Like many topics I’ve covered in this column, technologies developed for other industries often find applications in food and beverage. Take, for example, breweries having to pump spent grain—usually caked up—to silos or storage tanks. The stuff plugs up piping and pumps. Been there, done that, however, for sewage. In fact, SEEPEX had already invented a solution for sewage handling where sludge with 20% to 40% dry matter content needs to be pumped over distances up to 1,000 meters.

The company was recently awarded a patent for its Smart Air Injection (SAI) technology, which involves pulsing compressed air into a progressive cavity (PC) pump, giving the sludge a push in the right direction. Open-hopper SAI systems with smart conveying technology reduce maintenance time by up to 85% with maintain-in-place, requiring no disassembly of discharge piping.

“The pressure reductions are so dramatic that almost all installations can make use of low-pressure thermoplastic piping over incredible distances,” says Gordon Fenton, SEEPEX vice president of engineering. “The total lifetime operational costs of the piping, compacted material pump, air compressor, boundary layer injection pumps, installation, maintenance of equipment, required power consumption, and incremental polymer usage can save up to 72% over technologies previously used.”

I asked Fenton to fill in some details on the new pump.

FE: What was the incentive to develop this “pressure assisted” SAI pump?

Gordon Fenton: SEEPEX is seeing a rise in the adoption of open-hopper progressive cavity pumps to transport previously nonflowable product over long distances. Screw conveyors and conventional conveyors were previously used for these applications. The conveyors’ maintenance and reliability issues pushed plant owners to find more reliable, self-contained solutions. SEEPEX solved their problem by using open-hopper PC pumps to move the product through sealed pipe. Longer distances required larger pipe diameters to counteract the discharge pressures. Although the high-pressure piping required no maintenance, the installation costs of long distances of class 300 or class 600 pipe were prohibitive. Higher pressures also meant longer multistage PC pumps or piston pumps that were difficult to service and had large power requirements.

Customers needed a solution that was reliable, reduced installation costs, pump footprint, pipe size/class, reduced operating pressures—and lowered operating costs. SEEPEX listened and created Smart Air Injection.


FE: How does this pump work?

Fenton: The SEEPEX SAI system utilizes short, pneumatic pulses of compressed air to convey compacted plugs. SAI takes low shear and laminar flow a step further by applying the physical phenomenon of plug flow. The flow from the pump must be laminar and low-shear to properly form long compacted plugs of product within the pipe. Dilute polymer is injected around the outer diameter of flow as it exits the discharge end of the pump. Controlled pulses of compressed air then divide the flow into plugs and force the plugs down the pipe, similar to a pellet being fired from an air rifle or pneumatic tube transport system. The polymer is used to lubricate and seal the exterior of the individual plugs to prevent the plugs from deteriorating during the air injection phase.

This process essentially creates a plug of expanding air following the plug of conveyed product. The process then continuously repeats where a lubricated plug of product is followed by a plug of air that rapidly expands.


FE: Normally, a cavity pump is used to move products with low shear. Adding compressed air would tend to shear a product, correct?

Fenton: Actually, the operating design of SAI lends itself as an ideal solution when the conveyed product is shear-sensitive. As mentioned earlier, utilizing a diluted polymer solution on the exterior surface of the plug creates a super-slippery surface that almost eliminates all of the friction losses between the pipe and plug. The controlled pulses of air—in combination with the polymer injection—ensures the flow does not shear. Other technologies utilize continuous air, which does not lend itself to low shear.


FE: You said that this technology can save as much as 72% over previous technologies. What technologies?

Fenton: Previously there were only a few options. The equipment included piston pumps, conventional conveyor, screw conveyor or PC pumps without SAI. All of the aforementioned technologies require very large amounts of power from the pressure encountered. The lower pressures required to move the product through the use of SEEPEX SAI reduces power consumption proportionately. The power required by the air compressor is still far less than using the aforementioned technologies. The complete cost of ownership for the SEEPEX pump, air compressor power and lubricating polymer pump power can be less than one-third the cost to operate a piston pump in the same application.


FE: How much compressed air is needed to drive the pump, say a range of volume, pressure?

Fenton: Much of the compressor size and receiver size is determined by pipe diameter chosen, distance the product needs to be conveyed and maximum desired operating pressure. Higher operating pressures limit the expansion capability of the air requiring more SCFM. When we design a system, we look to optimize the system according to the customer’s concerns. Some customers are sensitive to installation costs, some are more interested in reduced maintenance/labor costs, and some are more concerned with continuous operating costs. Each of these pain points may be addressed with a slightly different design to make sure the customer’s concerns are addressed with the turnkey system.


FE: Can this system be automated?

Fenton: The secret to the entire process is the automation provided by the SEEPEX SAI controller. All of the process variables are monitored to find the optimum efficiency point(s) including solids product pump speed, polymer pump speed and compressed air usage. The SEEPEX SAI controller was hardened through real-world testing in a number of customer applications during alpha and beta testing. Without the SEEPEX SAI controller, the operator would constantly be tweaking the process to maintain operation and/or optimization of the current operating point.


FE: What other food/pet food/beverage applications have you thought about?

Fenton: Brewer’s yeast and spent grain are the two immediate applications. SEEPEX SAI process caters mostly to dry product waste streams that can be piped and can form a solid product plug within piping. Caffeine extraction, corn oil production, ethanol production, vegetable oil extraction, soybean oil extraction and CBD oil extraction all provide exciting possibilities to use SEEPEX SAI technology.


FE: Is this pumping technology now available?

Fenton: The SEEPEX SAI system is currently available from SEEPEX. We have numerous installations already up and running and a plant conversion scheduled for December 2020. Multiple installations are already slated for 2021 and beyond. 


FE: Can existing pumps be retrofitted?

Fenton: Plant retrofits are possible. SEEPEX needs to perform a site survey to assess the pump capability, piping size, pipe condition and desired conveying distances. A retrofit may not have all of the benefits of a truly optimized design, but will certainly have advantages over their current process. Once again, SEEPEX needs the opportunity to find the customer’s pain points and specifically address those concerns within the proposed solution.


FE: Anything else?

Fenton: Smart Air Injection coupled with Smart Conveying Technology (SCT) creates exceptional customer value. SCT allows the user the simple serviceability for rotor and/or stator replacement. The SCT allows the pump piping to remain in place during the servicing process. This simplicity allows a single service person the ability to refurbish a pump in 25% of the time that it took two men to rebuild a conventional pump without SCT. As an added bonus, SCT also permits the stator adjustment to counter wear in an application. This allows the SCT stator the longevity of 2-3 conventional stators in the same application. All of these benefits are realized, and replacement stators are a fraction of the cost of stators without the SCT design.


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