Autopro Blog

PLC vs DCS - How to Choose the Right Control System for Your Facility Q&A

May 31, 2019

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Our recent webinar, PLC vs DCS - How to Choose the Right Control System for Your Facility resulted in some excellent questions submitted by participants. Here are a few that we thought would be especially informative for many of you.

Is the industry trending towards Programmable Logic Controllers (PLC) over Distributed Control Systems (DCS), or a combination of the two?

The trend is leaning more so towards a combination of PLC and DCS. It often depends on the size and complexity, but most of the projects we're working on see benefit from having a combination. We often see controls that come in packages (compressors, turbines) that require a more complicated interface that already have a PLC built in.

If you have multiple PLC systems, which have become obsolete, would it be cost beneficial to move them over to a DCS?

This is largely dependent on how many I/O you have, but yes it could be cost beneficial. Keep in mind if your staff is already familiar with the PLC framework, you will have to invest in qualified training.

We often recommend an online migration in these cases, as it reduces the strain on existing infrastructure and mitigates downtime.

What would you suggest when considering PLC vs DCS for an unmanned control room or site?

Typically unmanned sites have very few controls. You may have a few valves, meter stations etc., and what we have done in the past goes against using a PLC or even a DCS. We typically will implement a Remote Terminal Unit (RTU) as they prove to be sufficient for these applications. As technology changes modern RTUs are becoming more and more like mini PLCs.