A pump is a device used to move liquids or slurries. A pump moves liquids from lower pressure to higher pressure, and overcomes this difference in pressure by adding energy to the system (such as a water system). A gas pump is generally called a compressor, except in very low pressure-rise applications, such as in heating, ventilating, and air-conditioning, where the operative equipment consists of fans or blowers.
Pumps work by using mechanical forces to push the material, either by physically lifting, or by the force of compression.
The earliest type of pump was the Archimedes screw, described by Archimedes in the 3rd century BC, but used earlier by Sennacherib, King of Assyria, in the 7th century BC.[1] In the 13th century AD, al-Jazari described and illustrated different types of pumps, including reciprocating pumps, double acting pumps with suction pipes, water pumps, and pistons.[2][3]
2007年7月31日星期二
Types
Pumps fall into two major groups: rotodynamic pumps and positive displacement pumps. Their names describe the method for moving a fluid. Rotodynamic pumps are based on bladed impellors which rotate within the fluid to impart a tangential acceleration to the fluid and a consequent increase in the energy of the fluid. The purpose of the pump is to convert this energy into pressure energy of the fluid to be used in the associated piping system.
Positive displacement pumps
A positive displacement pump causes a liquid to move by trapping a fixed amount of fluid and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can be further classified as either rotary-type (for example the rotary vane pump) or reciprocating-type (for example the diaphragm pump).A common type is the Wendelkolben pump or the helical twisted Roots pump. 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, 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.
Centrifugal Pumps
Centrifugal Pumps are rotodynamic pumps which convert Mechanical energy into Hydraulic energy by centripetal force on the liquid. Typically, a rotating impeller increases the velocity of the fluid. The casing, or volute, of the pump then acts to convert this increased velocity into an increase in pressure. So if the mechanical energy is converted into a pressure head by centripetal force, the pump is classified as centrifugal. Such pumps are found in virtually every industry, and in domestic service in developed countries for washing machines, dishwashers, swimming pools, and water supply.
A wide range of designs are available, with constant and variable speed drives. Horizontal shafts are the most common. Single-stage pumps are usual in the smaller ratings. Pumps with up to 11 stages are in service. A demanding duty is boiler feed, and today's designs are typically 3 - 4 stage, with speeds of up to 6000 r/min.
After motors, centrifugal pumps are arguably the most common machine, and they are a significant user of energy. Given design margins, it is not unusual for a pump to be found to be over-sized, having been selected poorly for its intended duty. Running a constant speed pump throttled causes energy waste. A condition monitoring test can detect this condition and help size a smaller impeller, either new, or by machining the initial one, to achieve great energy reduction.
Pumps also wear internally, at a rate varying with the liquid pumped, materials of construction and operating regime. Again, condition monitoring can be applied to detect and quantify the extent and rate of wear and also help decide when overhaul is justified on an energy-saving basis.
A wide range of designs are available, with constant and variable speed drives. Horizontal shafts are the most common. Single-stage pumps are usual in the smaller ratings. Pumps with up to 11 stages are in service. A demanding duty is boiler feed, and today's designs are typically 3 - 4 stage, with speeds of up to 6000 r/min.
After motors, centrifugal pumps are arguably the most common machine, and they are a significant user of energy. Given design margins, it is not unusual for a pump to be found to be over-sized, having been selected poorly for its intended duty. Running a constant speed pump throttled causes energy waste. A condition monitoring test can detect this condition and help size a smaller impeller, either new, or by machining the initial one, to achieve great energy reduction.
Pumps also wear internally, at a rate varying with the liquid pumped, materials of construction and operating regime. Again, condition monitoring can be applied to detect and quantify the extent and rate of wear and also help decide when overhaul is justified on an energy-saving basis.
Kinetic Pumps
Continuous energy addition Conversion of added energy to increase in kinetic energy (increase in velocity) Conversion increased velocity to increase in pressure Conversion of Kinetic head to Pressure Head. Meet all heads like Kinetic , Potential, and Pressure
[edit] Positive DisplacementPeriodic energy addition Added energy forces displacement of fluid in an enclosed volume Fluid displacement results in direct increase in pressure
[edit] Positive DisplacementPeriodic energy addition Added energy forces displacement of fluid in an enclosed volume Fluid displacement results in direct increase in pressure
Application
Pumps are used throughout society for a variety of purposes. 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, sewage movement, flood control, marine services, etc.
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
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
[edit] Pumps as public water supplies
One sort of pump once common was a hand-powered water pump over a water well or water main where people could work it to extract water, before most houses had individual water supplies.
From this came the expression "parish pump" for "the sort of matter chattered about by people when they meet when they go to get water", "matter of only local interest".
From this came the expression "parish pump" for "the sort of matter chattered about by people when they meet when they go to get water", "matter of only local interest".
Power source
Pumps may be powered by an internal combustion engine, electric motor, manually (as with the hand pump used for pumping groundwater, called walking beam pump), or by wind power (common for irrigation). Solar power has been used to power an electric motor, for remote locations.[1]
2007年7月29日星期日
In Canada and the United States
Windmills feature uniquely in the history of New France, particularly in Canada, where they were used as strong points in fortifications.[7] Prior to the 1690 Battle of Québec, the strong point of the city's landward defenses was a windmill called Mont-Carmel, where a three-gun battery was in place.[7] At Fort Senneville, a large stone windmill was built on a hill by late 1686, doubling as a watch tower.[8] This windmill was like no other in New France, with thick walls, square loopholes for muskets, with machicolation at the top for pouring lethally hot liquids and rocks onto attackers.[8] This helped make it the "most substantial castle-like fort" near Montréal.[9]
In the United States, the development of the water-pumping windmill was the major factor in allowing the farming and ranching of vast areas of North America, which were otherwise devoid of readily accessible water. They contributed to the expansion of rail transport systems throughout the world, by pumping water from wells to supply the needs of the steam locomotives of those early times. They are still used today for the same purpose in some areas of the world where a connection to electric power lines is not a realistic option.
