The 515 BF02 application is a batching flow controller for the delivery of pre-set quantities at pre-set flowrates using a volumetric analogue input. Batch control can operate in pre-set or on-off modes, while flow control can be set to local manual or PI loop mode.
This application provides the operator with clear local readout including flowrate deviation and can be controlled via communications in more automated systems. There is quick access to commonly used pre-set values directly from the front panel (if access has been authorized).
The PI control of the process flow is via a 4-20mA proportional valve or pump controller. It has integral wind-up protection, a deadband, output hold and ramp time that can be programmed to reduce wear on valves and actuators and provide for smooth operation.
To derive the flow rate, the analogue input is normalised to a value (A) between 0 and 1.
mass flow = (Mf max – Mf min)A + Mf min mass = ∫( massflow × Δt )
Automatic overrun compensation calculates the new valve closure point to ensure correct delivery by averaging the overrun amount from the last three complete batches.
The overrun compensation value is valid for a new pre-set value provided the stored overrun is less than 20% of the new pre-set.
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