ISA-5 Series of Standards: Documentation of Measurement and Control Instruments and Systems
What Is ISA-5?
Developed by the International Society of Automation (ISA), the ISA-5 series of standards are essential for industries that rely on complex instrumentation and control systems, including chemical processing, oil and gas, power generation and manufacturing. By establishing uniform guidelines for documentation, design and communication, the standards promote consistency, safety and efficiency across systems worldwide.
These ISA-5 standards not only simplify the communication of complex information among engineers, operators and technicians but also enhance system performance, minimize risks and support the integration of advanced automation technologies. Whether you're designing, implementing or maintaining control systems, the ISA-5 series provides the framework to ensure clear, consistent and effective documentation for streamlined operations. Explore how the ISA-5 series of standards can help optimize your automation systems and drive efficiency across your organization.
Comprehensive List of ISA-5 Standards and Technical Reports
ANSI/ISA-5.1-2024, Instrumentation and Control – Symbols and Identification
ANSI/ISA-5.1, also known as ISA-5.1, is the oldest and most widely used standard published by ISA. ANSI/ISA-5.1-2024, Instrumentation and Control – Symbols and Identification, provides a standardized system for depicting and identifying instruments, devices and their functions within instrumentation and control systems. The goal is to ensure these elements are represented uniformly and clearly. This standard establishes consistent symbols and identification methods — facilitating better communication and understanding among professionals involved in the design, installation, operations and maintenance of instrumentation and control systems.
Originally published in 1949, ISA-5.1 continues to play an essential role for automation professionals in the global process industries. It helps improve the accuracy and efficiency of documentation and communication across a wide range of industries that rely on instrumentation and control systems. The most recent version, ANSI/ISA-5.1-2024, includes an update to the title to emphasize that symbols for control are included as well as improvements to readability. The ISA5 standards committee — the body that updated the standard — also added new symbols, recognized new automation technology, added new reference sections and added a loop instrument diagrams symbol table.
Add PDF to CartISA-TR5.1.02-2024, Instrumentation and Control – Identification System Guidelines
This technical report was created as a supplement to ISA-5.1. It offers additional guidance, rationale and examples in general terms for those identifying and implementing instrumentation and control equipment and its functions.
Add PDF to CartISA-TR5.1.03-2024, Instrumentation and Control – Graphic Symbol Guidelines
This technical report provides more guidance in general terms on how to apply the symbols for instrumentation and control equipment drawings and systems found in ISA-5.1.
ISA-5.4-1991, Instrument Loop Diagrams
ISA-5.4-1991 establishes guidelines for creating and using instrument loop diagrams through the various stages of instrumentation systems, from design and construction to startup, operation, maintenance and modification.
Instrument loop diagrams serve multiple purposes, including the depiction of control philosophy, instrument hardware specification, aid in construction and installation and the facilitation of troubleshooting and maintenance. This standard outlines the minimum content requirements for loop diagrams, including identification of loop components, interconnections, energy sources and control actions. ISA-5.4 emphasizes consistency in format and the use of standardized symbols as found in ISA-5.1.
ISA-5.4 aims to help users in the process industries — including chemical, petroleum and power generation — understand and improve communication through instrument loop diagrams. These diagrams consolidate information that would otherwise be spread across multiple documents, helping to reduce engineering costs, improve loop integrity and facilitate maintenance troubleshooting.
Add PDF to CartISA-5.5-1985, Graphic Symbols for Process Displays
The purpose of the ISA-5.5 standard is to establish a system of graphic symbols for process displays that plant operators, engineers and other professionals use for process monitoring and control. The system established in this standard facilitates quick understanding of the information conveyed through displays and helps to create uniformity of practice throughout the process industries.
For guidance related to human-machine interfaces (HMIs) of process automation systems, refer to ANSI/ISA-101.01 and its technical reports.
Add PDF to CartISA-5.06.01-2007, Functional Requirements Documentation for Control Software Applications
This standard defines functional requirements specifications for control software documentation in real-time batch, discrete and continuous process automation systems. It covers the classes of industrial automation equipment and systems consisting of distributed control systems, programmable controllers and industrial personal computers — encompassing both digital and analog control devices in addition to non-control actions (for example, operator messages and batch end reports).
ISA-5.06.01-2007, Functional Requirements Documentation for Control Software Applications, is intended to provide techniques for documenting control system software, using a set of terms that relate directly to the languages commonly used by plant operators. This standard also offers a basis for validation of run-time application software after it is developed and tested to ensure that the initial requirement specification has been met.
