Chemical Files

Agitator/Mixer Data Sheet

2015-01-23T04:29:00.000+05:30

Hi all,

Today I am going to focus on Agitators/Mixers and how to interpret a data sheet for procuring. This article is largely based on my experience.

Note:

The vendor/manufacturer decides appropriate mixing equipment for your operation to achieve the desired mixing performance. So it is very vital to give the manufacturer the necessary details of the process. This article will help you to understand what goes into an Agitator and understand its basics, so that you can have effective discussion with your vendors and make the right first choice thus avoiding confusions and misconceptions.

I will strictly focus on Interpretation of Agitators data sheet. This being a very vast topic, it is beyond my scope to discuss its various types and specialties in this article.

Think & ask yourself:

1. What is the purpose of an agitator? How many impellers would I need?

2. Components of an agitator?

3. What basic details would an agitator manufacturer would require?

Purpose:

Agitator or mixers are of various types and the basic purpose of having them in your industry would be one of the following reasons or sometimes may be to serve multiple purposes.

1. Uniform mixing of liquids.

2. To keep solid in suspension.

Components:

Motor, gearbox, shaft, impeller all of which forms the mechanical parts of an agitator.
Let’s study them in more detail.

First of all what do you need to run an agitator? A Motor right. It’s as easy as ABC.

Motor:

Now Motors have fixed rpm (900, 1450 and 2900) based on the number of poles it has. For example, 2 pole motor will have rpm of 2900, 4 pole as 1450 rpm and 6 pole offers 900 rpm. This rpm may vary within a small range around the mentioned rpm depending on the losses inside the motor. The rpm required by your agitator may not necessarily be same as motor’s rpm to serve the process purpose. It may be less or may be more compared to motor’s rpm. What would you do then? You would then definitely look for something that will reduce/increase its rpm in order to meet the agitator’s rpm requirement. This something is – A Gearbox.

Gearbox:

Gearbox is used in Process industries to match the motor speed with that to the process speed requirement. The combination of gears within the gearbox reduces/increases the rpm to match the requirement. It is thus very vital to get the right gearbox for your process and not get an over sized or undersized one, thus details like make, model, reduction ratio, loading rating and capacity of gearbox are included in the data sheet.
Make:
It is the brand type of the gearbox.
Model:
Model number of the gearbox, typically for cross checking the vendor filled data from the brand catalog/website.
Reduction ratio:
It is the ratio of motor rpm to the process rpm.
Loading Rating:
The loading rating of the gearbox is the maximum power bearing capacity of the gearbox. It is expressed in the power units - kW or HP.
Service factor: It is the ratio of the Loading rating of the gearbox to the rated power of the motor. It is also called as the safety factor. During the start-up of the system, the torque generated by the gearbox requires a lot of power which is more than the motor power. Thus the gearbox must have this high power bearing capacity in the initial phase and thus service factor is important. It is also known as the safety factor. The minimum service factor usually recommended is 1.5

Coupling:

Coupling ‘couples’ two drive elements to transfer torque/motion between them. The correct gearbox selection ensures that the process runs on required rpm. Thus the output of the gearbox needs to be transferred to the agitator shaft. This transfer is done using Coupling, where the gearbox output is coupled with the agitator shaft.

Shaft:

Gearbox is connected to the shaft. So, the next logical question would be how long my shaft should be? Well, if it is a top entry agitator, then the length of the shaft depends on the vessel height (leaving some clearance at the bottom depending on the type of agitation and the type of fluid handled) including the overhead assembly up to the gearbox.
If it is a side entry agitator, then the minimum length should be half of impeller’s diameter.

Shaft is connected to impeller. So what type of impeller? What would be the diameter of the impeller? It is your call, based on your process application. There are many types of impellers available in the market - pitched blade, hydrofoil type, propeller type, turbine type etc. each having its own characteristics and applicability.

How many impellers would I need? This would depend on the dimension of your vessel and the degree of agitation you aiming for (which would actually depend on the type of system you would be using it for). Discuss it with your vendor before your purchase or place an order, ensuring that the vendor gives you the best fit for your system within your budget and that he guarantees the desired mixing quality as required.

Calculate the pumping flow rate i.e. the rate of mixing (m3/hr) or flow discharged by the rotating impeller.

Critical Speed:

Critical speed is usually considered as 30-35 % over the rpm required in your process. It is at this speed that your agitator would produce a lot of vibrations and noise. Necessary actions should be taken if the process rpm reaches -10% of the critical speed.

