.2 Standard Solution
Chose a convenient level for the hydrazine concentration of the
standard solution – typically 30 or 80 µg kg
-1
. Other
concentrations can be used if required.
Prepare a stock solution of 1000 mg l
-1
hydrazine as follows:
1. Weigh out 4.058 (±0.001) g analytical reagent grade
hydrazine sulphate (N
2
H
4
,H
2
SO
4
) and dissolve in
approximately 800 ml (27.0 fl oz) high purity water.
2. Transfer to a 1 l (33.81 fl oz) volumetric flask and top up to
the mark with more high purity water.
3. Dilute the stock solution to provide the required standard
solution for the particular measuring range (usually 30 or
80 µg kg
-1
).
9.2 Scheduled Servicing
The procedure outlined is a guide to the maintenance
requirements of the monitor. The actual servicing schedule
depends on the particular installation and sample conditions.
9.2.1 Weekly
1. Check level of reagent container. When level is near the
bottom of the container remove the container from panel,
empty contents, rinse with high purity water and refill with
reagent. Clean up any spillages and do not top-up
container.
2. Perform a calibration as described in Section 4.
9.2.2 Six-Monthly
1. Replace tubing if stained or age hardened – see Section
9.2.3, page 22.
2. Replace the porous disc as follows:
a. Close the sample isolator valve to the monitor.
b. Close the outlet valve on the reagent solution
container and remove the reagent tube from the
membrane clamp, located on the top of the reagent
dosing chamber – see Fig. 4.6, page 11.
c. Remove the two sample tubes from the chamber,
unscrew the bracket and remove the chamber from
the panel.
d. Locate the lugs of the tool provided in the recesses
in the membrane clamp on top of the reagent
dosing chamber and unscrew the membrane clamp.
Retain the 'O'-ring located in the recess of the
clamp.
3. Remove the old disc with the end of a screwdriver and
dispose of it safely. Rinse the chamber and fit a new 'O'
ring (part number 0211 068) and disc. Fit the membrane
clamp and 'O' ring (part number 0211 120) and tighten
the clamp.
4. Fit the chamber to the panel and connect the sample inlet
tube.
5. Hold the reagent tube over the tundish and open the
reagent outlet valve to allow the reagent to flow through
the tube to displace any air bubbles.
6. Close the reagent outlet valve and connect the reagent
tube to the top of the reagent dosing chamber.
7. Open the reagent outlet valve.
Warning.
Sodium Hydroxide is extremely caustic and must
be handled with great care. Wear gloves and eye protection.
Warning.
Hydrazine Sulphate is an irritant to skin and eyes.
Avoid breathing the dust. Wear gloves, eye protection and a
dust mask when handling this substance.
Note.
Hydrazine solutions deteriorate with time: replace the
stock solution at monthly intervals. Dilute standard solutions
must be freshly prepared.
Warning.
It is imperative that all leaks of potentially
aggressive chemical solutions receive attention as
soon as possible and all spillages are cleaned up.
Warning.
The reagent is extremely caustic and
must be handled with great care. Wear gloves
and eye protection.
