Continuous process environments tend to be stable — until they’re not. When that happens, the consequences can be catastrophic. Think Deepwater Horizon.
The very stability of a continuous production process often induces a false sense of security in operators. Lack of experience with system failure or unexpected alarms can lead operators to freeze when systems suddenly cascade out of control.
Procedural automation standards originally developed for batch processes and discrete manufacturing hold promise for helping continuous process operators deal more effectively with sudden emergencies, as well as the more routine changes in state that can occur.
Processing’s Most Vulnerable Areas
The fact is, every continuous process has non-continuous elements, such as startup, ramp-up, emptying and filling of tanks, shutdown, emergency shutdown and clean-in-place activities. A continuous process is really just a batch process with a very long steady state in the middle.
The ISA-88 standard has established a common terminology and a framework for writing software to control batch production processes and procedures. ISA-95 did the same for enterprise to manufacturing data integration. ISA-95’s “common denominator” data structure facilitates communication between business and process systems, so that operators and managers can make better decisions.
The thinking behind both of these standards has important implications in areas where continuous process control is most vulnerable—process variations and disruptions. These can result in unanticipated shutdowns that plant operators can be ill equipped to counter because they’re not confronted with them frequently enough to hone their skills.
Automating procedural steps can counteract variations in operator skills and will become increasingly important as the current generation of experienced process control engineers retires. Defining common process procedures can also provide additional support for employees who are executing operations that can be more manual, as is typical in equipment and plant startups, shutdowns and transitions.
ISA-106 Defines Continuous Process Procedures
A new ISA committee is working to develop standard methods and terminology for automating continuous process procedures. “ISA-106, Procedural Automation for Continuous Process Operations”, will define repeatable procedural steps that can lower the chances of accidents due to human error. The intent of the new standard is to reduce process variability, reduce risk to facilities and increase operational productivity in continuous process industries.
The ISA-106 committee plans to issue a series of documents to help users standardize designs to handle operator errors in normal, critical, and abnormal situations.
As a first step, the ISA-106 committee, which includes representatives from the largest companies in the petrochemical industry, is working on its first technical report targeted at oil refineries, upstream offshore oil rigs and chemical plants. The report will give users common definitions to describe the requirements in improvements, upgrades, and changes in procedural automation to system integrators and automation suppliers.
The technical report will also include standards for modularizing procedural steps, exception handling for abnormal situations, state mode procedural logic, process unit orientation and current practices.
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