3 Benefits of PLC Code Re-Use
While it might seem apparent why control engineers and programmers at Huffman Engineering, Inc. are motivated to re-use PLC code for customers, why should it matter to them? What is the actual benefit?
Code re-use allows for easier and improved testing. How is easier testing better? Using a Factory Demonstration Test (FDT) as an example, much of the code that we re-use includes simulation within it. PLC code libraries such as Rockwell 
Software PlantPAx objects and Schneider Electric PES objects, as well as some of the code we have developed, are designed to simulate the running of motors, pumps, and opening of valves and gates, that can be “seen” using SCADA/HMI graphical interfaces. If during the FDT, we do not re-use code developed with simulation, the customer is simply watching us, forcing inputs and confirming that the correct outputs turn on; however, they are not watching the whole picture. If the code we re-use has simulation built in, the customer can focus on the whole process during the FDT. This makes the chances of finding a problem with the process before equipment is started up in the field much higher. Anytime an issue can be identified and resolved before start-up, the customer saves money.
A quicker startup can also save the end user money, especially for a utilities project that is not “greenfield.” For example, in the water and wastewater industries, the utility must keep the processes flowing no matter what. This generally requires extra operators running equipment in local or hand. If a large portion of the programming is re-used code, the chance of the startup going better is significantly increased. If the startup goes quickly, everyone including the customer comes out ahead.
A less obvious way that code re-use benefits the customer is in training, on-site maintenance and troubleshooting. Generally, a programmer will only re-use code that they can understand; and this makes perfect sense. No one wants to use something that they can’t make sense of. If the programmer re-uses code (or coding styles) and then implements it throughout the PLC program, it is easier to learn and understand. If it can be understood then it can be taught to others and, more importantly, it makes the equipment easier to maintain and troubleshoot.
In the end there are many benefits to the customer which also mirror the benefits that the control engineer encounters. Most of them result in cost savings and who doesn’t like that?