Things vs. Stuff: The World of Process Control
Next weekend I am flying out to Denver for another adventure in the automation world. This time I will be a little out of my element as I will be at a water plant, which brings up the topic of process control.
Most of the work I do deals with making Things, that is, handling and testing many discrete components. Sometimes the things may be part of a continuous process, such as web lines or injection molding, but the end result is usually some kind of object that must be built, tested and often packaged.
Process control usually deals with Stuff. This means that properties such as flow, pressure, temperature, pH and viscosity must be measured on a continuous basis and controlled by means of PID loops and instrumentation. Piping and Instrumentation Diagrams (P&ID, not to be confused with PID) are also an important element of the process world.
There are many places in industry where the techniques for dealing with things and stuff overlap. Things must often be weighed, measured and guided as a flow, and stuff often has to be placed in containers which then become things. Process control and what was once called “discrete” automation used to be very different fields, with DCS systems that could handle the hundreds or thousands of analog I/O points being the only option for large installations. With the advent of cheaper electronics and advances in hardware, new crossover systems called “Programmable Automation Controllers (PACs) have filled the gap between the DCS and PLC.
Twenty or so years ago I often attended trade shows exhibiting products for my employer. Back then there were several ISOA (Industrial Shows of America) shows across my state, devoted primarily to so called “discrete” controls. PLC and sensor manufacturers as well as machine builders would set up displays and thousand of people would attend from across the region. This was a major source of information before the internet effectively killed these local shows. Because we also sold instrumentation, we often had a booth at the ISA show too. My employer called this a “tabletop” show because rather than the full booth full of machinery and application-oriented displays, we would simply lay out all of the instrumentation on a table and people would stop by and take a look. Back then ISA stood for “Instrumentation Society of America”, they have since changed their name to “International Society of Automation”. This group still puts much more of an emphasis on the process industry than it does on manufacturing.
As I mentioned earlier, my experience has been much more in the manufacturing arena than that of the process world. I have had to learn documentation techniques such as P&ID and worked with intrinsic safety, instrumentation and liquid transport, but I am pretty green when it comes to wastewater utilities, petrochemicals and the language involved in the making of “stuff”. At the same time, many of the control techniques and products I have used in the past are used in both the manufacturing and process industries, so hopefully I will be able to pick up on the language and techniques quickly.