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20 mars 2011 7 20 /03 /mars /2011 09:24

A fan is a machine used to create flow within a fluid, typically a gas such as air.

A fan consists of a rotating arrangement of vanes or blades which act on the air. Usually, it is contained within some form of housing or case   SONY VAIO VGN-FW21E Battery .

This may direct the airflow or increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors and internal combustion engines   Asus M52N Battery .

Fans produce air flows with high volume and low pressure, as opposed to compressors which produce high pressures at a comparatively low volume. A fan blade will often rotate when exposed to an air stream, and devices that take advantage of this, such as anemometers and wind turbines, often have designs similar to that of a fan  Dell Latitude E6400 ATG Battery .

Typical applications include climate control, vehicle and machinery cooling systems, personal comfort (e.g., an electric table fan), ventilation, fume extraction,winnowing (e.g., separating chaff of cereal grains), removing dust (e.g. in a vacuum cleaner), drying (usually in combination with heat) and to provide draft for a fire  SONY VAIO VGN-FW21J Battery .

It is also common to use electric fans as air fresheners, by attaching fabric softener sheets to the protective housing. This causes the fragrance to be carried into the surrounding air  SONY VAIO VGN-FW21L Battery .

In addition to their utilitarian function, vintage or antique fans, and in particular electric fans manufactured from the late 19th century through the 1950s, have become a recognized collectible category, and in the U.S.A. an active collector club, the Antique Fan Collectors Association, supports the hobby  SONY VAIO VGN-FW21M Battery .

History

The punkah fan was used in the India in the early 500 BC. It had a canvas covered frame that was suspended from the ceiling. Servants, known as punkawallahs, pulled a rope connected to the frame to move the fan back and forth SONY VAIO VGN-FW21Z Battery .

The Industrial Revolution in the late 19th century introduced belt-driven fans powered by factory water wheels. Attaching wooden or metal blades to shafts overhead that were used to drive the machinery, the first industrial fans were developed. One of the first workable mechanical fans was built by Omar-Rajeen Jumala in 1832  SONY VAIO VGN-FW25T/B Battery .

He called his invention, a kind of a centrifugal fan, an "air pump." Centrifugal fans were successfully tested inside coal mines and factories in 1832–1834. When Thomas Edison and Nikola Tesla introduced electrical power in the late 19th and early 20th centuries for the public, the personal electrical fan was introduced  SONY VAIO VGN-FW26T/B Battery .

Between the years 1882 and 1886, New Orleans resident Schuyler Skaats Wheeler invented the first electric fan.It was commercially marketed by the American firm Crocker & Curtis electric motor company. In 1882, Philip Diehl introduced the electric ceiling fanDell Latitude E6400 battery,10400mAh,11.1V .

Heat-convection fans fueled by alcohol, oil, or kerosene were common around the turn of the 20th century.

The first American fans were made from around the late 1890s to the early 1920s, when domestic electric fans were first sold in America  Dell Latitude E6400 battery,10400mAh,11.1V .

They hadbrass  blades, many of them also had brass cages, and though they were built very well internally, they were far from finger safe, as a lot of them had cage openings so big that one could put an entire hand or arm right through it. Many children had hands and fingers severely injured by those fans  Dell Latitude E6500 battery,10400mAh,11.1V .

In the 1920s, industrial advances allowed steel to be mass produced in different shapes, bringing fan prices down and allowing more homeowners to afford them. In the 1930s, the first art deco fan (the "swan fan") was designed. In the 1950s, fans were manufactured in colors that were bright and eye catching  SONY VAIO VGN-FW27/B Battery .

Central air conditioning in the 1960s caused many companies to discontinue production of fans. In the 1970s, Victorian-style ceiling fans became popular.

In the 20th century, fans have become utilitarian. During the 2000s, fan aesthetics have become a concern to fan buyers  SONY VAIO VGN-FW27/W Battery .

The fan is part of everyday life in theFar East, Japan, and Spain (among other places). The basic design of electric air fans have not changed significantly since their beginning in 1890 to the present. Electric fans have been largely replaced by air conditioners in offices, but they are still a common household appliance  SONY VAIO VGN-FW31ZJ Battery .

Types of fans

Mechanical revolving blade fans are made in a wide range of designs. In a home you can find fans that can be put on the floor or a table, or hung from the ceiling, or are built into a window, wall, roof, chimney, etc   SONY VAIO VGN-FW27T/H Battery .

They can be found in electronic systems such as computers where they cool the circuits inside, and in appliances such as hair dryers and space heaters. They are also used for moving air in air-conditioning systems, and in automotive engines, where they are driven by belts or by direct motor  SONY VAIO VGN-FW29/B Battery .

Fans used for comfort create a wind chill, but do not lower temperatures directly. Fans used to cool electrical equipment or in engines or other machines do cool the equipment directly by forcing hot air into the cooler environment outside of the machineSONY VAIO VGN-FW290JRB Battery .

There are three main types of fans used for moving air, axial, centrifugal (also called radial) and cross flow (also called tangential).

Axial fans

The axial-flow fans have blades that force air to move parallel to the shaft about which the blades rotate SONY VAIO VGN-FW290JTB Battery .

Axial fans blow air along the axis of the fan, linearly, hence their name. This type of fan is used in a wide variety of applications, ranging from small cooling fans for electronics to the giant fans used in wind tunnels  SONY VAIO VGN-FW290JTH Battery .

Examples of axial fans are:

  • Table fan: Basic elements of a typical table fan include the fan blade, base, armature and lead wires, motor, blade guard, motor housing, oscillator gearbox, and oscillator shaft. The oscillator is a mechanism that moves the fan from side to side SONY VAIO VGN-FW33G/E1 Battery .
  • The axle comes out on both ends of the motor, one end of the axle is attached to the blade and the other is attached to the oscillator gearbox. The motor case joins to the gearbox to contain the rotor and stator   SONY VAIO VGN-FW33G/W Battery .
  • The oscillator shaft combines to the weighted base and the gearbox. A motor housing covers the oscillator mechanism. The blade guard joins to the motor case for safety.
  • Ceiling fan: A fan suspended from the ceiling of a room is a ceiling fan  SONY VAIO VGN-FW33GW Battery .
  • In automobiles, a mechanical fan provides engine cooling and prevents the engine from overheating by blowing or sucking air through a coolant-filled radiator. It can be driven with a belt and pulley off the engine's crankshaft or an electric fan switched on or off by a thermostatic switch  (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .
  • Computer cooling fan
  • Variable Pitch Fan: A variable-pitch fan is used where precise control of static pressure within supply ducts is required. The blades are arranged to rotate upon a control-pitch hub  Dell Studio XPS 1640 Battery .
  • The fan wheel will spin at a constant speed. As the hub moves toward the rotor, the blades increase their angle of attack and an increase in flow results Dell Vostro 1710 Battery .

