What is Open Process Automation?
Open Process Automation (OPA) is a vendor-neutral architecture for process control, defined in The Open Group’s O-PAS Standard, in which a control system is assembled from interchangeable hardware and software components from different suppliers that work together through open standards. Whereas a conventional DCS is a closed system from a single vendor, O-PAS specifies the interfaces between controllers, I/O, applications and system management. A plant can therefore replace or extend individual parts without migrating the entire system.
🎯 Why was Open Process Automation created?
Refineries and chemical plants often run on the same DCS for 20 to 40 years. Replacing it costs millions and nearly always means a full rip-and-replace: hardware, software, configuration and operator displays are all swapped at once, because they only work with each other. This dependence on one supplier, known as vendor lock-in, also makes it hard to add new technology such as edge computing, analytics or virtualisation.
ExxonMobil therefore looked for an open alternative and worked with Lockheed Martin on an early proof of concept. In 2016 ExxonMobil initiated the Open Process Automation Forum (OPAF) within The Open Group, the consortium that also maintains TOGAF and the UNIX specification. End users, suppliers, system integrators and research institutes collaborate there on a single standard; by 2021 the forum had more than 105 member organisations.
🕰️ Which versions of the O-PAS Standard exist?
| Version | Date | Main content |
|---|---|---|
| Technical Reference Model | June 2018 | Snapshot of the architectural direction |
| O-PAS 1.0 (preliminary) | January 2019 | Interoperability of components |
| O-PAS 1.0 (standard) | December 2019 | Final version 1.0 |
| O-PAS 2.0 (preliminary) | February 2020 | Configuration portability, information model |
| O-PAS 2.1 (preliminary) | May/June 2021 | Extended information model, basic configuration |
| O-PAS 2.1 (standard) | February 2023 | Final version, basis for product certification |
| O-PAS 3.0 | In development | Physical platform, application portability, orchestration |
O-PAS is described as a standard of standards: it invents very little itself, instead selecting existing standards and defining how they must work together.
🔧 How is the O-PAS architecture structured?
At the heart of O-PAS is the Distributed Control Node (DCN): a secure, managed device that exchanges process data over the network and runs control functions or connects field I/O. A DCN consists of two layers, supported by two further building blocks:
- Distributed Control Platform (DCP) — the hardware plus system software, such as a small industrial controller or an I/O module
- Distributed Control Framework (DCF) — the software environment on top of the DCP in which control applications run, offering the same interfaces on every DCN
- Advanced Computing Platform (ACP) — a more powerful server with scalable computing resources for tasks that do not fit on a small DCN, such as optimisation or historical data
- O-PAS Connectivity Framework (OCF) — the common communication layer between all components, based on OPC UA
The standard itself is divided into parts:
| Part | Subject | Underlying standard |
|---|---|---|
| Part 1 | Technical architecture (informative) | — |
| Part 2 | Security | IEC 62443 |
| Part 3 | Profiles, the basis for certification | — |
| Part 4 | Connectivity Framework (OCF) | IEC 62541 (OPC UA) |
| Part 5 | System management | DMTF Redfish |
| Part 6 | Information and exchange models | OPC UA, ISA-18.2/IEC 62682 (alarms), IEC 61131-3, IEC 61499 |
For the portability of control applications, O-PAS refers to IEC 61131-3 and IEC 61499. IEC 61499 is particularly relevant: it describes event-driven function blocks that can be distributed across several DCNs, so the same control logic can run on hardware from another vendor.
🔄 How does O-PAS differ from a traditional DCS?
| Characteristic | Traditional DCS | Open Process Automation |
|---|---|---|
| Suppliers | One vendor for the whole system | Components from multiple vendors |
| Communication | Proprietary, closed protocols | OPC UA via the OCF |
| Replacement | Full migration after 20–40 years | Component by component |
| Applications | Tied to one engineering tool | Portable via IEC 61131-3 / IEC 61499 |
| Security | Varies by vendor | IEC 62443-4-2 as a mandatory baseline |
| Integration | System vendor | End user or independent integrator |
The trade-off is equally clear: if you combine components from different suppliers, you must handle integration and lifecycle management yourself or outsource them to a system integrator. With a conventional DCS, a single party carries that responsibility.
🔐 How is security built into O-PAS?
