The post Batch Process Automation Can Make Continuous Processes Run Better first appeared on the ISA Interchange blog site.
I have many years of experience in process control engineering, starting with continuous processes and later with automating batch processes. I find batch automation to be largely about sequential operations and states. To a lesser extent, sequential operations and changing states exist in many 
continuous processes as well.
Extending the lessons learned in automating batch processes to continuous processes seemed like a natural progression, and I recall discussing this concept with colleagues at technical conferences. In 1999, I got the opportunity to put this idea into practice. When a new technology was commercialized, we converted a batch reactor system at our plant to a continuous process. The operations staff had more than 10 years of experience operating highly automated batch processes. They realized the benefit of sequential automation for managing state changes and transitions, so they strongly supported implementing procedure automation for the new continuous process.
Once the decision was made to design for multiple products, as well as campaigning on the new process, procedure automation made sense. The original batch programming was also a strong basis for automating the new continuous process. The plant started up in late 2000 and used procedure automation for startup, shutdown, restart, and rate changes. We added an automated deinventory procedure and a rate optimizer later, as well as other functions and corresponding procedures. Adding a second product manufactured in the process ushered in additional changes.
That experience made me a firm believer in the value of procedure automation, and in the following paragraphs I will share my experiences as a long-time user. I hope to encourage you to implement procedure automation on your process to benefit as we did.
Figure 1. A report issued in 2012 by the Energy Practice of Marsh Ltd., a division of insurer Marsh McLennan, examines the five-year loss rate (adjusted for inflation) from 1972 to 2011 in the refinery industry. Incidents during startups and shutdowns continue to be a significant factor.
Procedure automation is not new, nor is it some theoretical concept. It has existed for many years, mostly in batch and semibatch processes, but also in continuous processes by some forward-thinking users. It is all about automating specific tasks in a process that typically require a lot of manual intervention from operators, because many problems originate in manual intervention (figure 1).
There are real benefits in its application to continuous processes, and even a casual examination shows all sorts of opportunities. Procedure automation is beneficial not only in chemical and petroleum processing, but in any process with sequential operations. Procedure automation has been applied to a wide range of processes from offshore platform operation to cracking furnaces to processing nuclear materials.
Procedures exist in all processes. Sometimes they are written down on paper, sometimes kept in digital form in a document control system, and sometimes they are in somebody’s head (tribal knowledge). Well-written procedures enable safe, consistent operations. In fact, in some industries, written procedures are a legal requirement. However, having procedures and following them are often different things. To maximize the benefit of any procedure, it must be faithfully followed day in and day out. Thus, the basis for the main benefit of procedure automation: it enforces adherence to the procedure.
Automating procedures enforces consistent operation of the process, resulting in improved quality and higher throughput. Operators are able to operate with fewer errors and delays, creating maximum utilization. This translates into real dollars to the bottom line—something any manager can appreciate!
More importantly, procedure automation contributes to safe operations. As previously mentioned, it reduces the opportunity for operator error. In one study, the ASM Consortium found that approximately one-third of incidents were caused by procedures being used incorrectly or not at all. Further, procedures performed less frequently are less familiar to operators and more subject to failure, and these situations generally occur in abnormal operations where the risk of a safety incident (and likely the consequences) is larger. Procedure automation also provides a means for a controlled shutdown, which is less hazardous than an emergency “crash” shutdown.
Procedure automation improves safety through automated management of shutdown and alarm systems in the process. Procedure automation also helps coordination between the basic process control system (BPCS) and the safety instrumented system (SIS), ensuring functions specific to a given operating state are recognized by both. This is especially important during transients or processes where steady-state conditions change due to factors such as different product grades or feedstock. Using procedure automation combined with appropriate SIS programming can eliminate manual startup bypasses of interlocks.
Alarm management is as an important contributor to operator awareness and hence safe operation. Here as well, procedure automation can be used to help manage alarms (e.g., determining which alarms are active or inactive at appropriate times and avoiding “chaff” that confuses operators), especially during severely abnormal conditions, such as an emergency shutdown.
The benefit of improved safety is often difficult to quantify in dollars, but the cost of unsafe operation is painfully obvious. Losses from safety incidents in the U.S. alone are estimated at $10
Figure 2. Many procedures are not well documented, and different operators may practice them differently. Part of automating such procedures is determining the best practices and incorporating those approaches, so they will be followed consistently.
billion annually. Single events can cost companies upwards of $2 billion, not to mention many lives lost.
Earlier we considered the issue of operator familiarity with procedures and the effects on operators’ abilities to properly execute those procedures. As we all know, our workforces are
changing, as senior operators with 30 or more years operating experience are retiring and new blood is entering our control rooms. Senior operators that I have worked with generally do a good job mentoring the new hands, but the knowledge transfer is never complete. Procedure automation is a great tool for knowledge retention, and having well-documented procedures and automating those procedures greatly improves personnel transitions (figure 2).
Bill Wray, P.E., began his career as a process engineer, later discovering his passion for process control, a field he entered in the early 1980s. Beginning with automation of large continuous petrochemical processes, he later moved to batch automation and is recognized among his peers for his expertise. Wray was a founding member of World Batch Forum (WBF) and served in various leadership roles. Since the merger of WBF and MESA, he has joined the international board of MESA. He was the first chairman of the ISA95 committee, leading this effort to publication of the ISA-95 Part 1 standard, and is currently co-chair of ISA106. Wray is employed by Bayer Material Science as a senior engineering consultant and holds a B.S. in chemical engineering from Virginia Polytechnic Institute.
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Source: ISA News
