Hello there, I am new to PLC programming and have had some basic classes in college. However, my experience has mostly been on the instrument side of the job. Recently, I have been given the task of automating a pipeline pump station. The goal is to have operators remotely enable the station, with the pumps kicking on and regulating suction pressure based on their input when the producer is pumping. For example, a suction pressure of 68 PSI will result in a discharge pressure of 325 PSI, with the pump running at 3085 RPM out of a possible 3700 RPM. The current station uses a SEIMENS system, but we plan to replace it with a 1756-L61 that we obtained from a decommissioned station. The SEIMENS system has 3 PIDs for Suction, Discharge, and AMP (potentially for VFD control, with a high select to prioritize pumps with the highest amp load). The scaling for the AMP PID is 0-400 amps. I am facing some challenges: 1. Replicating the High select feature in the current setup and configuring the PID to switch to it. 2. Managing 2 producers with 2 different FCV, possibly requiring a select function for the Suction PID. 3. Integrating shutdowns for the pump controlled by the PID. If there are any unclear points in my explanation, please let me know.
Do you have a process in place to automatically detect the active producer, or is it reliant on control room operators to make the decision? In either scenario, assigning a separate PID to each option would likely be necessary. The routine would then dictate which one to utilize based on the situation.
Currently, our control room authorizes producers to activate their pumps for suction. The pumps operate in parallel, allowing either one to transport the product. By sending a permissive signal to the producer, we can adjust the process variables of the proportional-integral-derivative controller for optimal flow control. Our pipeline configuration includes 12-inch, 8-inch, and 6-inch meters at various stations, limiting simultaneous pumping by both producers. If we were to upgrade the 8-inch section back to 12-inch and install a larger meter, each pump would require its own proportional-integral-derivative controller. However, the likelihood of this modification is currently very low.
After consulting with our seasoned programmers, here is the current status: Although we have 2 pumps available, we are currently only utilizing one. To address this, we have implemented a Low select for all 3 PID controls and a ramp for the VFD to ensure the lowest output is set. This system allows for the amps to adjust the suction pressure or discharge pressure as needed to maintain stability. The operator can then select which pump to output to. What are your thoughts on this approach?
Hello and welcome to the world of PLC programming! The task you've been given sounds both challenging and interesting. For the high select feature, you could consider using the GSV and SSV commands to read and write the status of the system's components respectively. As for the two different FCV producers, you could use an AOI (Add-On Instruction) to handle the selection process. This should streamline your code and make it easier to manage. For integrating shutdowns, you might want to explore 'Interlock' techniques which can safely halt a process should certain conditions arise. Remember to consider the factors that would necessitate a shutdown and to account for them in your programming. It may seem daunting, but break it down into small tasks and tackle them one at a time, consulting the manual or this forum whenever you're unsure. Good luck with your project!
Hey, welcome to the world of PLC programming! Starting off with a SEIMENS to 1756-L61 transition does sound like quite a thrill ride. For your first challenge, use built-in functions of RSLogix 5000 like the "Find Maximum Value" block (FMAX) to mimic the High Select feature. For switching your PID control to prioritize a signal, consider designing a controller mode switching logic within your program. For the issue with the two producers, I'd recommend using a selector switch tied to the suction PIDs. This will help in managing your flow control valves. Integration of shutdowns mainly revolves around your PID tuning and error thresholds. Add failsafe conditions in your program, so when a certain error value is surpassed, this automatically triggers your shutdown procedure. The job might seem daunting in the beginning, but remember, tackling it one step at a time makes it manageable. Good luck, and feel free to reach out if you hit any roadblocks!
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Answer: - To replicate the High select feature in the PID setup, you would need to configure the PID controller to switch to the desired setpoint based on specific conditions or inputs. This may involve programming logic that monitors parameters such as amp load or other relevant variables to determine when to switch to the High select mode.
Answer: - Managing 2 producers with 2 different Flow Control Valves (FCVs) can be achieved by implementing a select function for the Suction PID. This select function would allow you to switch between the control parameters for each producer based on specific criteria or inputs, ensuring proper regulation and control of the pump station.
Answer: - Integrating shutdowns for the pump controlled by the PID system is crucial for ensuring safe operation of the pipeline pump station. You can implement shutdown logic within the PLC program that monitors critical parameters such as pressure, temperature, or any abnormal conditions. When these conditions exceed predefined thresholds, the shutdown sequence can be initiated to stop the pump and prevent any potential damage or hazards.
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