Testing Throughout an Automation Integration Project is Key to Success
For any size automation integration project, testing is vital to a success. Planning for testing in the design phase and developing your code to allow for proper testing will lead to well-executed factory and site acceptance tests, as well as successful startups. This article will focus on testing throughout new or upgraded programmable logic controller (PLC) and human machine interface (HMI).
Design phase lays the groundwork
The design specification will specify what devices will be tested and how the process will be tested. Even with experience in the industry, communication with the client early in the project is essential for a proper plan. While writing your design specification, including details on how processes are supposed to work will assist you when writing the test specification later in the project. If the thought process for testing begins early in the automation integration project, the transition to the test specification and code development should be easy.
Testing During Development
Development of code will begin after the design specification is complete and approved by the client. Testing during this phase is aided by your simulation logic. How each device is simulated is where you can get creative. The more you can simulate and integrate the process into the simulation, the better.
You usually add the simulation logic after you complete most code development and download the PLC. Start with basic devices like valves, motors and switches. Write simulation code for each, then verify the simulation works correctly. Once proven, you can add the same simulation for the rest of these common devices. Adding the process simulation at the end will ensure that all the valves and motors that trigger the process value changes work. This is where the creativity is; making sure that everything flows properly is essential.
For example, if you are adding a material into a container, and if a conveyor slows down, a valve closes, or pump stops you want your simulation logic to reflect that. When filling a tank, if the control valve allowing product into the tank closes a certain percentage, your simulation logic should slow the filling rate based on the control valve percent change. If the process is transferring 50 pounds of raw materials from one vessel to another, your simulation logic should subtract 50 pounds from the source tank and add 50 pounds to the destination tank. This type of detailed simulation code will aid greatly in commissioning of the real world process.
Simulations help in integrating PLC and HMI
Integration testing between PLC and HMI will begin parallel with the simulation logic development. This will help ensure that you programmed HMI correctly and all devices work as designed. When the PLC and HMI have been tested, the integration of batch software, historians, and other third-party software typically begins.
Testing to prove the design specification is accurate will begin once the simulation code is entered. It can be tough to test properly since you are typically the one that develops all the code for the process. You know what button to press when and what not to do. You will have to go through many rounds of starting and stopping, triggering alarms and faults, and operator interventions. The more rounds you do, the more robust your system will be.
Rehearse FAT for flawless functionality
At this point, your system has been tested thoroughly and you just need to have the client verify it during a factory acceptance test (FAT). You will create your test specification based on the design specification and have it approved by the client. Conduct trial FATs beforehand with colleagues to ensure proper function.
During the FAT, the system should run flawlessly, except during your intervention to prove the design/test specification. The client should leave the FAT feeling confident that the system will perform how it is intended. Before the site acceptance test (SAT), create another test specification as a guide for onsite testing. This will be the final testing with actual devices to prove the system works as designed. The SAT should be very similar to the FAT, where applicable and safe to do so. Following these steps will pay off when you start supporting production.
Laying out a plan for testing during the design phase and simulating automation integration during code development leads to successful acceptance test and startup. Matrix Technologies has extensive experience in designing, testing, and installing successful automation projects.
Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. To learn more about our manufacturing operations management capabilities and manufacturing process control solutions, contact Bill Warnke, Senior Consultant.