Centrifugal fan

Often called a "squirrel cage" (because of its similarity in appearance to exercise wheels for pet rodents), the centrifugal fan has a moving component (called animpeller) that consists of a central shaft about which a set of blades, or ribs, are positioned Dell KM958 battery .

Centrifugal fans blow air at right angles to the intake of the fan, and spin the air outwards to the outlet (by deflection and centrifugal force). The impeller rotates, causing air to enter the fan near the shaft and move perpendicularlyfrom the shaft to the opening in the scroll-shaped fan casing  Dell Studio 1555 battery .

A centrifugal fan produces more pressure for a given air volume, and is used where this is desirable such as in leaf blowers, blowdryers, air mattress inflators, inflatable structures, climate control, & various industrial purposes. They are typically noisier than comparable axial fans  Sony VGP-BPS13 battery .

Crossflow fan

The crossflow or tangential fan, sometimes known as a tubular fan was patented in 1893 by Mortier, and is used extensively in the HVAC industry  Sony VGP-BPS13/B battery .

The fan is usually long in relation to the diameter, so the flow approximately remains two-dimensional away from the ends. The CFF uses an impeller with forward curved blades, placed in a housing consisting of a rear wall and vortex wall. Unlike radial machines, the main flow moves transversely across the impeller, passing the blading twice Sony VGP-BPS13/S battery .

The flow within a crossflow fan may be broken up into three distinct regions: a vortex region near the fan discharge, called an eccentric vortex, the through-flow region, and a paddling region directly opposite. Both the vortex and paddling regions are dissipative, and as a result, only a portion of the impeller imparts usable work on the flow  Sony VGP-BPS13A/B battery .

The crossflow fan, or transverse fan, is thus a two-stage partial admission machine. The popularity of the crossflow fan in the HVAC industry comes from its compactness, shape, quiet operation, and ability to provide high pressure coefficient  Sony VGP-BPS13B/B battery .

Effectively a rectangular fan in terms of inlet and outlet geometry, the diameter readily scales to fit the available space, and the length is adjustable to meet flow rate requirements for the particular application  Sony VGP-BPL9 battery .

Much of the early work focused on developing the crossflow fan for both high and low-flow-rate conditions, and resulted in numerous patents. Key contributions were made by Coester, Ilberg and Sadeh, Porter and Markland, and Eck. One interesting phenomenon particular to the crossflow fan is that, as the blades rotate, the local air incidence angle changes  Sony VGP-BPS13B/B battery .

The result is that in certain positions the blades act as compressors (pressure increase), while at other azimuthal locations the blades act as turbines (pressure decrease).

Bladeless fan

These fans have a 3-dimensional mixed-flow impeller in a lower compartment  Sony VGP-BPL15 battery .

Air is drawn in and compressed, before being expelled though an annulus, and accelerated over an airfoil ramp. Inducing and entraining ambient air through viscous shearing, the loop-shaped upper section multiplies the total airflow many times. Only around 7% of the total airflow actually passes through the fan itself  Dell Inspiron E1505 battery .

Fan motor

A standalone fan is typically powered with an electric motor. Fans are often attached directly to the motor's output, with no need for gears or belts. The electric motor is either hidden in the fan's center hub or extends behind it  Dell Latitude E6400 battery .

For big industrial fans, three-phase asynchronous motors are commonly used, placed near the fan and driving it through a belt and pulleys. Smaller fans are often powered byshaded pole AC motors, or brushed or brushless DC motors. AC-powered fans usually use mains voltage, while DC-powered fans use low voltage, typically 24 V, 12 V or 5 V  HP Pavilion dv6000 Battery .

Cooling fans for computer equipment exclusively use brushless DC motors, which produce much less electromagnetic interference.

In machines that already have a motor, the fan is often connected to this rather than being powered independently  HP Pavilion dv8000 battery .

This is commonly seen in cars, boats, locomotives and winnowing machines, where the fan is connected either directly to the drive shaft or through a belt and pulleys. Another common configuration is a dual-shaft motor, where one end of the shaft drives a mechanism, while the other has a fan mounted on it to cool the motor itself  HP PAVILION DV6000 Battery,  8800mAh, 10.8V .

Industrial fans and blowers are machines whose primary function is to provide a large flow of air or gas to various processes of many industries. This is achieved by rotating a number of blades, connected to a hub and shaft, and driven by a motor or turbine HP PAVILION DV8000 Battery,  8800mAh, 10.8V .

The flow rates of these fans range from approximately 200 to 2,000,000 cubic feet (5.7 to 57000 cubic meters) per minute. A blower is another name for a fan that operates where the resistance to the flow is primarily on the downstream side of the fanSONY VAIO VGN-FZ Battery .

Functions and Industries:

There are many uses for the continuous flow of air or gas that industrial fans generate, including combustion, ventilation, aeration, particulate transport, exhaust, cooling, air-cleaning, and drying, to name a few  HP Pavilion DV6000 battery - 8800mAh .

The industries served include electrical power production, pollution control, metal manufacturing and processing, cement production, mining, petrochemical, food processing, cryogenics, and clean rooms.

Centrifugal Fans and Axial Fans

Most industrial fans may be categorized into one of two general types: centrifugal fans and axial fans HP Pavilion DV8000 battery - 7800mAh .

Centrifugal Fans: As the name suggests, the centrifugal design uses the centrifugal force generated by a rotating disk, with blades mounted at right angles to the disk, to impart movement to the air or gas and increase its pressure  HP Pavilion DV6000 battery - 8800mAh .

The assembly of the hub, disk and blades is known as the fan wheel, and often includes other components with aerodynamic or structural functions. The centrifugal fan wheel is typically contained within a scroll-shaped fan housing, resembling the shell of the nautilus sea creature with a central hole  HP Pavilion DV8000 battery - 6600mAh .

The air or gas inside the spinning fan is thrown off the outside of the wheel, to an outlet at the housing's largest diameter. This simultaneously draws more air or gas into the wheel through the central hole  . Inlet and outlet ducting are often attached to the fan's housing, to supply and/or exhaust the air or gas to the industry's requirements SONY VAIO VGN-FZ18 Battery .

There are many varieties of centrifugal fans, which may have fan wheels that range from less than a foot (0.3 meters) to over 16 feet (5 m) in diameter.

Axial Fans: The axial design uses axial forces to achieve the movement of the air or gas, spinning a central hub with blades extending radially from its outer diameter   SONY VAIO VGN-FZ21E Battery .

