Mixing

Three components – two fluids and one powder – are required for manufacturing a paste. The flow rate of the two fluids must be controlled in a specific ratio. The powder is added in proportion to the flow rate.

The quantity of fluid 1 is detected by means of a flow-rate measuring instrument and controlled continuously by a globe control valve. The lower quantity of fluid 2 is also measured and controlled by a second globe control valve in a given ratio with respect to the flow rate of fluid 1. Fluids and powder are mixed in a mixing vat. The quantity of the paste pumped from the mixing vat is detected with a magnetic inductive flow meter and controlled by a general-purpose controller with a stainless steel diaphragm valve.
The set-point values of the closed-loop flow-rate control system for fluid 1, the feed velocity of the powder, the speed of rotation of the agitator and the paste dose are output via an electric/pneumatic automation system. The set-point value of the closed-loop flow-rate control system for fluid 2 is generated directly in the positioner of the control valve as a function of the flow rate of fluid 1. The flow rate of fluid 2 is controlled in the required ratio via the process controller integrated in the positioner. In addition, pneumatically operated on/off valves controlled directly by the automation system are fitted in all of the system’s delivery lines.