The multi-bladed wind turbine atop a lattice tower made of wood or steel was, for many years, a fixture of the landscape throughout rural America. These mills, made by a variety of manufacturers, featured a large number of blades so that they would turn slowly with considerable torque in low winds and be self regulating in high winds. A tower-top gearbox and crankshaft converted the rotary motion into reciprocating strokes carried downward through a rod to the pump cylinder below.
Windmills and related equipment are still manufactured and installed today on farms and ranches, usually in remote parts of the western United States where electric power is not readily available. The arrival of electricity in rural areas, brought by the Rural Electrification Administration (REA) in the 1930s through 1950s, contributed to the decline in the use of windmills in the US. Today, the increases in energy prices and the expense of replacing electric pumps has led to an increase in the repair, restoration and installation of new windmills.
In the United States, the development of the water-pumping windmill was the major factor in allowing the farming and ranching of vast areas of North America, which were otherwise devoid of readily accessible water. They contributed to the expansion of rail transport systems throughout the world, by pumping water from wells to supply the needs of the steam locomotives of those early times. They are still used today for the same purpose in some areas of the world where a connection to electric power lines is not a realistic option.
The multi-bladed wind turbine atop a lattice tower made of wood or steel was, for many years, a fixture of the landscape throughout rural America. These mills, made by a variety of manufacturers, featured a large number of blades so that they would turn slowly with considerable torque in low winds and be self regulating in high winds. A tower-top gearbox and crankshaft converted the rotary motion into reciprocating strokes carried downward through a rod to the pump cylinder below.
Windmills and related equipment are still manufactured and installed today on farms and ranches, usually in remote parts of the western United States where electric power is not readily available. The arrival of electricity in rural areas, brought by the Rural Electrification Administration (REA) in the 1930s through 1950s, contributed to the decline in the use of windmills in the US. Today, the increases in energy prices and the expense of replacing electric pumps has led to an increase in the repair, restoration and installation of new windmills.
Horizontal axle windmills
Fixed windmills, oriented to the prevailing wind were, for example, extensively used in the Cyclades islands of Greece. The economies of power and transport allowed the use of these 'offshore' mills for grinding grain transported from the mainland and flour returned. A 1/10th share of the flour was paid to the miller in return for his service. This type would mount triangular sails when in operation.
In North Western Europe, the horizontal-shaft or vertical windmill (so called due to the dimension of the movement of its blades) dates from the last quarter of the 12th century in the triangle of northern France, eastern England and Flanders. These earliest mills were used to grind cereals. The evidence at present is that the earliest type was the post mill, so named because of the large upright post on which the mill's main structure (the "body" or "buck") is balanced. By mounting the body this way, the mill is able to rotate to face the (variable) wind direction; an essential requirement for windmills to operate economically in North-Western Europe, where wind directions are various. By the end of the thirteenth century the masonry tower mill, on which only the timber cap rotated rather than the whole body of the mill, had been introduced. Due to the fact that only the cap of the tower mill needed to be turned the main structure could be made much taller, allowing the blades to be made longer, which enabled them to provide useful work even in low winds. Windmills were often built atop castle towers or city walls, and were a unique part of a number of fortifications in New France, such as at Fort Senneville.
The familiar lattice style of windmill blades allowed the miller to attach cloth sails to the blades (while applying a brake). Trimming the sails allowed the windmill to turn at near the optimal speed in a large range of wind velocities.
Upminster (Essex, UK) Windmill in June 2006; a smock mill - before it lost one of its sails in an early 2007 storm.The fantail, a small windmill mounted at right angles to the main sails which automatically turns the heavy cap and main sails into the wind, was invented in England in 1745. The smock mill is a later variation of the tower mill, constructed of timber and originally developed in the sixteenth century for land drainage. With some subsequent development mills became versatile in windy regions for all kind of industry, most notably grain grinding mills, sawmills (late 16th century), threshing, and, by applying scoop wheels, Archimedes' screws, and piston pumps, pumping water either for land drainage or for water supply.
With the industrial revolution, the importance of windmills as primary industrial energy source was replaced by steam and internal combustion engines. Polder mills were replaced by steam, or diesel engines. The industrial revolution and increased use of Steam and later Diesel power however had a lesser effect on the Mills of the Norfolk Broads in the United Kingdom, these being so isolated (on extensive uninhabitable marshland), therefore some of these mills continued use as drainage pumps till as late as 1959. More recently historic windmills have been preserved for their historic value, in some cases as static exhibits when the antique machinery is too fragile to put in motion, and in other cases as fully working mills.
With increasing environmental concern, and approaching limits to fossil fuel consumption, wind power has regained interest as a renewable energy source. This new generation of wind mills produce electric power and are more generally referred to as wind turbines.
See Flood control in the Netherlands for use of windmills in land reclamation in the Netherlands.
In North Western Europe, the horizontal-shaft or vertical windmill (so called due to the dimension of the movement of its blades) dates from the last quarter of the 12th century in the triangle of northern France, eastern England and Flanders. These earliest mills were used to grind cereals. The evidence at present is that the earliest type was the post mill, so named because of the large upright post on which the mill's main structure (the "body" or "buck") is balanced. By mounting the body this way, the mill is able to rotate to face the (variable) wind direction; an essential requirement for windmills to operate economically in North-Western Europe, where wind directions are various. By the end of the thirteenth century the masonry tower mill, on which only the timber cap rotated rather than the whole body of the mill, had been introduced. Due to the fact that only the cap of the tower mill needed to be turned the main structure could be made much taller, allowing the blades to be made longer, which enabled them to provide useful work even in low winds. Windmills were often built atop castle towers or city walls, and were a unique part of a number of fortifications in New France, such as at Fort Senneville.
