Reactor Control Using US1000-11

Overview

Yokogawa's US1000-11 Digital Indicating Controller is the newest member of the Measurement & Control Division family of industrial and process controllers. One application that can easily be implemented is a reactor cascade control, using product and steam jacket temperatures as the process variables (PV's). The "primary" control loop is the product temperature, using a thermocouple as the PV. The output of this PID control action is firmware connected as the cascade (remote) set point of the "secondary" steam jacket PID control function block. The second PV is the thermocouple installed in the steam jacket. The control output is transmitted to the actuator on the steam control valve. Refer to the drawing below.

Inputs/Outputs

• Universal inputs for the PV's allow selection of T/C, RTD or VDC. The inputs can be scaled for engineering units. Input bias and first order lag filter are available for each input.
• A third analog input (VDC) can be used as a cascade (remote) set point provided by an external device, e.g., PLC or DCS.
• There is a universal control output allowing a DC current output (4-20 or 0-20mADC).
• Two analog outputs (4-20mADC and 1-5VDC respectively) can be used to retransmit the process variables to a recorder.
• Two independent 25.5VDC loop power supplies are available if T/C or RTD field transmitters are preferred.
• Up to seven discrete inputs are standard. Functions are pre- assigned for OPEN/CLOSE of the cascade control action, forcing the control output to a PRESET value, or mode switching (CASCADE/AUTO/ MANUAL). Functions can be reassigned for custom requirements.
• Up to seven discrete outputs are available. The first three are relays, with contact ratings of 1A resistive at 240VAC. Others are solid state relays (open collector) rated at 30VDC & 200mA maximum. DO1-DO4 are assigned as high and low alarms for the product and steam jacket control loops. They can be assigned as normally open (NO) or normally closed (NC) on alarm.
  Instead of high or low limits, the contacts can be assigned as deviation alarms. DO5-6 can be user assigned while DO7 is dedicated as a FAIL output.

Implementation

The US1000-11 can be configured using front panel display push buttons or a PC-based parameter setting tool. The cascade control action with two universal inputs (US Mode 13) is a resident strategy and only needs to be selected during configuration.

Front Panel Configuration:

•  Press the SET/ENT key for three seconds to enter the configuration mode. Follow the parameters setting map in the appendix of the instruction manual to make any changes.
•  Default settings for the PV inputs are 1-5VDC. 1 of 14 different T/C types can be selected. If using a 100Ω platinum RTD, three different temperature ranges are available.
•  The default control output is 4- 20mADC. This can be inverted for a 20-4mADC output.
• The high and low alarm set points can be set while in the configuration mode.

Refer to the functional block diagram to the right.

PC-based Configuration Tool:

Using the LL1100 Parameter Setting Tool, configuration is a snap. This Windows-based software package allows the user to develop the necessary configuration and download to the US1000 using the unique light loader optical interface at the front panel or through the optional RS485 connection at the rear field terminations. Refer to the drawing below. The configuration can be saved as a file and loaded into other US1000 controllers, minimizing start-up time.

Need to customize the configuration of the single station cascade controller? Are math or logic function blocks required for the application? The LL1200 Custom Computation Tool allows use of up to 60 custom function blocks for unique control/logic requirements. This provides the most versatility available.

Summary

The new US1000-11 Digital Indicating Controller has 14 resident control strategies and custom computation capabilities. The single station cascade control strategy with universal inputs is described here. Multiple discrete inputs and outputs allow interactive control. Easy front panel or PC-based configuration minimizes start-up time and gets the process under control in no time.