Mass flow measurement of pigment and plastic additives

Application Note | Chemical

  • Constant quality monitoring during production with changing viscosities
  • Bulk mass flow measurement right down to precise dosing
  • Automatic dosing of chemicals in a mixing tank


One of the world's leading manufacturers of pigment and plastic additives also produces in Germany. During the production of the additives, up to 8 chemicals with viscosities varying between approx. 50 and 400 mPa · s are added in sequence to a mixing tank. The Flow rates range from 20000 kg/h down to low flow dosing at 500 kg/h.

Products to be measured include

  • Xylol with extremely low viscosity,
  • Bupol with a viscosity of approx. 200 mPa · s, and
  • Polyglycol with a high viscosity of approx. 400 mPa · s.

Measurement requirements

To keep pump capacity to a minimum, only mass flowmeters with a single straight measuring tube are used. The chemicals used to manufacture the pigment and plastic additives are stored in tanks, and then flow through the mass flowmeters to the mixers. Accuracy must remain constant with all changes in viscosity. The measurements must be repeatable. With the automated process, the mass flowmeters add the exact amount of chemicals to the mixers. The meters must be self-draining, easy to clean and maintenance-free.

KROHNE Solution

Following comparative tests with other suppliers, KROHNE supplied mass flowmeters from the OPTIMASS 7300 C series, in sizes T 06, T 10, T 25 and T 40 for these applications.

The meters measure the precise mass flow of the various chemicals flowing to the mixers. Once the desired quantity has been reached, the instruments stop the flow to the mixers.

The single straight measuring tube of the OPTIMASS 7300 C compact meters, together with the vertical mounting of the devices, enable complete drainage of the measuring tubes without residue.

Customer benefits

The KROHNE OPTIMASS flowmeters considerably reduced the filling time of the mixers. In addition, the filling of the mixers now stops automatically. Precise adherence to the mixing ratios of the chemicals increases the quality of the colour and paint additives. The long-term stability and excellent reproducibility of the OPTIMASS meters also contributes to this.

The increased in accuracy when filling the mixers with the various chemicals increases product quality. Self-drainage and the lack of need for maintenance also lower operating costs.

Products used


Coriolis mass flowmeter for advanced process and custody transfer (CT) applications

  • High accuracy flow measurement of gases and viscous, aggressive or shear-sensitive liquids
  • OIML R117, MI-005; also certified for hygienic use
  • Flange: DN10…100 / ½…4", max. PN100 / ASME Cl 600; various other connections
  • 3 x 4…20 mA, HART®, Modbus, FF, Profibus-PA/DP