Machine and Process Management

GUEST POST: Don’t Get Complacent When Modernizing “Simple” PLC Systems

As a system integrator, we have performed many PLC system modernization projects – some more challenging than others. What we always find is key is ensuring they’re well planned; the job specifications are understood and we deliver to the designated time constraints.GTH pic (1)

In a recent project one of our control engineers and sales representatives completed a system evaluation for a seemingly simple job – a small single rack PLC system that was tied into a generator control system via a communication gateway with a touch screen interface. We determined that the best approach was to convert the PLC application using the PLC vendor’s software and replace the communication gateway with a similar unit.

Sounds pretty straight forward, right?

But consider some of the problems that could arise with this kind of project and reflect on these important questions: The touch screen will probably need to change with the new PLC platform; do you have the programming software for the screen? Even if you do, does it support upload of the application? Does your client have a copy? Is this copy the latest revision?

Another challenge to consider is the communication gateway. Does the existing in-rack model need replacing and, if so, is the configuration different? Also, will the maintenance engineer require training on the new system? If so, what is the learning curve?

Finally, the most important aspect of this project was startup and commissioning. When we took on the project the system was not operational due to a PLC failure so we were not able to evaluate the functionality. We were provided with a copy of what was thought to be the current program application but unfortunately changes had been made so when we tested the system it did not function to the customer’s expectations.

As we were unable to witness the system operation prior to failure we had to rely on the description of functionality by the operator. This lead to a number of misunderstandings and miscommunications in regards to their operational requirements and many trips to the site were required to resolve the issues.

In summary, it is sometimes easy to get complacent when bidding control systems, particularly smaller projects that may seem simple and straightforward. As the requirements of system automation and modernization continue to grow, it is important to define and document the expectations of your client as well as your scope of work to mitigate the chance of miscommunications.

Think about how you would have managed this project. Do you have systems and procedures in place to ensure even your smallest jobs are handled proficiently? What would you have done differently?

 

Contributor:

Mike HowardGTH photo (2) – As an integral part of the George T Hall (www.georgethall.com) management team, Mike has been involved in all aspects of our business from control panel fabrication, programming and field services to sales team management. With over 20 years experience in the system integration business he currently directs our engineering, estimating and project staff. Mike can be reached on Twitter @GeorgeTHall


2 Responses
  1. Eric Pierrel

    Hi Mike –
    Nice post pretty representative of most migration projects for which our customers use our PLC Converter.
    We keep saying that conversion with our tools is only one step of the whole project and for sure no magic wand. It aims at saving (a lot of) time but converted programs shall be tested as usual and scope of the project shall be defined as precisely as possible before usage of the tool.

    Reply
  2. Jean-Pierre Mondange

    I do like your post, Mike (we have this motto in french: ‘expérience passe science’). And I’d like you to continue and develop the conclusion of this blog in further posts. Thank you

    Reply

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