ABB LWT300 series, Руководство пользователя

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Installing the LWT
15
• Avoid routing cables with other electrical cables (with inductive load, motors, etc.) or near large
electrical equipment.
• Where cable glands are used, they shall be certified/listed for the explosive atmosphere/hazardous
location, local temperatures, and required enclosure environmental (ingress protection [IP] or Type)
rating.
• These cable glands
must only be used with braided shielded cables
. When installing them, make
sure to fold the cable shield over the O-ring which presses the braiding against the inside wall of the
body, thus ensuring good contact.
NOTICE
If you plan on using cable glands that are not supplied by ABB, refer to your supplier’s data
sheet for proper installation.
Vessel considerations
• For best performance, install the LWT flush with the top of a metallic vessel with a good ground
connection between the coupler and the tank.
• Avoid installing the LWT while the probe is close to the filling stream.
• If using a cable probe in the presence of heavy turbulence, use an anchor at the bottom of the tank.
• Avoid installations too close to inlet pipes or other internal metallic objects.
Plastic and fiberglass tanks, and open air installations
LWT instruments installed in a non-metallic vessel or in open air environments will be subject to
interference from other electromagnetic devices, e.g., radios. You may need to use stilling wells to
eliminate such interferences.
Also, with non-metallic vessels use an instru ment equipped with a flange, or replace the flange with a
metal sheet insert (>150 mm/8 in) to make contact with the coupler.
Concrete tanks
Concrete tanks require mounting the probe:
• 30 cm (1 ft) from the wall (for measuring lengths
up to
6.1 m [20 ft]);
• 61 cm (2 ft) from the wall (for measuring lengths
over
6.1 m [20 ft]).
The face of the LWT mounting/launch plate should be even with the inner surface of the concrete roof.
Sockets
• If the installation requires the use of a socket, you may need to increase the blocking distance to
avoid false echoes (see “Diagnosing from a waveform” on page 78).
• Avoid stacking multiple sockets of different sizes as this creates false echoes.
Nozzle considerations
• Nozzle length is configured for system operation and not for calibration purposes. It is automatically
taken into account (subtracted) when measurements are made.
• Probes installed in side-vessel connections require additional support within the nozzle connection.
• Probes installed in very agitated processes need a spacer at the top connection to prevent the probe
from touching any part of the nozzle.