Pump Fundamentals

GLOSSARY NAVIGATION

BOTTOM Absolute pressure Absolute viscosity Accumulator Affinity laws Agitator Air entrainment (ingestion) Allowable pipe stress ANSI ANSI B73.1 Anti Vortex Plate API 610 ASME Atmospheric pressure (video) Axial flow pump Back vanes Back plate Balje diagram Baseplate Barometric pressure B.E.P. (best efficiency point) Bernoulli's law Bingham plastic Bourdon pressure gauge Bowl (vertical turbine pump) Bypass line Calculation software Capacity Casing Cavitation Centrifugal force Characteristic curve Check valve Colebrook equation Closed or open impeller Chopper pump CV coefficient

Cutwater Darcy-Weisbach equation Dead head Diaphragm pump Diffuser Dilatant Discharge static head Double suction pump Double volute pump Drooping curve Dynamic viscosity Efficiency End suction pump Equivalent length Expeller External gear pump Eye of the impeller Flat curve Flow splitter Foot valve Forum Friction loss (pump) Friction (pipe) Friction head loss (pipe) Friction factor (pipe) Front cover Front plate Hazen-Williams equation Gland Glandless pumps Head Hydraulic gradient Impeller Impeller eye Internal gear pump Inch of Mercury Inducer

Internal recirculation Jet pump K factor Laminar flow Lobe pump Low NPSH pump Mechanical seal Mercury Minimum flow Minimum NPSHA Motor frame Moody diagram NPSH guidelines N.P.S.H.A. N.P.S.H.R. Newtonian fluid Operating point Packing Partial emission pump Peripheral pump Performance curve Pipe roughness Piping pressure (maximum) Pitot pump Pressure Pressure head Progressive cavity pump Pseudoplastic Pump animation Pump curve Pumps as turbines Radial flow pump Radial vane pump Recessed impeller pump Recirculation Regenerative pump or regenerative turbine pump Reynolds number

Rheopectic Rubber pump liner Screw impeller Sealless pumps Self-priming pump Shroud Shut-off head Side channel pump Siphon Slurry pump Sludge pump Specific gravity Specific speed Standard volute pump Static head Strain Stress Stuffing box Submersion (minimum) Suction energy Suction flow splitter Suction guide Suction specific speed Suction static head Suction static lift Suction vane System System curve System requirements Swamee-Jain equation Thixotropic Total dynamic head Total head Total static head Turbulent flow Vacuum Vanes (no. of)

Vane pass frequency Vane pump Vane pump (hydraulic) Vapor pressure Venturi (video) Vibration Viscosity Viscosity correction Viscous drag pump Volute Vortex Vortex pump Water hammer (pressure surge) TOP

HO ME

TUTORI ALS VIDE OS HOW-TO BOOK FAQ

MICROHYDRO TURB INE

VISU AL GLOS SARY

SHORT CUTS

ONLINE CALCULA TIONS

PU MP SEA RCH

MO RE IN FO

FOR UM

SOFT WARE LIN KS

TRO UBLE SHOO TING

FREE software LINKS

UTF-8 UTF-8

Search http://w w w .pump

Web www.pumpfundame ntals.com Join the forum

PUMP AND PUMP SYSTEM GLOSSARY Absolute pressure: pressure is measured in psi (pounds per square inch) in the imperial system and kPa (kiloPascal or bar) in the metric system. Most pressure measurements are made relative to the local atmospheric pressure. In that case we add a "g" to the pressure measurement unit such as psig or kPag. The value of the local atmospheric pressure varies with elevation (see this pressure vs. elevation chart on this page). It is not the same if you are at sea level (14.7 psia) or at 4000 feet elevation (12.7 psia). In certain cases it is necessary to measure pressure values that are less then the local atmospheric pressure and in those cases we use the absolute unit of pressure, the psia or kPa a.

pa(psia) = pr(psig) + patm(psia), patm = 14.7 psia at sea level.

where pa is the absolute pressure, pr the relative pressure and patm the absolute pressure value of the local atmospheric pressure.

and in the metric system

pa(kPa a) = pr(kPag) + patm(kPa a), patm = 100 kPa a at sea level.