For eg:

If the rpm required = 300,

Critical speed should be 1.35*300 = 405 rpm.
Necessary actions to reduce the rpm at -10% i.e. at {405 – (0.1*405)} = 365 rpm.

Note that, this is just an approximate calculation showing the significance and importance of this parameter. However, in the plant noises and vibration would serve as an indication of increasing speed and immediate action has to be taken at that time to avoid any mishaps.

For top entry agitator:

Pumping rate (m³/hr)

Where,
N_Q = Flow number
D_I = Impeller Diameter (m)
rpm = Speed of an impeller (rpm)

Bulk fluid velocity can be calculated using the following equation:

Where,
D = Diameter of the vessel

Bulk velocity table:

Scale of agitation	Bulk Velocity (m/s)	Application
1	0.03	For uniform mixing of miscible fluids
2	0.06	For uniform mixing of miscible fluids
3	0.09	For uniform mixing as well as keeping solids in suspension.
4	0.12
5	0.15
6	0.18
7	0.21	Vigorous agitation
8	0.24
9	0.27

Where,
N_p = Power number
rpm = Speed of an impeller (rpm)
D_I = Impeller diameter (m)
S.G. = Specific Gravity of the fluid.

Miscellaneous features:

Packing, Material of construction, tank coupling, motor weight, total weight, torque, bending moment all are provided by the vendor.

Packing:
Mechanical seal or gland packing.

Material of construction:
MOC is to be defined for the wetted parts (parts in contact with the liquid) which include the shaft and the impeller. MOC is selected by studying the nature and the characteristics of the fluid to be agitated.

Weights:
Motor weight and the total weight of the agitator is required not from process but from structural point of view. The structures/columns/beams are designed to bear the full load of the equipment and its accessories and thus the weight of the equipment is necessary to be included in the specification sheet.

Friction Factor - Confusion

2013-08-10T20:13:00.000+05:30

This topic has often caused a lot of confusion in many people while calculating pressure drop of fluids in pipe. Many people are even unaware of the presence of 2 types of friction factor, wherein one is 4 times the other.

Moody's friction factor (also known as the Darcy friction factor) and Fanning friction factor are the two types of friction factor used in this world for pressure drop calculations.

Relationship:

f = Friction factor.
fd = Darcy friction factor
ff = Fanning friction factor.

NOTE: The third friction factor (which is mentioned above in the correlation) is used in Coulson & Richardson Vol. 6 for pressure drop calculation.

In text books you'll come across various pressure drop equations, the only difference lies in the type of friction factor used. Darcy / Moody friction factor is most widely used for pressure drop calculations, as they can be easily interpreted from moody's chart.

To keep it simple and straight forward, note the following points and equations very carefully to avoid any confusion on this topic henceforth.

Equations:

1. Darcy Friction Factor --- Laminar condition

Pressure drop equation:

Moody's Chart representing Darcy Friction factor:

The graph above is a Moody's chart for calculating friction factor using Reynolds Number (Re) and relative roughness. The " f '" on Y-axis is Darcy friction factor and not Fanning friction factor.

TRICK:
Follow the red line marked on the graph, it indicates that for Re = 1000, f = 0.064 which satisfies the Darcy's equation for laminar case. Thus this moody's chart gives us the Darcy friction factor and now I can, without any hesitation, use this " f D " value to calculate the pressure drop by using the corresponding pressure drop equation.

2. Fanning Friction Factor --- Laminar condition

Pressure drop equation:

BEWARE !! Many a times the graph that you might be referring to will give a value of f = 0.016 for Re = 1000 i.e. using f = 16 / Re, so this is fanning friction factor. The following Moody's chart shows the aforementioned case.

3) Friction Factor:

According to Coulson and Richardson vol. 6, we have the following equation for pressure drop calculation and for that particular equation if you are using, make sure you use the correct graph for that equation which is shown below.

NOTE: Its not necessary to have Laminar condition to use this equations / graphs as I have highlighted and focused only on the laminar region. Its just to make my point clear of explaining you the trick to help you to check whether the curve that you are referring to gives you Darcy or Fanning friction value and which graph and equation you need to use for calculation of pressure drop.

I have here made it easy by putting the pressure drop equation inline with their respective graphs.

I Hope, the point of this article is clear and friction factors won't be any confusion in any minds from now on. I follow the same practice while determining the value of friction factor and this check has never failed me.

