1. Scope

This standard on Procedure Automation for Continuous Process Operations provides the framework for automating operational procedures in continuous manufacturing environments (like chemical plants, refineries, and power generation facilities). It defines the key building blocks including models, implementation styles, control strategies, design philosophies, and the complete lifecycle approach needed to successfully automate procedures in these industries.

Definition: Procedure automation refers to the systematic conversion of manual operating procedures into automated control sequences that can be executed by distributed control systems (DCS) or programmable logic controllers (PLCs).

The standard includes comprehensive terminology that clarifies how these different elements work together and relate to each other in practice. This terminology section is particularly valuable for understanding the connections between automation strategy decisions and their implementation.

Industrial Example: In a chemical plant, this standard would guide the automation of startup sequences, product transitions, and shutdown procedures that operators currently perform manually using written procedures.

Procedures for continuous process operations cover several key operational scenarios: start-up, shutdown, abnormal situations, hold steps, and transitions involving process feed or output changes. These procedures often already exist as manual documentation (typically written step-by-step instructions) before any automation implementation begins.

Definition: Hold steps are programmed pauses in automated sequences that wait for operator confirmation or specific process conditions before continuing.

The primary objectives of automating these procedures are to: - Increase uniformity and consistency across all procedure executions (eliminating operator-to-operator variations) - Reduce operational risks associated with human error during critical process transitions - Lower long-term costs through improved efficiency and reduced incidents - Minimize programming and implementation errors when converting manual procedures to automated control logic

Note: When transitioning from manual to automated procedures, it’s essential to validate that the automated logic accurately reflects the proven manual steps while incorporating appropriate safety interlocks and exception handling.

This standard covers automated procedures that run primarily on control systems at the field and supervisory levels of a manufacturing process. These systems correspond to ISA-95 functional levels 1 and 2, which include basic control (level 1 - field devices like sensors, actuators, and PLCs) and supervisory control (level 2 - SCADA systems, HMIs, and process controllers), while the actual production equipment operates at level 0.

Note: ISA-95 is the international standard that defines the hierarchical structure of manufacturing systems, from field devices up to business planning systems.

This standard does not cover procedure execution at the operations management level (ISA-95 level 3), which handles production scheduling, quality management, and inventory tracking functions typically performed by MES (Manufacturing Execution Systems).

While this standard considers how automated procedures interact with manual procedures, it does not define the manual procedures themselves. Manual procedures refer to any operations where an operator directly uses control system interfaces, such as HMI screens or control panels, to manually start equipment, adjust setpoints, or override automatic functions.

Industrial Example: An automated startup sequence for a distillation column would fall under this standard, but the MES scheduling when to run that sequence would not.

This standard applies to continuous processes (operations that run steadily without interruption, like oil refining or chemical production). The automation of procedures for Batch Process Operations (manufacturing that processes materials in discrete quantities or “batches,” such as pharmaceutical production or food processing) is outside the scope of this standard.

Note: While both process types use similar control principles, batch operations require different automation approaches due to their sequential, recipe-based nature compared to the steady-state control typically used in continuous processes.

This standard applies to automated procedures that operate within control systems at Levels 0, 1, and 2 of the ANSI/ISA-95 automation hierarchy. This includes Basic Process Control Systems (BPCS), but specifically excludes any systems that perform Safety Instrumented Functions (SIF) with a claimed Safety Integrity Level (SIL) of 1 or higher.

Definition: ANSI/ISA-95 levels refer to the manufacturing control hierarchy - Level 0 covers field devices like sensors and actuators, Level 1 includes controllers like PLCs and DCS, and Level 2 encompasses supervisory control and HMI systems.

Note: Safety Instrumented Systems (SIS) with SIL ratings are intentionally excluded because they require separate, more stringent standards due to their critical safety functions.

This standard also applies to the interfaces of such procedures with a Safety Instrumented System (SIS - the independent protection system that brings your process to a safe state when dangerous conditions occur). However, automated procedures which are implemented within a Safety Instrumented System (SIS) itself are outside of the scope of this standard.

Note: Think of it this way - this standard covers how your basic process control system communicates with the SIS, but not the internal logic and procedures that the SIS uses to make its safety decisions.

This standard separates its mandatory requirements from informational content by marking each requirement with a “Requirement” heading. Every mandatory clause specifies which party (such as the system integrator, end user, or equipment manufacturer) must implement that particular requirement. You can find the complete list of these responsible parties and their definitions in Table 10 – Description of Roles.

Note: Normative clauses contain binding requirements that must be followed for compliance, while informative clauses provide helpful guidance or background information that supports understanding but isn’t mandatory.

Two automation styles are defined in the Automation Style chapter of this standard: State-Based Control (SBC) and Sequence-Based Control (SqBC). These styles share many similarities but each offers distinct documented advantages. The choice between these styles depends on your company’s procedure automation philosophy and the capabilities of your selected DCS (Distributed Control System - the main control platform managing your plant operations).

State-Based Control automation style should be used when only one step can be active at any given time within a single control module, and your selected process automation design covers the complete operational cycle from start-up through normal operation to shutdown and back to start-up again.

Key Advantage: This style allows operators to run the entire selected process in automatic mode with minimal manual intervention.

Sequence-Based Control represents a direct translation of command sets that sequentially change device states following your Standard Operating Procedures (SOPs).

Note: This approach essentially converts your written procedures into automated control logic, executing each step in the predetermined order outlined in your SOPs.