The fluid is moved parallel to the fan wheel's shaft, or axis of rotation. The axial fan wheel is often contained within a short section of cylindrical ductwork, to which inlet and outlet ducting can be connected SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

Axial fan types have fan wheels with diameters that usually range from less than a foot (0.3 meters) to over 30 feet (9 m), although axial cooling tower fan wheels may exceed 82 feet (25 m) in diameter SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

In general, axial fans are used where the principal requirement is for a large volume of flow, and the centrifugal design where both flow and higher pressures are required.

Design Paths

There are several paths to determining a fan design for an application. Dell Latitude E6400 battery,10400mAh/7800mAh

For industries where the application requirements do not vary greatly and applicable fan designs have diameters of around 4 feet (1.2 meters) or less, a standard or pre-engineered design might be selected  Dell Latitude E6400 Battery,10400mAh/7800mAh .

When the application involves more complex specifications or a larger fan, then a design based on an existing model configuration will often satisfy the requirements. Many model configurations already cover the range of current industry processes  Dell Latitude E6400 Battery,10400mAh/7800mAh .

An appropriate model from the fan company's catalogue is selected, and the company's engineers apply design rules to calculate the dimensions and select options and material for the desired performance, strength and operating environment Dell Latitude E6400 Battery,10400mAh/7800mAh .

Some applications require a dedicated, custom configuration for a fan design to satisfy all specifications.

All industrial fan designs must be accurately engineered to meet performance specifications while maintaining structural integrity. For each application, there are specific flow and pressure requirements  Dell Latitude E6500 battery,10400mAh/7800mAh .

Depending on the application, the fan may be subject to high rotating speeds, an operating environment with corrosive chemicals or abrasive air streams, and extreme temperatures. Larger fans and higher speeds produce greater forces on the rotating structures; for safety and reliability Dell Latitude E6500 battery,10400mAh/7800mAh ,

the design must eliminate excessive stresses and excitable resonant frequencies. Computer modeling programs for computational fluid dynamics (CFD) and finite element analysis (FEA) are often employed in the design process, in addition to laboratory scale model testing  Dell Latitude E6500 battery,10400mAh/7800mAh .

Even after the fan is built the verification might continue, using fan performance testing for flow and pressure, strain gage testing for stresses and tests to record the fan's resonant frequencies.

Fan Sub-Categories

Fan types and their sub-categories are industry standard, recognized by all major fan producers Dell Latitude E6500 battery,10400mAh/7800mAh .

Centrifugal Fan Sub-Categories

Any of these fan sub-types can be built with long-lasting erosion-resistant liners.

Airfoil (Air Foil) – Used for a wide range of applications in many industries, fans with hollow, airfoil-profiled blades are designed for use in airstreams where high efficiency and quiet operation are required  HP Pavilion DV6-1210SA battery - 5200mAh/8800mAh .

They are used extensively for continuous service at ambient and elevated temperatures in forced and induced draft applications in the metals, chemical, power generation, paper, rock products, glass, resource recovery, incineration and other industries throughout the worldCXXXCX  HP Pavilion DV7 battery - 7200mAh .

Backward Curve – These fans have efficiencies nearly as high as the airfoil design. Anadvantage is that their single-thickness, curved plate blades prevent the possibility of dust particle buildup inside the blade, as may occur if advanced wear perforates a hollow airfoil blade   Ibm THINKPAD X200 Battery 8800mAh, 11.1V Replacement .

The robust design allows high tip-speed operation, and therefore this fan is often used in high-pressure applications.

Backward Inclined – These fans have simple flat blades, backwardly inclined to match the velocity pattern of the air passing through the fan wheel for high-efficiency operation  Ibm THINKPAD X200 Battery 8800mAh, 11.1V Replacement .

These fans are typically used in high-volume, relatively low-pressure, clean air applications.

Radial Blade – The flat blades of this type are arranged in a radial pattern. These rugged fans offer high pressure capability with average efficiency  Ibm THINKPAD X200 Battery 8800mAh, 11.1V Replacement .

They are often fitted with erosion-resistant liners to extend rotor life. The housing design is compact to minimize the floor space requirement  SONY VAIO VGN-FW21E Battery .

Forward-Curved Radial Tip – This rugged design is used in high-volume flow rate applications when the pressure requirement is rather high and erosion resistance is necessary. It offers medium efficiencies. A common application is the dirty side of a baghouse or precipitator  SONY VAIO VGN-NR11S/S Battery .

The design is more compact than airfoil, backward curved or backward inclined fans.

Paddle-Wheel – This is an open impeller design without shrouds  SONY VAIO VGN-NR11M/S Battery .

Although the efficiency is not high, this fan is well suited for applications with extremely high dust loading. It can be offered with field-replaceable blade liners from ceramic tiles or tungsten-carbide. This fan may also be used in high-temperature applicationsSONY VAIO VGN-NR11Z/S Battery .

Forward-Curve – This “squirrel cage” impeller generates the highest volume flow rate (for a given tip speed) of all the centrifugal fans. Therefore, it often has the advantage of offering the smallest physical package available for a given application. This type of fan is commonly used in high-temperature furnaces  SONY VAIO VGN-NR11Z/T Battery .

Industrial Exhausters – This is a relatively inexpensive, medium-duty, steeply inclined flat-bladed fan for exhausting gases, conveying chips, etc.

Pre-engineered Fans (PE) – A series of fans of varying blade shapes that are usually available in only standard sizes Sony VAIO VGN-FZ21E Battery .

Because they are pre-engineered these fans may be available with relatively short delivery times. Often, pre-engineered rotors with various blade shapes may be installed into a common housing. These are often available in a wide range of volume and pressure requirements to meet the needs of many applications  Sony VAIO VGN-FW21E Battery .

Pressure Blowers – These are high-pressure, low-volume blowers used in combustion air applications in furnaces or to provide “blow-off” air for clearing and/or drying applications  Sony VAIO VGN-NR11S/S Battery .

Surgeless Blowers – These high-pressure, low-volume blowers have a reduced tendency for “surging” (periodic variation of flow rate) even at severely reduced fan speeds. This allows extreme turndown (low-flow) without significant pulsation  Sony VAIO VGN-NR11Z/S Battery .

Mechanical Vapor Recovery Blowers -These specially designed centrifugal fans are designed to increase temperature and pressure of saturated steam in a closed-loop system.

Acid Gas Blowers - These veryheavy construction blowers are suitable for inlet pressures from full vacuum to 100psig Sony VAIO VGN-NR11M/S Battery .

Materials are selected for corrosion resistance to the gases and particulate handled.

Specialty Process Gas Blowers - These blowers are for high pressure petrochemical processes  Sony VAIO VGN-NR11Z/T Battery.

Axial Fan Sub-Categories

High-Temperature Axial Fans – These are high-volume fans designed to operate against low flow resistance in industrial convection furnaces. They may be of either single-direction or bi-directional designs SONY VAIO VGN-FZ180E Battery .