O-PAS follows the principle of security by design: security is not an option but a conformance requirement. Part 2 builds on IEC 62443, and suppliers of O-PAS products must meet the component requirements of IEC 62443-4-2 at security level 2 (SL2). That level protects against intentional attacks using simple means and matches the security functions OPC UA provides, such as certificates, encryption and role-based access.
In August 2024 OPAF selected ISASecure as the exclusive provider for verifying the cybersecurity requirements of O-PAS. At system level, the zones and conduits model and network segmentation remain necessary, because an open architecture with many components increases the number of potential points of attack.
🏭 Where is Open Process Automation already in use?
In 2020 a prototype at ExxonMobil’s research centre in Clinton, New Jersey, became the first OPA system to control a hydrocarbon process at high pressure and temperature; over the same period ExxonMobil and Yokogawa worked together on a test bed. In January 2022 ExxonMobil selected Yokogawa as system integrator for the first field trial of an O-PAS system controlling an entire production facility: more than 2,000 I/O at the Resin Finishing Plant in Baton Rouge, Louisiana, which makes adhesive resins for products such as tapes and sealants. The system replaced both the existing DCS and the PLCs with a single integrated O-PAS 2.1 system. After the factory acceptance test in May 2024 it went live at the end of 2024.
BASF, Cargill, Dow, Equinor, Petronas, Saudi Aramco and Shell, among others, have also built test beds. The O-PAS Certification Program has existed since October 2024; the first certifiable profiles are the Connectivity Framework and the Global Discovery Server.
🧭 How does O-PAS relate to NOA and MTP?
O-PAS does not stand alone. In August 2018 NAMUR and The Open Group signed a memorandum of understanding to align three initiatives:
- NAMUR Open Architecture (NOA) — opens a second channel alongside the DCS to send field device data securely to monitoring and optimisation, without interfering with control
- Module Type Package (MTP) — describes modular process units so that an orchestration layer can control them as services
- O-PAS — makes the control system itself open and interchangeable
The first integrated MTP–O-PAS application was demonstrated at the NAMUR General Assembly in November 2023. In practice the three complement each other: MTP for modular plants, NOA for monitoring and O-PAS for core control. At field level, Ethernet-APL fits the same picture of open, Ethernet-based communication right down to the sensor.
Want to explore O-PAS? Start with a test bed alongside your existing installation, choose a well-defined process unit for a pilot, ask suppliers about certified O-PAS profiles, and agree upfront who is responsible for integration and maintenance.
❓ Frequently asked questions
What does O-PAS stand for?
O-PAS stands for Open Process Automation Standard. It is the standard of The Open Group’s Open Process Automation Forum that defines how components from different suppliers together form a process control system. The final version 2.1 of O-PAS was published in February 2023.
Does Open Process Automation replace the DCS?
Open Process Automation replaces the concept of a single closed DCS from one vendor, but not the function of process control. An O-PAS system does the same job as a DCS, only with interchangeable components. At ExxonMobil in Baton Rouge, such a system replaced the existing DCS and PLCs at the end of 2024.
What role does OPC UA play in O-PAS?
OPC UA is the foundation of the O-PAS Connectivity Framework (OCF), the communication layer between all components. O-PAS also uses OPC UA information models for configuration and alarms. As a result, controllers, I/O and applications from different suppliers can understand the same data.
Is O-PAS secure enough for critical process plants?
O-PAS requires components to meet IEC 62443-4-2 at security level 2, verified through ISASecure. Security is therefore a mandatory part of O-PAS conformance rather than an optional extra. At system level, the end user remains responsible for segmentation, access control and monitoring.
What is a Distributed Control Node?
A Distributed Control Node (DCN) is the basic building block of an O-PAS system: a secure, managed device that runs control functions or connects field I/O. A DCN consists of a hardware platform (DCP) with a software environment (DCF) for applications on top. Because every DCN exposes the same interfaces, DCNs from different suppliers are interchangeable.
Is Open Process Automation mature yet?
Open Process Automation has been in production at ExxonMobil since the end of 2024 and is being trialled in test beds by a series of major end users. Product certification started in October 2024, and version 3.0 of the standard is still in development. For new projects O-PAS is therefore a realistic option, but the range of certified products is still growing.
📌 In summary
Open Process Automation makes process control vendor-neutral: O-PAS uses OPC UA, IEC 62443 and IEC 61499 to define how components from different suppliers together form one control system. Plants can thus renew their control systems step by step, instead of carrying out a full DCS migration every 20 to 40 years.