Avoid the Pitfalls of PLC and SCADA Control System Integration

Avoid the Pitfalls of PLC and SCADA Control System Integration

by Gerhard Greeff – Divisional Manager Process Management & Control, Iritron


13 June 2024: Taken at face value, upgrading your control system by integrating Programmable Logic Controllers (PLCs) with Supervisory Control and Data Acquisition (SCADA) systems should be a simple seamless process.

Regrettably, the industry is plagued with control system integration and upgrade myths and misconceptions that can lead to liability issues, project delays, cost overruns and decreased plant performance.

In modern manufacturing, PLCs with SCADA systems is a prevalent practice, as it enables manufacturers to collect and monitor real-time data from various production processes. This integration allows manufacturers to optimize production processes, decrease disruptions, and enhance overall efficiency.

In the manufacturing industry, PLCs have become indispensable as the brain that controls and monitors various systems and processes. With the ability to integrate with other systems and applications, PLCs have become increasingly sophisticated and potent over time. So the integration of PLCs provides numerous benefits, including increased productivity, efficiency, and quality.

But integrating PLCs with other systems and applications is not straightforward and requires a high degree of skill and understanding. It is the system’s complexity that can be difficult to comprehend and requires an ‘eat the elephant’ process of careful planning and design logic.

Many factors can influence your choice when it comes to specifying a PLC model for your integration application. Some key considerations include:

  • Electrical Capacity: PLCs have different voltage requirements for their power supplies, so check to ensure that your selection is compatible with your electrical system.
  • Processing Speed: Check a PLC model’s CPU speed to determine whether it meets your application’s needs.
  • Compatibility: Ensure that your PLC model is compatible with any new or existing system hardware, whether that’s power supplies or DIN rails.
  • Temperature Tolerance: Most PLCs are designed for safe operation within the range of 0 to 60°C. There are some specialized PLC models can operate at extreme temperatures, which is important for facilities with unusually hot or cold manufacturing conditions.
  • Memory: A PLC needs sufficient ROM and RAM to execute the processes it’s intended to automate. The controller uses ROM to store its operating system and instructions and RAM to execute its functions.
  • Connectivity: Make sure your PLC has enough input and output ports, and make sure it’s able to connect to the type of peripherals that your system requires.
  • Analog I/O: Although PLCs are primarily used for discrete functions, some models also have analog inputs and outputs that can control processes with continuous variables.

Taking all these issues on board, one can see that besides skill and understanding, planning is crucial in ensuring the success of an integration or upgrade project. During the planning process the following steps are recommended:

  • Define the project deliverable limits
  • Have an approved and documented control philosophy – without this, the project is set up for failure.
  • Define and document the PLC and SCADA standards
  • Develop a Functional Design Specification based on the control philosophy before PLC programming start.

Although it might seem obvious, it is imperative to define the state of the equipment:

  • Check the switchgear; contactors, and auxiliaries are working properly- they may have changed.
  • PLC connections – Ensure that the PLC connections are on and there is communication between them through a proper channel and not via the I/O server.
  • Field instrumentation -Check the state of the field panels and the proxy readings.
  • PLC communication – Look for missing parts in the PLC and SCADA systems.
  • SCADA scripts:Identify and find the scripts in the SCADA system. This will help you avoid any hurdles during commissioning.
  • Take before and after videos and make notes to record what is currently in the plant and more importantly, what you have delivered and installed.

Proper planning is crucial to the success of a project and by following these steps; you can ensure that you have the right control philosophy, standards, and communication to avoid issues during commissioning.

About Iritron

Iritron is a Level 2, B-BBEE empowered engineering, integration and manufacturing company providing solutions in the fields of electrical, instrumentation, control systems and decision support systems. We have extensive local and international engineering expertise and a proven track record across various industries.

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