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.
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.
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.
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
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
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
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
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
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.
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.
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.
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 fT 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 <2000). It is characterized by
fluid particles in layers moving past one another without mixing.
Lobe pump: a positive displacement pump. Primarily used in food applications because they handle solids
without damaging them. Lobes are driven by external timing gears as a result the lobes do not make