The familiar lattice style of windmill blades allowed the miller to attach cloth sails to the blades (while applying a brake). Trimming the sails allowed the windmill to turn at near the optimal speed in a large range of wind velocities.
Upminster (Essex, UK) Windmill in June 2006; a smock mill - before it lost one of its sails in an early 2007 storm.The fantail, a small windmill mounted at right angles to the main sails which automatically turns the heavy cap and main sails into the wind, was invented in England in 1745. The smock mill is a later variation of the tower mill, constructed of timber and originally developed in the sixteenth century for land drainage. With some subsequent development mills became versatile in windy regions for all kind of industry, most notably grain grinding mills, sawmills (late 16th century), threshing, and, by applying scoop wheels, Archimedes' screws, and piston pumps, pumping water either for land drainage or for water supply.
With the industrial revolution, the importance of windmills as primary industrial energy source was replaced by steam and internal combustion engines. Polder mills were replaced by steam, or diesel engines. The industrial revolution and increased use of Steam and later Diesel power however had a lesser effect on the Mills of the Norfolk Broads in the United Kingdom, these being so isolated (on extensive uninhabitable marshland), therefore some of these mills continued use as drainage pumps till as late as 1959. More recently historic windmills have been preserved for their historic value, in some cases as static exhibits when the antique machinery is too fragile to put in motion, and in other cases as fully working mills.
With increasing environmental concern, and approaching limits to fossil fuel consumption, wind power has regained interest as a renewable energy source. This new generation of wind mills produce electric power and are more generally referred to as wind turbines.
See Flood control in the Netherlands for use of windmills in land reclamation in the Netherlands.
The first windmills had long vertical
The first windmills had long vertical shafts with rectangle shaped blades and appeared in Persia in the 9th century.[3] The authenticity of an earlier anecdote of a windmill involving the second caliph Umar (634-644 AD) is questioned on the grounds of being a 10th century amendment.[5] Made of six to twelve sails covered in reed matting or cloth material, these windmills were used to grind corn or draw up water, and quite different from the European versions. A similar type of vertical shaft windmill with rectangle blades, used for irrigation, can also be found in 13th century China, introduced by the travels of Yelü Chucai to Turkestan in 1219.[6]
History
A windwheel operating an organ is described as early as the 1st century AD by Hero of Alexandria, marking probably the first instance of a wind powering machine in history.[1][2] Vertical axle windmills were first used in eastern Persia (Sistan) by the 9th century AD as described by Muslim geographers.[3] Horizontal axle windmills of the type generally used today were invented in Northwestern Europe in the 1180s.[4]
2007年7月25日星期三
Gerotor
A Gerotor is a positive displacement pumping unit. The name gerotor is derived from "Generated Rotor". A Gerotor unit consists of an inner and outer rotor. The inner rotor has N teeth, and the outer rotor has N+1 teeth. One rotor is located off-center and both rotors rotate. During part of the assembly's rotation cycle, the area between the inner and outer rotor increases, creating a vacuum. This vacuum creates suction, and hence, this part of the cycle is where the intake is located. Then, the area between the rotors decreases, causing compression. During this compression period, fluids can be pumped, or compressed (if they are gaseous fluids).
A gerotor can also function as a motor. High pressure gas enters the intake area and pushes against the inner and outer rotors, causing both to rotate as the area between the inner and outer rotor increases. During the compression period, the exhaust is pumped out. This is an Otto cycle engine.
An engine created by the Starrotor Corporation combines both uses of a gerotor. It uses the Brayton cycle, the same thermodynamic cycle employed by jet engines. A first gerotor compresses gas, this gas is then ignited in a combustor. The gaseous products of this combustion have a much higher pressure, which drives a second gerotor. Then, some of the output of the second gerotor is used to drive the 1st.
A gerotor can also function as a motor. High pressure gas enters the intake area and pushes against the inner and outer rotors, causing both to rotate as the area between the inner and outer rotor increases. During the compression period, the exhaust is pumped out. This is an Otto cycle engine.
An engine created by the Starrotor Corporation combines both uses of a gerotor. It uses the Brayton cycle, the same thermodynamic cycle employed by jet engines. A first gerotor compresses gas, this gas is then ignited in a combustor. The gaseous products of this combustion have a much higher pressure, which drives a second gerotor. Then, some of the output of the second gerotor is used to drive the 1st.
Fire pump
A fire pump is a part of a fire sprinkler system's water supply. The pump intake is either connected to the public underground water supply piping, or a static water source (e.g., tank, reservoir, lake). The pump provide water flow at a higher pressure to the sprinkler system risers and hose standpipes. A fire pump is tested and listed for it's use specifically for fire service by a third-party testing and listing agency, such as UL or FM Global. The main code that governs fire pump installations in North America is the National Fire Protection Association's (NFPA) NFPA 20 Standard for the Installation of Stationary Fire Pumps for Fire Protection.
Fire pumps may be powered either by an electric motor or a diesel engine. If the local building code requires power independent of the local electric power grid, a pump using an electric motor may utilize the installation of an emergency generator.
The fire pump starts when the pressure in the fire sprinkler system drops below a threshold. The sprinkler system pressure drops significantly when one or more fire sprinklers are exposed to heat above their design temperature, and opens, releasing water.
Fire pumps are needed when the local municipal water system cannot provide sufficient pressure to meet the hydraulic design requirements of the fire sprinkler system. This usually occurs if the builidng is very tall, such as in high-rise buildings, or in systems which require a relatively high terminal pressure at the fire sprinkler in order to flow a large volume of water, such as in storage warehouses. Fire pumps are also needed if fire protection water supply is provided from a ground level water storage tank.
Types of pumps used for fire service include: horizontal split case, vertical split case, vertical inline, vertical turbine, and end suction.
