For small nozzles, it may be necessary to increase the Hold Off Distance/Upper Null Zone
(UNZ) to reduce the measuring range in the upper part of the tank. See Change the upper
null zone. Amplitude Threshold adjustments may also be needed in this case. A Trim Near
Zone is recommended in most nozzle installations, for example, when there are disturbing
obstacles in the near zone. See Trim near zone function.
Note
The probe must not be in contact with the nozzle (except for the coaxial probe). If the
nozzle diameter is less than recommended, the measuring range may be reduced.
Table 3-5: Nozzle Considerations
Single (rigid/segmented/
flexible)
Coaxial/Large
coaxial
Twin (rigid/
flexible)
Recommended nozzle
diameter (D)
6 in. (150 mm) > probe diameter 4 in. (100 mm)
Minimum nozzle diameter
(D)
(1)
2 in. (50 mm) > probe diameter 2 in. (50 mm)
Recommended nozzle
height (H)
(2)
4 in. (100 mm) + nozzle
diameter
(3)
N/A 4 in. (100 mm) +
nozzle diameter
(1) The Trim Near Zone (TNZ) function may be necessary or an Hold Off Distance/Upper Null Zone
(UNZ) setup may be required to mask the nozzle.
(2) Longer nozzles may be used in certain applications. Consult your local Emerson representative
for details.
(3) For nozzles taller than 4 in. (100 mm), the Long Stud version is recommended (option code LS)
to prevent the flexible portion from touching the edge of the nozzle.
A long stud - 9.8 in. (250 mm) - is recommended for single flexible probes in a tall nozzle.
Figure 3-5: A Single Flexible Probe with a Long Stud
A. Long Stud (9.8 in./250 mm)
Note
For single lead probes, avoid 10-in. (250 mm)/DN250 or larger diameter nozzles,
especially in applications with low dielectric constant. An alternative is to install a smaller
nozzle inside the nozzle.
Mechanical installation Reference Manual
April 2019 00809-0100-4530
34 Rosemount 5300 Level Transmitter
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