Extremely rugged, they are most often used in high-temperature furnace (up to 1800 degF) applications.

Tube Axial Fans – These are axial fan units with fan wheels located in cylindrical tubes, without inlet or outlet dampers.

Vaneaxial Fans – These axial flow fans have a higher pressure capability due to the presence of static vanes SONY VAIO VGN-FZ220E Battery .

Variable Pitch Axial fans – The blades on these axial fans are manually adjustable to permit the blade angle to be changed. This allows operation over a much wider range of volume/pressure relationships. The blades are adjusted periodically to optimize efficiency by matching the blade pitch to the varying conditions for the application SONY VAIO VGN-FZ340E Battery .

These fans are often used in mining applications.

Variable Pitch on-the-fly Axial Fans – These are similar to “Variable Pitch Axial Fans” except they include an internal mechanism that allows the blade pitch to be adjusted while the fan rotor is in motion  SONY VAIO VGN-FZ430E Battery .

These versatile fans offer high-efficiency operation at many different points of operation. This instantaneous blade adjustment capability is an advantage that is possible with axial fans only  SONY VAIO VGN-FZ460E Battery .

Cooling fans - (also referred to as "cooling tower fans") - These are axial fans, typically with large diameters, for low pressures and large volumes of airfloe. Applications are in wet mechanical cooling towers, air-cooled steam condensers, air-cooled heat exchangers, radiators, or similar air-cooled applications  SONY VAIO VGN-FZ480E Battery .

Mixed-flow fans - The gas flow patterns these fans produce resemble a combination of axial and centrifugal patterns, although the fan wheels appear similar to axial wheels. There are various types of mixed-flow fans, including gas-tight high-pressure fans and blowers  SONY VAIO VGN-FZ4000 Battery .

Flow Control

There are several means of controlling the flow rate of a fan, e.g., temporarily reducing the air or gas flow rate; these can be applied to both centrifugal and axial fans  SONY VAIO VGN-FZ31E Battery .

Speed Variation - All of the fan types described above can be used in conjunction with a variable speed driver. This might be an adjustable frequency AC controller, a DC motor and drive, a steamturbine driver, or a hydraulic variable speed drive unit ("fluid drive")  SONY VAIO VGN-FZ31B Battery .

Flow control by means of variable speed is typically smoother and more efficient than by means of damper control. Significant power savings (with reduced cost of operation) are possible if variable speed fan drives are used for applications that require reduced flow operation for a significant portion of the system operating life  SONY VAIO VGN-FZ31J Battery .

Industrial Dampers - These devices also allow fan volumetric flow control during operation, by means of panels so as to direct gas flow or restrict the inlet or outlet areas.

There is a variety of types of dampers available  SONY VAIO VGN-FZ31M Battery :

Louvered Inlet Box Dampers
Radial Inlet Dampers
Variable Inlet Vane (VIV) Dampers
Vortex Dampers   SONY VAIO VGN-FZ31Z Battery
Discharge Dampers

A pump is a device used to move fluids, such as liquids, gases or slurries.

A pump displaces a volume by physical or mechanical action. Pumps fall into five major groups: direct lift, displacement, and gravity pumps.Their names describe the method for moving a fluid  SONY VAIO VGN-FZ38M Battery .

Positive displacement pumps

A positive displacement pump causes a fluid to move by trapping a fixed amount of it then forcing (displacing) that trapped volume into the discharge pipe  SONY VGP-BPS8 Battery .

or

A positive displacement pump has an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapsesSONY VGP-BPS13/S Battery .

The volume is constant given each cycle of operation.

A positive displacement pump can be further classified according to the mechanism used to move the fluid SONY VGP-BPS13A/B Battery :

  • Rotary-type, internal gear, screw, shuttle block, flexible vane or sliding vane, circumferential piston, helical twisted roots (e.g. the Wendelkolben pump) orliquid ring vacuum pumps  SONY VGP-BPS13B/B Battery .

Positive displacement rotary pumps are pumps that move fluid using the principles of rotation. The vacuum created by the rotation of the pump captures and draws in the liquid. Rotary pumps are very efficient because they naturally remove air from the lines, eliminating the need to bleed the air from the lines manually SONY VGP-BPS13A/S Battery .

Positive displacement rotary pumps also have their weaknesses. Because of the nature of the pump, the clearance between the rotating pump and the outer edge must be very close, requiring that the pumps rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids will cause erosion  SONY VGP-BPS13AS Battery .

Rotary pumps that experience such erosion eventually show signs of enlarged clearances, which allow liquid to slip through and detract from the efficiency of the pump.

Positive displacement rotary pumps can be grouped into three main types  Dell Inspiron 1320n Battery .

Gear pumps are the simplest type of rotary pumps, consisting of two gears laid out side-by-side with their teeth enmeshed. The gears turn away from each other, creating a current that traps fluid between the teeth on the gears and the outer casing, eventually releasing the fluid on the discharge side of the pump as the teeth mesh and go around again Dell Inspiron 1464 Battery .

Many small teeth maintain a constant flow of fluid, while fewer, larger teeth create a tendency for the pump to discharge fluids in short, pulsing gushes.

Screw pumps are a more complicated type of rotary pumps, featuring two or three screws with opposing thread Dell Inspiron 1564 Battery

—- that is, one screw turns clockwise, and the other counterclockwise. The screws are each mounted on shafts that run parallel to each other; the shafts also have gears on them that mesh with each other in order to turn the shafts together and keep everything in place  Dell Inspiron 1764 Battery .

The turning of the screws, and consequently the shafts to which they are mounted, draws the fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal  Dell Studio 1450 Battery .

Moving vane pumps are the third type of rotary pumps, consisting of a cylindrical rotor encased in a similarly shaped housing. As the rotor turns, the vanes trap fluid between the rotor and the casing, drawing the fluid through the pump Dell Studio 1457 Battery .

  • Reciprocating-type, for example, piston or diaphragm pumps.

Positive displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side Dell Latitude D610 Battery .

Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation.

The positive displacement pumps can be divided into two main classes  Toshiba NB100 Battery

  • reciprocating
  • rotary

The positive displacement principle applies whether the pump is a  Toshiba Satellite M65 battery

Positive displacement pumps, unlike centrifugal or roto-dynamic pumps, will produce the same flow at a given speed (RPM) no matter what the discharge pressure  Dell Latitude D620 Battery .

  • Positive displacement pumps are "constant flow machines"

A positive displacement pump must not be operated against a closed valve on the discharge side of the pump because it has no shut-off head like centrifugal pumps  Dell Inspiron Mini 10 Battery .

A positive displacement pump operating against a closed discharge valve, will continue to produce flow until the pressure in the discharge line are increased until the line bursts or the pump is severely damaged - or both  Sony VGN-FW11S Battery .

