Hydromation Filter – Control System Commissioning

The role was to commission the interface between the Allen Bradley PLC’s with the clients Yokogawa DCS system, tune the water inlet modulating valve PID loops (1x inlet valve per filter) and modify the backwash routine software.

Read/Write data between the DCS system and the PLC’s over Modbus TCP/IP was tested and commissioned over a 5-day period. This involved working closely with the Yokogawa software engineers, with the aid of an interpreter. Integer and Boolean data was read from Modbus addresses pre-defined in the PLC systems. This included PV’s, machine status and alarm codes. In addition the DCS system needed to have the ability to write to certain process set-point registers. Any changes to the register details were fully documented; this included scaling factors, TAG reference names, min/max settings, default values and the actual Modbus addresses themselves. A number of water inlet valve PID loops were commissioned. The water flow (PV) was regulated to a set-point (SP) by adjusting the water valve (CV) position. This required a quick response PID loop that exhibited a small gain (0.4) a responsive integral time (0.07 min/r) and no derivative. Loop time was set to 0.050ms, this needed to be several times slower than the PLC max scan time. The native RaLogix trend facility was utilised to assist tuning the loop. Water flow SP was set to 462m3/hr by the client. Additional software modifications to the backwash routines as directed by the Cameron commissioning engineers.

Daily reports had to be written and signed off by the client.