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Posted by Julie Gruenholz

Replacing Your Obsolete Control System. Step 1 – Replace the SCADA

January 10, 2022

Upgrading your obsolete control system is a helpful 7-part blog series addressing the important technical aspects of upgrades and written by an industry professional with over 25 years of experience.

Here are links to the other blogs in this series:

6 Questions to Ask When Upgrading an Obsolete Control System While Keeping Your Plant Running

KISS and 5 Other Items to Consider when Choosing to Upgrade Your PLC Platform

Replacing Your Obsolete Control System. Step 1 – Replace the SCADA

Replacing Your Obsolete Control System.  Step 2 – Upgrade the PLC Hardware

Replacing Your Obsolete Control System.  Step 3 – Key Considerations when choosing the new SCADA/HMI.

Upgrading your obsolete control system - Why and how to ground your ungrounded control system before a system upgrade.

A note for Mechanical Engineers… Don’t be afraid of the PLC programmer or the control system software. 

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How can your operators effectively run your plant during an automation system conversion with a mix of old and new hardware and software?

When you plan and implement a complete automation system upgrade, the hardest part is keeping the plant running during the conversion. In most cases this is a multi-year project. It is fine to have a valve manually manipulated by a human over one night while the folks upgrading the control system get some sleep, but in general the system needs to be fully functional at the end of each step along the way.

You need to make the system operators happy and as comfortable as possible. As you upgrade the control system on their equipment you are going to create all kinds of havoc. Your project will not be successful without their help.

Two Options to Consider

Assuming your control system upgrade will include a front end (SCADA or HMI) upgrade, there are two ways that this upgrade can happen:

  1. Upgrade the control system front end (SCADA or HMI) first and make it work with your obsolete system. Then, as you upgrade each chunk of control system and add a new PLC, the new portion of the control system will seamlessly replace an existing picture on the front end and the operators will interact with the system the same way.
  2. Upgrade chunks of the control system and put the new chunks on a new front end (SCADA or HMI) as you go. This may be a much less desirable solution as your operators will be not only be dealing with new control system hardware (that may have glitches when first implemented), but they will also have to deal with changes to the front end, or work with two different front ends at the same time. Unnecessarily annoying your operators is a very bad idea. You will need their support.

The control system front end (SCADA or HMI) is the most visible window into the workings of the plant. If you screw with this, it makes people uncomfortable. Again, your operators should be comfortable with each step you take. If your new control system needs a new front end, then I advocate for you to upgrade the front end first. The system operators can adjust to a new front end, completely controlling the obsolete control system, before you even start the hardware upgrade. This way the operators will be minimally affected during the hardware conversion.

Tools to Assist in the Conversion

There are many software tools available to make a new front end communicate with an obsolete control system. These are some options that you could consider:

  1. HMS AnyBus. This is a company that makes black boxes that can translate from one software protocol to another or from one network type to another. This is a can be a good temporary solution to get new and obsolete hardware to both talk to a modern HMI or SCADA. This should be a temporary solution during a multi-year upgrade that can be removed when the obsolete hardware disappears.
  2. OPC drivers. OPC stands for “OLE for Process Control.” OLE stands for Object Linking and Embedding. Almost all modern SCADAs can talk to an OPC Server. An OPC Server can be purchased or created for almost any obsolete control system and can port information over to a modern SCADA. If there is not an existing OPC Server for your existing control system, it might be worth paying someone to build one so your transition is seamless to your operators. Matrikon makes many obscure OPC servers and might be a helpful place to search for an OPC server compatible with your obsolete control system.

Our customer couldn’t believe we could get it all put back together:


Read more in Step 2–Upgrade the PLC Hardware

Read the next blog in this series

Replacing Your Obsolete Control System Step 2- Upgrade the PLC Hardware

There is a good chance that we have already helped a customer with your exact problem figure out how to upgrade their front end software. For advice on upgrading your front end (SCADA or HMI) you can contact us via

Help Desk

About the Author

Julie has left Hallam-ICS to pursue other endeavors, but her contributions to the company continue to be valued.

About Hallam-ICS

Hallam-ICS is an engineering and automation company that designs MEP systems for facilities and plants, engineers control and automation solutions, and ensures safety and regulatory compliance through arc flash studies, commissioning, and validation. Our offices are located in Massachusetts, Connecticut, New York, Vermont and North Carolina and our projects take us world-wide.

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Topics: Process Control and Plant Automation

Julie Gruenholz

By Julie Gruenholz

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January 10, 2022

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