Accumulator: used in domestic water applications to stabilize the pressure in the system and avoid the pump cycling on and off every time a tap is opened somewhere in the house. The flexible bladder is pressurized with air at the pressure desired for acheiving the correct flow rate at the furthest point of the house or system. As water is pulled from the tank the bladder expands to fill the volume and maintain the pressure. When the bladder can no longer expand the water pressure drops, the pressure switch of the pump is activated on low pressure, and the pump starts and fills the water volume of the accumulator. The bladder keeps the air from entering into solution with the water resulting in less frequent repressurisation of the accumulator.

Pumps are often sold as a package with an accumulator.

Affinity laws: the affinity laws are used to predict the change in diameter required to increase the flow or total head of a pump. They can also predict the change in speed required to achieve a different flow and total head. The affinity laws can only be applied in circumstances where the system has a high friction head compared to the static head and this is because the affinity laws can only be applied between performance points that are at the same efficiency. see affinity laws.pdf

The following figure shows a system that has a friction head (curve A) higher than its static head for which the affinity laws apply, as compared to curve B, a system with a high static head as compared to the friction head where the affinity laws do not apply.

Domain of application of the affinity laws for an axial flow pump.

The affinity laws are expressed by the three following relationships where Q is the flow rate, n the pump rpm, H the total head and P the power. You can predict the operating condition for point 2 based on the knowledge of the conditions at point 1 and vice versa.

The process of arriving at the affinity laws assumes that the two operating points that are being compared are at the same efficiency. The relationship between two operating points, say 1 and 2, depends on the shape of the system curve (see next Figure). The points that lie on system curve A will all be approximately at the same efficiency. Whereas the points that lie on system curve B are not. The affinity laws do not apply to points that belong to system curve B. System curve B describes a system with a relatively high static head vs. system curve A which has a low static head.

Diameter reduction To reduce costs pump casings are designed to accommodate several different impellers. Also, a variety of operating requirements can be met by changing the outside diameter of a given radial impeller. Euler's equation shows that the head should be proportional to (nD)2 provided that the exit velocity triangles remain the same before and after cutting. This is the usual assumption and leads to:

which apply only to a given impeller with altered D and constant efficiency but not a geometrically similar series of impellers.If that is the case then the affinity laws can be used to predict the performance of the pump at different diameters for the same speed or different speed for the same diameter. Since in practice impellers of different diameters are not geometrically identical, the author's of the section called Performance Parameters in the Pump Handbook recommend to limit the use of this technique to a change of impeller diameter no greater than 10 to 20%. In order to avoid over cutting the impeller, it is recommended that the trimming be done in steps with careful measurement of the results. At each step compare your predicted performance with the measured one and adjust as necessary.

Try this affinity law calculator.

Air entrainment (ingestion): air in the pump suction can reduce the performance of a pump considerably. The following chart from Goulds shows that even 2% air by volume in the liquid can have an effect on performance.

Performance reduction due to air in the pump

There are many causes of air entrainment, the air may be coming in at the suction tank due to improper piping

or due to leakage iin the pump suction line (assuming that conditions are such that low pressure is produced in the suction line).

Leakage in a suction pipe under low pressure will cause air to enter the pump. Centrifugal pumps can be designed to handle more air if required. Viscous drag pumps can handle large quantities of air.

ALLOWABLE PIPE STRESS: the allowable or maximum pipe stress can be calculated using the ASME Power Piping Code B33.1. The allowable pipe stress is fixed by the code for a given material, construction and temperature from which one can calculate the allowable or maximum pressure permitted by code. See this applet's Help File for more info.

ANSI: American National Standards Institute. A term often used in connection with the classification of flanges, ANSI class 150, 300, etc. See this excerpt of the ASME B16.5 code

for the pressure rating

of ANSI class flanges.

ANSI B73.1: this is a standard that applies to the construction of end-suction pumps. It is the intent of this standard that pumps of all sources of supply shall be dimensionnally interchangeable with respect to mounting dimensions, size and location of suction and discharge nozzles, input shafts, baseplates, and foundation bolts. This next image shows the dimensions that have been standardized (source: the Pump Handbook by McGraw-Hill)

This next image shows a cross-section of an end-suction pump built to the B73.1standard (source: the Pump Handbook by McGraw-Hill).

This web page from the McNally Institute gives comments on the scope of pump standards and recommends various changes to apply to pumps prior to ordering and modifications that will increase the operating life after receipt of a pump.