Fix your steps of calculating pressure drop, but I insist on using Darcy equation i.e. Darcy friction factor. This should not lead to a conclusion that fanning friction factor should not be used. Remember either of it can be used, and both will lead to correct pressure drop, provided you use the right set of equations and keep the relationship in mind

Just in case you get confused again, you can re-visit this article and if you have any doubts in mind you can leave a comment here.

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Ball Valve

2013-04-26T09:43:00.000+05:30

Purpose: ON-OFF / Isolation valve

P&ID symbol:

General points:

Ball valves can be manufactured from minimum of 1/4" to maximum of 10" (some manufacturers also give upto 16")
Due to cost and bulkiness of the valve,Butterfly valves are always preferred over globe and ball for larger sizes i.e. more than 6" or 8".
For smaller size Ball valves are favorite of all, from cost, handling and installation and service point of view.
In most household applications, ball valves are used.

Types of Ball valve:

Full bore: Valve size = line size
Reduced port: Valve size < Line size (by 1 inch)

Advantages:

Requires only 1/4th turn to operate.
Excellent for shut-off application & preferred over gate & globe valve (for sizes < 60 mm)
Ease of operation
Supports & sustain high P (<10,000 psi), T (<200 C) & Q (flow).
Long service life.
Better sealing.
Sturdy device.
Relatively low cost.
Inspection & repair of seats & seals can be done without removing of valve body from the pipeline.

Disadvantages:

Flow control is not possible.
Tightens with age, implies require more maintenance.
Regular replacement of seal is required.
Abrasive solids will damage seal & ball surface.

Pump Encounter - Visitors contribution # 3

2013-03-18T23:05:00.002+05:30

Pump Encounter:

Mark Brein

General Manager

Penguin Pumps

In the following article Mr. Mark Brein, General Manager, Penguin Pumps shares with us one of his personal experience and also gives us wise advice's. Its a great way to learn form the mistakes of other's and I thus, sincerely request you to go through this article and appreciate Mr. Mark's efforts of writing all through this and sharing with us his personal experience to help us learn and grow.

The following brief pump encounter took place in the wet fume scrubber Industry dating back 35 years. For many years this industry has used Cantilevered vertical pumps to pump liquid from an open reservoir, through spray nozzles, back to the reservoir. The tanks holding the liquid were taller than they were wide by a 2 to 1 margin or greater. The liquid level height inside these tanks was always 3 ft minimum. The volume of liquid inside these tanks was always 3-4 times the pumping flow rate. Pump problems encountered over the years were practically zero.

READ MORE ...

Most pump troubles should never happen - Visitors Contribution # 2

2013-03-18T23:01:00.005+05:30

MOST PUMP TROUBLES SHOULD NEVER HAPPEN:

“GENERAL RULES OF THUMB”

Mark Brein

General Manager

Penguin Pumps

Size a pump to operate on the midpoint, plus or minus ¼, on its performance curve. This simple rule has been around for many years, and it still holds true.

Pump suction conditions:

The piping on the suction side of the pump is much more important than the piping on the pump discharge. If any mistakes are made on the discharge side, they can usually be compensated for by increasing the performance capability from the pump. Problems on the suction side, however, can be the source of ongoing and expensive difficulties, which may never be traced back to that area.

READ MORE ...

NPSH - Visitor Contribution # 1

2013-03-18T22:56:00.001+05:30

NET POSITIVE SUCTION HEAD—NPSH

Mark Brien,

General Manager,

Penguin Pumps

This phenomenon can get complicated if allowed to do so and is a subject about which complete books have been written. So let’s just accept the premise that every impeller requires a minimum amount of pressure in the liquid being supplied in order to perform without the liquid being pumped vaporizing inside the pump, which we may simply define as cavitation.

READ MORE ...

Gate Valve

2013-02-20T19:48:00.000+05:30

GATE VALVE:

Introduction

Gate valves are used in most of chemical process industries, predominantly in Petroleum industries, because of the attention that it has gained as a good flow isolation valve with very little or negligible leakage. Nearly 70% of the valves in petroleum industries are gate valves. They are suitable for services which require ON/OFF application. Throttling is not preferred with this valve type.

READ MORE ...

NPSH

2012-11-04T21:25:00.001+05:30

NPSH:

Net positive suction head measures the difference in head (differential head) & not the difference in pressure.

