Presentation Pump

PUMP Pump is a device that moves liquids and gases. Pumps are used in a variety of  machines and other devices, including home heating systems, refrigerators, oil wells and water wells, and turbojet and automobile engines.Most pumps are made of steel or  cast iron. Gas pumps are also called compressors, compressors, fans, or blowers..

 Table 4.3.1 Classification of Pumps

TYPES OF PUMP

CENTRIFUGAL OR ROTOR DYNAMIC POSITIVE DISPLACEMENT

ROTO DYNAMIC Dynamic pumps maintain a steady flow of fluid

ROTO DYNAMIC OR CENTRIFUGAL

End suction pumps In-line pumps Double suction pumps Vertical multistage pumps Horizontal multistage pumps Submersible pumps Self-priming pumps  Axial-flow pumps

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Axial-flow pump

The main advantage of an AFP is that it can easily be adjusted to run at peak efficiency at low-flow/high-pressure and high-flow/lowpressure by changing the pitch on the propeller (some models only). These pumps have the smallest of the dimensions among many of the conventional pumps and are more suited for low heads and higher discharges.

General components of a Centrifugal Pump

Cut-away of a pump showing volute casing

Diffuser The purpose of the diffuser is to increase the efficiency of the centrifugal pump by  allowing a more gradual expansion and less turbulent area for the liquid to reduce in  velocity. This increase in flow area causes a reduction in flow velocity, converting kinetic energy  into flow pressure

Wearing rings

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To minimize the cost of pump maintenance, many centrifugal pumps are designed with wearing rings which are replaceable rings that attached to the impeller and/or the pump casing to allow a small running clearance between the impeller and the pump casing without causing wear of the actual impeller or pump casing material.

One of the simplest types of shaft seal is the stuffing box which is cylindrical space in the pump casing surrounding the shaft.The packing rings are held in place by a gland which is in turn, held in place by  studs with adjusting nuts. As the adjusting nuts are tightened, they move the gland in and compress the packing. This axial compression causes the packing to expand radially, forming a tight seal between the rotating shaft and the inside wall of the stuffing box.

POSITIVE DISPLACEMENT

Different between rotary and reciprocating pump Reciprocating pumps are those which cause the fluid to move using one or more oscillating pistons, plungers or membranes (diaphragms).

Rotary pumps are pumps that move fluid using the principles of rotation.

RECIPROCATING PUMPS

Typical reciprocating pumps are plunger pumps diaphragm pumps

PLUNGER PUMPS Plunger pumps comprise of a cylinder with a reciprocating plunger in it. In the head of the cylinder the suction and discharge valves are mounted. In the suction stroke the plunger retracts and the suction  valves opens causing suction of fluid into the cylinder. In the forward stroke the plunger push the liquid out the discharge valve.

Diaphragm pump 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.

Rotary pumps

TYPE OF PUMPS Internal Gear. Internal gear pumps carry fluid between the gear teeth from the inlet to outlet ports. The outer gear (rotor) drives the inner or idler gear on a stationary pin. The gears create voids as they come out of mesh and liquid flows into the cavities. As the gears come back into mesh, the volume is reduced and the liquid is forced out of the discharge port. The crescent prevents liquid from flowing backwards from the outlet to the inlet port.

Flexible Member. This principle is similar to the Vane principle except the vanes flex rather than slide. The fluid pumping and sealing action depends on the elasticity of  the flexible members. The flexible members may be a tube, a vane, or a liner. shows a flexible vane pump.

Lobe. Fluid is carried between the rotor teeth and the pumping chamber. The rotor surfaces create continuous sealing. Both gears are driven and are synchronized by  timing gears. Rotors include bi-wing, trilobe, and multi-lobe configurations. is a trilobe pump.

External Gear. External gear pumps also use gears which come in and out of mesh. As the teeth come out of mesh, liquid flows into the pump and is carried between the teeth and the casing to the discharge side of the pump. The teeth come back into mesh and the liquid is forced out the discharge port. External gear pumps rotatetwo identical gears against each other. Both gears are on a shaft with bearings on either side of the gears.

Vane. The vanes - blades, buckets, rollers, or slippers - work with a cam to draw fluid into and force it out of the pump chamber. The vanes may bein either the rotor or stator. The vane-in rotor pumps may be made with constant or variable displacement pumping elements. shows a sliding vane pump.

Circumferential Piston. Fluid is carried from inlet to outlet in spaces between piston surfaces. Rotors must be timed by separate means, and each rotor may have one or more piston elements.

Screw pumps carry fluid in the spaces between the screw threads. The fluid is displaced axially as the screws mesh. Single screw pumps are commonly called progressive cavity pumps. They have a rotor with external threads and a stator with internal threads. The rotor threads are eccentric to the axis of rotation. Multiple screw pumps have multiple external screw threads.  These pumps may be timed or untimed.

VANE PUMP

Lobe Pumps

INTERNAL GEAR PUMP

EXTERNAL GEAR PUMP

CAVITATIONS Suction Cavitations occurs when the pump suction is under a low pressure/high  vacuum condition where the liquid turn into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump where it no longer sees  vacuum and is compressed back into liquid by the discharge pressure. This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitations condition has large chunks of  material removed from its face causing premature failure of the pump.

Discharge Cavitations occurs when the pump discharge is extremely high. It normally occurs in a pump that is running at less than 10% of its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge. As the liquid flows around the impeller it must pass through the small clearance between the impeller and the pump cutwater at extremely high velocity. This velocity causes a vacuum to develop at the cutwater similar to what occurs in a venturi and turns the liquid into vapor