IM 12B7J1-01E
< 3. Maintenance on operation >
3-1
3. Maintenance on operation
3.1
Operation and Periodic Maintenance
3.1.1
Calibrating pH Sensor Using Buffer Solutions
Calibrate pH sensors with buffer solutions before starting normal operation because the emf of
glass electrodes differs somewhat from each other.
The emf of a glass electrode gradually changes due to electrode staining or deterioration.
Therefore, buffer solution calibration must be carried out periodically within a given period of time
to keep the measurement errors within the limits specified.
For more detailed information on the calibration procedures, see relevant pH transmitter/
converter IMs .
3.1.2
Pressurizing Reserve Tank
When the pH sensor with medium pressure reserve tank is used, apply air pressure to the
reserve tank before flowing the measured solution through the holder.
Set the air pressure a little higher than the maximum pressure of the measured solution during
the operation.
The flow rate of the KCl solution from the liquid junction is maximum 3 mL/day for general
junction, maximum 20 mL/day for PTFE junction,when the pressure difference between air and
measured solution is 10 kPa ,and the flow rate increases in proportion to the pressure difference.
Therefore, it is important to minimize the consumption of the KCl solution by minimizing the
pressure variation of the measured solution and making sure that the air pressure is not set too
high.
3.1.3
Replenishment of KCl Solution
When the KCl solution in the tank seems to be nearly exhausted while using a pH sensor with
general type reserve tank, replace the reserve tank with new one (provided separately as spare
part).
Instead of tank replacement, when a KCl solution prepared using KCl powder is used for
replenishment, use 3.3 mol/L solution by dissolving 246 g of KCl powder in pure water to make
exactly one liter of solution. When pouring the solution into the tank, be careful that KCl solution
does not overflow from the vent holes of the tank.
When a pH sensor with a medium pressure reserve tank is used, replenish the KCl solution
when the KCl solution in the tank seems to be nearly exhausted. Carry out replenishment of KCl
solution as follows:
(1) Close the valves to shut off the (low of measured solution (see Figure 3.1) - first in the inlet
then the outlet valves in the flow-through type holder.
F3.1.ai
Outlet side
Stop Valve
Inlet side
Stop Valve
Figure 3.1
Process Piping of Flow-through Type Holder.
12th Edition : Dec.14,2018-00