A relief or safety valve on the discharge side of the positive displacement pump is therefore necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves  Sony VGN-FW11M Battery .

The internal valve should in general only be used as a safety precaution, an external relief valve installed in the discharge line with a return line back to the suction line or supply tank is recommended.

Reciprocating pumps   Sony VGN-FW139E/H battery

Typical reciprocating pumps are

A plunger pump consists of a cylinder with a reciprocating plunger in it. The suction and discharge valves are mounted in the head of the cylinder. In the suction stroke the plunger retracts and the suction valves open causing suction of fluid into the cylinder. In the forward stroke the plunger pushes the liquid out of the discharge valve  Dell Latitude E4200 Battery .

With only one cylinder the fluid flow varies between maximum flow when the plunger moves through the middle positions, and zero flow when the plunger is at the end positions. A lot of energy is wasted when the fluid is accelerated in the piping system. Vibration and "water hammer" may be a serious problem  Dell Inspiron 300M Battery .

In general the problems are compensated for by using two or more cylinders not working in phase with each other.

In diaphragm pumps, the plunger pressurizes hydraulic oil which is used to flex a diaphragm in the pumping cylinder. Diaphragm valves are used to pump hazardous and toxic fluids  Dell Vostro A840 Battery .

Gear pump

This uses two meshed gears rotating in a closely fitted casing. Fluid is pumped around the outer periphery by being trapped in the tooth spaces. It does not travel back on the meshed part, since the teeth mesh closely in the centre  Dell Studio 1737 battery .

Widely used on car engine oil pumps. it is also used in various hydraulic power packs .

Progressing cavity pump

Widely used for pumping difficult materials such as sewage sludge contaminated with large particles, this pump consists of a helical shaped rotor, about ten times as long as its width  Dell Inspiron E1505 battery .

This can be visualized as a central core of diameter x, with typically a curved spiral wound around of thickness half x, although of course in reality it is made from one casting. This shaft fits inside a heavy duty rubber sleeve, of wall thickness typically x also. As the shaft rotates, fluid is gradually forced up the rubber sleeve  Dell RM791 battery .

Such pumps can develop very high pressure at quite low volumes.

Roots-type pumps

The low pulsation rate and gentle performance of this Roots-type positive displacement pump is achieved due to a combination of its two 90° helical twisted rotors  Dell XPS M1530 battery ,

and a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous and non-vorticuless flow with equal volume. High capacity industrial "air compressors" have been designed to employ this principle  Dell XPS M2010 battery ,

as well as most "superchargers" used on internal combustion engines, and even a brand of civil defense siren, the Federal Signal Corporation's Thunderbolt.

Peristaltic pump

A peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids  Toshiba Satellite P10 Battery .

The fluid is contained within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A rotor with a number of "rollers", "shoes" or "wipers" attached to the external circumference compresses the flexible tube Acer Aspire One battery 10400mAh .

As the rotor turns, the part of the tube under compression closes (or "occludes") thus forcing the fluid to be pumped to move through the tube. Additionally, as the tube opens to its natural state after the passing of the cam ("restitution") fluid flow is induced to the pump  SONY VGN-FZ210CE Battery .

This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract.

Reciprocating-type pumps

Reciprocating pumps are those which cause the fluid to move using one or more oscillating pistons, plungers or membranes (diaphragms)  Dell Precision M70 Battery .

Reciprocating-type pumps require a system of suction and discharge valves to ensure that the fluid moves in a positive direction. Pumps in this category range from having "simplex" one cylinder, to in some cases "quad" four cylinders or more. Most reciprocating-type pumps are "duplex" (two) or "triplex" (three) cylinder  Toshiba Satellite L305 Battery .

Furthermore, they can be either "single acting" independent suction and discharge strokes or "double acting" suction and discharge in both directions. The pumps can be powered by air, steam or through a belt drive from an engine or motor. This type of pump was used extensively in the early days of steam propulsion (19th century) as boiler feed water pumps  Toshiba Satellite T4900 Battery .

Reciprocating pumps are now typically used for pumping highly viscous fluids including concrete and heavy oils, and special applications demanding low flow rates against high resistance  Toshiba PA3399U-2BRS battery .

Compressed-air-powered double-diaphragm pumps

One modern application of positive displacement diaphragm pumps is compressed-air-powered double-diaphragm pumps. Run on compressed air these pumps are intrinsically safe by design, although all manufacturers offer ATEX certified models to comply with industry regulation  Toshiba Satellite A200 Battery .

Commonly seen in all areas of industry from shipping to processing, SandPiper, Wilden Pumps or ARO are generally the larger of the brands. They are relatively inexpensive and can be used for almost any duty from pumping water out of bunds, to pumping hydrochloric acid from secure storage  Toshiba Satellite 1200 Battery

(dependent on how the pump is manufactured - elastomers / body construction). Lift is normally limited to roughly 6m although heads can reach almost 200 Psi.

Hydraulic ram pumps

A hydraulic ram is a water pump powered by hydropower  Toshiba Satellite M300 Battery .

It functions as a hydraulic transformer that takes in water at one "hydraulic head" (pressure) and flow-rate, and outputs water at a higher hydraulic-head and lower flow-rate. The device utilizes the water hammer effect to develop pressure that allows a portion of the input water that powers the pump to be lifted to a point higher than where the water originally started SONY VGP-BPS13A/Q Battery .

The hydraulic ram is sometimes used in remote areas, where there is both a source of low-head hydropower, and a need for pumping water to a destination higher in elevation than the source. In this situation, the ram is often useful, since it requires no outside source of power other than the kinetic energy of flowing water SONY VGP-BPS13A/Q Battery .

Velocity pumps

Rotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe SONY VGP-BPS13B/Q Battery .

This conversion of kinetic energy to pressure can be explained by the First law of thermodynamics or more specifically by Bernoulli's principle. Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved.

These types of pumps have a number of characteristics  SONY VGP-BPS13B/Q Battery :

  1. Continuous energy
  2. Conversion of added energy to increase in kinetic energy (increase in velocity)
  3. Conversion of increased velocity (kinetic energy) to an increase in pressure head  SONY VGP-BPS13/Q Battery

One practical difference between dynamic and positive displacement pumps is their ability to operate under closed valve conditions. Positive displacement pumps physically displace the fluid; hence closing a valve downstream of a positive displacement pump will result in a continual build up in pressure resulting in mechanical failure of either pipeline or pump SONY VGP-BPS13/Q Battery .

Dynamic pumps differ in that they can be safely operated under closed valve conditions (for short periods of time).

Centrifugal pump

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a fluid SONY VGP-BPS21A/B Battery .

Centrifugal pumps are the most common type of pump used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward or axially into a diffuser or volute chamber, from where it exits into the downstream piping system  SONY VGP-BPS21/S Battery .

