Pumps Slides

8/13/2019 Pumps Slides

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Technical case study

Topic Name Pumps

Groups Members Name

M ArslanM umar

THE UNIVERSITY OF LAHORE1


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Presentation on Pumps


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An Overview

Introduction

Types of Pumps

Features of various Pumps

Selection of pumps

Performance Calculation Installation

Maintenance


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Pumps Definition

The purpose of a pump

is to add energy to afluid, resulting in an

increase in fluid

pressure, not

necessarily anincrease of fluid speed

across the pump.


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Types of Pumps

Dynamic Pumps

Centrifugal

Axial

Radial

Displacement Pumps

Positive Displacement


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Dynamic Pumps

A pump that uses

the momentum ofthe fluid to move

from inlet to

outlet


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Positive Displacement Pumps

Pumps that deliver a

specific volume of

water for each cycle,irrespective of the

head that they are

pumping against.

Such pumps includepiston, plunger and

screw pumps.


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Centrifugal Pumps

Very simple design

Two main parts are

the impeller and thediffuser

Impellers

Bronze

poly carbonate

cast iron

stainless steel


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Pressure developed by the Pump

depends upon

Impeller dia

No.of impellers

size of the impeller eye

shaft speed


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Size of the pump

Depends on

Head

Capacity


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Advantages of centrifugal Pump

Very efficient

Produce smooth and even flow

Reliable with good service life


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Disadvantages

Loss of priming easily

Efficiency depends upon operating design

head & speed.


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Diameterofthe Impeller

Thickness

of the impel ler

Centrifugal Impellers

Thicker the Impeller- More Water

Larger the DIAMETER - More Pressure

Increase the Speed - More Water and Pressure

Impeller

Vanes

Eye of the

Impeller

Water Entrance


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Two Impellers in Series

Direction of F low

Twice the pressure

Same amount of water


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Multiple Impellers in Series

Placing impellers in series increases theamount of head produced

The head produced = # of impellers x head of

one impeller

Dir ection of Fl ow Dir ection of Fl ow


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Overall Efficiency = Hydraulic power ( P2) X

100/ Power input ( P1)

Pump efficiency. = Hydraulic power ( P2) X

100/ Power input to pump shaft ( P3)

Hydraulic Power ( P2) = Q X Total Head ( hd -

hs ) X p X g / 1000

Q = discharge in m/s

Pump Performance calculation


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Pumps Performance Curves


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Centrifugal Pumps - Cavitations

When the pressure falls below the

vapor pressure of the liquid at a given

temperature, boiling occurs and small

bubbles of vapor are formed. These

bubbles will grow in the low-pressure

area and implode when they are

transported to an area of pressure

above vapour pressure. The term givento this local vaporisation of the fluid is

Cavitation.


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Centrifugal pumps - Priming

Where the liquid to be pumped is at a higher level thanthe pump, opening an air release cock near the pumpsuction will enable the air to be forced out as the pipeline

fills up under the action of gravity. This is often referred toas "flooding the pump".

Alternatively, an air-pumping unit can be provided toindividual pumps or as a central priming systemconnected to several pumps.

The water ring or liquid ring primer can be arranged as anindividual unit mounted on the pump and driven by it, oras a motor driven unit mounted separately and servingseveral pumps, known as a central priming system.


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Centrifugal pumps - losses

- Friction loss in bearings and glands,surfaces of impeller and casing. Someimpellers are highly polished to minimizefriction loss.

- Head loss in pumps due to shock at entryand exit to impeller vanes and eddies

formed by vane edges. - Leakage loss in thrust balance devices,gland sealing and clearances between cutwater and casing and bearing seals.


