what is pump and its type..??

Pump:-

    

 A small, electrically powered pump

A large, electrically driven pump (electro pump) for waterworks near the Hengsteyee, Germany.

A pump is a drive used to move fluids, such as liquids or slurries, or gases. A pump displaces a volume by physical or mechanical action. One common misconception about pumps is the thought that they create pressure.

Pumps alone do not create pressure; they only displace fluid, causing a flow. Adding resistance to flow causes pressure. Pumps fall into five major groups: direct lift, displacement, velocity, buoyancy and gravity pumps. Their names describe the method for moving a fluid.

Types:

Positive displacement pumps

  

 A lobe pump

Mechanism of a scroll pump

        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. A positive displacement pump can be further classified according to the mechanism used to move the fluid:

1.               Rotary –type, for example, the lobe, external gear, internal gear, screw, shuttle lock flexible vane or sliding vane, helical twisted roots (e.g. the wendelkolben pump) or the liquid ring vacuum pumps.

Positive displacement rotary pump that moves fluid using the principle 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.

Positive displace3ment rotary pumps also have their weakness. 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 the high speeds, the fluid will cause erosion, much as ocean waves polish stones or erode rock into sand. Rotary pumps that experience such erosion eventually show signs of enlarged clearances that allow the liquid to slip through and detract from the efficiency of the pump.

          Positive displacement rotary pumps can be grouped into their main types. 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 by side of the pumps as the teeth mesh and go around again.

         

          The screws are each mounted on shafts that run parallel to each other; the shafts also have gears of them that mesh with each other to turn the shafts together and keep everything in place. The turning of the screws, and consequently the shafts to which they are mounted, draws the fluid through the pumps.

          As with other forms of rotary pumps, the clearances between moving parts and the pump casing is minimal. 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.

2.               Reciprocating – type, for example, the piston or diaphragm pumps.

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

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

Reciprocating pumps:

Fluid is accelerated in the piping system. Vibration and “water hammer” may be a serious problem. In general, the problems are compensated for by using two or more cylinders not working in phase with

Typical reciprocating pumps are

3.               Plunger pumps

4.               Diaphragm pumps

A plunger the pump consists of a cylinder with a reciprocating plunger in it. The suction and discharge valves open causing suction o fluid into the cylinder. In the forward stroke, the plunger pushes the liquid out of the discharge valve.

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 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.

Gear pump

          This uses two meshes gears rotating in a closely fitted casing. The 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. Widely used on car engine oil pumps.

Progressing cavity pump

          Widely used for pumping difficult material such as sewage sludge contaminated with large particles, this pump consist of a helical shapes rotor, about 10 times as long as its width. This can be visualized as a the central core of diameter x, with typically a curved spiral, wound around of thickens half x although of course, in reality, it is made from one casting.

          This shaft inside a heavy-duty rubber sleeve, of wall thickness typically x also. As the shaft rotates, fluids are gradually forced up the rubber sleeve. Such pumps can develop very high pressure at quite low volumes.

Reciprocating-type-Pumps:

Hand-operated, reciprocating, positive displacement, water pump in Kosice-Tahannovce, Slovakia (walking beam pump).

Reciprocating pumps are those high cause the fluid to move using one or more oscillating pistons, plunges or membranes (diaphragms).

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 “simple” one cylinder, to in some cases “quad” four-cylinder or more. Most reciprocating-type pumps are “duplex” (two) or “triplex” (three) cylinder.

          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 drove from an engine or motor.

          This type of pump was used extensively in the early days of steam propulsion (19th century) as boiler feedwater pumps though still used today, reciprocating pumps are typically used for pumping highly viscous fluids including concrete and heavy oils and special applications demanding low flow rates against high resistance.

BUOYANCY PUMP

COMPRESSED-AIR-POWERED DOUBLE- DIAPHRAGM PUMPS

          One modern application of positive displacement diaphragm pumps is compressed-air-powdered double- diaphragm pumps. Run-on compressed air these pumps are intrinsically safe by design although all manufacture offer ATEX certified models to comply with industry regulation.

