Choosing sensor mounting location - PR-21-S

PR-21 Series User Guide

Document code
IM-EN-PR21S
Revision
C
Language
English
Product
PR-21-S
Document type
User guide

The sensor is delivered with mounting guides attached. The sensor is designed to be installed directly in a process line. If the sensor is located outdoors, protect the sensor against direct exposure to sunlight and rain.

Air-cooling

Normally, draught and natural convection provide sufficient air cooling. Criteria for efficient air-cooling:

  • Mount the sensor with the main axis horizontal, see Figure 2.
  • Make sure that there are no obstacles for air to flow around the sensor head.
  • Make sure that the sensor cover is not exposed to high temperature radiation.

If the ambient temperature is higher than 45 °C (113 °F) the air-cooling should be improved by blowing pressurized air against the sensor cover. This is also recommended when the process temperature is above 110 °C (230 °F) and the ambient temperature is above 35 °C (95 °F). The pressurized air can be supplied by the ventilation system. If no air is available it is possible to wrap a copper coil for cooling water around the sensor head cover.

Process flow conditions

The sensor is designed to make the prism self-cleaning. To ensure a representative sample and also prism cleaning action, a good process flow should be directed against the prism surface. A flow velocity above 1.5 m/s (5 ft/s) is recommended. For lower velocities prism wash (Section 4) should be considered. Flow velocity is calculated from v[m/s] = 21.2 * Flow[lit/min]/d²[mm]; v[m/s] = 0.125 * Flow[Gpm]/d²[in]. Accumulation of sediment or of gas bubbles should be prevented. If the process pipe vibrates, support the pipe.

Figure 1. Mounting guide 1/2
Figure 2. Mounting guide 2/2