Level measurement

34 Continuous level measurement in liquids

4. Instrument selection within the measuring principle

Radar

Required application data • Pressure and temperature • Dielectric constant of the medium (DC)/media group

Dielectric constant (DC) The reflection properties of a medium are determined by the dielectric constant (DC).

The following table shows the allocation of different DC values to media groups. If the dielectric constant of a medium is not known, we recommend to use a DC value of 1.9 for sizing in order to maintain a safe measurement. Absorption The following media can absorb the radar signal from 80 GHz sensors depending on pressure, temperature and the concentration of the respective medium: • Aceton (Dimethylketon) • Dichloromethane/Methylene Chloride • Ethylene oxide • Methyl Ethyl Ketone • Methyl Isobutyl Ketone (MIBK) • Propylene oxide • SMR (Xylene 30 %, Toluene 30 %, Acetone 40 %) • Silicon tetrachloride • Trichlorosilane • Tetrafluoroethane • Toluol • VCM (Vinyl Chloride Monomer) • Ammonia • Ethyl Acetate

• Required material compatibility • Nozzle diameter/nozzle height

• Measuring range • Required accuracy • For stilling well/bypass: Internal pipe diameter

Application limits for radar level measurement • Temperature up to –196°C/–321°F • Temperature up to +450°C/+842°F • Pressure up to 160bar/2320psi • Measuring range up to 80m/262ft

• Dielectric constant from 1,2 • Process connection from ¾“

C

Advantages • Non-contact, maintenance-free measurement • Unaffected by medium properties like density and conductivity • For high temperatures up to +450°C/+842°F • Measurement from outside of the tank

• Acetic Acid • Acrylnitril