A jockey pump is a small pump connected to a fire sprinkler system in parallel with the fire pump. It maintains pressure in a fire protection piping system to an artificially high level so that the operation of a single fire sprinkler will cause an appreciable pressure drop which will be easily sensed by the fire pump automatic controller, causing the fire pump to start. The jockey pump is essentially a portion of the fire pump's control system.
Fire pumps may be powered either by an electric motor or a diesel engine. If the local building code requires power independent of the local electric power grid, a pump using an electric motor may utilize the installation of an emergency generator.
The fire pump starts when the pressure in the fire sprinkler system drops below a threshold. The sprinkler system pressure drops significantly when one or more fire sprinklers are exposed to heat above their design temperature, and opens, releasing water.
Fire pumps are needed when the local municipal water system cannot provide sufficient pressure to meet the hydraulic design requirements of the fire sprinkler system. This usually occurs if the builidng is very tall, such as in high-rise buildings, or in systems which require a relatively high terminal pressure at the fire sprinkler in order to flow a large volume of water, such as in storage warehouses. Fire pumps are also needed if fire protection water supply is provided from a ground level water storage tank.
Types of pumps used for fire service include: horizontal split case, vertical split case, vertical inline, vertical turbine, and end suction.
A jockey pump is a small pump connected to a fire sprinkler system in parallel with the fire pump. It maintains pressure in a fire protection piping system to an artificially high level so that the operation of a single fire sprinkler will cause an appreciable pressure drop which will be easily sensed by the fire pump automatic controller, causing the fire pump to start. The jockey pump is essentially a portion of the fire pump's control system.
2007年7月23日星期一
Centrifugal Pumps
Centrifugal Pumps are rotodynamic pumps which convert Mechanical energy into Hydraulic energy by centripetal force on the liquid. Typically, a rotating impeller increases the velocity of the fluid. The casing, or volute, of the pump then acts to convert this increased velocity into an increase in pressure. So if the mechanical energy is converted into a pressure head by centripetal force, the pump is classified as centrifugal. Such pumps are found in virtually every industry, and in domestic service in developed countries for washing machines, dishwashers, swimming pools, and water supply.
Positive displacement pumps
Pumps fall into two major groups: rotodynamic pumps and positive displacement pumps. Their names describe the method for moving a fluid. Rotodynamic pumps are based on bladed impellors which rotate within the fluid to impart a tangential accelaration to the fluid and a consequent increase in the energy of the fluid. The purpose of the pump is to convert this energy into pressure energy of the fluid to be used in the associated piping system.
A pump is a device
Pumps work by using mechanical forces to push the material, either by physically lifting, or by the force of compression.
The earliest type of pump was the Archimedes screw, described by Archimedes in the 3rd century BC, but used earlier by Sennacherib, King of Assyria, in the 7th century BC.[1] In the 13th century AD, al-Jazari described and illustrated different types of pumps, including reciprocating pumps, double acting pumps with suction pipes, water pumps, and pistons.[2][3]
The earliest type of pump was the Archimedes screw, described by Archimedes in the 3rd century BC, but used earlier by Sennacherib, King of Assyria, in the 7th century BC.[1] In the 13th century AD, al-Jazari described and illustrated different types of pumps, including reciprocating pumps, double acting pumps with suction pipes, water pumps, and pistons.[2][3]
Gambol and Japes Wizarding Joke Shop
Gambol and Japes sells practical joke and trick items including Fred and George Weasley's favourite Dr. Filibuster's Fabulous No-Heat, Wet Start Fireworks. CS Ch.4
Weasleys' Wizard Wheezes
Weasleys' Wizard Wheezes was founded by Fred and George Weasley around 1994 or previous and they started selling, or at least advertising, in the summer of 1995. The following summer they opened premises at 93 Diagon Alley. Weasleys' Wizard Wheezes sells joke and trick items, useful novelties and Defence Against the Dark Arts items. Customers include the Weasley family, Harry Potter,Hermione Granger, Draco Malfoy, Romilda Vane and the Ministry of Magic themselves. Hogwarts Caretaker Argus Filch, however, has placed a blanket ban on all Weasleys' Wizard Wheezes products at Hogwarts.
Stalls
As well as many shops, Diagon Alley also contains small stalls. These stalls sell a wide range of things; including magical sweets. In Harry Potter and the Half-Blood Prince, many witches and wizards try to take advantage of the fear created by Lord Voldemort's return. They set up stalls selling amulets and other objects, which (according to them) protect you against werewolves, dementors and inferi. These 'dark magic protection' stalls, however, are illegal.
2007年7月22日星期日
Positive displacement pumps
A positive displacement pump causes a liquid to move by trapping a fixed amount of fluid and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can be further classified as either rotary-type (for example the rotary vane pump) or reciprocating-type (for example the diaphragm pump).A common type is the Wendelkolben pump or the helical twisted Roots pump. 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, 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.
2007年7月16日星期一
Drainage in New Orleans
In the 1830s state engineer George T. Dunbar proposed an ambitious system of underground drainage canals beneath the streets. The goal was to drain water by gravity into the low lying swamps, supplementing this with canals and mechanical pumps. The first of the city's steam engine powered drainage pumps, adapted from a ship's paddle wheel and used to push water along the Orleans Canal out to Bayou St. John, was constructed in this decade. However, only a few of Dunbar's plans were actually implemented as the panic of 1837 largely ended major systematic improvements for a generation.
In 1859 surveyor Louis H. Pilié improved the drainage canals, bricking in some portions. Four large steam "draining machines" were built to push water through the canals into the lake.
Vertical cross-section of New Orleans, showing maximum levee height of 23 feet.In 1871, some 36 miles of canals were built in the city for both improved drainage and small vessel shipping within town. However, despite earlier efforts, at the end of the 19th century it was still common for water to cover streets from curb to curb after rainstorms, sometimes for days.
