Executing a control systems lifecycle, from concept to delivery, is primarily the responsibility of the system vendor. While a significant portion of the lifecycle activity is opaque to the eventual owner, every lifecycle has numerous checkpoint milestones where the owner can either state requirements or verify that the delivered system will meet stated requirements. Control system factory acceptance test (FAT) is one of the earliest of these milestones.
In many cases a substantial financial payment to the vendor is triggered by a successful FAT, therefore the FAT must be well planned, formally conducted, and be witnessed by the owner. A record of the result of all acceptance tests including a plan to handle all discrepancies and non-conformities is the desired result.
All too often, common misconceptions about the definition and purpose of FAT, coupled with poor planning and execution, lead to the delivery of control systems that simply do not work as required and need expensive on site re-work, revision and repair.
The International Electrotechnical Commission (IEC) provides a very simple yet powerful definition of the FAT in IEC 62381:
2.3 factory acceptance test
Activity to demonstrate that the vendor system and additionally supplied systems are in accordance with the specification
The purpose of the FAT is to identify manufacturing defects. Manufacturing defects are those that are introduced in manufacturing, which result in a deviation from stated requirements. FAT is not the time to discover missed or misunderstood requirements, correct poor design, or identify problems with the operational procedures for the control system. By definition, all of these tasks should have completed before a FAT is scheduled.
Other common misconceptions about control systems FAT include:
- The FAT is a chance for the vendor to demonstrate how the control system works – FAT is a test, not a demonstration. The owner should have already specified how the system should work through stated and verified requirements. The FAT is the proof of conformance to those already stated and agreed to requirements. Proof of conformance is established by executing a test plan with specific operational and performance criteria.
- FAT is an incoming inspection test – FAT is not an incoming quality inspection for the owner. It’s a witnessed outgoing quality test for the vendor. The vendor is responsible to prove to the owner that the system is ready to leave the factory and be delivered to the owner.
- FAT is a quick trip to the factory – Preparation and planning is critical to a successful FAT. Prior to starting FAT, the test plans should be reviewed and verified to ensure that they cover all requirements and that the test criteria and expected results are understood. In many cases, the FAT could require several trips to different factories over several months. This is particularly true of FAT processes that include HIL testing.
- Controls system FAT verifies my control system will work – In most cases, the physical equipment is not available when the control system FAT is executed. Without the equipment, the FAT can only verify the construction of the control system hardware (cabinet construction and wiring) and the integrity of the signal paths (I/O and network). In order to verify he ability of the control system to control the equipment you need to either connect it to the actual equipment, or use equipment simulation (HIL testing)
In order to ensure a successful FAT that provides sufficient proof of system performance to owner requirements, Athens Group recommends a 5-step control system FAT process, based on our Proven Practice℠ methodologies. The first 4 steps provide verification of the control system hardware and associated signal I/O and communications paths. The 5th step, HIL testing, provides verification of the control system’s ability to control the equipment.
The 5-step control system FAT process is detailed below.
(1) Control Cabinet Mechanical Completion FAT
Verify the construction of the individual cabinet to the drawings through visual inspection and electrical check of the power supplies and ground paths.
- Verify overall mechanical condition of the cabinet is sound. All frames, bolts, doors, vents etc. are securely attached; all cables and wires are secure and strain relieved
- Verify all components are correct, and installed and labeled as per the layout and system topology drawings
- Record serial numbers for all installed modules
- Verify all cabling and wiring is installed as per the termination and internal wiring drawings
- Verify power supplies are installed and configured to the correct voltage
- Verify grounds are earthed correctly and no ground loops exist
(2) Control Cabinet I/O Signal FAT
Verify PLC I/O signal and path integrity using signal generators/detectors (analog, digital, pulse).
- Verify cable and wire installation, connections and terminations were accepted in the Control Cabinet Mechanical Completion FAT and all critical punch list items are cleared before beginning the I/O Signal FAT
- Verify hardwired digital, analog, and pulse I/O lines function correctly
- Input signals reach the correct PLC input address
- PLC output address causes the correct output signal
- Record all PLC module firmware and O/S revision
(3) HMI/Software Functionality FAT
Verify the HMI and calculation and messaging functions of server based software applications using the actual HMI platform, message simulators and signal generators/detectors (analog, digital, pulse, and profibus message).
- Verify cable and wire installation, connections and terminations were accepted in the relevant Control Cabinet Mechanical Completion FAT and all critical punch list items are cleared before beginning the HMI/Software Functionality FAT
- Verify HMI I/O functionality
- Inputs generate appropriate network message
- Network message/responses generate correct HMI display
- Verify application calculation functions
- Verify application interlock functions
- Record all application revision numbers
(4) PLC Network Signal FAT
Verify communication between the operator chairs and associated equipment PLCs.
- Verify the relevant Control Cabinet Mechanical Completion, Control Cabinet Signal I/O, and HMI/Software Functionality FATs were completed, and all critical punch list items are cleared before beginning the PLC Network Signal FAT
- Verify revision numbers and serial numbers have not changed from prior FATs
- Verify the integrated operation of the operator chair HMI to equipment PLC system
- Operator chair HMI inputs generate appropriate response in the equipment PLC
- Equipment PLC activity generates the correct response on the operator chair HMI
- Equipment PLC alarms are generated and reported correctly
(5) HIL testing
- Verify all control system actuator signals and feedback sensors behave as specified
- Verify the control system safely handles all common signal and sensor fault modes
- Verify all owner specified operational procedures can be executed through the control system
In summary, the first 4 steps of a properly executed FAT process provide a verification of the control system construction from the operator HMI to the control cabinet termination. Executing the 5th step (an HIL test) adds verification of the control system operation of the equipment. Taken together this 5-step process provides a comprehensive FAT that demonstrates the overall system meets customer requirements and is ready to accept for delivery and installation.
Please contact us for information about Athens Group Services Proven Practices℠ for factory acceptance testing.