Mixing
Paste production
Task
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.
Solution
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.
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返回流量控制
