Most, if not all, of us have been involved in a project that constantly changes. That project where change orders are sent almost as frequently as status reports. Managing such changes is not impossible. The most important step in managing frequent changes is to understand that change happens.
Designing an electrical control system capable of adapting to changes should be in the mind of every engineer. Anticipating those changes will help us design flexible electrical panels, PLC programs and HMI graphics.
While we are more likely to be asked to add to a system mid-process than remove from it, adding is more difficult than removing. With that in mind, allow space for adding I/O on top of the 15-20 percent of planned spares. These spares should also be dynamic. Think about how you would handle the different types of I/O, including DC voltage, AC voltage, RTD, 4-20ma and 0-10V DC. Anticipate change and be ready for it.
Most programming software for PLCs gives us tools for organizing our program, such as user defined types, sub-routines, tasks, data blocks and objects. Utilization of these, when appropriate, gives us that edge when changes begin. Keeping the code systematically organized will help with future changes and understanding the tasks and processes. Monitor design changes carefully, for they will most likely incur changes in the program.
HMI programming software also provides tools that help maintain organization in our graphics. Using faceplates or templates is a great way to minimize change time and design. Imagine having finished adding 20 pumps to the main screen, and then wanting to see the runtime for each motor. With faceplates or templates, this will be a minor change. The planning for panel design space and spares should be considered in HMI design as well. Keep some space next to that last pressure meter in case another pressure transmitter is added in the field during commissioning. A flexible HMI design will allow for quick adaption to changes in the system.
Everything around us changes. People grow older, pick new hobbies and learn new skills. Companies, likewise, grow in size, relocate to new locations and restructure management. The only constant is change. It is important to understand that projects will change, as well, throughout their duration. The key to managing this change is expecting and planning for it.
Juan Escolarte is control systems engineer at Loman Control Systems Inc., a certified member of the Control System Integrators Association. Learn more about Loman Control Systems on the Industrial Automation Exchange.
