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Maintenance
7.2.2
Please clean contamination on the glass electrodes as follows:
• Oily and greasy films:
Clean with detergent (grease dissolvers, such as alcohol, acetone, poss. washing-up
liquids).
#
Warning!
When using the following cleaning agents, make sure to protect your hands, eyes and clothing!
• Lime and metal hydroxide layers:
Dissolve layers with diluted hydrochloric acid (3 %) and then rinse carefully with a lot of clear
water.
• Layers containing sulphide (from flue gas desulphurising or sewage treatment plants):
Use mixture of hydrochloric acid (3 %) and thiocarbamide (usual commercial) and then rinse
carefully with a lot of clear water.
• Layers containing proteins (e.g. food industry):
Use mixture of hydrochloric acid (0.5 %) and pepsin (usual commercial) and then rinse
carefully with a lot of clear water.
Clogged diaphragms can be cleaned mechanically (does not apply to Teflon diaphragms and
open ring junction electrodes):
• Use a small warding file.
• Only file in one direction.
Air bubbles in the electrode:
• Air bubbles can indicate incorrect mounting. For this reason check the orientation.
• The range 15 to 165 to the horizontal is allowed.
• Not permitted: horizontal installation or installation with the plug-in head pointing downwards.
Fig. 39:
ORP electrodes:
Carefully clean the metal pins or surfaces mechanically.
!
Note!
After mechanical cleaning, the ORP sensor can require several hours conditioning time. For
this reason, check the calibration after a day.
7.2.3
• The KCl must be free of bubbles. In the case of an unpressurised version, check whether the
cotton thread is present in the hose.
• In the case of counterpressure, check whether the pressure in the KCl tank is min. 0.8 bar
(11.6 psi) above the medium pressure.
• The KCl consumption should be low but noticeable. Approx. 1 ... 10 ml/day is typical.
• The opening for sensors with a KCl top-up opening at the glass shaft must be clear.
7.2.4
Please refer to the corresponding assembly Operating Instructions for information on
maintaining and trouble-shooting the assembly. Here you can find a description for assembling
and disassembling, sensor replacement, seal replacement, stability as well as information on
spare parts and accessories.
72
Cleaning the pH/ORP sensors
> 15°
Permitted angle of installation for glass electrodes
Liquid KCl supply
Assembly
OPM223/253
> 15°
C07-OPM2x3xx-05-06-00-xx-006.eps
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