Centrifugal pumps are typically used for large discharge through smaller heads.

Centrifugal pumps are most often associated with the radial flow type. However, the term "centrifugal pump" can be used to describe all impeller type rotodynamic pumps including the radial, axial and mixed flow variations SONY VGP-BPS21B Battery .

Radial flow pumps

Often simply referred to as centrifugal pumps. The fluid enters along the axial plane, is accelerated by the impeller and exits at right angles to the shaft (radially). Radial flow pumps operate at higher pressures and lower flow rates than axial and mixed flow pumpsSONY VGP-BPS21A Battery .

Axial flow pumps

Axial flow pumps differ from radial flow in that the fluid enters and exits along the same direction parallel to the rotating shaft. The fluid is not accelerated but instead "lifted" by the action of the impeller  SONY VGP-BPS21 Battery .

They may be likened to a propeller spinning in a length of tube. Axial flow pumps operate at much lower pressures and higher flow rates than radial flow pumps  Sony VGP-BPS21A/B Battery .

Mixed flow pumps

Mixed flow pumps, as the name suggests, function as a compromise between radial and axial flow pumps, the fluid experiences both radial acceleration and lift and exits the impeller somewhere between 0-90 degrees from the axial direction  Sony VGP-BPS21/S Battery .

As a consequence mixed flow pumps operate at higher pressures than axial flow pumps while delivering higher discharges than radial flow pumps. The exit angle of the flow dictates the pressure head-discharge characteristic in relation to radial and mixed flow Sony VGP-BPS21A Battery .

Eductor-jet pump

This uses a jet, often of steam, to create a low pressure. This low pressure sucks in fluid and propels it into a higher pressure regionSony VGP-BPS21 Battery .

Gravity pumps

Gravity pumps include the syphon and Heron's fountain - and there also important qanat or foggara systems which simply use downhill flow to take water from far-underground aquifers in high areas to consumers at lower elevations Sony Vaio PCG-5G2L Battery .

The hydraulic ram is also sometimes referred to as a gravity pump.

Steam pumps

Steam pumps are now mainly of historical interest. They include any type of pump powered by a steam engine and also pistonless pumps such as Thomas Savery's pump and the Pulsometer steam pump  Sony Vaio PCG-5G3L Battery .

Valveless pumps

Valveless pumping assists in fluid transport in various biomedical and engineering systems. In a valveless pumping system, no valves are present to regulate the flow direction  Sony Vaio PCG-5J1L Battery .

The fuid pumping efficiency of a valveless system, however, is not necessarily lower than that having valves. In fact, many fluid-dynamical systems in nature and engineering more or less rely upon valveless pumping to transport the working fluids therein Sony Vaio PCG-5K2L Battery .

For instance, blood circulation in the cardiovascular system is maintained to some extent even when the heart’s valves fail. Meanwhile, the embryonic vertebrate heart begins pumping blood long before the development of discernable chambers and valvesSony Vaio PCG-5J2L Battery .

In microfuidics, valveless impedance pump have been fabricated, and are expected to be particularly suitable for handling sensitive biofuids.

Pump Repairs

Examining pump repair records and MTBF (mean time between failures) is of great importance to responsible and conscientious pump users  Sony Vaio PCG-5K1L Battery .

In view of that fact, the preface to the 2006 Pump User’s Handbook alludes to "pump failure" statistics. For the sake of convenience, these failure statistics often are translated into MTBF (in this case, installed life before failure)  Sony Vaio PCG-6S2L Battery .

In early 2005, Gordon Buck, John Crane Inc.’s chief engineer for Field Operations in Baton Rouge, LA, examined the repair records for a number of refinery and chemical plants to obtain meaningful reliability data for centrifugal pumps. A total of 15 operating plants having nearly 15,000 pumps were included in the survey  Sony Vaio PCG-6S3L Battery .

The smallest of these plants had about 100 pumps; several plants had over 2000. All facilities were located in the United States. In addition, considered as "new," others as "renewed" and still others as "established." Many of these plants—but not all—had an alliance arrangement with John Crane  Sony Vaio PCG-6V1L Battery .

In some cases, the alliance contract included having a John Crane Inc. technician or engineer on-site to coordinate various aspects of the program.

Not all plants are refineries, however, and different results can be expected elsewhere  Sony Vaio PCG-6W1L Battery .

In chemical plants, pumps have traditiona

lly been "throw-away" items as chemical attack can result in limited life. Things have improved in recent years, but the somewhat restricted space available in "old" DIN and ASME-standardized stuffing boxes places limits on the type of seal that can be fitted  Sony Vaio PCG-6W2L Battery .

Unless the pump user upgrades the seal chamber, only the more compact and simple versions can be accommodated. Without this upgrading, lifetimes in chemical installations are generally believed to be around 50 to 60 percent of the refinery values  Sony Vaio PCG-6W3L Battery .

It goes without saying that unscheduled maintenance often is one of the most significant costs of ownership, and failures of mechanical seals and bearings are among the major causes. Keep in mind the potential value of selecting pumps that cost more initially, but last much longer between repairs   Sony Vaio PCG-7111L Battery .

The MTBF of a better pump may be one to four years longer than that of its non-upgraded counterpart. Consider that published average values of avoided pump failures range from $2600 to $12,000. This does not include lost opportunity costs. One pump fire occurs per 1000 failures. Having fewer pump failures means having fewer destructive pump fires  Sony Vaio PCG-7112L Battery .

As has been noted, a typical pump failure based on actual year 2002 reports, costs $5,000 on average. This includes costs for material, parts, labor and overhead. Let us now assume that the MTBF for a particular pump is 12 months and that it could be extended to 18 months  Sony Vaio PCG-7113L Battery .

This would result in a cost avoidance of $2,500/yr—which is greater than the premium one would pay for the reliability-upgraded centrifugal pump.

Applications

Pumps are used throughout society for a variety of purposes  Sony Vaio PCG-7133L Battery .

Early applications includes the use of the windmill or watermill to pump water. Today, the pump is used for irrigation, water supply, gasoline supply, air conditioning systems, refrigeration (usually called a compressor), chemical movement, sewagemovement, flood control, marine services, etc  Sony Vaio PCG-7Z2L Battery .

Because of the wide variety of applications, pumps have a plethora of shapes and sizes: from very large to very small, from handling gas to handling liquid, from high pressure to low pressure, and from high volume to low volume Sony Vaio PCG-8Y1L Battery .

Priming a pump

Liquid and slurry pumps can lose prime and this will require the pump to be primed by adding liquid to the pump and inlet pipes to get the pump started. Loss of "prime" is usually due to ingestion of air into the pump  Sony Vaio PCG-8Y2L Battery .

