- By Michael B. Fedenyszen, II
- The Final Say
By Michael B. Fedenyszen, II
The investment in a solid factory acceptance test (FAT) pays big dividends and makes a large contribution to a successful project. Rushing to startup, taking shortcuts, or bypassing the FAT typically means many engineering mistakes and problems that will need to be fixed later in the field\, where it is significantly more expensive and time consuming.
The plant control system (PCS) usually includes distributed control systems consisting of complex control panels housing programmable logic controllers (PLCs), remote terminal units, and various other control technologies that operate and control the purposed processes.
Today's startup and commissioning environment requires many operations personnel, trades contractors, technicians, and engineers to be on hand during this scheduled event. System component manufacturers will also be onsite tweaking and proving their equipment, balancing systems, and adjusting loops. When troubleshooting becomes necessary, it is easy to see how the cost of labor can add up when workers are standing ready while the pertinent troubleshooting players sort out the system quirks.
Specifications traditionally call for witness testing and review of the PCS at the manufacturer's facility before it is shipped to the site. A hardware factory acceptance test (HFAT) and a software factory acceptance test (SFAT) are required tests in order to confirm that the hardware selection and its installation and wiring are in conformance with specifications, and that the software, code, and inputs and outputs operate as required.
Items to look for during the HFAT are specific. The control panels and panel hardware are visually inspected, and observations are documented to be complete, clean, and ready for shipment to the site. All ground bonding is checked, and circuits are checked to be isolated from short circuit. Should UL 508A have been specified, fusing amperage and terminal torque requirements must be identified inside the panel enclosure; components must be UL and FM approved; and the UL 508A certification must be adhered within the enclosure. Wiring in general will be reviewed to conform to industry standards and best practices.
The SFAT will include all reference documents, drawings, and process and instrument diagrams and follow a predetermined test procedure defining the acceptance criteria, detailed instructions, and expected results. The procedure is generated by the system integrator and approved by the engineer before the FAT.
With the system powered up, primary and redundant power supplies, as well as primary and redundant PLCs, will be verified for failover operation. All digital inputs and outputs will be tested with temporary switches or jumpers for their operation. If human-machine interfaces (HMIs) are configured into the system, input and outputs could be checked from the HMI touchscreen. Analog inputs will be confirmed using a current simulator signaling 4 mA, 12 mA, and 20 mA while witnessing the corresponding value in the code representative of 0, 50, and 100 percent of the control value. Analog outputs would be read with a current meter while manipulating a 0, 50, and 100 percent process signal in the code.
FAT results, incidents, or abnormal findings are recorded in a document approval record, and at the conclusion of the test, signed by both the systems integrator and the owner's representative. All incidents would then be attended to before the control system is released for shipment to the site. Once concluded, the HFAT and SFAT will be most worthwhile, preventing any delay in system startup and commissioning as a result of the PCS integration.
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