Mounting The Sensor; Choosing Sensor Mounting Location - Vaisala K-PATENTS PR-23 Series Instruction Manual

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PR-23 instruction manual

2.2 Mounting the sensor

The sensor mounting location should be chosen with care to ensure reliable read-
ings from the process. Some basic rules, described in this section, apply to all sensor
models. The model specific instructions can be found in Chapter 9, "Sensor specifica-
tions". For the Sanitary compact refractometer PR-23-AC see Section 9.3, for the Probe
sanitary refractometer PR-23-AP see Section 9.4, for the Process probe refractometer
PR-23-GP see Section 9.6, for the Teflon body refractometer PR-23-M and Teflon body
semicon refractometer PR-23-MS see Section 9.8 and for the Saunders body refrac-
tometer PR-23-W see Section 9.9. For mounting an ATEX/FM/CSA approved sensor
in explosive atmosphere, see Section 9.10.2. For mounting an intrinsically safe refrac-
tometer PR-23-...-IA, see Section 9.11. For mounting of the Safe-Drive™ system with
the PR-23-SD sensor, see Section 11.4.

2.2.1 Choosing sensor mounting location

A PR-23 refractometer sensor can be located either indoors or outdoors in most cli-
mates. However, when a sensor is located outdoors, some basic protection against
direct exposure to sunlight and rain should be provided. Special care should be taken
if the pipe wall is translucent (e.g. of fiberglass), as light from outside reaching the
prism through the pipe wall may disturb the measurement.
The mounting location needs to be such that sediments or gas bubbles cannot accu-
mulate by the sensor. Good flow velocity is essential in keeping the prism clean.
Important: If the process pipe vibrates, support the pipe. A vibrating pipe might
damage the in-line sensor mounted on it.
Always check that the sensor head is kept cool enough; the sensor head should not be
too hot to keep a hand on. The sensor cover should not be exposed to high temperature
radiation. In most cases, draft and natural convection provide sufficient air cooling if
the air gets to flow freely around the sensor head.
Additional cooling is necessary when the ambient temperature is higher than 45 °C
(113 °F) or when the process temperature is above 110 °C (230 °F) and the ambient
temperature is above 35 °C (95 °F). The air cooling is improved by blowing pressurized
air against the sensor cover. The pressurized air can be supplied by the ventilation
system. If no air is available it is also possible to install water cooling with PR-10038
cooling cover (except for PR-23-SD where sensor head needs to be kept in original
size for insertion and retraction).
Important: Always mount the sensor so that the interconnecting cable points down-
wards from the sensor head.