NPSHA	NPSHR
Absolute Pressure required at the pump suction above the vapor pressure of the liquid at that temperature. (Psuction > Pvap)	It is the minimum absolute pressure required at the pump suction to avoid vaporization. (Psuction = Pvap)
It is the function / requirement of your actual process / system	It is pump specific.
Hence it is calculated with the help of process parameters & conditions.	It is provided by pump manufacturer. It is calculated using water at room temperature by the manufacturer.

It is worth noting that while NPSHa must be greater than NPSHr, NPSHr test values stem from a procedure defined by Hydraulic Institute.
When the NPSHr value is determined by the pump manufacturer using water, the pump performance has already decreased by 3% in order to measure the change & so, NPSHa must actually be atleast a few feet/meter greater than NPSHr, not just equal.

READ MORE...

Pumps - Affinity Laws

2012-08-31T21:19:00.000+05:30

Affinity laws allows engineers to estimate changes in critical performance parameters like

Flow rate (Q)
Head (H)** / Pressure (P)
Brake horsepower (BHP)

due to variation in

Shaft / motor speed (N)
Impeller diameter (D)

** Head refers to Total dynamic head (static head + losses OR differential head), since static head (process requirement) does not change with either shaft speed or impeller diameter or with flow rate.

Affinity laws are applicable on centrifugal pumps, fans or turbines (these are applicable only for centrifugal pumps, laws for fans are different) assuming the points on the system curve have approximately the same efficiency. The system curve changes with change in either shaft/motor speed or impeller diameter.

The following affinity laws are for a specific centrifugal pump.

Affinity law set 1	Affinity law set 2
Constant impeller diameter (d)	Constant motor speed (N)
Q α N	Q α D
H α N²	H α D²
BHP α N³	BHP α D³

Usually, there is no appreciable change in efficiency with range of normal operating speeds. Hence Affinity law set 1 can be considered accurate & reliable.

Whereas, on the other hand set 2 laws (same casing size, but different impeller diameter) are not as accurate as set 1 because large diameter reductions involve changes in the geometry of the blades (outlet width, blade angle, blade length) thus increasing the mismatch with the casing volute, which in turn causes change in the efficiency.

Note: The new impeller diameter should not be more than 10-20% of the original diameter.

The following affinity laws are for a geometrically similar pumps (meaning the pumps will run with same specific speed but with different impeller size.)

For set of geometrically similar pumps

Q α ND³

H α N²D²

BHP α N³D⁵

Absorption

2012-05-08T21:07:00.003+05:30

ABSORPTION

Falling Liquid solvent absorbs the gas in the absorption column & is then sent into any one of he following unit:- Distillation, stripping section, removal through precipitation & settling, neutralization, oxidation, reduction & hydrolysis.

Purpose:

Gas purification
Gas separation
Product recovery
Solvent recovery

Solvent Properties:

Solubility of gas should be high in selected solvent. ( If not, then absorption is a waste!! )
Low volatility organic liquid ( but water is preferred in many cases, due to easy availability & removal of water soluble gases like, HF, HCl, SiF4 ).
Low vapor pressure ( to reduce evaporative loss of solvent )
non-toxic, non-flammable, non- corrosive
Low viscosity

Types of columns:

Packed Column

Smaller column diameter application.
Large inter facial area for mass transfer
Simple and cheap in construction
Preferred for corrosive gases because of availability of ceramic / plastic MOC packing

Material & types of packing

Internals of Packed tower

Packing support plate: It must bear the weight of the packings & allow unrestricted flow of down coming liquid. Drawback is that, that the packing blocks some holes, thus reducing the tower capacity.
Liquid distributor: Placed 6-12 inch above packing for allowing gas disengagement from the bed. Absorption & stripper columns require only one distributor, whereas, Distillation column requires 2 (feed & reflux)
Liquid re-distributor: Some part of entering liquid flows through the wall without coming in contact with the gas flowing counter currently, thus we need a liquid re-distributor to collect the down coming liquid and distribute it uniformly throughout the bed and thus increase the efficiency of the tower.
Demisters / Entrainment separators: Generally installed in exit gas streams for arresting the liquid droplets entrained in the gases. If demisters are not installed they can corrode / choke downstream equipments like heat exchangers tubes, damage tube sheets, contaminate products etc.

Types of packing :

Material of construction:

Against all acid gases, metal tower, metal plates, metal packing or any other metal internals can have deleterious effect.
Same is the case with organic liquid and plastic packing.
Ensure internal cooling facility is available when materials and gases releases high heat of absorption.

