Table of Acronyms & Definitions

Index

Acronyms
Definitions

Acronyms

TermDescription
AORAllowable operating region
BEPBest efficiency point
NPSH3Net positive suction head required resulting in 3% loss of total head
NPSHANet positive suction head available
NPSHRNet positive suction head required
PORPreferred operating region
VFDVariable frequency drive
VSDVariable speed drive

Definitions

TermDescriptionHI SourceEDL Section
Abrasive wear (or abrasion)Wear due to hard particles or hard, small surface protrusions forced against and moving along a material surface. Wear occurring by the mechanical action of suspended abrasives or by abrasives that crystallize on the atmospheric side of the seal. ANSI/HI 14.1-14.1Solids and Slurries
Affinity rulesDescribe the relationship of the pump performance curve relative to pump rotational speed changes and limited changes in impeller diameter.Pump Curves
Allowable operating region (AOR)A wider range of rates of flow, inclusive of the POR, over which the service life of a pump, although reduced, is within acceptable limits.ANSI/HI 9.6.3Pump Curves
Best efficiency point (BEP)The best efficiency point (BEP) is the rate of flow and head at which the pump efficiency is a maximum at rated rpm or at a given speed and impeller diameter.ANSI/HI 14.1-14.2Pump Curves
CavitationCavitation is the process of vapor cavity formation in a flowing liquid, in a region where the pressure falls below the liquid’s vapor pressure, followed by rapid collapse of cavities due to an increase in pressure downstream.ANSI/HI 3.1-3.5Pump Principles
Concentration of solids by mass (or weight)The mass (or weight) of dry solids in a given volume of slurry, divided by the total mass (or weight) of that volume of slurry, multiplied by 100 and expressed in percent.ANSI/HI 12.1-12.6Solids and Slurries
Concentration of solids by volumeThe actual volume of the solid material in a given volume of slurry, divided by the given volume of slurry, multiplied by 100, and expressed in percent.ANSI/HI 12.1-12.6Solids and Slurries
CorrosionLoss of material created by chemical or electrochemical reaction within the pump environmentANSI/HI 12.1-12.6Solids and Slurries
Francis-vane impellerIn impellers of this type, the liquid enters the eye of the impeller axially and exits semi-radially, at about a 60° to 70° angle to the shaft axis. ANSI/HI 14.1-14.2Pump Principles
Friction headFriction head is the hydraulic energy required to overcome frictional resistance of a piping system to liquid flow expressed in meters (feet) of liquid.ANSI/HI 14.1-14.2System Curves
Impeller, axial flowAn axial-flow impeller has a single inlet with the flow entering and discharging axially (or nearly axially). ANSI/HI 14.1-14.2Pump Principles
Impeller, BarskeThis impeller design represents the lowest range of specific speed for rotodynamic pumps and consists of straight, radial vanes with open or semi open construction. ANSI/HI 14.3Pump Principles
Impeller, enclosedAn enclosed impeller has both a inlet and hub shroud with leakage controlled by internal running clearances. ANSI/HI 14.1-14.2Pump Principles
Impeller, mixed flowThe mixed-flow impeller has a single inlet with the flow entering axially and discharging about 45° with shaft axis, to the periphery. ANSI/HI 14.1-14.2Pump Principles
Impeller, openAn impeller with no front shroud and no (or a minimum) back shroud with the vanes running in close proximity to mating casing walls, side plates, or liners. ANSI/HI 14.1-14.2Pump Principles
Impeller, radial flowIn radial flow (vaned) impellers the liquid enters the eye of the impeller axially and is turned by the impeller vanes and shroud to exit perpendicular to the axis of the pump shaft ANSI/HI 14.1-14.2Pump Principles
Impeller, semi-openAn impeller with a shroud only on one side, leaving the vanes exposed on the other side. ANSI/HI 14.1-14.2Pump Principles
K value (valves and fittings)Head loss though valves and standard fittings (minor losses) can be expressed in terms of a resistance coefficient K and the velocity head. The value of K can be found for various fittings in the referenced sources and the Losses in Valves, Fittings and Bends section of the EDL. Combined Pump & System Curves
Major losses (pipe friction)The friction head loss associated with fluid moving through straight pipe. Refer to Friction Loss Calculator (https://edl.pumps.org/tools/frictional-losses.html) Pipe Frictional Losses
Minor losses (valves & fittings)The friction head loss associated with fluid moving through anything that is not straight pipe (valves, fittings, bends, nozzles, tank entrance and exits, etc.). Also see K value. Losses in Valves, Fittings, and Bends
Net positive suction head 3% (NPSH3) The value of NPSHR at which the first-stage to head drops by 3% due to cavitation.ANSI/HI 14.1-14.2Pump Principles
Net positive suction head available (NPSHA)(14.1-14.2) The total suction head of liquid absolute, determined at the NPSH datum, less the absolute vapor pressure head of the liquid.
(6.1-6.5) For a reciprocating pump, acceleration head loss is subtracted from the total suction head of the liquid absolute.		ANSI/HI 14.1-14.2, HI 6.1-6.5Pump Curves
Net positive suction head required (NPSHR)NPSHR is a minimum NPSH given by the manufacturer/supplier for a pump achieving a specified performance at the specified rate of flow, speed, and pumped liquid.ANSI/HI 14.1-14.2Pump Curves
