Who Is Responsible for System Integration Testing in Complex Automation Projects?

Hello everyone,
My name is NIKOLAI RIABOV. I am a Lead Engineer at a Russian engineering company with more than 17 years of experience in Industrial Automation and Process Control Systems for oil industry facilities.
My professional experience is related to automation of oil pipeline transportation systems, including pumping stations and other process facilities where integration of field devices, electrical equipment, control systems, and supervisory systems is required.
My main area of work is system integration, verification, diagnostics, testing, and commissioning of integrated industrial automation systems.
My work is not focused on developing PLC program code. My main specialization is verification, diagnostics, and commissioning of already integrated automation systems.
I verify that all system components — field devices, electrical equipment, controllers, communication systems, and control software functions — correctly interact with each other as a complete solution.
During my projects, I work with different levels of industrial automation systems, including:

• field instrumentation and actuators;
• electrical control panels;
• I/O systems;
• PLC-based control systems;
• industrial communication networks;
• SCADA/HMI systems.

My typical activities include:

• Factory Acceptance Testing (FAT);
• Site Acceptance Testing (SAT);
• commissioning and startup support;
• verification of signals from field level to control systems;
• checking analog and digital signals;
• testing control algorithms, interlocks, and protection functions;
• troubleshooting technical issues during integration and commissioning;
• root cause analysis;
• verification of corrective actions after identified issues are resolved.

In complex industrial automation projects, many problems cannot be assigned to only one component or one engineering discipline. They often occur at the interfaces between different parts of the system.
For example, a problem with information display or control function operation may be related to:

• field equipment;
• electrical connections;
• I/O module configuration;
• communication between devices;
• controller configuration;
• SCADA/HMI;
• engineering documentation.

Therefore, troubleshooting requires analysis of the complete interaction chain — from field devices to control systems and operator interfaces.
I would like to ask engineers working in industrial automation, system integration, and commissioning:

1. How is this type of engineering activity usually defined in your companies?
2. Do your organizations have a separate engineering function responsible for system integration testing, verification, and diagnostics of complex automation systems?
3. What job titles are commonly used for specialists performing these activities?
4. How important is experience in system integration, diagnostics, and commissioning for modern industrial automation projects?
5. Who usually performs these tasks in your companies: Controls Engineers, Commissioning Engineers, System Engineers, or specialists from other areas?

I am interested in understanding how this type of engineering function is defined and organized in different industrial organizations, especially in companies working with complex automation systems and critical process facilities.
I would appreciate professional opinions and comments from engineers working with industrial automation, process control, system integration, and commissioning.
Thank you.