This topic aligns with the thread discussed by Robert, but here I am, ready to tackle the challenge. I am tasked with programming a unique pump skid that features 5 pumps of varying capacities, each equipped with VFDs, all feeding into a common pressure header. Unlike my previous projects with VFDs on a single pump, this one requires a different approach. I aim to sequentially activate the pumps, starting the next one once the previous reaches 100% capacity. Additionally, I plan to rotate the 'first' pump in the series to ensure all pumps are exercised. Is there a more sophisticated solution than implementing complex PID control methods? Could cascading PID control be the answer, where the second PID kicks in once the first maxes out? How should I approach this challenging task effectively?
When designing a pump control system, consider running a single PID controller to regulate the pumps' speed based on system capacity. Distribute the load among the 5 pumps with varying capacities to achieve optimal performance. Handle sequencing separately for efficiency. For example, if pump capacities are 30, 30, 20, 20, and 20, and the system requires 55% capacity, adjust the pump speeds accordingly. Keep in mind that this is a simplified approach and may need adjustments based on pressure variations. Consider starting the second pump when the first reaches 80-90% capacity. Implementing a Variable Frequency Drive (VFD) for cost savings by optimizing pump performance is a common practice. Experiment with adjusting pump speeds and valve positions to achieve energy savings and improve system efficiency.
Running multiple pumps at half speed was once thought to be more energy efficient due to the inverse square law, but newer drives have dispelled this idea. However, running all five pumps at once is not ideal for energy efficiency. The situation you are encountering is similar to what I have been managing for years, but now with all VFDs. Grundfos offers a system with an integrated controller that effectively controls multiple VFD pumps. They showcase their pump control capabilities by demonstrating a floating ball moving in a circle on the jets of multiple VFD pumps, which is quite impressive.
It's late in my time zone and I've had a rough day, but it seems like your skid is designed to only require 2 large pumps and one small pump, which simplifies things to some extent. I might follow your suggestion and aim to maintain pressure with the large pumps (either 2 or 1) and then use the small pump as needed. Incorporating joseph's PID idea seems effective, or you could adjust your current strategy. Are there any resources available on the energy consumption comparison between using two pumps versus one? While considering pump wear and potential failures, I am curious to see any energy calculations.
The two large pumps are designated for emergency situations, although they are seldom utilized. However, it is crucial that they remain operational as the other three pumps may not suffice in such cases. To ensure their functionality, I intermittently rotate them and utilize their capacity. While the specifics are hazy, the concept of reducing motor speed by 10% leading to a 20% decrease in energy consumption was discussed. Although these numbers are approximate, the underlying principle remains the same. In one instance, when a bypass relay was activated at maximum speed and the VFD was not in use, the system did not perform as effectively, indicating a potential issue originating from earlier configurations.
TheWaterboy expressed his thoughts on a topic raised by @robertmeetalks, highlighting a unique challenge he is facing. He is tasked with programming a pump skid, a task unfamiliar to him as it involves multiple pumps of varying capacities controlled by VFDs towards a common pressure header. Unlike his previous projects with a single pump and VFD, the complexity of this skid requires a different approach. He aims to sequentially activate the pumps, one by one, and rotate the "first" pump in the series to ensure all are functioning properly. The question arises whether cascading a PID control is a more elegant solution than intricate programming to achieve this. By having the second PID aware of the first one's maxed-out status, a smoother operation can be achieved. The challenge lies in implementing this approach effectively. The familiarity with the term PID showcases expertise in control systems, distinguishing one from being a novice in the field.
Your approach of sequential activation and rotation of pumps seems quite efficient, however, considering the complexity of the set-up and to ensure optimal results, integrating a PLC (Programmable Logic Controller) system with your pump skid could be a more sophisticated solution. The PLC would automate the sequential activation of pumps and manage the rotation based on % capacity, easing your task significantly. Regarding PID control, cascading PID is a good option where the output of one PID controller is used as the set point for the next. This helps in better tuning of PID algorithms and reducing the dependency on a single controller for all processes. Remember, data gathering, system understanding, and timing plays a key role when dealing with multiple PID loops in a cascading manner.
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Answer: - The challenge lies in programming a unique pump skid with 5 pumps of varying capacities, each equipped with VFDs, to sequentially activate the pumps and rotate the 'first' pump in the series to ensure all pumps are exercised.
Answer: - Yes, one potential solution could be implementing cascading PID control, where the second PID controller kicks in once the first pump reaches 100% capacity.
Answer: - Cascading PID controls can be applied by setting up a control scheme where the second PID controller activates once the first pump reaches its maximum capacity, ensuring efficient operation of the pump skid system.
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