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ControlLogix L73 Installation


Power from waste is a great idea, providing green electricity for the grid. The smooth running is essential for water companies

In this instance, the legacy multi-level control system consisted of seven Allen Bradley PLC 5’s controlling one stream. They were close to end of life and, therefore, unable to provide optimal levels of control with delayed communications using legacy DH+ protocol. The project required replacement with a super quick ControlLogix L73, to consolidate the seven legacy units into one and provide the opportunity for process optimisation, with reduced maintenance costs.


  • Seven, 17 slot racks (800 digital and 400 analogue I/O) change in one day.
  • Multiple specialist engineering disciplines required.

Key solutions:

  • Z-Tech worked closely with the water company's Systems Engineer, who designed the system.
  • The ControlLogix L73 is running enhanced redundancy. This means that there is high availability CPU’s and a fast redundant Ethernet ring for the IO.
  • After Z-Tech’s initial upgrade of the Ethernet communication, the PLC5’s were changed over in a single day. This ensured the plant was up-and-running in the shortest possible time.


  • Systems engineering
  • Electrical engineering.

Key benefits:

Z-Tech’s multi-skilled teams understood the core objectives, working together across the specialist areas in order to complete this change over in the shortest possible time.

  • "Z-Tech has proven a professional and technical approach to delivery on our automation projects. This has resulted in a long-term business relationship built upon good service, project delivery and trust."

    Philip Smith, Johnson Matthey PLC

  • "The customer focus and flexibility of Z-Tech makes it easy for a water utility to deal with. When we have a large and complex programme to deliver, planning every detail can be a challenge. Working with Z-Tech means that we can maintain delivery, knowing that resources are available to pick up the loose ends."

    Jim Grandison, Thames Water