Anti Vortex Plate: An anti vortex plate prevents the formation of a vortex and and therefore air entrainment into the pump by forcing any emerging vortex to go around a plate and then into the suction pipe. The swirling motion cannot be maintained and the vortex dissipates and cannot form if the path is too long and contorted. Source: NFPA 22, Standard for water tanks for private fire protection 2008 edition . You can find the entire code here.

API 610: American Petroleum Industry, a pump standard adopted by the petroleum industry. The intent being to make pumps more robust, leak-free and reliable.

ASME: American Society of Mechanical Engineers. The Boiler pressure power piping code B31.3 is a code that is often used in connection with the term ASME, the maximum pressure safely allowable can be calculated using this code.

Try this calculator to determine the maximum allowable piping pressure. The help file of this applet shows some excerpts of B31.3 ASME code.

Atmospheric pressure: usually refers to the pressure in the local environment of the pump. Atmospheric pressure varies with elevation, it is 14.7 psia at sea level and decreases with rising elevation. The value of the local atmospheric pressure is required for calculating the NPSHA of the pump and avoiding cavitation.

Take a look at this video of an interesting experiment

with atmospheric pressure.

The variation of atmospheric pressure with elevation.

The Goulds pump catalogue provides more information on atmospheric pressure vs. elevation.

Axial flow pump: refers to a design of a centrifugal pump for high flow and low head. The impeller shape is similar to a propeller. The value of the specific speed number will provide an indication whether an axial flow pump design is suitable for your application. see axial flow pumps.

They are used extensively in the state of Florida to control the water level in the canals of low lying farming areas. The water is pumped over low earthen walls called burms into the South Florida Water Management Disctrict main collecting canals.

MWI in Florida is a reputable supplier of these pumps.

Back vanes: see end-suction pump.

Back plate: see end-suction pump.

Barometric pressure: the same as atmospheric pressure, the pressure in the local environment. Barometric pressure is a term used in meteorology and is often expressed in inches of Mercury.

Baseplate: all pumps require some sort of steel base that holds the pump and motor and is anchored to a concrete base.

see this Goulds web page for more information, these baseplates are built to the ANSI standard B73.1 and will therefore accomodate any pump built to the same standard.

Best Efficiency Point (B.E.P.): The point on a pump's performance curve that corresponds to the highest efficiency. At this point, the impeller is subjected to minimum radial force promoting a smooth operation with low vibration and noise.

Figure 1 Important points of the pump characteristic curve.

Radial force on the impeller vs. the flow rate (source: the Pump Handbook by McGrawhill). When selecting a centrifugal pump it is important that the design operating point lie within the desirable selection area shown in the next figure.

see articles on best efficiency on this web page: pumpworld.htm

Bingham plastic: A fluid that behaves in a Newtonian fashion (i.e. constant viscosity) but requires a certain level of stress to set it in motion.

For more information see non-newtonian fluids.pdf

Bourdon pressure gauge: the Bourdon tube is a sealed tube that deflects in response to applied pressure and is the most common type of pressure sensing mechanism.

Bowl (vertical turbine pump): the casing of one stage a multi-stage vertical turbine pump.

Bypass line: a line used to connect the discharge side of the pump to a low pressure area, often the pump's suction tank, for the purpose of moderating the flow in the system and/or to bring the pump's operating point within a favorable area of the pump's performance curve.

To find out more about control systems, this is an excellent treatment of the types of control systems for a centrifugal pump. Thanks to Walter Driedger of Colt Engineering a consulting engineering firm for the petro-chemical industry in Alberta, Canada.

Calculation software: doing pump system calculations and pump selection can be a long manual process with opportunities for many errors. Help yourself produce accurate, consistent and error free total head calculation results with PIPE-FLO software. This sofware can resolve complicated systems with multiple branches, handle control valves and other equipment and help you do the final pump selection with the manufacturer's electronic pump performance curves providing you with customizable search features to obtain the optimum selection. see Engineered Software

Capacity: refers to a pump's flow rate capacity. Often expressed in USgpm (US gallons per minute) or l/min (litre per minutre) or m^3/h (meter cube per hour).

Casing: The body of the pump, which encloses the impeller, syn. volute.

Cavitation: the collapse of bubbles that are formed in the eye of the impeller due to low pressure. The implosion of the bubbles on the inside of the vanes creates pitting and erosion that damages the impeller. The design of the pump, the pressure and temperature of the liquid that enters the pump suction determines whether the fluid will cavitate or not.

