Energy efficiency and air-operated diaphragm pumps

Tuesday, 31 May, 2011

Recent technology has been developed that increases the pumping efficiency of air-operated double-diaphragm pumps and reduces energy costs by up to 50%.

Air-operated double-diaphragm (AODD) pumps are known for their positive attributes of handling fluids that are heavily laden with solids, abrasive materials, shear-sensitive liquids and the ability to pump soft solids without damaging the product. They are also popular because they are lightweight, portable and easy to use due to their pneumatic power.

Now new technology is available that optimises pump efficiency and uses adaptive optimisation as pump application parameters change. This method maintains all the positive attributes of AODD pumps while employing the latest control technology. The devices are electromechanically controlled using a microprocessor and linear feedback system to monitor pump actuation and adjust the air supply according to the required performance, thus optimising energy efficiency.

The technology still allows for simple installation by integrating electrical power generation into the system, eliminating the need to provide electrical power to the AODD pump. Ease of installation for the end user is, therefore, maintained. This new technology is also fail-safe in the event of any failures within the device. The pump will operate as a standard AODD pump and will maintain the end user’s processing objectives without interruption. By maintaining the robust characteristics of standard AODD pumps, this technology eliminates the risk of any increase in process downtime for the end user due to the integration of this type of solution.

The energy reduction technology manipulates the air supply to obtain the same geometrical characteristics of pump operation and efficiency gains with respect to diaphragm deformation and force reduction at the beginning of the pump stroke, which is the same as what occurred with the earlier methods. One of the key differences is that this latest technology automatically adjusts to maintain optimum efficiency for different and changing pump application parameters. This is made possible through the application of a feedback technology that monitors the full range of motion of the diaphragm movement including position, velocity and acceleration. This information is read by the microprocessor. Then, associated algorithms are applied to control a valve system that manipulates the flow of air supplied to the pump.

The airflow is manipulated in a way that allows for full air supply flow at the beginning of the pump stroke and then reduces the air supply flow at different points during the stroke that are dependent on the specific application parameters. This flexible supply flow reduction enables increased pump efficiency regardless of differing pump applications. As the pump discharges pressure, the air supply pressure and fluid viscosity changes, and the system automatically adapts and optimises the pump efficiency.

The end user does not need to supply the operating parameters to the processor. The system contains a learning algorithm that learns the pump’s operation without air manipulation, as standard pump operation, and then starts the optimisation process. The feedback and control systems continually monitor servos about the diaphragm velocity and enable continuous optimisation for maximum energy savings across a real-world pump application. The system will relearn as the application parameters change or the pump is placed into a new application, providing utmost ease of use for the end user.

The combination of adaptive optimisation, self-learning capability and integrated power generation advantages found in this technology enables end users to enjoy all the positive attributes of traditional AODD pumps while reducing energy costs.

Vegetable oil producer saves energy

Feed Energy, based in Sioux City, Iowa, has been the premier supplier of high-quality liquid feed solutions for livestock and poultry for nearly 25 years. The company specialises in premium vegetable oil production.

The manufacture of this type of product requires liquid transfer capabilities to mix, blend and circulate fluids for proper formulation and to separate water content for maximum yield. The company uses AODD pumps for high-transfer, high-circulation processes because they are portable and require minimal maintenance.

Because these pumps require compressed air for operation, capacity limitations can arise as companies add more pumps to expand production. In Feed Energy’s case, additional online pumps constrained system air volume capacity to a point that the company considered purchasing an additional air compressor to increase productivity and performance.

Understanding the challenges at Feed Energy, Warren Rupp proposed a solution of installing a new air control technology to reduce compressed air usage. Pump curve calculations showed that over 50% air savings was possible, which would lead to many benefits for the company including energy savings of as much as $1500 per year and a reduction of 10 horsepower at the air compressor. In total, Feed Energy would reduce energy consumption by as much as 60 KW and save over $12,000 in annual operating costs by deploying the air-saving technology to all eight of its three-inch pumps within the Sioux City manufacturing plant.

The company participated in a three-month performance trial to confirm projected savings. The product was evaluated at 10, 30, 60 and 90 days post installation. During this period the system was confirmed to reduce air usage from 125 SCFM to 61 SCFM, which is a 51% energy reduction from baseline equipment measurements. The results were taken to MidAmerica Energy, the local electrical utility, which then certified the engineered solution and rewarded Feed Energy with a $1200 rebate towards the purchase of this equipment (a system currently supported by the US government).

In summary, Feed Energy benefited from using the new technology by qualifying for a government-funded utility rebate, saving energy costs and expanding its plant-wide compressed air volume without having to purchase new air compressors or capital equipment.

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