All Type of Pump
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Transcript of All Type of Pump
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Pump
Technical report on pumps and application
By;Majid hamedina
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Technical report on pumps and application
Introduction
Industrialization imposed an ever increasing demand for moving liquids from one location to
another far more practically than by gravity. In order to motivate the liquid to move through the
pipes and channels, energy has to be imparted to the liquid.
The energy, usually mechanical, provided by a prime mover is transferred to the liquid by a device
called a pump. It has also gained wide acceptance in the hydraulic machinery field both by the
manufacturers and by their customers.
Pump is a device used to move fluids, such as gases,liquids or slurries. 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.
Classification of pump
One general source of pump terminology, definitions, rules, and standards is the Hydraulic Institute
(HI) Standards, approved by the American National Standards Institute (ANSI) as national
standards. A classification of pumps by type, as defined by the HI, is shown in below diagram.
Pumps are divided into two fundamental types based on the manner in which they transmit energy
to the pumped media: kinetic or positive displacement. In kinetic displacement, a centrifugal force
of the rotating element, called an impeller, impels kinetic energy to the fluid, moving the fluid from
http://en.wikipedia.org/wiki/Gaseshttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Slurryhttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Slurryhttp://en.wikipedia.org/wiki/Gases -
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pump suction to the discharge. On the other hand, positive displacement uses the reciprocating
action of one or several pistons, or a squeezing action of meshing gears, lobes, or other moving
bodies, to displace the media from one area into another (i.e., moving the material from suction to
discharge). Sometimes the terms inlet (for suction) and exit or outlet (for discharge) are used.
The pumped medium is usually liquid; however, many designs can handle solids in the forms of
suspension, entrained or dissolved gas, paper pulp, mud, slurries, tars, and other exotic substances,
that, at least by appearance, do not resemble liquids. Nevertheless, an overall liquid behavior must
be exhibited by the medium in order to be pumped. In other words, the medium must have
negligible resistance to tensile stresses.
The HI classifies pumps by type, not by application. The user, however, must ultimately deal with
specific applications. Often, based on personal experience, preference for a particular type of pump
develops, and this preference is passed on in the particular industry. For example, boiler feed pumps
are usually of a multistage diffuser barrel type, especially for the medium and high energy (over
1000 hp) applications, although volute pumps in single or multistage configurations, with radials or
axially split casings, also have been applied successfully. Examples of pump types and applications
and the reasons behind implicational preferences will follow.
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All type of pump diagram
Liquid transfer
To truly understand pump operation, one need to carefully examine the specifics of each individual
system in which a pump is installed and operating (see below picture).The main elements of a
pumping system are:
Supply side (suction or inlet side)
Pump (with a driver)
Delivery side (discharge or process)
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Pump in a system
The energy delivered to a pump by the driver is spent on useful energy to move the fluid and to
overcome losses:
From the pump user viewpoint, there are some major parameters of interest:
Flow:Flow is a parameter that tells us how much of the fluid needs to be moved (i.e., transferring
from a large storage tank to smaller drums for distribution and sale, adding chemicals to a process,
etc.).
Pressure:Tells us how much of the hydraulic resistance needs to be overcome by the pumping element,
in order to move the fluid.
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In a perfect world of zero losses, all of the input power would go into moving the flow against
given pressure. We could say that all of the available driver power was spent on, or transferred to, a
hydraulic (i.e., useful) power.
Capacity:
Imagine a piston steadily pushed against pressure, p, inside a pipe filled with liquid. During the
time t, the piston will travel a distance L, and the exerting force F on a piston, is doing work
to get this process going. From our school days, we remember that work equals force multiplied by
distance W=F*d for a steady motion, the force is balanced by the pressure p,
acting on area, A:
Work per unit of time equals power. So, dividing both sides of the equation by t, we get:
Q is the volume per unit of time, which in pump language is called flow, capacity, or
delivery. Inside the pump, the fluid is moved against the pressure by a piston, rotary gear, orimpeller, etc. (thus far assuming no losses).
