Electro-Chemical Devices (ECD) SMS22 - Manual (Page 28)

5.0 MAINTENANCE
5.1 pH and Sulfide electrodes
All electrochemical sensors require periodic cleaning and/or replacement. The life of an electrode is
completely dependent on the process conditions it is exposed to. An electrode may last a year or longer
in potable water and only a few weeks in a hot caustic bath. The chemical constituents in the process
may coat the electrode surfaces requiring the electrode to be removed and cleaned or replaced.
Cleaning agents should be specific to the type of coating the electrode was exposed to, detergents and
alcohols for removing greases and oils, acids for removing hard water scales and metallic deposits or
high pressure spray washing for flocculants and biofilms.
5.1.1 Electrode Cartridge Installation
Unless ordered separately, electrode cartridges are generally shipped installed in a sensor. Sensors
ordered without an electrode are shipped with a shipping plug to keep contamination from getting
inside the sensor during shipment or storage. The following procedure explains how to install the
electrode cartridge in the sensor assembly:
1. Remove the shipping plug by turning it counterclockwise.
2. Remove the electrode cartridge from the protective soaker boot. Be careful not to flex the
electrode body while removing the tape and the protective boot.
3. Rinse the electrode tip in tap water and wipe the electrode body dry then lubricate the o-ring
seals with the included lubricant. Save the protective soaker boot in the event the electrode must
be stored at a future time.
4. Carefully insert the electrode cartridge into the sensor assembly by turning until hand tight. The
first o-ring, closest to the front of the electrode, will be slightly visible if held horizontally.
NOTE: IF EXCESS FORCE IS REQUIRED DURING ELECTRODE INSTALLATION, CHECK FOR PROPER THREAD
ENGAGEMENT OR FOR AN OBSTRUCTION.
5.1.2 Electrode Cartridge Replacement
Periodic replacement of the electrode cartridge is required for pH, ORP and Specific Ion sensors. The
following procedure explains how to replace the electrode cartridge in the sensor assembly:
1. Remove the electrode cartridge from the front of the sensor assembly by turning it
counterclockwise.
2. For installation procedure follow steps 2, 3, and 4 in section 8.3.1 electrode cartridge
installation.
5.1.3 Electrode Cleaning
An important aspect of sensor maintenance is the service of the electrode cartridge. After being in
operation, an electrode may begin to exhibit slow response or non-reproducible measurements. This
may be due to coating of the measurement electrode or clogging of the reference junction. Regular
electrode cleaning reduces problems associated with the coating and clogging. Frequency of cleaning
will depend on the process and application. The following procedures are used to clean pH electrodes.
SMS-22 Page 19