MoE 1: Automation 201 – Coding and SCADA Strategies

Automation 201

is a continuation of the Tech Meeting held in February. Automation 101 is not a prerequisite.

The automation strategies given are based on the author’s experience with PLC/SCADA systems in the process industry and lean heavily on these methodologies. There are other means to “automate” which are just as valid. The presentation is meant to convey the concepts and strategies for safe and effective process operation.

Start from the P&ID – the Process engineer will assist in developing a process algorithm.

Ladder Logic

• Digital Inputs
  • Switches, Buttons
  • Temperature, Pressure, Level, Flow, etc.
  • Alarming Strategy
  • “Reverse” Alarm

• Digital Outputs
  • Motors, Heaters
  • Start/Stop Strategy
  • E-Stops

• Valves – a special case
  • Typically both Di and DO
  • Can also have AI and AO
  • Alarming Strategies

• Analog Inputs
  • Transmitters, RTDs, Thermocouples, VFDs, Metering
  • Temperature, Pressure, Level, Flow, etc.
  • Alarming Strategy
  • “Reverse” Alarm

• Analog Outputs
  • Controllers, Positioners, Dampers, VFDs

• PID Loops
  • PV, MV, SP
  • P, I, D: Math
  • Loop Tuning
  • Alarm Strategies and levels
  • Cascade loops – MV becomes SP

• Auto/Off/Manual Operation
  • Individual A/O/M per device
  • Local start/stops (PB) for each motor
  • Local open/close (PB) for each valve
  • Remote (HMI) start/stop for valves and motors
  • System-wide A/O/M

• Process sequence and timing
  • System start/stop from PB or HMI
  • Start each device in time
  • Avoid starting too many things at the same time
  • Shutdown – also typically with timers between devices

• FAILBUS
  • All alarms show here
  • FAILBUS stops the system
  • Can have more than one

SCADA

• HMI Graphics
  • Color palette
  • Moving graphics – yes or no?
  • Text/Annunciator vs P&ID view
    • How much data to show per graphic?
  • Graphic representation for DI, DO, AI, AO
    • Animation of pipes, motors, valves, switches, instrument values
  • Control via the HMI
    • Setpoints
    • Start/Stop
    • A/O/M
  • Data from the HMI
    • Trends and data logging
    • Alarm viewers and logging
    • Data mining

More information about the Morning of Education (MoE) and the text expo can also be found on the Tech Expo page on our website.