In 1893, the city government formed the Drainage Advisory Board to come up with better solutions to the city's drainage problems. Extensive topographical maps were made and some of the nation's top engineers were consulted. In 1899, a bond was floated, and a 2 mill per dollar property tax approved, which funded and founded the Sewerage & Water Board of New Orleans. The Sewerage & Water Board had the responsibility of draining the city along with constructing a modern sewage and tap water system for the city, which, at the time, still relied heavily on cisterns and outhouses. (A different entity, the Orleans Levee Board, is in charge of supervision of the city's levee and floodwall system.)
The Sewerage & Water Board found A. Baldwin Wood, a young engineer who not only supervised the plans for improved drainage and pumping, but also invented a number of improvements in pumps and plumbing in the process. These improvements were not only used in New Orleans, but adopted all over the world.
As the 20th century progressed, much of the land that had previously been swampland or considered fit for no other use than cow pasture (due to periodic flooding), was drained. The city then expanded back from the natural higher ground close to the river and the natural bayou formed ridges.
On 15 April 1927, the city was deluged by a downpour of some 15 inches of rain within 19 hours. At the time, almost all of the city's pumps relied completely on the municipal electricity system, which went out early in the storm, thus knocking the pumps off line, which lead to extensive flooding in the city. After this, back up diesel generators with enough fuel to run the pumps for at least a day if electricity failed were added to the pumping stations. The "Good Friday Flood", as it was known locally, happened during the Great Mississippi Flood when the Mississippi River levels were dangerously high along the levees at the city, but was not directly connected to the more wide-ranging flood.
1927 also saw the start of a project to build a more extensive system of levees on the shoreline of Lake Pontchartrain. After 1945, all land up to the lake had been developed.
The city's system demonstrated its worth in times of crisis when the 1947 Fort Lauderdale Hurricane directly hit the city. Wood's drainage pumps kept the city proper mostly dry, while the neighboring suburbs on the East Bank of Jefferson Parish (which at the time did not have a comparable system operational), flooded under up to 6 feet of water.
Most of the city weathered Hurricane Betsy in 1965 without severe floodings, with the major exception of the Lower Ninth Ward neighborhood. The Lower Ninth Ward is separated from the rest of the city by the Industrial Canal and Gulf Intracoastal Waterway. It was flooded not by rainfall, but by a breach in the Industrial Canal levee, resulting in catastrophic flooding and loss of life in the neighborhood.
By the 1980s, the city boasted a system of 20 pumping stations with 89 pumps, with a combined capacity of 15,642,000 gallons per minute, 22.5 billion gallons per day, equal to the flow of the Ohio River.
In May of 1995, torrential rains (up to 20 inches in 12 hours in some places) overwhelmed pumping capacity (compounded, according to some, by a few pumps not being turned on until the deluge was already well underway), flooding substantial portions of the city. Slab houses in some low areas were flooded, and great numbers of automobiles on the city's flooded streets were declared totaled. This prompted projects increasing drainage capacity in the worst hit areas.
By early 2005, the city had 148 drainage pumps.
pumpchina pumpDiaphragm PumpsScrew PumpsResistant PumpsCentrifugal PumpsVertical PumpSuction PumpMulti-Stages PumpsOil PumpsSewage PumpsChemical Pumps
In 1859 surveyor Louis H. Pilié improved the drainage canals, bricking in some portions. Four large steam "draining machines" were built to push water through the canals into the lake.
Vertical cross-section of New Orleans, showing maximum levee height of 23 feet.In 1871, some 36 miles of canals were built in the city for both improved drainage and small vessel shipping within town. However, despite earlier efforts, at the end of the 19th century it was still common for water to cover streets from curb to curb after rainstorms, sometimes for days.
In 1893, the city government formed the Drainage Advisory Board to come up with better solutions to the city's drainage problems. Extensive topographical maps were made and some of the nation's top engineers were consulted. In 1899, a bond was floated, and a 2 mill per dollar property tax approved, which funded and founded the Sewerage & Water Board of New Orleans. The Sewerage & Water Board had the responsibility of draining the city along with constructing a modern sewage and tap water system for the city, which, at the time, still relied heavily on cisterns and outhouses. (A different entity, the Orleans Levee Board, is in charge of supervision of the city's levee and floodwall system.)
The Sewerage & Water Board found A. Baldwin Wood, a young engineer who not only supervised the plans for improved drainage and pumping, but also invented a number of improvements in pumps and plumbing in the process. These improvements were not only used in New Orleans, but adopted all over the world.
As the 20th century progressed, much of the land that had previously been swampland or considered fit for no other use than cow pasture (due to periodic flooding), was drained. The city then expanded back from the natural higher ground close to the river and the natural bayou formed ridges.
On 15 April 1927, the city was deluged by a downpour of some 15 inches of rain within 19 hours. At the time, almost all of the city's pumps relied completely on the municipal electricity system, which went out early in the storm, thus knocking the pumps off line, which lead to extensive flooding in the city. After this, back up diesel generators with enough fuel to run the pumps for at least a day if electricity failed were added to the pumping stations. The "Good Friday Flood", as it was known locally, happened during the Great Mississippi Flood when the Mississippi River levels were dangerously high along the levees at the city, but was not directly connected to the more wide-ranging flood.
1927 also saw the start of a project to build a more extensive system of levees on the shoreline of Lake Pontchartrain. After 1945, all land up to the lake had been developed.
The city's system demonstrated its worth in times of crisis when the 1947 Fort Lauderdale Hurricane directly hit the city. Wood's drainage pumps kept the city proper mostly dry, while the neighboring suburbs on the East Bank of Jefferson Parish (which at the time did not have a comparable system operational), flooded under up to 6 feet of water.
Most of the city weathered Hurricane Betsy in 1965 without severe floodings, with the major exception of the Lower Ninth Ward neighborhood. The Lower Ninth Ward is separated from the rest of the city by the Industrial Canal and Gulf Intracoastal Waterway. It was flooded not by rainfall, but by a breach in the Industrial Canal levee, resulting in catastrophic flooding and loss of life in the neighborhood.
