Setting up a process plant is a complex task and delays are inevitable. This means that commissioning activities always end up being on the critical path. With massive investments already made and product delivery contracts in place, end users are hardly amused if a particular sub-system develops a snag during commissioning – potentially delaying the start-up of the entire plant. Pressure keeps building as dates for integrated cold trials are missed quite a few times and start-up seems like a distant possibility.
So, we cannot over emphasize the importance of a comprehensive Factory Acceptance Test (FAT) which involves days of continuous internal trials and culminates in thorough examination by customer representatives and third party inspectors. This helps to identify any functional defects in the factory itself and saves precious commissioning downtime. All identified punch points can now be resolved by involving all concerned departments.
The following are just some of the things to look out for during the FAT of a process package
This might seem like a waste of time. Despite all in process checks, gauges, transmitters and valves do get interchanged during installation! After commissioning, we may need to pull out the calibration and test certificates for these components. Wrong tag numbers can cause hindrances while transferring data from control systems (plant) to databases (enterprise). Tag numbers will prove important identifiers for IoT and physical verification is essential.
From field instruments, analysers, actuated vales to junction boxes and finally to the control panel, each and every cable has to be checked for continuity as per the approved cable schedule. Ferrule marking is checked along with QC verification of termination, crimping and gland filling work.
Panel power-up and control logic verification
This step is beneficial for smaller packages which are controlled by a dedicated PLC system. While the control logic has been checked, approved and programmed into the system, some minor changes may be needed till the date of start-up. So the control logic must be checked during FAT and the system run in auto sequence to ensure that things are moving as planned.
Transmitters power-up and simulation
We need to ensure that all transmitters are working fine. This means checking the various types – pressure, differential pressure, temperature, flow and level. Simulation using specialized devices and hand held HART calibrators should be carried out.
Actuated on-off and control valve functional testing
This is one of the most important steps in the FAT. Actuated valves have already been functionally tested at sub-vendor works. However its very important to operate these valves using the package PLC and check that position feedbacks are being received. Partial stroking should be checked if applicable. Basic setting of PID values can be done in the factory and finetuning left for site.
Any component or skid specific tests and certifications
These are project or skid specific checks which the end user or PMC consultant can specify so as to ensure smooth installation, commissioning and statutory clearance. Typical examples would be UL certification for NFPA 496 Z purge panels, reduced tolerances for transfer points, simulated load testing for thyristor control panels.
Aesthetics and other expectations of the end user
This rather nebulous point sometimes makes a real difference to smooth commissioning. No matter in which continent the plant is being set-up, shift operators, maintenance and other site personnel have a set of expectations that are generally not fully covered in construction codes and tender specifications. Customer’s engineering team does try and convey their inputs but many a times the packages are already built by the time they are articulated. Some amount of convincing is necessary in the factory so as to get their full endorsement at site. (In fact its best if plant operators are part of the 3D model review process)
Some points to ponder on.
- It is always easier to rectify something in the factory instead of at site.
- FAT does not ensure that no glitches will happen during commissioning. It does significantly lower the chances though.
- Commissioning team has less burn-out when packages are thoroughly factory tested.