Contrec 515 Series with CR02 application is a single loop process controller measuring the volume flow a in main and process line using analog flow inputs. It can operate in local (manual), loop, ratio or blend mode and has a tuning menu to easily determine the Proportional Band and Integral Time Values used in the PI control algorithm.
The main and process flows are used to determine the net volume flow. The operator can view the actual ratio and deviation and has the ability to change the controlling setpoint directly from the main menu if access has been authorised.
The PI control of the process flow is via a 4-20mA proportional valve or pump controller. It has integral wind-up protection and a deadband and output ramp time can be programmed to reduce wear on valves and actuators and provide for bumpless operation.
CALCULATIONS
There are three types of control modes in which the process flow is dependent on the main flow. These are RATIO, BLEND-1 and BLEND-2 modes where the relationship between the flows are as follows:
Ratio Control Mode.
The process flow is a ratio of the main flow (o-400% range)
Pflow
Ratio% = —————- × 100
Mflow
Blend Control Modes.
These modes cater for blending points before and after the main flowmeter. The process flow is a ratio of the net (combined) flow (o-80% range).
Pflow
Ratio% = —————- × 100
Netflow
