Technical Information Guide (Glossary)

The Technical Information Guide is a complete glossary for anybody engaged in the purchase, operation, or maintenance of pumps. Understanding fundamental concepts is critical for optimizing pump performance and longevity. This guide seeks to clarify important issues such as cavitation, dry running, flow rate, impeller dynamics, and much more. When looking for a pump, it’s easy to become overwhelmed by the technical language. NPSH, flooded suction, and pressure loss are not often used phrases.

While some of the terminology may be common “engineers’ language”, some terms are considerably more specialized to pumps, and if you are not an expert, you could reasonably get confused. Here, we’ll walk you through important terms you’re likely to encounter when purchasing or using a pump.

Cavitation: Cavitation is the creation of vapor cavities in a liquid, mainly due to rapid pressure changes. Cavitation occurs in pump systems when the pressure dips below the liquid’s vapor pressure, causing vapor bubbles to develop and collapse. If not treated promptly, this occurrence has the potential to harm pump components and diminish efficiency.

Dry Running: Dry running refers to the operating of a pump without an appropriate supply of fluids. This scenario can result in overheating and damage to the pump’s internal components, such as seals and bearings. It is critical to maintain optimum priming and liquid levels to avoid dry runs.

Flow Rate: Flow rate, defined in gallons per minute (GPM) or cubic meters per hour (m³/h), refers to the volume of fluid going through the pump within a given time frame. Understanding the needed flow rate is critical when selecting a suitably sized pump for a given application. The flow rate is influenced by factors like system pressure, pipe diameter, and fluid viscosity.

Impeller: The impeller is a critical component of centrifugal pumps that transfers kinetic energy to the fluid. It is made from of vanes or blades that revolve and generate centrifugal force, pushing the fluid outward. Different impeller designs are tailored to certain applications, providing diverse performance features such as high efficiency, low NPSH (Net Positive Suction Head) requirements, and the ability to handle abrasive or viscous fluids.

Net Positive Suction Head (NPSH): Net Positive Suction Head (NPSH) is a measurement of absolute pressure at the pump suction port that takes into account both the fluid’s vapor pressure and the pressure drop caused by flow velocity. Sufficient NPSH keeps the fluid in a liquid state and prevents cavitation inside the pump. The NPSH needs vary according to pump design, operating conditions, and fluid characteristics.

Back Pull Out: Back pull out refers to a design feature in certain pump types that allows the spinning assembly, which includes the impeller and shaft, to be removed from the pump casing without disturbing the pipes or motor. This simplifies maintenance and repair chores, lowering downtime and labor costs.

Best Efficiency Point (BEP): The best efficiency point (BEP) is the operating condition under which a pump performs at its peak efficiency. Operating a pump close to its BEP saves energy and lowers wear on its components. Deviating greatly from the BEP might result in decreased efficiency, increased vibration, and premature failure.

Close Coupled: Close-coupled pumps are designed with the pump impeller placed directly onto the motor shaft, eliminating the need for separate couplings or alignment mechanisms. This small form simplifies installation, saves space, and improves mechanical efficiency by reducing power transmission losses.

End Suction: End suction pumps are centrifugal pumps that have a single inlet at one end of their casing. Fluid enters the pump axially and exits radially via the impeller. This design is widely used in industrial and commercial applications due to its simplicity, adaptability, and ease of maintenance.

Flooded Suction: Flooded suction refers to a pump installation where the pump inlet is submerged in the fluid being pumped. This setup ensures a constant supply of liquid to the pump, minimizing the risk of cavitation and ensuring reliable operation, particularly in applications with variable fluid levels or suction lift requirements.

Flow Rate: Flow rate, often measured in gallons per minute (GPM) or cubic meters per hour (m³/h), represents the volume of fluid passing through the pump within a specified time frame. Understanding the required flow rate is essential for selecting an appropriately sized pump for a specific application. Factors such as system pressure, pipe diameter, and fluid viscosity influence the flow rate.

Friction Loss: Friction loss refers to the pressure drop experienced by a fluid as it flows through piping, fittings, and other system components. Minimizing friction loss is crucial for maintaining adequate flow rates and optimizing pump performance. Factors such as pipe diameter, fluid velocity, and surface roughness affect frictional losses in a system.

Head: Head, often measured in feet or meters, represents the energy imparted to a fluid by a pump, typically expressed as the height to which the pump can raise the fluid. Total head accounts for both static head (elevation difference) and dynamic head (pressure head). Understanding head requirements is essential for selecting a pump capable of meeting the system’s hydraulic demands.

Magnetic Drive / Coupling: Magnetic drive or coupling systems eliminate the need for mechanical seals in pump applications by using magnetic force to transfer torque from the motor to the impeller. This hermetically sealed design prevents leakage of hazardous or corrosive fluids, enhances safety, and reduces maintenance requirements in critical processes.

Self-Priming: Self-priming pumps have the ability to evacuate air from the suction line and create a partial vacuum, allowing them to prime and start pumping without external assistance. This feature is particularly advantageous in applications where the pump is located above the fluid source or where intermittent operation is common.

Shear: Shear refers to the mechanical force exerted on a fluid as it flows through a pump or piping system. Excessive shear can cause degradation or alteration of the fluid properties, such as viscosity or particle size distribution. Understanding and controlling shear are essential in applications where maintaining fluid integrity is critical, such as food processing or pharmaceutical manufacturing.

Viscosity: The thickness of a fluid and its ability to flow, measured in Centistokes (cSt) or Centipoise (cP). Some fluids’ viscosity can vary depending on temperature (butter thins as it melts) or force (cream thickens as it is beaten!). Most pumps have a maximum viscosity that they can handle effectively.

The Technical Information Guide provides useful insights into the critical aspects that influence pump operation and maintenance. Understanding concepts like cavitation, flow rate, impeller dynamics, and NPSH allows you to make informed decisions while purchasing, operating, and maintaining pumps for a variety of purposes. Adherence to the recommended practices outlined in this handbook is critical for achieving consistent and efficient pump performance.