By the 1980s, the city boasted a system of 20 pumping stations with 89 pumps, with a combined capacity of 15,642,000 gallons per minute, 22.5 billion gallons per day, equal to the flow of the Ohio River.
In May of 1995, torrential rains (up to 20 inches in 12 hours in some places) overwhelmed pumping capacity (compounded, according to some, by a few pumps not being turned on until the deluge was already well underway), flooding substantial portions of the city. Slab houses in some low areas were flooded, and great numbers of automobiles on the city's flooded streets were declared totaled. This prompted projects increasing drainage capacity in the worst hit areas.
By early 2005, the city had 148 drainage pumps.
pumpchina pumpDiaphragm PumpsScrew PumpsResistant PumpsCentrifugal PumpsVertical PumpSuction PumpMulti-Stages PumpsOil PumpsSewage PumpsChemical Pumps
Hurricane Katrina
This is the largest civil engineering disaster in the history of the United States. Nothing has come close to the $300 billion in damages and half-million people out of their homes and the lives lost." [1]
The greatest catastrophe in the city's drainage history started at the end of August 2005, when the city was hit by Hurricane Katrina, after which the majority of the city flooded. Katrina brought tropical storm conditions to the city starting the night of 28 August, with Hurricane conditions the following day through the afternoon.
The hurricane itself did not flood the city. Rather a series of failures in mis-designed levees and floodwalls allowed water from the Gulf of Mexico and Lake Pontchartrain to flow into the city.
The Industrial Canal was overwhelmed when storm surge, funneled in by the Mississippi River Gulf Outlet, overflowed and breached levees and floodwalls in several locations, flooding not only the Lower Ninth Ward, but also Eastern New Orleans and portions of the Upper Ninth Ward west of the Canal.
Meanwhile, waters from storm-swollen Lake Pontchartrain poured into the city, first from a breach in the 17th Street Canal, and then from a pair of breaches in both sides of the London Avenue Canal. These canals were among those used to channel water pumped from city streets into the lake. The storm caused the flow to reverse, and as water levels rose the entire drainage system failed. Examinations afterwards showed that water levels in these locations never topped the floodwalls, but instead the levees failed with a water level supposedly within their safe tolerance.
In much of town west of the Industrial Canal, residents who did not evacuate before the storm reported that after the storm they were relieved to see their streets dry and the precipitation from the storm successfully pumped out. However, disaster was already spreading from the series of levee breaches. In areas of town far from the breaches, flood water came not in through the streets, but up from the storm drains beneath the street, in some places changing streets from dry to under 3 feet of water within half an hour.
Flood lines show levels of high water on this Mid City New Orleans houseBy the evening of August 30th, some 80% of the city was under water. (This figure includes areas of widely differing flood levels, ranging from areas where streets were covered with water which never rose into homes to areas where homes were entirely submerged over the rooftops.) Most of the city's pumping stations were submerged. The few above the water line had no power and the emergency diesel fuel had run out. These few were often tiny islands in the flood, inaccessible even if intact enough to hypothetically be turned back on.
For most of the city to the west of the Industrial Canal, the flood levels were much the same as those reached in mid 19th century storms when, like Katrina, major hurricanes created a "lake flood" by pushing Lake Pontchartrain up into the South Shore. At the time of these earlier storms the lower lying areas of the city had little development, so effects on life and property were much less severe.
West of the Industrial Canal, the parts of the city unflooded or minimally flooded largely corresponded with areas of the city developed on naturally higher ground before 1900.
On August 31st, flood levels started to subside. The water level in the city had reached that of Lake Pontchartrain, and as the lake started to drain back into the Gulf, some water in the city started to flow into the lake via the same levee breeches they had entered through. In 19th century lake floods, the water soon flowed back into the lake as there were no levees on that side. In 2005, while the levees proved inadequate to keep the lake out of the city, even in breached form they were sufficient to keep much of the flooding from flowing back out. As breaches were gradually filled, some city pumps were reactivated, supplemented by additional pumps brought in by the Corps of Engineers. Some of the city's pumps which survived could not be reactivated because of the failures of the canals that they pumped flood waters into. The combined task of closing breaches and pumping the flood waters out took weeks and was compounded by a setback in late September due to further flooding from Hurricane Rita. See: Civil engineering and infrastructure repair in New Orleans after Hurricane Katrina.
pumpchina pumpDiaphragm PumpsScrew PumpsResistant PumpsCentrifugal PumpsVertical PumpSuction PumpMulti-Stages PumpsOil PumpsSewage PumpsChemical Pumps
The greatest catastrophe in the city's drainage history started at the end of August 2005, when the city was hit by Hurricane Katrina, after which the majority of the city flooded. Katrina brought tropical storm conditions to the city starting the night of 28 August, with Hurricane conditions the following day through the afternoon.
The hurricane itself did not flood the city. Rather a series of failures in mis-designed levees and floodwalls allowed water from the Gulf of Mexico and Lake Pontchartrain to flow into the city.
The Industrial Canal was overwhelmed when storm surge, funneled in by the Mississippi River Gulf Outlet, overflowed and breached levees and floodwalls in several locations, flooding not only the Lower Ninth Ward, but also Eastern New Orleans and portions of the Upper Ninth Ward west of the Canal.
Meanwhile, waters from storm-swollen Lake Pontchartrain poured into the city, first from a breach in the 17th Street Canal, and then from a pair of breaches in both sides of the London Avenue Canal. These canals were among those used to channel water pumped from city streets into the lake. The storm caused the flow to reverse, and as water levels rose the entire drainage system failed. Examinations afterwards showed that water levels in these locations never topped the floodwalls, but instead the levees failed with a water level supposedly within their safe tolerance.