Dry & wet random packing:

Packed & plate column:

Dimensionless Numbers & their significance - 2 (Fluid Mechanics)

2012-02-06T22:48:00.005+05:30

Significance:

Used in fluid flow calculations where local pressure drop is necessary (dp = upstream pressure - downstream pressure)
Used to characterize the losses in the flow.
NEu = 1 corresponds to a perfect frictionless fluid flow.

=========================================================================

Significance:

It gives the possibility / potential of a fluid to cavitate.
If Ca < 0, Cavitation occurs & if Ca > 0 no cavitation will occur, since the condition to avoid cavitation is that the minimum pressure (Pmin)within the entire pump should be greater than the vapor pressure (Pv) of the fluid at that temperature. (Pmin > Pv )

=======================================================================

Significance:

It is the ratio of mean flow velocity to the speed of small gravity wave along the water surface.
It is an indication of resistance to partially submerged object moving through to water.
Greater Fr value, greater is the resistance to flow.
Fr < 1 indicates subcritical flow (tranquil flow)
Fr > 1 indicates supercritical flow (rapid flow)
Fr = 1 indicates critical flow.
Used in ship design i.e. to analyze water flow around ships.
Inverse of the square of Fr is called Richardson Number ( importance of natural convection to forced convection)

=======================================================================

Significance:

To check whether the fluid can be considered compressible or not.
If M < 0.2-0.3, then the fluid medium can be considered steady & isothermal & hence incompressible.
Used for fluids flowing with high speeds in channels, nozzles, diffusers etc.
It is analogous to Froude Number

C = speed of sound = 345m/s (at 15 deg. celsius temperature)

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Significance:

It is the square of mach number (Mach number can also be expressed in terms of bulk modulus as the square root of cauchy number number).
Used to study compressible flow.

K = bulk modulus of elasticity

========================================================================

Significance:

Used to study fluid friction in pipes.

Tw = wall stress
ef = friction loss

=========================================================================

Dimensionless Numbers & their Significance

2011-12-22T23:56:00.005+05:30

Nomenclature:

D = diameter of pipe
D_{H =}Hydraulic diameter
L = Length of the pipe
Lch = characteristic length
R = Length through which conduction occurs.
u = mean characteristic velocity of the object relative to the fluid.
Vch = Characteristic velocity
Cp = specific heat capacity at constant pressure.
k = thermal conductivity
μ = dynamic viscosity of the fluid
= density of fluid.
DAB = mass diffusivity
h = heat transfer coefficient.
g = acceleration due to earths gravity.
t = characteristic time
ν = Kinematic viscosity of fluid.
α = Thermal diffusivity
β = volumetric thermal expansion coefficient ( = 1/T for ideal fluids, T = absolute temperature)
Ts = surface temperature

T_∞= Bulk Temperature

Significance:

Ratio of Inertial forces to viscous forces.
Primarily used to analyse different flow regimes namely Laminar, Turbulent, or both.
When Viscous forces are dominant its a laminar flow & when Inertial forces are dominant it is a Turbulent flow.

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Significance:

Depends only on fluid & its properties. It is also ratio of velocity boundary layer to thermal boundary layer
Pr = small, implies that rate of thermal diffusion (heat) is more than the rate of momentum diffusion (velocity).
Also the thickness of thermal boundary layer is much larger than the velocity boundary layer.

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Significance:

Analogous of Prandtl number in Heat Transfer.
Used in fluid flows in which there is simultaneous momentum & mass diffusion.
It is also ratio of fluid boundary layer to mass transfer boundary layer thickness.
To find mass transfer coefficient using Sherwood number, we need Schmidt number.

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Heat Exchanger - 3

2011-09-02T23:18:00.003+05:30

Fouling in Heat Exchanger

-----------------------------------------------------------------------------------------------------------

General :

Deposition of extraneous material on Heat transfer (HT) area.
Resistance to flow
increases Pressure drop in order to maintain the flow rate.
Must be considered during designing & ease of cleaning must be permitted.
More fouling fluid allocated to tube side & allow access for cleaning
keep fluid velocity constant
5 ft/s for tube side & 3 ft/s for shell side for fouling fluid

Fouling Types:

Fig. 1. Types of Fouling

fig. 2. Corrosion Fouling

fig. 3. Chemical Fouling

fig. 4. Crystallization Fouling

fig. 5. Biological Fouling

Heat Exchanger - 2

2011-08-30T19:51:00.010+05:30

LMTD & Correction Factor (F)

-----------------------------------------------------------------------------------------------------

---------------------------------------------------- (1)

Q = Heat transferred in H-E-X

U = Overall Heat transfer coefficient

F = Correction Factor.

