State-Based Control: The Next Step in Industrial Automation
The 1960s animated sitcom character George Jetson had an essential job at Spacely Space Sprockets, Inc. His job was to ‘push the button.’ The automation system did the rest. While we aren’t in the George Jetson era, we are fast approaching the age of autonomous automation – the self-driving car. Today’s cars are commonly equipped with sensors and automation for proximity alerts, backup, automatic braking, lane drift control and of course, the long-used cruise control. Such automation aides in operation and greatly improves safety.
What does this all mean for industrial automation? To embrace the future, we must evaluate and invest in various automation approaches that initially seem costly and challenging but eventually pay back handsomely as an investment in reducing long-term cost of ownership.
To improve margins and mitigate risk, industry is looking more and more to state-based control, which is literally and figuratively the next step in industrial automation. Literally in that it uses steps or states to control processes. Figuratively, in that while state-based control isn’t a new approach, industry is increasingly interested in how it can improve facility operations. So much so that the International Society of Automation (ISA) has gotten firmly behind the state-based control concept and is in the process of developing ISA-106, procedural-based control standards to support it.
A Procedural Process
Automating the operating procedure is at the center of state-based control. State-based control is built around the premise that every process – even those that are in a steady state for lengthy periods – moves through a set of steps or states. Every process starts out idle or waiting. To start up, it runs through a set of states to reach its steady state or run step. Conversely, to shut down, it moves through a set of states to reach a safe condition and/or move back to its original wait state.
Many facilities use step-by-step procedures and manual operations to move through these states. With today’s smart technologies, these procedures can be automated to a significant degree. This is where state-based control comes in. Instead of operators having to make decisions on each and every step and change in the procedure, state-based operations can reduce the operator’s needed interactions to a few key points, like making the step transition to start. The automated system can do much of the rest, such as lining up equipment to relieve operators from a multitude of tasks and allow them to focus on key decision points and monitor events more effectively.
The Cost to Automate
Each time Evonik restarted the unit, operators charted the time necessary to reach stable production, which ranges from 2.5 to 5 hours. Once the procedure was automated, quick and consistent startups became routine.
Source: InTech magazine (June 2015)
Oftentimes, we look at the cost of automating and must consider how to mitigate such costs. But we also must consider the cost of not automating the procedure. Optimizing a facility for the Run State makes sense in terms of time, but it doesn’t make sense in terms of risk, since 70% of all incidents occur during startup or shutdown. Operating errors account for greater than $80 million in costs, as well as 42% of unscheduled shutdowns.
Not automating can also cost you in terms of startup time. A typical state-based project will improve startup time by more than 30% for various units. The figure represents a migration to state-based control for a set of columns.
A facility that takes 8 days to get up to capacity and on specification may take only 36 hours using state-based control. From this data, we can realize the losses due to not automating the procedure and compare it to the cost of automating the procedure using state-based control. While in the short term the cost favors not automating, in the long term, it favors automating. So, ask yourself, can you afford not to automate your procedures? The answer depends on how long you plan on owning it.
Managing process upsets and alarms is also much easier making operations more effective and efficient. Leveraging state-based control also significantly improves asset management and reliability.
On a personal note, I’ve been utilizing state-based control since the mid-1980s. It is typical for projects migrating from loop controls along with operating procedures to state-based control to be looked at with a big question mark. I was a skeptic at first. Afterall, the facility we were modifying ran fine and operated in the run condition 90% of the time. I was quickly converted after the first startup and wanted to know how soon the rest would be done. It is typical to be skeptical of such change, but one look at the ease and orderliness of startup is often the convincer for the skeptic.
As we move closer to George Jetson’s world of autonomous automation and the self-driving car, industry will move toward approaches like state-based control to improve operational effectiveness and efficiency, as well as reduce cost. To that end, we need to explore topics that help us gain a fuller understanding of what it means to integrate state-based control into a processing facility. Those topics would include:
- What is state-based control? What does it look like and how does it work?
- What are the advantages and disadvantages of implementing and using state-based control?
- How does state-based control fit in the hierarchy of automation? Specifically, when compared against the most common practices, which use loop-based controls.
- How does object-oriented programming lend itself to state-based control?
- Is agile methodology best suited as the work process for implementing state-based control projects?
- Why are simulation and iterative testing essential elements for implementing a state-based control package?
Understanding the answers to these questions will give us the knowledge and courage to go the extra miles a state-based control project requires. Future blog posts on state-based control will cover these important topics.
Nolan, Tim (2016). “State-Based Control and the Value Delivered from the Initial Design through the Operating Life of the Facility” Paper presented at the AIChE Conference, Houston, Texas.
About the Author
Rocky Chambers (email@example.com) Rocky is a control systems specialist at MAVERICK Technologies, a leading automation solutions provider offering industrial automation, strategic manufacturing, and enterprise integration services for the process industries. MAVERICK delivers expertise and consulting in a wide variety of areas including industrial automation controls, distributed control systems, manufacturing execution systems, operational strategy, business process optimization and more.