In much of town west of the Industrial Canal, residents who did not evacuate before the storm reported that after the storm they were relieved to see their streets dry and the precipitation from the storm successfully pumped out. However, disaster was already spreading from the series of levee breaches. In areas of town far from the breaches, flood water came not in through the streets, but up from the storm drains beneath the street, in some places changing streets from dry to under 3 feet of water within half an hour.
Flood lines show levels of high water on this Mid City New Orleans houseBy the evening of August 30th, some 80% of the city was under water. (This figure includes areas of widely differing flood levels, ranging from areas where streets were covered with water which never rose into homes to areas where homes were entirely submerged over the rooftops.) Most of the city's pumping stations were submerged. The few above the water line had no power and the emergency diesel fuel had run out. These few were often tiny islands in the flood, inaccessible even if intact enough to hypothetically be turned back on.
For most of the city to the west of the Industrial Canal, the flood levels were much the same as those reached in mid 19th century storms when, like Katrina, major hurricanes created a "lake flood" by pushing Lake Pontchartrain up into the South Shore. At the time of these earlier storms the lower lying areas of the city had little development, so effects on life and property were much less severe.
West of the Industrial Canal, the parts of the city unflooded or minimally flooded largely corresponded with areas of the city developed on naturally higher ground before 1900.
On August 31st, flood levels started to subside. The water level in the city had reached that of Lake Pontchartrain, and as the lake started to drain back into the Gulf, some water in the city started to flow into the lake via the same levee breeches they had entered through. In 19th century lake floods, the water soon flowed back into the lake as there were no levees on that side. In 2005, while the levees proved inadequate to keep the lake out of the city, even in breached form they were sufficient to keep much of the flooding from flowing back out. As breaches were gradually filled, some city pumps were reactivated, supplemented by additional pumps brought in by the Corps of Engineers. Some of the city's pumps which survived could not be reactivated because of the failures of the canals that they pumped flood waters into. The combined task of closing breaches and pumping the flood waters out took weeks and was compounded by a setback in late September due to further flooding from Hurricane Rita. See: Civil engineering and infrastructure repair in New Orleans after Hurricane Katrina.
pumpchina pumpDiaphragm PumpsScrew PumpsResistant PumpsCentrifugal PumpsVertical PumpSuction PumpMulti-Stages PumpsOil PumpsSewage PumpsChemical Pumps
2007年7月14日星期六
Performance measures
pumping speed refers to the volume flow rate of a pump at its inlet, often measured in litres per second, cubic feet per minute, or cubic metre per hour. Because of compression, the volume flow rate at the outlet will always be much lower than at the inlet. Momentum transfer and entrapment pumps are more effective on some gases than others, so the pumping speed can be simultaneously different for each of the gases being pumped, and the average pumping speed will vary depending on the chemical composition of the gases remaining in the chamber. Throughput refers to the pumping speed multiplied by the gas pressure at the inlet, and is measured in units such as torr-litres/second. At a constant temperature, throughput is proportional to the number of molecules being pumped per unit time, and therefore to the mass flow rate of the pump. (Think PV=nRT) When discussing a leak, backstreaming or outgassing, throughput refers to the volume leak rate multiplied by the pressure at the vacuum side of the leak, so the leak throughput can be compared to the pump throughput. Positive displacement and momentum transfer pumps have a constant volume flow rate, (pumping speed,) but as the chamber's pressure drops, this volume contains less and less mass. So although the pumping speed remains constant, the throughput and mass flow rate drop exponentially. Meanwhile, the leakage, evaporation, sublimation and backstreaming rates produce a constant throughput into the system. When the pump's mass flow drops to the same level as the mass flows into the chamber, the system asymptotically approaches a constant pressure called the base pressure.
Evaporation and sublimation into a vacuum is called outgassing, and the most common source is water absorbed by materials in the chamber. If the dominant mass flow into the vacuum system is chamber leakage or outgassing of materials under vacuum, then the vacuum can be improved simply by installing bigger pumps with a higher volume flow rate. However, there is a point where backstream leakage through the pump and outgassing of the pump oils become the dominant mass flows into the chamber. In this situation, the vacuum will approach the pump's ultimate pressure - the best vacuum that this type of pump can achieve under ideal conditions. Adding more pumps in parallel or bigger pumps of the same type can still improve the pump-down speed, but they will not reduce the base pressure below ultimate. Better pumping technologies must be used to go beyond this barrier.
Evaporation and sublimation into a vacuum is called outgassing, and the most common source is water absorbed by materials in the chamber. If the dominant mass flow into the vacuum system is chamber leakage or outgassing of materials under vacuum, then the vacuum can be improved simply by installing bigger pumps with a higher volume flow rate. However, there is a point where backstream leakage through the pump and outgassing of the pump oils become the dominant mass flows into the chamber. In this situation, the vacuum will approach the pump's ultimate pressure - the best vacuum that this type of pump can achieve under ideal conditions. Adding more pumps in parallel or bigger pumps of the same type can still improve the pump-down speed, but they will not reduce the base pressure below ultimate. Better pumping technologies must be used to go beyond this barrier.
2007年7月12日星期四
Application
Pumps are used throughout society for a variety of purposes. 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, sewage movement, flood control, marine services, etc.
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.
Centrifugal Pumps
Centrifugal Pumps are rotodynamic pumps which convert Mechanical energy into Hydraulic energy by centripetal force on the liquid. Typically, a rotating impeller increases the velocity of the fluid. The casing, or volute, of the pump then acts to convert this increased velocity into an increase in pressure. So if the mechanical energy is converted into a pressure head by centripetal force, the pump is classified as centrifugal. Such pumps are found in virtually every industry, and in domestic service in developed countries for washing machines, dishwashers, swimming pools, and water supply.
A wide range of designs are available, with constant and variable speed drives. Horizontal shafts are the most common. Single-stage pumps are usual in the smaller ratings. Pumps with up to 11 stages are in service. A demanding duty is boiler feed, and today's designs are typically 3 - 4 stage, with speeds of up to 6000 r/min.