= Logarithmic Mean Temperature Difference (LMTD)

* LMTD is dependent only on inlet and outlet temperatures and is independent of type of HE used.

where,

1-stands for Inlet

2-Stands for Outlet

Normal Practice if to calculate LMTD for counter flow and apply correction factor F to it.

Fig.1. LMTD for single pass STHE

Fig.2. LMTD for 1/2 STHE

F (Correction Factor)

Shows departure form true counter current flow
F is correction factor for multi-pass and crossflow heat exchanger and given for two-pass shell-and-tube heat exchangers in equation (4) below.
0 < F < 1
fn { fluid Temperature, no. of passes }
F > 0.8, if not then redesign the HEX with more no. of passes or larger LMTD

Find F value:

Find R using:

------------------------- (2)

2. Find P using:

Heat Exchanger - 1

2011-08-28T03:39:00.010+05:30

Heat Exchanger – Classification

Applications :

Air Conditioners
Refrigeration
Natural gas processing
Petrochemical Plants
Power Plants
Radiators (cars, bikes, IC Engines and so on.)
99% of Chemical plants

Types :

Basic Classification:

Recuperative:

Fluid flows in separate conduits
Heat transfer from hot fluid to cold fluid across the walls

Plate H-E-X

Plate & Frame

Fig. 1 .Plate & Frame H-E-X

Series of rectangular parallel plates
Held firmly with each other.
Sealed by gaskets.
Hot fluid passes through alternate pairs of plates transferring heat to cold fluid in adjacent spaces.
Cleaning easy

Cooling Tower

2011-07-26T04:46:00.015+05:30

Cooling Tower (CT) Principle ?

CoolingTower

To decrease the temperature of hot water entering the CT.

Cooling by evaporation is the principle used.

Heat transfer from Water to Air.

High difference between Wet Bulb Temperature ( WBT ) and Dry Bulb Temperature ( DBT ) encourages more Heat Transfer ( HT ) between air and water inside the cooling tower. This is due to the fact that when WBT = DBT , air is fully saturated i.e 100% relative humidity (R.H) and no longer accepts water, thus no more HT.

Thus more difference between WBT and DBT => low R.H. => greater capacity to hold water => effective lowering of water temperature.

Final outlet water temperature will always be < WBT of entering air. ( suppose DBT = 30°C, WBT = 25°C find R.H from humidity chart, this implies the capacity of air to hold water i.e. hot water can maximum transfer heat till its drops to WBT of entering air )

Working of CT ?

Hot water from HE enters cooling tower

It is sprinkled from top with the help of nozzles

fills are used for better Heat Transfer between air and water.

Normally water is brought down to room temperature and is collected in the concrete basin at the bottom.

This water is re-used again and the same process follows.

small amount of water gets evaporated during the entire process hence make up water is used .

Types of CT

1. Natural Draft ( Hyperbolic CT ) :

ADVANTAGES : No fans, motors or gearboxes required, usually used for large quantity of water flow.

DISADVANTAGE : Large space required

uses the difference between ambient air temperature and the air inside tower.

Hot air rises upwards and cooler air is drawn inside through bottom.

Two types :

A) Cross flow Natural Draft CT: water and air flow are perpendicular. Fill is located outside CT.

B) Counter Flow Natural Draft CT: Air is dawn up through the falling water. Fill is located inside.

Centrifugal Pump

2011-07-15T05:08:00.001+05:30

Centrifugal Pump

Fluid flows in axially and leaves radially outward i.e. in centrifugal direction , hence the name Centrifugal pump

At the eye of impeller partial vacuum is created and due to atmospheric pressure at the suction side, pressure difference is created due to which fluid flows.

Fluid enters pump (suction side) ---> rotating impeller pushes the liquid increasing velocity ---> liquid is discharged (discharging side) .

Mechanical Energy (motor) ---> Kinetic Energy (fluid) --> Potential Energy

( The impeller provides more Kinetic energy to the fluid. This Kinetic energy decreases as it moves up giving rise to Potential energy (head). KE decreases due to pump casing which slows down the

fluid due to resistance. )

HEAD : The maximum height straight up, the fluid can travel. It is a function of outer dia. of Impeller & motor speed.

Pump Head + Suction Head = Discharge Head .

Typical properties of centrifugal pump : ( reason why it is widely used )

constant head

varying flow

can handle huge amount of fluid at a time

suitable for LOW viscous fluids.

high speed flow.