          Commonly seen in all areas of the industry from shipping to processing sandpiper Wilden pumps or ARO is 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 hydraulic acid from secure storage (dependent on how the pumps are manufactured- elastomers/body construction). Lift is normally limited to roughly 6m although heads can reach almost 200 psi.

Impulse pumps

Hydraulic ram pumps

         

A hydraulic ram is a water pump powered by hydropower.

         

It functions as a hydraulic transformer that takes in water at one “hydraulic head” (pressure) and flow-rate, an=d outputs water at a higher hydraulic-head and lower flow-rate.

          The devices utilize the water hammer effect to develop pressure that allows a portion of the input water that power the pump to be lifted to a point higher than where the originally started.

          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 on 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.

Velocity pumps:

A a centrifugal pump uses a spinning “impeller” which has backward swept arms 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 gain in potential energy (pressure) when the velocity is reduced before or as the flow exits the pump into the discharge pipe. 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 how the velocity gain is achieved.

These types of pumps can be further subdivided according to how the velocity gain is achieved.

These types of pumps have some characteristics:

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.

One practical difference between dynamic and positive displacement pumps are their ability to operate under closed valve condition.

Centrifugal pump

          A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pump used to move liquids through a piping system.

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

          The screw centrifugal impeller was invented in 60 by the late Martin Stahle, the founder of hydrostat AG. He had received an order from the Animal S.A. fish processing factory in Chimbote (Peru) for the development of a system for transporting fish from the nets into a boat, and from the boat into the fish processing plant.

          The pump was to work reliably without damaging the fish. The result was the pump with the characteristic screw centrifugal impeller. This invention was a great success. It has since been used in many ways throughout the world in countless other fluid handling systems.

          The screw centrifugal pump is a popular choice for handling delicate products such as food and crystal. Its low shear characteristics reduce emulsification when pumping mixtures making it ideal for pumping oily water and Return Activated sludge [RAS] as it does not damage the floc.

          The pump’s ability to pass long fibrous material such as rope without clogging makes it a frequent choice for municipal wastewater applications. A screw centrifugal pump typically has an operating efficiency of 70% to 85%. It has a relatively steeply rising head/capacity curve shape giving it good flow control capability over its allowable operating range.

          The impeller has a single blade, axially extended at the inlet and developed around its axis much like a corkscrew. Linking this to a centrifugal outlet allows pumping with the minimum of agitation and shear, essential factors when product bruising, liquid emulsification or clogging is to be avoided.

The screw centrifugal impeller features:

1.               Large free passage for pumping liquid with a solid object and fibrous materials

2.               Able to pump liquid and viscosity’s above values normally possible with conventional centrifugal pumps

3.               Steep H/Q curves with closed valve twice best efficiency point

4.               Low NPSH characteristics

5.               Flat non-overloading power curves high hydraulics efficiencies

6.               High hydraulic efficiencies

Screw centrifugal impeller pumps are widely accepted as state of the art pumps for handling raw sewage and sludge on treatment plants and incorporate many features, which benefits the end-user. Screw centrifugal impeller pumps are ideal for handling raw sewage, which contains stringy fibrous material impeller pumps are ideal for handling raw sewage, which contains stringy fibrous material and for handling sewage sludge with up to 10% dry solids content.

Typical application areas:

1.               Sump emptying

2.               Industrial effluent treatment

3.               Feeding oily water separators

4.               Transfers of live fish

5.               Oil and chemical spillages

6.               Mine drainage

7.               Parts washer equipment

8.               Processing of waste oil & sludge

9.               Transfer of fruit and vegetables

10.         Municipal wastewater treatment plants

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.

RADIAL FLOW PUMPS

          Often simply referred to as centrifugal pumps. The fluids enter long the axial plane, are accelerated by the impeller and exits at right to the shaft (radially). Radial flow pumps operate at a higher pressure and lower flow rates than axial and mixed flow pumps.

AXIAL FLOW PUMP

          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” the action of the impeller.

         

          They may be liked to a propeller spinning in the length of the tube. Axial flow pumps operate at much lower pressures and higher flow rates than radial flow pumps.