After motors, centrifugal pumps are arguably the most common machine, and they are a significant user of energy. Given design margins, it is not unusual for a pump to be found to be over-sized, having been selected poorly for its intended duty. Running a constant speed pump throttled causes energy waste. A condition monitoring test can detect this condition and help size a smaller impeller, either new, or by machining the initial one, to achieve great energy reduction.
Pumps also wear internally, at a rate varying with the liquid pumped, materials of construction and operating regime. Again, condition monitoring can be applied to detect and quantify the extent and rate of wear and also help decide when overhaul is justified on a energy-saving basis.
A wide range of designs are available, with constant and variable speed drives. Horizontal shafts are the most common. Single-stage pumps are usual in the smaller ratings. Pumps with up to 11 stages are in service. A demanding duty is boiler feed, and today's designs are typically 3 - 4 stage, with speeds of up to 6000 r/min.
After motors, centrifugal pumps are arguably the most common machine, and they are a significant user of energy. Given design margins, it is not unusual for a pump to be found to be over-sized, having been selected poorly for its intended duty. Running a constant speed pump throttled causes energy waste. A condition monitoring test can detect this condition and help size a smaller impeller, either new, or by machining the initial one, to achieve great energy reduction.
Pumps also wear internally, at a rate varying with the liquid pumped, materials of construction and operating regime. Again, condition monitoring can be applied to detect and quantify the extent and rate of wear and also help decide when overhaul is justified on a energy-saving basis.
Positive displacement pumps
A positive displacement pump causes a liquid to move by trapping a fixed amount of fluid and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can be further classified as either rotary-type (for example the rotary vane pump) or reciprocating-type (for example the diaphragm pump).A common type is the Wendelkolben pump or the helical twisted Roots pump. 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, 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.
2007年7月11日星期三
Airlift pump
An airlift pump is a simple pump which is powered by compressed air. Typically, the compressed air is pumped down a pipe into a well and bubbles into another larger diameter pipe. The air bubbles return to the surface in the larger pipe. A fizzy spurting flow of air and water results. Airlift pumps are often used in deep dirty wells where sand would quickly abrade mechanical parts. (The compressor is on the surface and no mechanical parts are needed in the well). However airlift wells must be much deeper than the water table to allow for submergence. Air is generally pumped at least as deep under the water as the water is to be lifted. (If the water table is 50 ft below, your air should be pumped 100 feet deep).
Centrifugal Pumps
Centrifugal Pumps are rotodynamic pumps which convert Mechanical energy into Hydraulic energy by centripetal force on the liquid. Typically, a rotating impeller increases the velocity of the fluid. The casing, or volute, of the pump then acts to convert this increased velocity into an increase in pressure. So if the mechanical energy is converted into a pressure head by centripetal force, the pump is classified as centrifugal. Such pumps are found in virtually every industry, and in domestic service in developed countries for washing machines, dishwashers, swimming pools, and water supply.
A wide range of designs are available, with constant and variable speed drives. Horizontal shafts are the most common. Single-stage pumps are usual in the smaller ratings. Pumps with up to 11 stages are in service. A demanding duty is boiler feed, and today's designs are typically 3 - 4 stage, with speeds of up to 6000 r/min.
After motors, centrifugal pumps are arguably the most common machine, and they are a significant user of energy. Given design margins, it is not unusual for a pump to be found to be over-sized, having been selected poorly for its intended duty. Running a constant speed pump throttled causes energy waste. A condition monitoring test can detect this condition and help size a smaller impeller, either new, or by machining the initial one, to achieve great energy reduction.
Pumps also wear internally, at a rate varying with the liquid pumped, materials of construction and operating regime. Again, condition monitoring can be applied to detect and quantify the extent and rate of wear and also help decide when overhaul is justified on a energy-saving basis.
A wide range of designs are available, with constant and variable speed drives. Horizontal shafts are the most common. Single-stage pumps are usual in the smaller ratings. Pumps with up to 11 stages are in service. A demanding duty is boiler feed, and today's designs are typically 3 - 4 stage, with speeds of up to 6000 r/min.
After motors, centrifugal pumps are arguably the most common machine, and they are a significant user of energy. Given design margins, it is not unusual for a pump to be found to be over-sized, having been selected poorly for its intended duty. Running a constant speed pump throttled causes energy waste. A condition monitoring test can detect this condition and help size a smaller impeller, either new, or by machining the initial one, to achieve great energy reduction.
Pumps also wear internally, at a rate varying with the liquid pumped, materials of construction and operating regime. Again, condition monitoring can be applied to detect and quantify the extent and rate of wear and also help decide when overhaul is justified on a energy-saving basis.
Pump
A pump is a device used to move liquids or slurries. A pump moves liquids from lower pressure to higher pressure, and overcomes this difference in pressure by adding energy to the system (such as a water system). A gas pump is generally called a compressor, except in very low pressure-rise applications, such as in heating, ventilating, and air-conditioning, where the operative equipment consists of fans or blowers.
Pumps work by using mechanical forces to push the material, either by physically lifting, or by the force of compression.
The earliest type of pump was the Archimedes screw, described by Archimedes in the 3rd century BC, but used earlier by Sennacherib, King of Assyria, in the 7th century BC. In the 13th century AD, al-Jazari described and illustrated different types of pumps, including reciprocating pumps, double acting pumps with suction pipes, water pumps, and pistons.
Pumps work by using mechanical forces to push the material, either by physically lifting, or by the force of compression.
The earliest type of pump was the Archimedes screw, described by Archimedes in the 3rd century BC, but used earlier by Sennacherib, King of Assyria, in the 7th century BC. In the 13th century AD, al-Jazari described and illustrated different types of pumps, including reciprocating pumps, double acting pumps with suction pipes, water pumps, and pistons.
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