Sounds like in general you need to continue your studies on industrial control systems. I have worked with many industrial engineers over the past 20 years, they come in all varieties and they all prefer different methods to accomplish the same goals. Its kind of like cooking, a cook will develop a liking to particular ingredients and they will use some of those same ingredients in every dish that they cook. As you learn, you will also develop your own methods and create a "tool set" that you will prefer to use to tackle automation projects. I myself have come to like using this company's products:
I do not work for them or have any affiliation with them. But, they offer free software for the bulk of their products and have many online video training sessions offered for free. I have used them for the past 10 years and have spent well over $100,000.00 (not my personal money, company money) on their products. The Click series of PLCs are a great learning platform and you can migrate up to the PAC series with a small learning curve.
As far as the pi goes for industrial use, I have used them in a manufacturing environment. At this point, I am not using them for anything "Mission Critical", just data collection and reporting. So far, absolutely no issues with heat, dirt, and 24/7 operation.