DMC has worked with this client on multiple systems, including the compressors themselves, aiding in code development, FAT test support, and commissioning in the field. The compressor machine, also running on a ControlLogix PLC, has several complex components and functions critical to production and safety, and must react well in any environmental condition (high pressures, temperatures and vibration levels). As part of the integration team, DMC worked with the client to evaluate opportunities in order to make commissioning the machine that much more efficient.

In previous FAT tests, machines have been put through an extensive IO checkout procedure; however, with the machine not physically installed in the field, it has often been difficult to demonstrate how the machine will react to shutdowns, alarms, and changes in PID control loop inputs. To increase the fidelity of the FAT, DMC developed a highly flexible IO simulator using a Allen Bradley ControlLogix PLC and HMI.

Using the ControlLogix PLC, DMC was able to simulate the role of the supervisory “Plant” PLC that would normally issue high-level commands to the compressor over EtherNet/IP. We also utilized physical IO (48 analog out and 16 digital out), which were wired to the machine, providing realistic 4–20 mA readings of motor current draw, temperatures, pressures, and gas flow.

The flexibility of the simulator now allows the operator to dynamically assign names, value ranges, alarm/shutdown limits, and signal ramp up/down times for the analog outputs. The HMI also contains push buttons which enable the user to immediately force a value to the user-defined shutdown limit in order to observe the response of the machine as it moves valves, shuts down the VFD, and returns to a safe state.

For this particular machine, this enabled the end user to start the compressor, adjust critical values in order to see how the machine’s PID loops would react, and test every shutdown the machine may face in the field. As the simulator was built to be flexible, this same simulator will be able to be used in any compressor FAT test in the future to ensure that the machine arrives to the end user in a thoroughly tested and debugged state.

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