PLC installation preparation and installation inspection, commissioning, inspection

System Installation and Commissioning

Properly planning and organizing the installation and commissioning process is essential to ensure that the system is installed efficiently and operates reliably. The overall procedure, following field inspection and further adjustments, is illustrated in the figure below.

1. Early Technical Preparation

The more thorough the technical preparations before installation and commissioning, the smoother the entire process will be. Key tasks during this phase include:

(1) Reviewing all technical documentation, including random data and original specifications, to fully understand the system’s performance, functions, and operational requirements, and then developing standard operating procedures.

(2) Gaining a deep understanding of the design data and the overall system process, especially the control requirements for each piece of production equipment. Based on this, it's important to create detailed diagrams such as process flow charts, system connection diagrams, and operation logic diagrams. These visual tools are crucial for grasping the system’s logic and form an essential part of the preliminary preparation.

(3) Familiarizing with the performance, design, and installation details of each process equipment, particularly the control and power wiring diagrams. Comparing these with the actual equipment helps identify and correct any discrepancies early on.

(4) Based on the comprehensive understanding of the design scheme and PC technical data, compiling a list of input and output points, including internal coils, I/O locations, corresponding equipment, and their functions.

(5) Studying the program provided by the design team and drawing timing diagrams for complex logical inputs and outputs. This can help detect potential logic errors during the design phase.

(6) Developing a preliminary debugging plan and integrating it into a comprehensive system-wide debugging strategy through team discussions.

2. Equipment Inspection

A joint inspection between both parties should be conducted to confirm the type, quantity, and specifications of the equipment, spare parts, technical documents, and accessories. The performance should be verified through laboratory testing and on-site commissioning. Both parties should sign the inspection report and exchange list once confirmed.

3. Laboratory Commissioning

(1) Installing the PLC on a metal bracket and securing the input/output modules at each workstation. Connecting the stations to the host computer, programmer, and printer according to the installation summary, ensuring correct wiring. After confirming the power supply matches the PLC voltage, follow the startup procedure to power up the system, load the configuration tape, and run the program according to the operating instructions. Conduct various operational tests.

(2) Entering the work program.

(3) Simulating analog I/O input and output to check and refine the program. This step ensures the program aligns with the design process control requirements. If the logic does not match or the program fails to complete the process, it indicates an error that needs correction. During this phase, the program is continuously improved, and any inefficiencies or flaws are identified for optimization.

There are two main debugging methods: 1) Simulation method – using a dedicated board to simulate input nodes with toggle switches and relay contacts, mimicking real-world conditions. This method offers high accuracy but increases costs. 2) Forced method – using the PLC’s forced function to manually set certain nodes to “on” or “off,” allowing the program to run without additional hardware. While easier and cheaper, it may miss some logical issues.

Based on our field experience, we often use simulation for critical nodes and the forced method for others, combining the strengths of both approaches.

During the logic verification phase, it is essential to maintain a daily commissioning log. This should include details like the personnel involved, time, content of the test, modifications made, faults encountered, and how they were resolved. This helps establish a clear responsibility system and provides valuable records for future reference. Any changes to the original program should be noted on the design drawings, and the designer should be consulted promptly to ensure the final implementation meets the original design intent.

4. On-Site Installation and Inspection of PLC

Once the laboratory commissioning is complete, the equipment is moved to the site when conditions are suitable. The installation must meet all required standards, with all connectors securely fastened and bolts tightened. Communication cables should be of uniform model and not mixed. If necessary, use instruments to check signal attenuation, ensuring it stays within the limits specified in the technical data. Inspect the grounding resistance of the measuring host, I/O cabinet, connecting cables, and the system grounding. Check the power supply and document all findings. Only after all items meet the requirements should the system be powered on.