Figure 2 Pressure profile inside a centrifugal pump.

as the liquid travels through the pump the pressure drops, if it is sufficiently low the liquid will vaporize and produce small bubbles. These bubbles will be rapidly compressed by the pressure created by the fast moving impeller vane. The compression creates the characteristic noise of cavitation

. Along with the

noise, the shock of the imploding bubbles on the surface of the vane produces a gradual erosion and pitting which damages the impeller.

Cavitation damage on an impeller of a Robot BW5000 pump (image provided by my pump friend Bart Duijvelaar).

You can join the pumpfundamentals centrifugal pump discussion forum at http://www.pumpfundamentals.com/forum

Centrifugal force: A force associated with a rotating body. In the case of a pump, the rotating impeller pushes fluid on the back of the impeller blade, imparting circular and radial motion. A body that moves in a circular path has a centrifugal force associated with it . Try this experiment, find a plastic cup or other container that you can poke a small pinhole in the bottom. Fill it with water and attach a string to it, and now you guessed it, start spinning it.

Figure 3 An experiment with centrifugal force.

The faster you spin, the more water comes out the small hole, you have pressurized the water contained in the cup using centrifugal force, just like a pump.

A CENTRIFUGAL PUMP ANIMATION

This animation shows my interpretation of what happens to fluid particles (represented by gray balls) once they enter the eye of the impeller and after they turn 90 degrees. At this point they are at the entrance of the volume formed by two adjacent impeller vanes. The rapid rotation of the vanes (impeller blades) displaces the fluid particles by moving them in a radial direction where they come into contact with the pump volute and are decelerated and pressurized. Check out the direction of rotation, not what one would expect at first glance.

For those of you who would like to have this image for your presentation here is an animated gif version.

Characteristic curve: same as performance curve.

Check valve: a device for preventing flow in the reverse direction. The pump should not be allowed to turn in the reverse direction as damage and spillage may occur. Check valves are not used in certain applications where the fluid contains solids such as pulp suspensions or slurries as the check valve tends to jam. A check valve with a rapid closing feature is also used as a preventative for water hammer. see also check valve CV coefficient.

Various check valves (source: The Crane Technical Paper no 410)

do your own calculation of Fitting friction loss with this java applet Colebrook equation: an equation for calculating the friction factor f of fluid flow in a pipe for Newtonian fluids of any viscosity. see also the Moody diagram figure 9. This factor is then used to calculate the friction loss for a straight length of pipe. Do your own calculation of pipe friction loss with this java applet

To understand how to solve the Colebrook equation for the friction factor f using the Newton-Raphson iteration technique, dowload this pdf file.

Here is an interesting article on alternate explicit and very precise version of the Colebrook equation.

Chopper pump: a pump with a serrated impeller edge which can cut large solids and prevent clogging.

Chopper pump

see specialty_pumps.pdf

for more information

Closed or open impeller: the impeller vanes are sandwiched within a shroud which keeps the fluid in contact with the impeller vanes at all times. This type of impeller is more efficient than an open type impeller. The disadvantage is that the fluid passages are narrower and could get plugged if the fluid contains impurities or solids.

In the case of an open impeller, the impeller vanes are open and the edges are not constrained by a shroud. This type of impeller is less efficient than a closed type impeller. The disadvantage is mainly the loss of efficiency as compared to the closed type of impeller and the advantage is the increased clearance available which will help any impurities or solids get through the pump and prevent plugging.

also read this article on closed vs. open impellers

by John Kozel, president of the Sims Pump Valve

Company re-printed with his permission. You can view the Sims company web site at www.simsite.com

CV coefficient: a coefficient developed by control valve manufacturers that provides an indication of how much flow the valve can handle for a 1 psi pressure drop. For example, a control valve that has a CV of 500 will be able to pass 500 gpm with a pressure drop of 1 psi. CV coefficients are sometimes used for other devices such as check valves.

CV coefficients for a wafer style check valve.

Cutwater: the narrow space between the impeller and the casing in the discharge area of the casing.

this is the area where pressure pulsations are created, each vane that crosses the cutwater produces a pulse. To reduce pulsations in critical process', more vanes are added.

Darcy-Weisbach equation: an equation used for calculating the friction head loss for fluids in pipes, the friction factor f must be known and can be calculated by the Colebrook, the Swamee-Jain equations or the Moody diagram.

