Technology tips for choosing the right pump
When evaluating pumps for biomass applications, we recommend approaching pump selection from a holistic viewpoint. Several different types of pumps, including positive displacement and centrifugal, may be used in the process as the materials are broken down and converted. Ideally, a pump supplier should be chosen on their ability to offer products that match the specification requirements as well as their knowledge of how the pump interacts with the system and materials.
When specifying pumps, a plant engineer should identify the biomass physical properties, system requirements and the total cost of owning and operating all of the pumps within the system. The total cost of ownership includes not only the initial investment, but life cycle costs such as energy used, downtime, maintenance and spare parts. An efficient pumping system is not just a system with an energy efficient motor. Energy and maintenance costs during the life of the pump system can be up to 20 times or more of the initial purchase price. In essence, efficiency means reliability.
When specifying pumps, a plant engineer should identify the biomass physical properties, system requirements and the total cost of owning and operating all of the pumps within the system. The total cost of ownership includes not only the initial investment, but life cycle costs such as energy used, downtime, maintenance and spare parts. An efficient pumping system is not just a system with an energy efficient motor. Energy and maintenance costs during the life of the pump system can be up to 20 times or more of the initial purchase price. In essence, efficiency means reliability.
You can calculate the cost of energy through the following formula:
Where,
Bhp: Motor full-load horsepower
0.746: kW/hp
Hours: Hours of Operation
Rate: Electricity cost in $/kW
Motor Efficiency: Motor nameplate full load efficiency
Bhp: Motor full-load horsepower
0.746: kW/hp
Hours: Hours of Operation
Rate: Electricity cost in $/kW
Motor Efficiency: Motor nameplate full load efficiency
There are many pumps offered in the market, with centrifugal pumps the most common selection. However, when looking at your system from a holistic perspective, engineers should be aware of select benefits that positive displacement pumps offer. One way to review an application is through the FDSO approach - F (fluid), D (discharge), S (suction) and O (operation).
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Fluid: If the pump will see viscosities above 20 centistokes (cst), entrained gas or pump shear sensitive fluid, a positive displacement pump should be considered for its efficiencies of operation and ability to pass fluid with minimum change or impact. Two and three-screw pumps may be the best choices. | 
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Suction: If the pump has varying supply conditions, a positive displacement pump is recommended due to its versatility in handling a wide range of NPSHA (net positive suction head available), fluid characteristics plus its ability to efficiently vary speed. |
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Discharge: If the system has varying pressure requirements, a positive displacement pump offers versatility and efficiency. |  |
Operation: If the specific application requires occasional or frequent demand changes in flow and pressure, a positive displacement pump will respond immediately and efficiently, and operates well at varying speeds. |
Special applications within the facility may warrant the need for other pumps, such as:
Kinetic, specialized chemical centrifugal pumps, offering a durable, robust design. They offer high process stability as well as modularity and provide a cost-effective means of stocking replacement parts. They can also be outfitted with oil-lubricated bearing brackets, a popular option that simplifies maintenance.
Propeller pumps should be considered for pre-stage mashes or sludge-like liquid when the application includes large volumes and somewhat low pressure, plus a high proportion of solids.
Hermetically-sealed pumps should be specified for any situation where leaks must be absolutely avoided.
High-quality stainless steel construction may be desirable. Such pumps will meet virtually every requirement regarding chemical resistance and temperature. Plant operators rely on these pumps due to ease of installation and maintenance, plus space saving designs.
If your facility has pumps in operation today, be sure to monitor their performance versus the best efficiency point (BEP) as pumps that move off of their design curve can lead to significant problems. For example, if a centrifugal pump has moved off of the BEP to the left, producing lower flow than designed, an operator may see increased vibration, axial or radial loads that overload the bearings or suction recirculation.
If your facility has pumps in operation today, be sure to monitor their performance versus the best efficiency point (BEP) as pumps that move off of their design curve can lead to significant problems. For example, if a centrifugal pump has moved off of the BEP to the left, producing lower flow than designed, an operator may see increased vibration, axial or radial loads that overload the bearings or suction recirculation.
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