The clearances and displacement ratios in pumps used for liquids and other more viscous fluids cannot displace the air due to its lower density.

Pumps as public water supplies

One sort of pump once common worldwide was a hand-powered water pump, or 'pitcher pump'  Sony Vaio PCG-8Z1L Battery .

It would be installed over a community water well that was used by people in the days before piped water supplies.

In parts of the British Isles, it was often called "the parish pump". Although such community pumps are no longer common, the expression "parish pump" is still used   Sony Vaio PCG-8Z2L Battery .

It derives from the kind of the chatter and conversation that might be heard as people congregated to draw water from the community water pump, and is now used to describe a place or forum where matter of purely local interest is discussed  SONY VAIO VGN-FW31J Battery .

Because water from pitcher pumps is drawn directly from the soil, it is more prone to contamination. If such water is not filtered and purified, consumption of it might lead to gastrointestinal or other water-borne diseases  SONY VAIO VGN-FW31E Battery .

Modern hand operated community pumps are considered the most sustainable low cost option for safe water supply in resource poor settings, often in rural areas in developing countries. A hand pump opens access to deeper groundwater that is often not polluted and also improves the safety of a well by protecting the water source from contaminated buckets SONY VAIO VGN-FW31B Battery .

Pumps like the Afridev pump are designed to be cheap to build and install, and easy to maintain with simple parts. However, scarcity of spare parts for these type of pumps in some regions of Africa has diminished their utility for these areas  SONY VAIO VGN-FW31M Battery .

Sealing Multiphase Pumping Applications

Multiphase pumping applications, also referred to as tri-phase, have grown due to increased oil drilling activity  SONY VAIO VGN-FW31Z Battery .

In addition, the economics of multiphase production is attractive to upstream operations as it leads to simpler, smaller in-field installations, reduced equipment costs and improved production rates. In essence, the multiphase pump can accommodate all fluid stream properties with one piece of equipment, which has a smaller footprint  SONY VAIO VGN-FW38M Battery .

Often, two smaller multiphase pumps are installed in series rather than having just one massive pump.

For midstream and upstream operations, multiphase pumps can be located onshore or offshore and can be connected to single or multiple wellheads  SONY VAIO VGN-AW41JF Battery .

Basically, multiphase pumps are used to transport the untreated flow stream produced from oil wells to downstream processes or gathering facilities. This means that the pump may handle a flow stream (well stream) from 100 percent gas to 100 percent liquid and every imaginable combination in between  SONY VAIO VGN-AW41JF/H Battery .

The flow stream can also contain abrasives such as sand and dirt. Multiphase pumps are designed to operate under changing/fluctuating process conditions. Multiphase pumping also helps eliminate emissions of greenhouse gases as operators strive to minimize the flaring of gas and the venting of tanks where possible  SONY VAIO VGN-AW41MF Battery .

Helico-Axial Pumps (Centrifugal) A rotodynamic pump with one single shaft requiring two mechanical seals. This pump utilizes an open-type axial impeller. This pump type is often referred to as a "Poseidon Pump" and can be described as a cross between an axial compressor and a centrifugal pump  SONY VAIO VGN-AW41MF/H Battery .

Twin Screw (Positive Displacement) The twin screw pump is constructed of two intermeshing screws that force the movement of the pumped fluid. Twin screw pumps are often used when pumping conditions contain high gas volume fractions and fluctuating inlet conditions. Four mechanical seals are required to seal the two shafts SONY VAIO VGN-FW30B Battery .

Progressive Cavity Pumps (Positive Displacement) Progressive cavity pumps are single-screw types typically used in shallow wells or at the surface. This pump is mainly used on surface applications where the pumped fluid may contain a considerable amount of solids such as sand and dirt  SONY VAIO VGN-FW50B Battery .

Electric Submersible Pumps (Centrifugal) These pumps are basically multistage centrifugal pumps and are widely used in oil well applications as a method for artificial lift. These pumps are usually specified when the pumped fluid is mainly liquid SONY VAIO VGN-FW51B/W Battery .

Buffer Tank A buffer tank is often installed upstream of the pump suction nozzle in case of a slug flow. The buffer tank breaks the energy of the liquid slug, smoothes any fluctuations in the incoming flow and acts as a sand trap  SONY VAIO VGN-FW51MF Battery .

As the name indicates, multiphase pumps and their mechanical seals can encounter a large variation in service conditions such as changing process fluid composition, temperature variations, high and low operating pressures and exposure to abrasive/erosive media  SONY VAIO VGN-FW51MF/H Battery .

The challenge is selecting the appropriate mechanical seal arrangement and support system to ensure maximized seal life and its overall effectiveness  SONY VAIO VGN-FW51ZF Battery .

Specifications

Pumps are commonly rated by horsepower, flow rate, outlet pressure in feet (or metres) of head, inlet suction in suction feet (or metres) of head. The head can be simplified as the number of feet or metres the pump can raise or lower a column of water at atmospheric pressure  SONY VAIO VGN-FW51ZF/H Battery .

From an initial design point of view, engineers often use a quantity termed the specific speed to identify the most suitable pump type for a particular combination of flow rate and head  SONY VAIO VGN-FW52JB Battery .

Pump material

Pump material can be of Stainless steel ( SS 316 or SS 304) , cast iron etc. It depend upon the application of pump. In water industry for pharma application, SS 316 is normally used. As at high temperature stainless steel give better result SONY VAIO VGN-FW54FB Battery .

Pumping power

The power imparted into a fluid will increase the energy of the fluid per unit volume. Thus the power relationship is between the conversion of the mechanical energy of the pump mechanism and the fluid elements within the pump   SONY VAIO VGN-FW70DB Battery .

In general, this is governed by a series of simultaneous differential equations, known as the Navier-Stokes equations. However a more simple equation relating only the different energies in the fluid, known as Bernoulli's equation can be used. Hence the power, P, required by the pump  SONY VAIO VGN-FW71DB/W Battery :

where ?P is the change in total pressure between the inlet and outlet (in Pa), and Q, the fluid flowrate is given in m^3/s. The total pressure may have gravitational, static pressure and kinetic energycomponents; i.e. energy is distributed between change in the fluid's gravitational potential energy (going up or down hill) SONY VAIO VGN-FW72JGB Battery ,

change in velocity, or change in static pressure. ? is the pump efficiency, and may be given by the manufacturer's information, such as in the form of a pump curve, and is typically derived from either fluid dynamics simulation (i.e. solutions to the Navier-stokes for the particular pump geometry), or by testing  SONY VAIO VGN-FW73JGB Battery .

The efficiency of the pump will depend upon the pump's configuration and operating conditions (such as rotational speed, fluid density and viscosity etc).