Add PDF to CartISA-TR5.1.01/ISA-TR77.40.01-2012 (R2016), Functional Diagram Usage
This technical report expands upon — and illustrates — usage of function block symbols and functions and prepares examples in development of complex function block symbols and functions. The goal is to provide advice and guidance in documenting application software through functional diagrams.
Add PDF to CartISA-TR5.9-2023, Proportional-Integral-Derivative (PID) Algorithms and Performance
This technical report documents common proportional-integral-derivative (PID) algorithms used in industrial control systems, including the various algorithms’ implementation methods, options and performance measurements.
Even though PID controllers have been used for more than a century, a standard describing fundamentals, terminology, best practices and special functions does not exist. This document is intended to lay the foundation for such a standard.
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Add PDF to CartThe Crucial Role of ISA-5 Standards in Instrumentation and Control Systems
Standardization and Consistency
ISA-5 standards provide a uniform framework for documenting and representing instrumentation and control systems. This consistency is essential for ensuring that different professionals—engineers, designers and operators—can understand and interpret diagrams, symbols and system details in the same way, regardless of location or organization. Consistency in documentation helps reduce misunderstandings and errors in complex systems.
Improved Communication
Clear communication is vital for safety and operational efficiency in industries like chemical processing, oil and gas, power generation and manufacturing. ISA-5 standards use standardized symbols and identifiers, making it easier for professionals from different disciplines to collaborate. They also bridge the gap between engineers, technicians and operators by offering a common language for instrumentation and control systems.
Efficiency in Design, Implementation and Maintenance
By following ISA-5 guidelines, teams can streamline the design, installation and ongoing maintenance of control systems. The clarity provided by these standards helps ensure that engineers design systems that are easy to implement, operate and troubleshoot. Maintenance teams also benefit, as they can quickly understand existing systems, leading to faster repairs and upgrades.
Safety and Risk Reduction
Clear and consistent documentation of control systems, especially in critical industries, is necessary to minimize risks and enhance safety. ISA-5 standards ensure that vital components, such as safety systems, alarms and control loops, are properly represented and easy to interpret. This can reduce the likelihood of human error and improve overall safety.
Regulatory Compliance
Many industries, particularly those dealing with hazardous materials or sensitive operations, require strict adherence to standards. ISA-5 standards often align with regulatory requirements, helping organizations comply with industry regulations while maintaining best practices for design and documentation. Compliance with these standards can be a critical factor during inspections or audits.
Support for Automation Technologies
As industries increasingly adopt advanced automation technologies, the ISA-5 series of standards provide the foundational guidelines needed to support these systems. They help ensure that modern automation systems, such as programmable logic controllers (PLCs) and distributed control systems (DCS), are well-documented, correctly configured and easily understandable.
Interoperability
In many cases, control systems and instrumentation come from multiple vendors or evolve over time. The ISA-5 standards promote interoperability by ensuring that different systems and components, regardless of manufacturer, are documented using a common framework. This is crucial in maintaining system flexibility, reducing integration challenges and supporting future upgrades or expansions.
Long-Term System Sustainability
The use of the ISA-5 standards contributes to the longevity and sustainability of instrumentation and control systems. Well-documented systems are easier to maintain, update and expand. The standards make it possible to track system performance over time, leading to better decision-making for system enhancements, replacements or expansions.
Global Adoption
The ISA-5 series of standards are widely accepted and used internationally, across industries. Professionals working in different parts of the world can use the same standards, simplifying collaboration on international projects, reducing errors and ensuring that systems meet global expectations for performance and safety.
Beyond ISA-5: A Note on the ISA-20 Standard
Parallel to the ISA-5 standard series, automation professionals looking for guidance around instrumentation symbols and documentation may also choose to seek out the ISA-20 standard. ISA-20 provides standardized specification forms for instruments, primary elements and control valves. ISA-TR20.00.01-2007 includes the original forms developed in 1981 in addition to dozens of other specification forms developed over the years. These forms are intended to aid in the design, purchase and manufacture of process measurement and control instrumentation.
ISA5 Committee
The ISA5 committee oversees the work of the working groups that produce standards, recommended practices, and technical reports for documenting and illustrating measurement and control instruments and systems suitable for all industries. The committee aims to establish the means for documenting and illustrating the uses and functions of measurement and control instruments and systems. Membership is open to those interested in instrumentation and control. You can view a list of standards committee members here. Interested in joining the ISA5 standards committee? Apply Now!
Specific Questions on ISA-5?
We welcome dialog on the ISA-5 series of standards. For more information, please contact us at standards@isa.org.