Centrifugal Pumps AM

7/27/2019 Centrifugal Pumps AM

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UVEES 1

Centrifugal PumpsTraining Program @ Petronet LNG


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PUMP

A pump is a machine that imparts

energy to the liquid in it to flow or rise

to a higher level / pressure or both.

PUMPA machine used for the

purpose of transferring

quantities of liquids from

one place to another.


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UVEES 3

PUMPS

POSITIVE

DISPLACEMENTROTODYNAMIC

Energy is imparted to the

fixed volume of liquid.

RECOPROCATING:

PISTON / PLUNGER

Kinetic energy of a rotor is

converted in to fluid energy

ROTARY:

LOBE, GEAR, VANE, PISTON

Types of Pumps


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UVEES 4

Positive

Displacement

Pumps

a. Reciprocating piston or

plunger

b.External gear

c. Double screw

d.Sliding vane

e.Three lobef. Twin circumferential pis

ton

g. Peristaltic .


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UVEES 5

Rotodynamic Pump Theory

The (rotational) kinetic energy of impeller istransferred to liquid in the casing of the pump

by dynamic action.

The velocity of the flow is reduced to convert it

in to potential energy and/or pressure energy.

The Bernoulli's principle says so.


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UVEES 6

Action of moving Blade


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UVEES 7

Kinetic EnergyPotential

& Pressure Energy

This is achieved by thevolute casing ordiffuser vanes in which

cross sectional area ofthe casing is graduallyincreased. This willdecrease velocity of flow

(KE) to result inincrease in pressure.


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Simplify? . .


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UVEES 10

Working of RDP (contd.)


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CENTRIFUGAL

PUMPS

IMPELLERS AXIS CASINGS STAGES

RADIAL FLOWCLOSED

AXIAL FLOW

VERTICAL

HOROZONTALVOLUTE

SINGLE

MULTI

SEMI OPEN

MIXED FLOW OPEN

DIFFUSER

(IN VERTICAL

TURBINE PUMP)

Classification ofRotodynamic Pump


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UVEES 12

Centrifugal Pumps


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UVEES 13

Multistage Pumps

Horizontal Centrifugal &

Vertical Turbine Pumps


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Vertical Turbine Pumps

Generally mixed flow type, Single stage

or Multi stage types.

Other components; viz. entry bell,

bearings, couplings and seals.


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UVEES 15

Cryogenic Pumps

Cryogenic pumps are

used for handling liquids attemperatures as low as -160C (-320F). Topsuction pump design has

become a standard in theindustry for handling fluidswhich are near or atboiling point without vapor

binding. such as LiquefiedOxygen, Nitrogen, NaturalGas, etc..


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Cryogenic Pumps (contd.)

Design considerations for cryogenic pumps include

special metallurgical considerations due to lowtemperatures and flammability of liquefied gases

such as LNG, liquid oxygen, thermal expansion and

contraction and material behavior at cryogenic

temperatures, and extremely low NPSH.

Impellers may be either of the semi-open or closed

design and are keyed to the shaft. Both single and

multi-stage cryogenic pumps can be designed toincorporate an inducer for low NPSH applications.

Inducers are individually sized for each application.


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UVEES 17

Cryogenic Pumps (contd.)

Shaft sealing is provided by a precision labyrinth

seal which operates at the pump suction pressure.

Thermocouples are used to detect and monitor theliquid level in the pump column. This safety featureensures that the labyrinth seals operate in vaporphase and icing at the support plate is eliminated.

In one of design, easily replaceable cartridgeassemblies are mounted in the bearing frame above

the top mounting plate. This configuration providesgreater support for the pump shaft and eliminatesthe reliance of the drive motor's bearings.


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UVEES 18

Selection of Pump

.. is very important decision making.

Important Parameters considered are . . .

Head and Flow : The Duty or Operation combo

Type of liquid; Clear, Contaminated, Corrosive,

Viscous, Volatile, etc/

Input Power & Efficiency

NPSH Required

Maintenance requirement


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UVEES 19

Estimation of Flow and Head +

The average flow/capacity requirement ofprocess most of the time and range of

variation.

The pressure sufficient to overcome total

dynamic head for the flow required.

NPSH available at suction side.


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UVEES 20

Total Dynamic Head (TDH)=

Static Lift + Static Height + Pressure

of Upstream System connected +Friction Losses + Other Losses


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UVEES 21

Pump Characteristic Curves

Interpretation of CC


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UVEES 22

Interpretation of CC

As flow increases the

head developed

decreases.

Power consumption

increases with increase

in flow NPSHr increases with

increase inflow

There exist a best

efficiency point, to betargeted for fixing duty

point near it

C it ti


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UVEES 23

Cavitation

Low pressure at the suction side of a pump

can encounter the fluid to start boiling with

reduced efficiency and cavitation damage

of the pump as a result. Boiling starts when the

pressure in the liquid is reduced to the vaporpressure of the fluid at the actual temperature.


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UVEES 25

Model Modification

Pumps are selected for its operation atbest efficiency point most of the time. If the

duty point is not matching with BEP, what

to do?

Pump affinity laws can help us in

necessary modification so that DP & BEP

for the modification match as far aspossible.


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Affinity LawsThe affinity laws express the mathematical relationship betweenthe several variables involved in pump performance. They apply to

all types of centrifugal and axial flow pumps. They are as follows:

2. With speed

N held

constant:

So by changing the diameter of impeller or rotational speed onecan bring DP and BEP nearer. Since it is not impractical to change

the speed, trimming of the impeller is done. Refer the

Interpretation of CC Slide

1. With impeller

diameter D held

constant:


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UVEES 27

Material of Construction

of Body - Impeller - Seals

Mainly made of Cast Iron or Steel. Stainless

Steel is used for corrosive liquids or food &

pharmaceutical application.

Special Material for reactive liquids: SpecialMetals (Alloys) e.g. Bronze, Hastelloy,

Carpenter 20 etc. or Nonmetals (Polymers) like

PVDF, PP etc.

Lined (coated internally) for harsh liquids

reducing cost of the special material, e.g. EPDM


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UVEES 28

Static Sealing Material

Gaskets and O-ringsEPDM

VITON

BUNA

Natural Rubber

Silicon Rubber

Pump Standards


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UVEES 29

Pump StandardsSome commonly used centrifugal pumps standards;

ANSI/API 610-1995 - Centrifugal Pumps for General Refinery Service -Covers the minimum requirements for centrifugal pumps, including pumps

running in reverse as hydraulic power recovery turbines, for use inpetroleum, heavy duty chemicals, and gas industry services. The pumptypes covered by this standard can be broadly classified as overhung,between bearings, and vertically suspended.

DIN EN ISO 5199 - Technical specifications for centrifugal pumps

ASME B73.1-2001 - Specification for Horizontal End Suction CentrifugalPumps for Chemical Process - This standard covers centrifugal pumps of

horizontal, end suction single stage, centerline discharge design. ThisStandard includes dimensional interchangeability requirements and certaindesign features to facilitate installation and maintenance. It is the intent ofthis Standard that pumps of the same standard dimension designation fromall sources of supply shall be interchangeable with respect to mountingdimensions, size and location of suction and discharge nozzles, inputshafts, baseplates, and foundation bolt holes

ASME B73.2-2003 - Specifications for Vertical In-Line Centrifugal Pumpsfor Chemical Process

BS 5257:1975 - Specification for horizontal end-suction centrifugal pumps(16 bar) - Principal dimensions and nominal duty point. Dimensions for sealcavities and base plate installations.
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Q & A

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Centrifugal Pumps AM