The definition of procedural automation is the “implementation of a specification of a sequence of tasks with a defined beginning and end that’s intended to accomplish a specific objective on a programmable mechanical, electric or electronic system.” By itself, this doesn’t say much, and you could argue it’s what any control program or application is meant to accomplish. However, the key words are “beginning and end.”
From an operational perspective, a procedure is one or more “implementation modules,” each consisting of a set of ordered tasks to provide plant operations with step-by-step instructions for accomplishing (implementing) and verifying the actionsto be performed.
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Looking at procedural automation as a logical sequence of steps makes it a natural fit for normal but infrequent operations. This includes startup, shutdown, product change, alarm response, abnormal situation response, complex or repetitive operations, equipment isolation and return to service, and regulatory requirement support.
Two automation styles are recommended and used to determine each transition for procedural automation:
- State-based control: a state of a module, such as block valve open/close, PID manual/auto/cascade, and pump run/stop.
- Sequence-based control: a set of actions in which the behavior of a procedure implementation module follows a set of rules with respect to its inputs and outputs.
"Looking at procedural automation as a logical sequence of steps makes it a natural fit for normal but infrequent operations."
There are also three degrees of automation and means of performing each task:
- Manual—the operator is responsible for command, perform and verify work items.
- Semi-automated—implementation modules are considered semi-automated, with operators and computers sharing coordinated responsibility for command, perform and verify work items.
- Fully automated—implementation modules are considered fully automated when the computer is responsible for the bulk of the command.
Implementing and maintaining procedural automation also comes with a cost, so there must be a corresponding benefit. A representative list of benefits arising from procedural automation includes:
- Improved safety performance—automating procedures and utilizing state awareness for alarm management reduces the workload on the operations staff during abnormal conditions, which reduces the probability of human error.
- Improved reliability—automated procedures can aid in maintaining maximum production rates, minimizing recovery time and avoiding shutdowns.
- Reduced losses from operator errors—automating procedures enable operations staffs to standardize operating procedures. A standardized approach reduces the likelihood of human error contributing to abnormal conditions, and reduces the time required to recover from abnormal conditions.
- Increased production by improving startups and shutdowns—operations benefit by achieving faster, safer and more consistent startup and shutdown of processes.
- Increased production and quality via efficient transitions—process transitions from one condition to another during normal operations, accomplishing transitions with reduced variability and in less time.
- Improved operator effectiveness—reduces the time an operator spends carrying out repetitive tasks.
- Higher retention and improved dissemination of knowledge—automated procedures can be used to retain the knowledge of the process.
- Improved Training—as knowledge and best practices are captured into automated procedures.