For a typical "pumping" configuration, the work is imparted on the fluid, and is thus positive  SONY VAIO VGN-FW74FB Battery .

For the fluid imparting the work on the pump (i.e. a turbine), the work is negative power required to drive the pump is determined by dividing the output power by the pump efficiency. Furthermore, this definition encompasses pumps with no moving parts, such as a siphon  SONY VAIO VGN-FW81HS Battery .

Pump efficiency

Pump efficiency is defined as the ratio of the power imparted on the fluid by the pump in relation to the power supplied to drive the pump. Its value is not fixed for a given pump, efficiency is a function of the discharge and therefore also operating head SONY VAIO VGN-FW81NS Battery .

For centrifugal pumps, the efficiency tends to increase with flow rate up to a point midway through the operating range (peak efficiency) and then declines as flow rates rise further. Pump performance data such as this is usually supplied by the manufacturer before pump selection  SONY VAIO VGN-FW81S Battery .

Pump efficiencies tend to decline over time due to wear (e.g. increasing clearances as impellers reduce in size).

One important part of system design involves matching the pipeline headloss-flow characteristic with the appropriate pump or pumps which will operate at or close to the point of maximum efficiency  SONY VAIO VGN-FW82DS Battery .

There are free tools that help calculate head needed and show pump curves including their Best Efficiency Points (BEP).

Pump efficiency is an important aspect and pumps should be regularly tested. Thermodynamic pump testing is one method SONY VAIO VGN-FW82JS Battery .

Pump selection is done by performance curve which is curve between pressure head and flow rate. And also power supply is also taken care of. Pumps are normally available that run at 50 hz or 60 hz  SONY VAIO VGN-FW82XS Battery .

A balancing machine is a measuring tool used for balancing rotating machine parts such as rotors for electric motors, fans, turbines, disc brakes, disc drives, propellers and pumps. The machine usually consists of two rigid pedestals, with suspension and bearings on top supporting a mounting platform  SONY VAIO VGN-FW83DS Battery .

The unit under test is bolted to the platform and is rotated either with a belt-, air-, or end-drive. As the part is rotated, the vibration in the suspension is detected with sensors and that information is used to determine the amount of unbalance in the part SONY VAIO VGN-FW83JS Battery .

Along with phase information, the machine can determine how much and where to add weights to balance the part .

Hard-bearing vs. soft-bearing

There are two main types of balancing machines, hard-bearing and soft-bearing SONY VAIO VGN-FW83XS Battery .

The difference between them, however, is in the suspension and not the bearings.

In a hard-bearing machine, balancing is done at a frequency lower than the resonance frequency of the suspension. In a soft-bearing machine, balancing is done at a frequency higher than the resonance frequency of the suspension SONY VAIO VGN-FW90NS Battery.

Both types of machines have various advantages and disadvantages. A hard-bearing machine is generally more versatile and can handle pieces with greatly varying weights, because hard-bearing machines are measuring centrifugal forces and require only a one-time calibration SONY VAIO VGN-FW90S Battery .

Only five geometric dimensions need to be fed into the measuring unit and the machine is ready for use. Therefore, it works very well for low- and middle-size volume production and in repair workshops.

A soft-bearing machine is not so versatile with respect to amount of rotor weight to be balanced SONY VAIO VGN-FW91NS Battery .

The preparation of a soft-bearing machine for individual rotor types is more time consuming, because it needs to be calibrated for different part types. It is very suitable for high-production volume and high-precision balancing tasks SONY VAIO VGN-FW91S Battery .

Hard- and soft-bearing machines can be automated to remove weight automatically, such as by drilling or milling, but hard-bearing machines are more robust and reliable. Both machine principles can be integrated into a production line and loaded by a robot arm or gantry, requiring very little human control  SONY VAIO VGN-FW92DS Battery .

How it works

With the rotating part resting on the bearings, a vibration sensor is attached to the suspension. In most soft-bearing machines, a velocity sensor is used. This sensor works by moving a magnet in relation to a fixed coil that generates voltage proportional to the velocity of the vibration SONY VAIO VGN-FW92JS Battery .

Accelerometers, which measure acceleration of the vibration, can also be used.

A photocell (sometimes called a phaser), proximity sensor, or encoder is used to determine the rotational speed, as well as the relative phase of the rotating part  SONY VAIO VGN-FW93DS Battery .

This phase information is then used to filter the vibration information to determine the amount of movement, or force, in one rotation of the part. Also, the time difference between the phase and the vibration peak gives the angle at which the unbalance exists. Amount of unbalance and angle of unbalance give an unbalance vector  SONY VAIO VGN-FW93JS Battery .

Calibration is performed by adding a known weight at a known angle. In a soft-bearing machine, trial weights must be added in correction planes for each part. This is because the location of the correction planes along the rotational axis is unknown, and therefore it is unknown how much a given amount of weight will affect the balance  SONY VAIO VGN-FW139E/H Battery .

By using trial weights, you are adding a known weight at a known angle and getting the unbalance vector caused by it. This vector is then compared to the original unbalance vector to find the resultant vector, which gives the weight and angles needed to bring the part into balance  SONY VAIO VGN-FW145E/W Battery .

In a hard-bearing machine, the location of the correction plane must be given in advance so that the machine always knows how much a given amount of weight will affect the balance.

Other types of balancing machines

Static balancing machines differ from hard- and soft-bearing machines in that the part is not rotated to take a measurementSONY VAIO VGN-FW190EBH Battery .

Rather than resting on its bearings, the part rests vertically on its geometric center. Once at rest, any movement by the part away from its geometric center is detected by two perpendicular sensors beneath the table and returned as unbalance. Static balancers are often used to balance parts with a diameter much larger than their length, such as fans  SONY VAIO VGN-FW190EDH Battery .

The advantages of using a static balancer are speed and price. However a static balancer can only correct in one plane, so its accuracy is limited.

A blade balancing machine attempts to balance a part in assembly, so minimal correction is required later on SONY VAIO VGN-FW21E Battery .

Blade balancers are used on parts such as fans, propellers, and turbines. On a blade balancer, each blade to be assembled is weighed and its weight entered into a balancing software package. The software then sorts the blades and attempts to find the blade arrangement with the least amount of unbalance SONY VAIO VGN-FW21J Battery

Portable balancing machines are used to balance parts that cannot be taken apart and put on a balancing machine, usually parts that are currently in operation such as turbines, pumps, and motors. Portable balancers come with displacement sensors, such as accelerometers, and a photocell  SONY VAIO VGN-FW21L Battery ,

which are then mounted to the pedestals or enclosure of the running part. Based on the vibrations detected, they calculate the parts unbalance. Many times these devices contain a spectrum analyzer so the part condition can be monitored without the use of a photocell and non-rotational vibration can be analyzed SONY VAIO VGN-FW21M Battery .

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