Guided Wave Radar (GWR) transmitters Best Practices for Guided Wave Radar Transmitters in Chambers

Author / Editor: Marianne Williams / Dr. Jörg Kempf

Guided Wave Radar (GWR) transmitters are often favoured devices, as they — unlike traditional mechanical technologies — virtually have no moving parts, reducing maintenance costs and extending operational life. Many GWR installations require a separate instrument chamber, and choosing the right chamber is important for rapid installation, accurate measurements and reliability.

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Figure 1a: Rosemount 9901 3-inch diameter chamber with insulation
Figure 1a: Rosemount 9901 3-inch diameter chamber with insulation
(Picture: Emerson)

A Guided Wave Radar (GWR) can be installed directly into a vessel. However, many vessels have restrictions that preclude this, including agitators, heat exchangers and other internal structures. To overcome this, instruments are usually installed in a chamber mounted on the outside of the vessel. This allows the instrument to be isolated for maintenance, which is particularly useful in applications involving hazardous liquids, high temperatures or high pressures. An additional benefit is that if there is turbulence in the vessel, the chamber acts as a stilling well.

To get accurate level measurements from a GWR installed in a chamber, it is important that the level within the chamber replicates as closely as possible the level inside the vessel. Factors that may affect the accuracy of the level measurements taken in the chamber include the chamber diameter, size of the process connections between the chamber and the vessel, and the ambient conditions. As a general rule the use of larger diameter chambers and effective insulation will help to avoid many of the issues described below.

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