4 Wiring PROline Promag 53
58 Endress+Hauser
Plastic pipes and isolating lined pipes
Normally, potential is matched using the reference electrodes in the measuring tube.
However, in exceptional cases it is possible that, due to the grounding plan of a system,
large matching currents flow over the reference electrodes. This can lead to destruction
of the sensor, e.g. through electrochemical decomposition of the electrodes. In such
cases, e.g. for fiberglass or PVC piping, it is recommended that you use additional
ground disks for potential matching (Fig. 38).
Mounting of ground disks → Page 27, 33
"
Caution:
Risk of damage by electrochemical corrosion. Note the electrochemical insulation rat-
ing, if the ground disks and measuring electrodes are made of different materials.
Fig. 38: Potential equalization/ground disks with plastic pipes or lined pipes
Lined pipes (cathodic protection)
In such cases, install the measuring instrument without potential in the piping:
• When installing the measuring device, make sure that there is an electrical connection
between the two piping runs (copper wire, 9 AWG Cu/6 mm
2
).
• Make sure that the installation materials do not establish a conductive connection to
the measuring device and that the installation materials withstand the tightening tor-
ques applied when the threaded fasteners are tightened.
• Also comply with the regulations applicable to potential-free installation.
Fig. 39: Potential equalization and cathode protection
a = isolating transformer power supply, b = electrically insulated
F06-5xxxxxxx-04-xx-xx-xx-004F06-5xxxxxxx-04-xx-xx-xx-005
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