Total system head:
"Head" is a very convenient term in the pumping business. Capacity is measured in gallons per
minute, and each gallon of liquid has weight, so we can easily calculate the pounds per minute
being pumped. Head or height is measure in feet, so if we multiply these two together we get foot-
pounds per minute which converts directly to work.Pressure is not as convenient a term because the amount of pressure that the pump will deliver
depends upon the weight (specific gravity) of the liquid being pumped and the specific gravity
changes with temperature, fluid, and fluid concentration.
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Head of pump definition
If you will refer to above figure, you should get a clear picture of what is meant by static head. Note
that we always measure from the center line of the pump to the highest liquid level. To calculate
head accurately we must calculate the total head on both the suction and discharge sides of the
pump. In addition to the static head we will learn that there is a head caused by resistance in the
piping, fittings and valves called friction head, and a head caused by any pressure that might be
acting on the liquid in the tanks including atmospheric pressure, called "surface pressure head".
Once we know these heads it gets simple, we will then subtract the suction head from the discharge
head and the amount remaining will be the amount of head that the pump must be able to generate
at the rated flow. Here is how it looks in a formula:
System head = total discharge head - total suction head
H = hd - hs
The total discharge head is made from three separate heads:
hd = hsd + hpd + hfd
1hd = total discharge head
2hsd = discharge static head
3hpd = discharge surface pressure head
4hfd = discharge friction head
The total suction head also consists of three separate heads;
hs = hss + hps - hfs
hs = total suction head
hss = suction static head
hps = suction surface pressure head
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hfs = suction friction head
As we make these calculations, you must sure that all calculations are made in either "feet of liquid
gauge" or "feet of liquid absolute". In case you have forgotten "absolute means that you have added
atmospheric pressure (head) to the gauge reading.
Kinetic pump
Kinetic pumps are dynamic devices that impart the energy of motion (kinetic energy) to a liquid by
use of a rotating impeller, propeller, or similar device. Kinetic pumps have the following
characteristics:
- Discharge is relatively free of pulsation.
- Mechanical design lends itself to high throughputs, so that capacity limits are seldom a problem.
- Efficient performance over a range of heads and capacities.
- Discharge pressure is a function of fluid density and operational speed.
- They are relatively small high speed devices.
- They are economical.
Centrifugal pump
A centrifugal pump is known to be a pressure generator, vs. a flow generator, which a rotary
pump is. Essentially, a centrifugal pump has a rotating element, or several of them, which impel
(hence the name impeller) the energy to the fluid. A collector (volute or a diffuser) guides the fluid
to discharge. A centrifugal pump is one of the simplest pieces of equipment in any process plant.
The below figure shows how this type of pump operates:
Liquid is forced into an impeller either by atmospheric pressure.
The vanes of impeller pass kinetic energy to the liquid, thereby causing the liquid to rotate.
The liquid leaves the impeller at high velocity.
The impeller is surrounded by a volute casing. The volute or stationary diffuser ring
converts the kinetic energy into pressure energy.
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Centrifugal pump component
Take a look at the below figure, with regard to performance of pump we can conclude:
The head and flow rate determine the performance of a pump, which is graphically shown in
the Figure.
Head
Flow
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The figure shows a typical curve of a centrifugal pump where the head gradually decreases
with increasing flow.
As the resistance of a system increases, the head will also increase. This in turn causes the
flow rate to decrease and will eventually reach zero. A zero flow rate is only acceptable for a
short period without causing to the pump to burn out.
A centrifugal pump has two main components. First, a rotating component comprised of an
impeller and a shaft. And secondly, a stationary component comprised of a casing, casing cover,
and bearings. In the below pictures are shown.
Centrifugal pump and its components
Casing:
have two functions
The main function of casing is to enclose the impeller at suction and delivery ends
and thereby form a pressure vessel.
