Understanding Your Pumping System Requirements 

Pumps transfer liquids from one point to another by converting mechanical energy from a rotating impeller into pressure energy (head). The pressure applied to the liquid forces the fluid to flow at the required rate and to overcome friction (or head) losses in piping, valves, fittings, and process equipment. The pumping system designer must consider fluid properties, determine end use requirements, and understand environmental conditions. Pumping applications include constant or variable flow rate requirements, serving single or networked loads, and consisting of open loops (nonreturn or liquid delivery) or closed loops (return systems). 

Fluid Properties 

The properties of the fluids being pumped can significantly affect the choice of pump. Key considerations include:

• • Acidity/alkalinity (pH) and chemical composition. Corrosive and acidic fluids can degrade pumps, and should be considered when selecting pump materials.
    
    
  • Operating temperature. Pump materials and expansion, mechanical seal components, and packing materials need to be considered with pumped fluids that are hotter than 200°F.
    
    
  • Solids concentrations/particle sizes. When pumping abrasive liquids such as industrial slurries, selecting a pump that will not clog or fail prematurely depends on particle size, hardness, and the volumetric percentage of solids.
    
    
  • Specific gravity. The fluid specific gravity is the ratio of the fluid density to that of water under specified conditions. Specific gravity affects the energy required to lift and move the fluid, and must be considered when determining pump power requirements.
    
    
  • Vapor pressure. A fluid’s vapor pressure is the force per unit area that a fluid exerts in an effort to change phase from a liquid to a vapor, and depends on the fluid’s chemical and physical properties. Proper consideration of the liquid's vapor pressure will help to minimize the risk of cavitation.
    
    
  • Viscosity. The viscosity of a fluid is a measure of its resistance to motion. Since kinematic viscosity normally varies directly with temperature, the pumping system designer must know the viscosity of the fluid at the lowest anticipated pumping temperature. High viscosity fluids result in reduced centrifugal pump performance and increased power requirements. It is particularly important to consider pump suction-side line losses when pumping viscous fluids.

End Use Requirements—System Flow Rate and Head 

The design pump capacity, or desired pump discharge in gallons per minute (gpm) is needed to accurately size the piping system, determine friction head losses, construct a system curve, and select a pump and drive motor. Process requirements may be met by providing a constant flow rate (with on/off control and storage used to satisfy variable flow rate requirements), or by using a throttling valve or variable speed drive to supply continuously variable flow rates. 

The total system head has three components: static head, elevation (potential energy), and velocity (or dynamic) head. Static head is the pressure of the fluid in the system, and is the quantity measured by conventional pressure gauges. The height of the fluid level can have a substantial impact on the system head. The dynamic head is the pressure required by the system to overcome head losses caused by flow rate resistance in pipes, valves, fittings, and mechanical equipment. Dynamic head losses are approxi-mately proportional to the square of the fluid flow velocity, or flow rate. If the flow rate doubles, dynamic losses increase fourfold. 

For many pumping systems, total system head requirements vary. For example, in wet well or reservoir applications, suction and static lift requirements may vary as the water surface elevations fluctuate. For return systems such as HVAC circulating water pumps, the values for the static and elevation heads equal zero. You also need to be aware of a pump’s net positive suction head requirements. Centrifugal pumps require a certain amount of fluid pressure at the inlet to avoid cavitation. A rule of thumb is to ensure that the suction head available exceeds that required by the pump by at least 25% over the range of expected flow rates. 

Environmental Considerations 

Important environmental considerations include ambient temperature and humidity, elevation above sea level, and whether the pump is to be installed indoors or outdoors.

Software Tools

Most pump manufacturers have developed software or Web-based tools to assist in the pump selection process. Pump purchasers enter their fluid properties and system requirements to obtain a listing of suitable pumps. Software tools that allow you to evaluate and compare operating costs are available from private vendors. 

Suggested Actions

• Accurately identify process flow rate and pressure requirements.
• Measure actual head and flow rate.
• Develop a system curve.
• Select a pump with high efficiency over the expected range of operating conditions.
• Specify electric motors that meet the NEMA Premium™ full-load efficiency standards.
• Use life cycle costing techniques to justify acquiring high efficiency pumps and designing efficient systems.

About Jonathon Bell

Jonathon Bell is an entrepreneur, focused on building his family's legacy in the industrial pump market.  Currently, he is focused in Latin America, building Dynapro Pumps Mexico from the ground up while contributing in Canada & the United States with Sales & Marketing efforts.

His commitment is developing teams through individual and partnered coaching, to bring out the best in each team member and giving them the tools to help them reach their goals. Guiding and teaching the core values of passion, evolving, and team communication, his teams and members become top performers in their respective fields.

He is honest, generous, and passionate about others success for them individually, their families, and their communities

About Dynapro:

A professional, trustworthy company, committed to create and maintain lasting relationships with our customers and our community.  Our focus is on constantly evolving our business practices and dedicated service to always be aligned with our clients and the environment.  

Our strong sense of responsibility to the environment and the communities we live and work in help encourage our clients and other companies to join forces with us to make a difference.  

We manufacture our own pump models and interchangeable high quality products, improve products, and materials.  We deliver them for less and faster to help achieve our goal of reduced consumption; energy & materials, and reduce maintenance.

For more information, please visit https://www.dynaproequipment.com/about-us.html

Reference

Centrifugal/Vertical NPSH Margin (ANSI/HI 9.6.1-1998), www.pumps.org, Hydraulic Institute, 1998

DOE/GO-102005-2156 October 2005 Pumping Systems Tip Sheet #2

U.S. Department of Energy Washington, DC 20585-0121 www.eere.energy.gov/industry

“Control Valve Replacement Savings,” U.S. Department of Energy Performance Optimization Tip, Energy Matters, July 1998; available online at: http://www.nrel.gov/docs/legosti/fy98/23382.pdf