Dead head: a situation that occurs when the pump's discharge is closed either due to a blocage in the line or an inadvertently closed valve. At this point, the pump will go to it's maximum shut-off head, the fluid will be recirculated within the pump resulting in overheating and possible damage.

Diffuser: located in the discharge area of the pump, the diffuser is a set of fixed vanes often an integral part of the casing that reduces turbulence by promoting a more gradual reduction in velocity. The following image comes from this web site http://www.tpub.com/content/doe/h1018v1/css/h1018v1_97.htm

Diaphragm pump: a positive displacement pump. Double Diaphragm pumps offer smooth flow, reliable operation, and the ability to pump a wide variety of viscous, chemically aggressive, abrasive and impure liquids. They are used in many industries such as mining, petro-chemical, pulp and paper and others.

An air valve directs pressurized air to one of the chambers, this pushes the diaphragm across the chamber and fluid on the other side of the diaphragm is forced out. The diaphragm in the opposite chamber is pulled towards the centre by the connecting rod. This creates suction of liquid in chamber, when the diaphragm plate reaches the centre of the pump it pushes across the Pilot Valve rod diverting a pulse of air to the Air Valve. This moves across and diverts air to the opposite side of the pump reversing the operation. It also opens the air chamber to the exhaust.

this type of diaphragm pump is driven by pneumatic air so these can be used where electric drives are not preferred, is self priming and can run dry for brief periods, an handle hazardous liquids with almost any viscosity, can pump solids up to certain sizes.

Wilden is a major manufacturer of such pumps http://www.wildenpump.com/

Dilatant: The property of a fluid whose viscosity increases with strain or displacement.

For more information see non-newtoninan fluids.pdf

Discharge Static Head: The difference in elevation between the liquid level of the discharge tank if the pipe end is submerged and the centerline of the pump. If the discharge pipe end is open to atmosphere than it is the difference between the pipe end elevation and the suction tank fluid surface elevation. This head also includes any additional pressure head that may be present at the discharge tank fluid surface, for example as in a pressurized tank.

Figure 4 Discharge, suction and total static head. See this tutorial for more information on discharge static head.

Double suction pump: the liquid is channeled inside the pump casing to both sides of the impeller. This provides a very stable hydraulic performance because the hydraulic forces are balanced. The impeller sits in the middle of the shaft which is supported on each end by a bearing. Also the N.P.S.H.R. of this type of pump will be less than an equivalent end-suction pump. They are used in a wide variety of industries because of their reliabilty. Another important feature is that access to the impeller shaft and bearings is available by removing the top cover while all the piping can remain in place. This type of pump typically has a double volute.

The following image is provided by the Flow Serve Corporation.

This sketch will help visualize the flow inside the pump.

Double volute pump: a pump where the immediate volute of the impeller is separated by a partition from the main body of the casing. This design reduces the radial load on the impeller making the pump run smoother and vibration free.

Double volute pump (source of image the Pump Handbook by McGraw-Hill).

see the pump type database for more information

For more information see this pdf file from Cornell Pumps

Drooping curve: similar to the normal profile except at the low flow end where the head rises then drops as it gets to the shut-off head point. see centrifugal-pump-tips.htm

Efficiency:: the efficiency of a pump can be determined by measuring the torque at the pump shaft with a torque meter and then calculating the efficiency based on the speed of the pump, the pressure or total head and flow produced by the pump. The standard equation for torque and speed provides power.

The power consumed by the pump is proportional to total head, flow, specific gravity and efficiency.

for a metric version of this formula see this page.

Flow and total head are measured and then the efficiency can be determined.

The efficiency is calculated for various flow rates and plotted on the same curve as the pump performance or characteristic curve. When several performance curves are plotted, the equal efficiency values are linked to provide lines of equal efficiency. This is a useful visual aide as it points out areas of the various pump curves that are at high efficiency, which will be the preferred areas or areas that the selected pump should operate within. The highest efficiency on a given pump curve is known as the B.E.P. (best efficiency point), more information is available in this area of the visual glossary.

Centrifugal pumps come in many designs and some are more suitable for low-flow high-head applications and others for high-flow low-head and some in between. They are designed to achieve their maximum efficiency to accommodate a particular application.

The specific speed number gives an indication of what type of pump is more suited to your application. The effect of specific speed on pump design and how to calculate this number is available in this area of the visual glossary.