A second function of casing is to provide a supporting and bearing medium for the
shaft and impeller.
There are two types of casings
Volute casing (see figure) has impellers that are fitted inside the casings. One of the
main purposes is to help balance the hydraulic pressure on the shaft of the pump.
Circular casing has stationary diffusion vanes surrounding the impeller periphery
that convert speed into pressure energy. These casings are mostly used for multi-
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stage pumps. The casings can be designed as solid casing (one fabricated piece) or
split casing (two or more parts together)
Impeller:
An impeller is a circular metallic disc with a built-in passage for the flow of fluid. Impellers
are generally made of bronze, polycarbonate, cast iron or stainless steel, but other materials
are also used.
The number of impellers determines the number of stages of the pump. A single stage pump
has one impeller and is best suited for low head (= pressure)
Impellers can be classified on the basis of (which will determine their use):
Major direction of flow from the rotation axis
Suction type: single suction and double suction
Shape or mechanical construction: Closed impellers have vanes enclosed by shrouds;
Open and semi-open impellers; Vortex pump impellers. The figure shows an open
type impeller and a closed type impeller. Impellers could be open, semi-open or
closed.
Pipe: Suction pipe is connected to the inlet of the pump and other side is dipped into the fluid in a
sump.
Delivery pipe is connected tothe outlet of the pump and other end delivers the fluid atrequired height.
Shaft:
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The shaft transfers the torque from the motor to the impeller during the startup and operation of
the pump.
On the next page there are two figure that show centrifugal pump and its related components and
how liquid to pump.
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Cavitations
If the suction pressure at the eye of the impeller falls below the vapor pressure of the fluid being
pumped, the fluid will start to boil. Any vapor bubbles formed by the pressure drop at the eye of theimpeller are swept along the impeller vanes by the flow of the fluid. When the bubbles enter a
region where local pressure is greater than saturation pressure farther out the impeller vane, the
vapor bubbles abruptly collapse. This phenomenon is called cavitation.
There are several effects of cavitations:
It creates noise, vibration, and damage for many of the components.
We experience a loss in capacity.
The pump can no longer build the same head (pressure).
The output pressure fluctuates.
The pump's efficiency drops.
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Effect of cavitation
Prevention of cavitation:
Raise the liquid level in the tank
Lower the pumping fluid temperature
Use a pump with a larger, impeller eye opening.
Pump should be airtight
Friction losses should be decreased
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Comparison Table
Parameter Centrifugal Pumps Reciprocating
Pumps
Rotary Pumps
Optimum Flow
and Pressure
Applications
Medium/High Capacity,
Low/Medium Pressure
Low Capacity,
High Pressure
Low/Medium
Capacity,
Low/Medium
Pressure
Maximum Flow
Rate
100,000+ GPM 10,000+ GPM 10,000+ GPM
Low Flow Rate
Capability
No Yes Yes
Maximum
Pressure
6,000+ PSI 100,000+ PSI 4,000+ PSI
Requires Relief
Valve
No Yes Yes
Smooth or
Pulsating Flow
Smooth Pulsating Smooth
Variable or
Constant Flow
Variable Constant Constant
Self-priming No Yes Yes
Space
Considerations
Requires Less Space Requires More Space Requires Less Space
Costs Lower InitialLower Maintenance
Higher Power
Higher InitialHigher Maintenance
Lower Power
Lower InitialLower Maintenance
Lower Power
Fluid Handling Suitable for a wide
range including clean,
clear, non-abrasive
fluids to fluids with
abrasive, high-solid
content.
Not suitable for high
viscosity fluids
Lower tolerance for
entrained gases
Suitable for clean,
clear, non-abrasive
fluids. Specially-
fitted pumps suitable
for abrasive-slurry
service.
Suitable for high
viscosity fluids
Higher tolerance for
entrained gases
Requires clean, clear,
non-abrasive fluid due
to close tolerances
Optimum
performance withhigh viscosity fluids
Higher tolerance for
entrained gases
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