All Type of Pump

7/31/2019 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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All Type of Pump