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Reference Manual
00809-0100-4026, Rev HA
Section 3: Mechanical Installation
November 2014
Mechanical Installation
Figure 3-7. Recommended Hole Size for Pipe Installations
3.3.4 Installation considerations
Generally, the radar signal is unaffected by condensation and low pressure steam. If affected,
the lower microwave frequencies are less affected. The critical point is the tank penetration,
which acts as a cold spot, where the condensation will form. The radar antenna is located at this
cold spot.
If droplets of water build up on the antenna parts, the microwave signal may get partially or
even entirely blocked if the antenna is not designed for easy drip-off. Therefore, here it is
beneficial to use as large opening for the microwaves as possible, which is the main reason for
the oversized PTFE seal in the Rosemount 5400 Series Cone Antennas. An even better solution is
to use a Process Seal Antenna if the process pressure permits that.
To reduce the cold spot within the nozzle, it is always recommended to insulate the nozzle. By
doing so, the temperature in the nozzle will be the same as in the rest of the vessel and
condensation will thus be reduced. If the temperature in the tank is much higher than the
ambient temperature (i.e. tank is heated and located in a cold area), it might be necessary to
heat trace the nozzle in addition to the insulation.
Figure 3-8. Insulate Nozzle to Avoid Condensation
min. 6 in. (150 mm)
max. Ø: D/10.
D
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