It is possible to predict efficiency. Some years ago, a survey of typical industrial pumps was made. The average efficiency was plotted against the specific speed and it shows what the ultimate efficiency limits are for pumps under various operating conditions. More information is available on the centrifugal pump tips page.

Suction specific speed is another parameter that can affect efficiency. This number is a measure of how much flow can be put through a pump before it starts to choke (reaches it's upper flow limit) and cavitates (the pressure at the suction becomes low enough that the fluid vaporizes). More information is available in the visual glossary here.

End suction pump: a typical centrifugal pump, the workhorse of industry. Also known as volute pump, standard pump, horizontal suction pump. The back pull out design is a standard feature and allows easy removal of the impeller and shaft with the complete drive and bearing assembly while keeping the piping and motor in place. Some of its components are: 1.Casing, volute

2. Impeller, vanes, vane tips, backplate, frontplate (shroud), back vanes, pressure equalising passages or balancing holes 3. Back cover parallel to Plane of the impeller intake 4. Stuffing Box Gland/mechanical

seal housing or packing/lantern ring 5. Pump shaft 6. Pump casing 7. Bearing housing 8. Bearings 9. Bearing seals 11. Back pull out 12. Bearings 13. Bearing seals

Balancing holes

Backvanes

Equivalent length: a method used to establish the friction loss of fittings (see next figure). The equivalent length of the fitting can be found using the nomograph below. The equivalent length is then added to the pipe length, and with this new pipe length the overall pipe friction loss is calculated. This method is rarely used today. See tutotial3.htm for the current method for calculating fittings friction head loss.

Energy gradient: see Hydraulic gradient.

Expeller: a hydro-dynamic seal that provides a seal without addition of water to the gland, specially useful for liquid slurries.

(image source: Worthington Pumpworld article, see below)

see an article on the expeller seal on this web page: pumpworld.htm

External Gear pump: a positive displacement pump. Two spur gears are housed in one casing with close clearance. Liquid is trapped between the gear tooth spaces and the casing, the rotation of the gears pumps the liquid. They are also used for high pressure industrial transfer and metering applications on clean, filtered, lubricating fluids.

Viking Pumps is a major supplier of these pumps http://www.vikingpump.com/.

Flat curve: head decreases very slowly as flow increases, see centrifugal-pump-tips.htm

Flow splitter: see suction flow splitter.

Foot valve: a check valve that is put on the end of the pump suction pipe, often accompanied with an integrated strainer. This is an example from a supplier.

Forum: the pumpfundamentals forum is a place where you can ask questions on centrifugal pumps and other types and also share you knowledge with others. A valuable resource. Join here.

Friction loss (pump): the following chart shows the distribution of friction losses and their relative size that occur in a pump.

Source: Centrifugal and Axial Flow Pumps by A.J. Stepanoff published by John Wiley and Sons 1957.

Friction (pipe): The force produced as reaction to movement. All fluids are subject to friction when they are in motion. The higher the fluid viscosity, the higher the friction force for the same flow rate. Friction is produced internally as one layer of fluid moves with respect to another and also at the fluid wall interface. Rough pipes will also produce high friction.

Friction head loss (pipe): the friction head loss is given by the Darcy-Weisbach equation and in many tables such as provided by the Cameron Hydraulic data book. It is normally given in feet of fluid per 100 feet of pipe.

Table of head loss factors for water from the Cameron Hydraulic data book.

Try this calculator for piping friction head loss. For more information on friction head .

Friction factor f (pipe): the friction factor f is required for the calculation of the friction head loss. It is given by the Moody diagram, or the Colebrook equation or the Swamee-Jain equation. The value of the friction factor will depend on whether the fluid flow is laminar or turbulent. These flow regimes can be determined by the value of the Reynolds number.

Front cover: see end-suction pump.

Front plate: see end-suction pump.

Gland: see stuffing box.

Glandless pumps: see sealless pumps.

Hazen-Williams equation: this equation is now rarely used but has been much used in the past and does yield good results although it has many limitations, one being that it does not consider viscosity. It therefore can only be applied to fluids with a similar viscosity to water at 60F. It has been replaced by the Darcy-Weisbach and the Colebrook equation. Interestingly the NFPA (National Fire Protection Association) mandates that the Hazen-Williams equation be used to do the friction calculations on sprinkler systems for example.

The C coefficients use in the above Hazen-Williams equation are given in the table below. The source of this equation is the Cameron Hydraulic Data book

.