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Centrifugal pumps losses

apacity reductioncould be the result of A damaged sealing ring

Leaking gland Obstruction (valve partly closed/foreign body)

Incorrect rotational speed

Excessive vibration may be caused by

Loose coupling

Loose impeller

Bearing damaged

Impeller imbalance


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Centrifugal pumps-component

parts


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Key Parameter for determining

efficiency

Flow

Head

Power


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Flow Measurement Techniques

Tracer Method

Ultrasonic flow measurement

Tank filling method

Installation of online flow meter


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Determination of total head

Suction head

measured from pump inlet pressure gauge

reading

Discharge head

This is taken from the pump discharge side Pr.

gauge


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Net Positive Suction Head

NPSHNPSHA

Otherwise (if NPSHA < NPSHpump), the pressure at the pumpinlet will drop to that of the vapor pressure of the fluid being

moved and the fluid will boil.

The resulting gas bubbles will collapse inside the pump as the

pressure rises again. These implosions occur at the impeller andcan lead to pump damage and decreased efficiency.


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Size pump correctly

Operate close to the best efficiency point.

Size all piping and valves correctly

Avoid all leakages.

Factors to be considered from

user side


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Flow control Strategies

Varying speed

Pumps in parallel

stop/start control

Flow control valve

By pass control valveTrimming impeller

Use of VFDS


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Energy conservation

opportunities in pumping

Operate pump near best efficiency point.

Replace old pumps by energy efficient

pumps

Reduce system resistance by pressure

drop assessment and pipe size

optimization.

Provide booster pump for few areas of

higher head.

E ti


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Energy conservation

opportunities in pumping

Conduct water balance to minimize water

consumption.

Ensure availability of instruments likepressure gauges, flow meters.

Repair seals and packing to minimize water

loss.

Avoid valves in discharge side as far as

possible.

Operate pumpset during non-peak hours.


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Energy Loss in Valves

Function of valve type

and valve position

The complex flow paththrough valves can

result in high head loss

(of course, one of the

purposes of a valve isto create head loss

when it is not fully

open)


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Centrifugal pumps - selection

Viscosity of the medium to be pumped,

Type of medium, e.g. corrosive or non-corrosive,

this would affect the choice of material (althoughfor salt and fresh water the difference is oftenjust the casing).

Materials for salt water could be, casing-

gunmetal (cast iron for fresh water), impeller-aluminium bronze, shaft-stainless steel, casingbearing ring seals-leaded bronze.


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Pump Installation

Installation of Pump, Motor and Base:

The foundation area should be rigid and level for maintaining pumpalignment.

The pump and motor assembly must be securely fastened to the base,

and the base must be securely attached to the ground.

For long-coupled pumps, the pump is coupled to the motor via a

mechanical coupling. To prevent excessive radial loads from beingapplied to the pump which can cause vibration and lead to premature

pump failure the pump and motor shafts must be manually aligned

after final installation. On larger machines laser alignment is

recommended.


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Pump Installation

The pump inlet should be as close to the liquid source as

practical and preferably below it.

The pump and motor should be accessible for servicing

and inspection.

The pump and motor should be cleaned periodically to

prevent the build-up of dust.

Whenever possible, install suction and discharge

pressure gauges as close to the pump ports for condition

monitoring and for checking hydraulic conditions.


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General Precautions:

Never operate the pump without safetydevices installed

Never operate the pump with suctionand/or discharge valves closed

Never operate the pump out of its designspecifications


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Piping design

Cavitation

Performance dropout

Impeller failure

Bearing and mechanical seal failures

Cracked casings

Leaks Spills

Fires


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Centrifugal pumps - maintenance

When the pump is due for overhaul, it will

be necessary to dismantle it to its

component parts to examine them for wear.The following procedures are intended as a

general guide only, and your attention

should be drawn to the manufacturer'soperational instructions regarding specific

pump requirements before commencing to

dismantle the pump.


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Centrifugal pumps maintenance

Lubrication

Drive Lubrication

Bearing Lubricant Grease

Inspection

Inspection of Rotor Tips

Inspection of Rotor, Shaft Key and Keyway

Inspection of Gears and Bearings


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Annual Maintenance

Cleaning

Fluid Head Disassembly Remove Rotor Nut

Assemblies

Remove Cover Remove Rotors

Remove Pump Body

Remove Mechanical Seal


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Gear Case

Disassembly

Remove Gear CaseCover

Remove Shaft


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Thank You

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