Dust; Solid Surface - Emerson Rosemount 5408 Reference Manual

Measurement in foamy applications depends largely on the foam properties. When the
foam is light and airy, the actual product level is measured. For heavy and dense foam, the
transmitter may measure the level of the foam's upper surface. The Double Surface
Handling function allows the user to select if the foam layer or product surface should be
used as output (see
2.2.3

Dust

Dust is often present in solids applications, and even if the non-contacting radar is not
affected by the dust in the vapor space, dust can be sticky and create a layer on the
antenna. If this layer becomes too thick, it may affect the measurement. This is best
managed by using air purging.
2.2.4

Solid surface

Solids have some common characteristics which may cause weak and varying surface
reflections. The surface is rarely flat or horizontal, the angle of the sloping surface differs
during filling and emptying, and the dielectric constant of many solids is fairly
low.Table 2-1
The parabolic antenna is ideal for applications with weak surface reflections. A larger
diameter concentrates the radar beam and ensures maximum antenna gain. The parabolic
antenna comes with a swivel connection that adjusts for angled tank roofs.
Table 2-1: Common Characteristics of Solids Applications
Applications
Wood chip bins
Grain silo - small kernel grains
Grain silo - large kernel grains
Lime stone silo
Cement - raw mill silo
Cement - finished product silo
Coal bin
Saw dust
High consistency - pulp stock
Alumina
Salt
Rosemount 5408 and 5408:SIS Level Transmitters
Double surface handling).
presents common characteristics of some solids applications.
Common characteristics
Particle size
Dust or powder Small (<1 in.) Larger (>1 in.) Dust
Yes Yes
Yes Yes
No Yes
No Yes
Yes Yes
Yes Yes
Yes Yes
Yes Yes
No No
Yes Yes
No Yes
Vapor space
Yes Yes
No Yes
No No
Yes Possible No
No Yes
No Yes
Yes Yes
No Yes
No No
No Yes
Yes No
Transmitter Overview
Steam or condensation
Possible
No
No
No
No
Yes
No
Yes
No
No
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