PUMP
PUMP
Pump is a device that moves liquids and
Pump is a device that moves liquids and
gases. Pumps are used in a variety of
gases. Pumps are used in a variety of
machines and other devices, including home
machines and other devices, including home
heating systems, refrigerators, oil wells and
heating systems, refrigerators, oil wells and
water wells, and turbojet and automobile
water wells, and turbojet and automobile
engines.Most pumps are made of steel or
engines.Most pumps are made of steel or
cast iron. Gas pumps are also called
cast iron. Gas pumps are also called
compressors
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
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/low-pressure 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
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.
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
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.
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.
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, lobe, and multi-lobe configurations. is a tri-lobe 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 rotate two 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 be in 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.
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.