Parallel operationParallel pumping is when two separate pumps operate at the same time using the same inlet and discharge piping.ANSI/HI 14.3Pump Curves
Preferred operating region (POR)The preferred operating region (POR) is a range of rates of flow to either side of predicted BEP within which the hydraulic efficiency and the operational reliability of the pump are not substantially degraded. ANSI/HI 9.6.3Pump Curves
Pump efficiency (ηP)The ratio of the pump output power to the pump input power; that is, the ratio of the liquid horsepower to the brake horsepower expressed in percent. Efficiency is expressed in percent. This term is used interchangeably with hydraulic efficiency. Also called pump mechanical efficiencyANSI/HI 14.1-14.2Pump Curves
Pump input power (PP)The power needed to drive the complete pump assembly, including bowl assembly input power, line-shaft power loss, mechanical seal or gland packing friction losses, and thrust bearing loss. It is also called brake horsepower.ANSI/HI 14.1-14.2Pump Curves
Pump performance curveA pump performance curve is a graphical representation of the head generated, power, efficiency, and NPSHR by a specific pump model at rates of flow from zero to maximum at a given operating speed.ANSI/HI 14.3Pump Curves
Pump rate of flow (Q)The rate of flow of a pump is the total volume throughput per unit of time at suction conditions. It includes both liquid and any dissolved or entrained gases at the stated operating conditions. Rate of flow is expressed in cubic meters per hour (gallons per minute).ANSI/HI 14.1-14.2Pump Curves
Pump runout (maximum flow)The highest flow rate shown on the published pump curve. Pump Curves
Series operationSeries pumping, sometimes referred to as staging, is when the discharge of one pump is routed into the inlet of the next pump.ANSI/HI 14.3Pump Curves
Shut-off headThe pump head at the condition of zero flow where no liquid is flowing through the pump, but the pump is primed and running.ANSI/HI 14.1-14.2Pump Curves
SlurrySlurry is a mixture of solids (specific gravity typically greater than 1) in a liquid carrier, usually water. ANSI/HI 12.1-12.6Solids and Slurries
Specific gravity of liquidSpecific Gravity is the ratio of density of a liquid relative to the density of water. The reference density for liquid used in Hydraulic Institute standards is based on water at 20 °C (68 °F) which is 998.2 kg/m³ (62.31 lbm/ft³)ANSI/HI 14.1-14.2Solids and Slurries
Specific gravity of slurry (or mixture)The relative density of the slurry (mixture) to that of water at the same temperature.ANSI/HI 12.1-12.6Solids and Slurries
Specific gravity of solidsThe relative density of solids with respect to water at standard temperature of 4 °C (39.2 °F).ANSI/HI 12.1-12.6Solids and Slurries
Specific speed (ns, Ns)An index of pump performance at the pump's best efficiency point (BEP) rate of flow, with the maximum diameter impeller, and at a given rotational speed. ANSI/HI 14.1-14.2Pump Principles
SubmergenceThe vertical distance from the free surface of the liquid pumped to the center point of entry at the pump inlet, suction piping, or formed suction intake.ANSI/HI 9.8Submergence
Suction specific speed (S, Nss)Suction specific speed is an index of pump suction operating characteristics determined at the BEP rate of flow with the maximum diameter impeller. ANSI/HI 14.1-14.2Pump Principles
System curveA system curve is a representation describing the head requirement of the system as a function of flow rate System Curves
System static headThe height a liquid must be lifted as measured from the free surface of the liquid supplying the pump to the free surface of the liquid's destination, plus the difference in pressure acting upon these surfaces, expressed in height of the liquid. System Curves
Total head (H)This is the measure of energy (work) increase per unit weight of the liquid, imparted to the liquid by the pump, and is the difference between the total discharge head and the total suction head. ANSI/HI 14.1-14.2Pump Principles
Type number (K)A variation of impeller specific speed. Type number is a dimensionless quantity calculated at the point of best efficiency.ANSI/HI 14.6Pump Principles
Variable frequency drive (VFD)An electronic device used primarily for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor.HI Application Guideline for Variable Speed PumpingPump Curves
Variable speed drive (VSD)Any device that can be used to vary the speed of the pump, either mechanically or electronically. This may include (but is not limited to) eddy current drives, magnetic drives, variable frequency drives, a hydraulic clutch, fluid drives, variable V-belt drives, and various variable mechanical drives, steam turbines, and gas turbines.HI Application Guideline for Variable Speed PumpingPump Curves
Velocity headVelocity head is the kinetic energy per unit mass of the liquid in movement divided by g at a given section.ANSI/HI 14.1-14.2System Curves
Viscosity (absolute viscosity, dynamic viscosity)A measure of a liquid's tendency to resist an internal shearing force. For the same given internal shear rate, a liquid that requires a high shear stress has a high viscosity and a liquid that requires a low shear stress has a low viscosity.ANSI/HI 10.1-10.5Viscosity

Last updated on April 19th, 2024