Hazen-Williams equation C coefficients.

Head: the height at which a pump can displace a liquid to. Head is also a form of energy. In pump systems there are 4 different types of head: elevation head or static head, pressure head, velocity head and friction head loss. For more information on head see this tutorial.

Also known as specific energy or energy per unit weight of fluid, the unit of head is expressed in feet or meters. see also tutorial2

Try this calculator to obtain head from pressure.

Hydraulic gradient: All the energy terms of the system ( for example velocity head and piping and fitting friction loss) are converted to head and graphed above an elevation drawing of the installation. It helps to visualize where all the energy terms are located and ensure that nothing is missed.

Impeller: The rotating element of a pump which consists of a disk with curved vanes. The impeller imparts movement and pressure to the fluid.

See this paper on impellers by the McNally Institute.

Figure 5 Major pump parts and terminology.

The impeller consists of a back plate, vanes and for closed impellers a front plate or shroud. It may be equipped with wear rings, back vanes and balancing holes.

for more on the different impeller types see impeller.htm.

Impeller eye: that area of the centrifugal pump that channels fluid into the vane area of the impeller. The diameter of the eye will control how much fluid can get into the pump at a given flow rate without causing excessive pressure drop and cavitation. The velocity within the eye will control the NPSHR, see this chart. see also centrifugal-pump-tips.htm

For more information on pump part terminology see this web page.

Inducer: an inducer is a device attached to the impeller eye that is usually shaped like a screw that helps increase the pressure at the impeller vane entrance and make viscous or liquids with high solids pumpable. It can also be used to reduce the NPSHR.

(image source: The Worthington Pump Co. - Pumpworld).

see articles on inducers on this web page: pumpworld.htm

Internal gear pump: a positive displacement pump. The internal gear pumping principle was invented by Jens Nielsen, one of the founders of Viking Pump. It uses two rotating gears which un-mesh at the suction side of the pump to create voids which allow atmospheric pressure to force fluid into the pump. The spaces between the gear teeth transport the fluid on either side of a crescent to the discharge side, and then the gears re-mesh to discharge the fluid.

Viking's internal gear design has an outer drive gear (rotor- shown in orange) which turns the inner, driven gear (idler-shown in white).

Viking Pumps is a major supplier of these pumps http://www.vikingpump.com/.

Jet pump: a jet pump is a commonly available residential water supply pump. It has an interesting clever design that can lift water from a well (up to 25 feet) and allow it to function without a check valve on the suction and furthermore does not require priming. The heart of the design is a venturi (source of water is from the discharge side of the impeller) that creates low pressure providing a vacuum at the suction and allowing the pump to lift fluids.

see this article for more information visit this manufacturer (and no, I don't get a commission) for more info Another good web site on this topic.

K factor: a factor that provides the head loss for fittings. It is used with the following equation

The K factor for various fittings can he found in many publications. As an example, Figure 6 depicts the relationship between the K factor of a 90° screwed elbow and the diameter (D). The type of fitting dictates the relationship between the friction loss and the pipe size. Note: this method assumes that the flow is fully turbulent (see the demarcation line on the Moody diagram of Figure 9).

Figure 6 K factor vs. diameter of fitting (source: Hydraulic Institute Engineering data book) Another good source for fitting K factors is the Crane Technical Data Brochure.

Figure 7 Values for the K factor with respect to the friction factor for a standard tee. The Crane technical paper gives the K value for a fitting in terms of the term fT as in this example for a standard tee.

As is the case for the data shown in Figure 6, the friction loss for fittings is based on the assumption that the flow is highly turbulent, in fact that it is so turbulent that the Reynolds number is no longer a factor and pipe roughness is the main parameter affecting friction. This can be seen in the Moody diagram. There is a line in the diagram that locates the position where full turbulence starts.

The term fT used by Crane is the friction factor and is the same as that given by the Colebrook or the Swamee-Jain equation.

When the Reynolds number becomes large the value of fT (using the Swamee-Jain equation) becomes:

furthermore the Crane Technical Paper No. 410 assumes that the roughness of the material will correspond to new steel whose value is 0.00015 ft. Therefore, the previous equation for f T becomes:

Therefore the value of the K factor is easily calculated based on the diameter of the fitting, the friction factor fT and the multiplication factor for each type of fitting.

Laminar: A distinct flow regime that occurs at low Reynolds number (Re