Phased PLC Upgrade Approach

PLC systems have been the basis of many automated processes for decades now. With installations ranging from Gas Plants and Oil Batteries to Manufacturing, Pulp & Paper, Water – Waste Water and even Original Equipment Manufacturers (OEM). Often these microprocessor-based platforms were built so robust that some are still in service decades later. While this is a testament to the longevity and reliability of these systems, there comes a time when they do need to be replaced.

Replacing a PLC system can be difficult, not only to carry out, but also to justify. While it may be relatively easy to decide you need an upgrade, justifying the downtime may be much more difficult. The time and resources it takes to literally rip out an old PLC system and replace it with a new one will most likely make the CFO’s head spin.

But there is an approach that can significantly ease the pain.

Phased PLC upgrades can greatly help in this area by upgrading the PLC processor and keeping the existing I/O modules and racks, giving companies the ability to leverage the advantages of new technologies while minimizing the impact of a rip and replace. Many PLC manufacturers have an approved “migration path” that can utilize that existing I/O while allowing the end user to upgrade the processor.

“But what if I don’t want to stay with that vendor and want to migrate to something totally different?”

This is much easier than one may think. With modern communications adapters this is brought well within the realm of reality.

Some may think that the HMI or graphical interface is where one should start. While there are definitely many reasons to upgrade the graphical interface, one really should start with the PLC Processor.

Advantages of upgrading a PLC can be realized and expanded on and can far outweigh the challenges. Many benefits can be realized including, but certainly not limited to:

  • Taking advantage of faster scan times
  • More efficient logic scanning options
  • Implementing automation “Objects”
    • Add-On Instructions
    • User Defined Data Types (UDTs)
    • Advanced Alarming Objects
  • Better integration to Historians
  • Higher capacity communications networks (Ethernet, Fieldbus systems, HART)
  • IIoT implementation compatibility

A phased PLC upgrade can take many forms, but one powerful option to leverage is by using communications adapters to be able to maintain operability of the existing I/O by connecting them to the new processor. Modern Process Automation Controllers (PACs) such as Rockwell Automation’s ControlLogix can be connected to a myriad of platforms such as:

  • AB RIO and DH+ (the PLC-5 and SLC Remote I/O)
  • Modicon S908 I/O
  • GE Ethernet Global Data
  • GE Genius I/O Bus
  • Square-D SY/MAX Remote I/O
  • Siemens Profibus/Profinet
  • Texas Instruments TI 505
  • IEC 104
  • Reliance AutoMax Remote I/O
  • Mitsubishi CC-Link
  • Honeywell IPC 620/621

Converting legacy systems to a modern PAC give way to other advantages as well, like redundant processors, higher reliability and greater compatibility. Did you know that there are ControlLogix communications cards that can also make data transfer to the following protocols possible?

  • Moore APACS DCS
  • Modbus RTU, ASCII, TCP
  • BACnet, LonWorks (Building Automation Systems)
  • BSAP (Bristol Babcock RTU network)
  • DNP 3.0, DNP over Ethernet
  • FL-net (FA Control Network)
  • Fisher PROVOX devices
  • IEC 60870-5
  • IEC 61850
  • Limitorque Valve Network
  • Johnson Controls metasys N2
  • Siemens 3964R Network

Once the PLC processor is replaced, other upgrades can be performed as opportunities arise, even under a maintenance budget. Also, when it’s time to upgrade the HMI, there can be so much more data available, giving operability and maintainability a tremendous boost. Additional diagnostic data can also go a long way in keeping production at its peak.

If you have a legacy PLC system that you know you need to upgrade but lack the capital to do a complete overhaul, contact us. We would be happy to work with you and help you take advantage of the tools that are available.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.