Newly introduced valve technology that uses sophisticated software algorithms to "learn" and control the operation of air-operated, double diaphragm (AODD) pumps creates very little loss in fluid throughput, while using up to 50 percent less energy.
The key to MizAir® technology from Proportion Air Inc.: to shut off air supply to the pump approximately at the midpoint of each stroke to create energy efficiency. But the challenge has been developing an approach that is cost-
effective and can be used with a wide variety of pumps.
"Like many inventions, the concept behind the product is simple, but the difficult part is that, like snowflakes, no two pumps are alike," says David Reed, vice president of engineering at Proportion Air. "Nuances in the diaphragms, check balls, supply air pressure and the piping that supplies the pump means that all pumps operate differently. Even the same pump moved to a different part of the building, or into a different application, will operate differently with the MizAir valve."
The challenge was how to make the valve smart enough to be able to adapt to different application environments. The MizAir basically needs to know when the stroke is ending on each cycle, and to synchronize both the exact delivery of the next shot of air and how much air the pump needs.
"If the pump is given too little air, it can't finish the stroke in a timely fashion, and throughput goes down," says Reed. "But if you give the pump too much air, you don't benefit from the savings."
Air-operated, double diaphragm pumps have a reputation of ruggedness and durability, the ability to be submerged under water, and can reliably pump large amounts of solids. The pumps can fit into applications and handle media other pump technologies can't, but the user pays a heavy price in the amount of energy and costs required to move the fluid.
The MizAir is a two-way, normally open, high-flow valve that only operates in on/off mode. It is installed immediately on the supply air side of an AODD pump. As the diaphragm chamber fills with compressed air, the diaphragm is pushed in one direction and the motion expels the fluid into a trap on the other side of the diaphragm. Supply air is always directly connected to the supply pressure, so when the diaphragm is finished with its stroke, there is a large volume of air at the supply pressure.
Reed says this perfect vessel of compressed air that has been dried, filtered and supplied to the pump is simply pushed into the atmosphere. What the MizAir does is to give the pump full supply pressure at the start of the stroke but, halfway through the stroke, the valve shuts off supply air to the pump. Trapped air in the pump at the midpoint of the stroke continues to expand and finishes the pump's stroke, and creates the 50 percent energy savings.
The first MizAir models utilized an inductive switch to monitor either the diaphragm motion of the pump or internal valving to determine when the pump had reached the end of stroke. That technology was very reliable, but also expensive to implement because it required modifications to the pump, plus additional hardware and wiring. The other big problem was that mechanical control of the pump needed to be designed specifically for each pump, and couldn't be mass produced.
"While we were developing the technology, we learned that the profile of the air pressure going into the pump provided clues about pump operation," Reed says. "Now instead of using external sensors, the MizAir has an internal pressure sensor to monitor the air going into the pump. We observe the unique characteristics of the pressure profile, which is what the MizAir software utilizes to learn about the pump's operation."
Software algorithms continually monitor each stroke, how fast the pump is operating, how much force it is generating, the supply pressure and the type of pump. The system is learning and adapting system operation based on the real-time sensor input, and profile of the air pressure being sent into the pump. Collecting the data made it possible to develop software to interpret the data, and produce computer logic to intelligently control the pump's operation.
"What started out as a simple problem ends up being thousands of lines of code and requiring a 32-bit ARM processor to process the information," says Rich Pfile, a professor at IUPUI who helped develop the software.
"Essentially the system runs at full air and collects stroke information from the sensor. Algorithms process that information and determine the exact timing of turning the air on and the exact parameters for detecting the end of stroke," says Pfile. "As the head pressure on the pump goes up or down, the system needs more or less air to optimally run the pump."
Using fuzzy logic and control algorithms that monitor pump operation in the same way a person would look at the pressure profile, the valve makes intelligent adjustments to the system. The software makes decisions at the end of every stroke to determine what changes need to be made in the next stroke. The system needs to know at all times where it is in the stroke, and not turn the air on right before the end of stroke where that would fill the chamber and waste air.
The air exiting the pump is extremely cold, as low as -40F. It gets cold due to Boyles Law which basically states that for gas kept at a fixed temperature, pressure and volume are inversely proportional. The air gets cold at the exhaust of the pump because pressure is rapidly decreasing, and with MizAir it gets even colder because the pressure drops much farther sooner. Mufflers developed for the exhaust side of AODD pumps offer anti-icing characteristics that can be used to resolve this issue.
The MizAir offers the most efficiency in applications that use a 3-inch line size because those pumps run at two to three strokes per second and have air requirements the equivalent of a 40 hp air compressor. It has also been used effectively with 1.5- and 2-inch line sizes.
The MizAir® valve determines when the stroke is ending on each cycle, and synchronizes both the precise delivery of the next shot of air and how much the air pump needs. View full size.