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The importance of PLC system in the field of industrial automation is self-evident, so do you know that there is a very important test before the PLC system is put into use? That's right, it's the PLC's SAT test. As a key part of system testing, debugging and acceptance, PLC SAT testing plays a vital role in ensuring system stability and reliability.
In this article, we will discuss how to perform a PLC System Site Acceptance Test (SAT). The site acceptance test of the PLC system is carried out on site after the PLC system is received by the factory.
The SAT of the PLC system includes a visual inspection of all components according to the BOM (Bill of Materials). Then booting up the system and checking all the features is the next step. There's more to deal with. Let us discuss this PLC system SAT program in detail.
Preparation before the SAT test
Before starting the SAT, some important documents are needed to do the SAT of the PLC system. These documents include the PLC's BOM, the PLC system's architecture, panel wiring diagrams, panel interconnection diagrams, power distribution diagrams, load distribution details, and input and output wiring.
The BOM is one of the most important files that contains the details of all the components or cards that are used for that particular system. Here we are talking about a PLC system, and the BOM of a PLC system will include a detailed package of power supply, MCB, analog input card, analog output card, digital input card, digital output card, and other special cards (if present). The BOM contains details such as the make and model or part number of the component, the number of components used, and the rating of the component such as the power supply, MCB, etc.
As mentioned earlier, the SAT is done at the installation location itself. The SAT is somewhat similar to the Factory Acceptance Test (FAT). In the SAT, the PLC system is tested under real process conditions and its performance is documented. The entire PLC system SAT is done in the presence of the manufacturer.
SAT pre-test checks
The first step is to physically check the presence of all components against the BOM. The main reason for doing this visual inspection is to make sure everything is in order. The reason for the inspection was that the PLC system had been transported from the manufacturer's place to the site. During shipping, damage may have occurred. Therefore, we need to visually check the condition of all components of the system.
Check the installation conditions, manufacturing, and condition of the panels.
Before starting the system, the MCB needs to be thoroughly checked against the rating of the design. Also check all wiring of the power supply.
Another thing to verify before powering on the panel is a grounding check. Make sure the system is properly grounded.
Now check the input voltage on the terminal board with a multimeter. Then check that the voltage between the ground and the neutral should be below 05 volts or as per manufacturer's guidelines. If you find that everything is fine, open the MCB one by one in the panel.
PLC power-on check
Now check the output voltage of the MCB and the input voltage of the power supply. Both should be the same. Again, check all contact points to confirm that the wiring is correct.
Also, check the condition of all modules. Usually, there will be a green LED on the module that will be used to show their health status. All modules should be healthy.
Check all inputs and outputs. In order to verify this, initiate the digital input and check that it is reflected on the card. Similarly, turn on the digital output and check that the output on the terminal block is on.
We also need to check the analog input and analog output. We usually check analog circuits from 4mA to 20mA. Use the program to generate any output and verify the same MA on the terminal block of the analog output. Again, check the analog inputs. Use the MA generator to feed the MA to the terminal block and check the same current at the address of that card.
Check that the correct alert is being generated with the correct label. Also, check the trend of the simulated values.
This is the system check in the SAT program of the PLC. If any deviations are found in the above procedures, the manufacturer will have to deal with the problem. After it is all cleared, the plant can begin.
SAT test confirmation
After the factory start-up, the production department and the QA QC department verify the quality of the products. This is done to ensure that the performance is qualified. After passing the above tests, the relevant department or quality department will decide whether to allow the PLC system to operate. That's all there is to for the Site Acceptance Test (SAT) of the PLC system.
Through an in-depth analysis of the SAT test of PLC, we not only have a clearer understanding of the testing process of industrial automation systems, but also better grasp the matters and skills that need to be paid attention to during testing. I hope today's introduction can bring you new inspiration and thinking!
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