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Reference Manual
00809-0700-4530, Rev AA
Section 2: Installation Considerations
September 2013
Installation considerations
For high pressure steam applications above 400 psi (28 bar), it is also important to limit the
overall distance from the flange to where the level is controlled (indicated by A in Figure 2-6),
since the high pressure affects the dielectric properties of the vapor causing an error in distance
measured, see Table 2-1 on page 8
(1)
. The overall error increases with the pressure and is a
percentage of distance measured. Even if DVC is used and corrects the error of 8.6% at 681 psi
(47 bar) to 2 %, the 2% error may be larger than desired.
Figure 2-6. Limiting the overall distance A helps to minimize accuracy errors caused by the
vapor
Table 2-3. The error in distance with and without DVC at a pressure of 600 psi (41 bar)
NOTE:
DVC has a minimum distance requirement from the flange to the upper inlet to dynamically
compensate up to level 100%. See Figure 2-9 on page 18 for details.
For example, if a GWR is installed in a chamber that covers the full height of a 10 ft (3 m) tank,
the distance to the surface level may be as much as 9 ft (2.75 m). A 2% error over 9 ft (2.75 m) is
2.16 in. (54.9 mm). If a shorter system is used, such as the minimum size needed to replace the
14 in. (355.6 mm) displacer (approximately 35 in. (889 mm) total), then the overall distance to
the surface would be about 24 in. (609.6 mm). With this distance, the 2% error shrinks to
± 0.48 in. (12.3 mm).
For further guidelines for choosing and installing radar in chambers or stilling wells, see the
Guidelines for Choosing and Installing Radar in Stilling Wells and Bypass Pipes (Document No.
00840-0300-4024), and Replacing Displacers with Guided Wave Radar (Document No.
00840-2200-4811) Technical Notes.
(1) See the Using Guided Wave Radar for Level in High Pressure Steam Applications Technical Note (Document No.
00840-0100-4530) for details.
Distance A Error with no correction Error corrected to 2% with DVC
100 in. (2540 mm) - 7.6 in. (- 193 mm) - 2 in. (- 50.8 mm)
50 in. (1270 mm) - 3.8 in. (- 96.5 mm) - 1 in. (- 25.4 mm)
A
A