Presentation of Flow Measuring Device.black

8/6/2019 Presentation of Flow Measuring Device.black

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PresentationOf FlowMeasuringDevices .


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Dr. S & S.SGhandhyCollage

Subject :- M & IBranch :- MECH (D-3)

Topic:- Flow MeasuringDevices.Prepared by :- Rampariya Milan

E .N nO :- 096120319052


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In metering liquids,gases,orstem and in process control invarious industries ,the quantity of fluid passing through the cross-section of a pipeline per unit timeor over a certain time interval isoften the requirement.

Introduction


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Classification of flowmesuring devices

Pressure differential createdby placing restriction in flow line

i.e. differential head meters. Local or point velocity and

pressure mesurement method-i.e.Pitot-tube velocity & flowmeters.

Constsnt differential head flowmeters or variable area fiow meters.

Volume flow meters,magneticflow meters.


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We will therefore,classifythem as::-(1) Head Type(2) Area Type(3) Mass flowmeter type(4) Positive Displacement type(5) Electric type

(6) Digital type(7) Open channel type(8) Solid flow meter


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Rotating ImpellerMeter:

An

impeller ishoused inthe casting

of the meter. The fluid enters the meter andflow through.

The impeller is rotatingbecause of fluid perssure on vanes. The impeller flotes on waterand the fluid leaves through outlet.

Its accuracy is +1 or -1.


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Rotating Lobes

MeterIt consists

of lobe typerotormounted ontwo parallel

shafts. Thefluid enters through inletand fills the space between two rotor;

and because of its pressure makesthe rotors move in opposite direction.The fluid is pushed towards outlet. Its accuracy varies from 0.1%

to 0.5%.


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Nutating Disc Meter It consists

of an

eccentricall y mounteddisc whichnatutes in a

hemispherical chamber.

The nutating motion is a working

motion of the disc to provide asweeping motion in addition torotating.

It has wide range and it also easyto use,however it can only be used forclean sufficient density liquid.


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Reciprocatingpiston meter:

This is also apositive-displacement typemeterlike,rotating vanes

and nutating discmeters. It has cylinder,piston andsliding valve arragement. The liquid enters both sideof piston in turn through inletvalve.

High accuracy +0.2 to +0.3or -0.2 to -0.3.


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Pitot tube It is usedto measure

flow rate ofliquid,gas andair. When

fluidenter thepitot tube withvelocity v itskinetic energyis convertedInto potentialenergy.

V.V=2gH.(a) Q=A*V.(b)

Where,A=cross-section area of thepipelines


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Venturi meter A U-tube manometer is usedto measure pressure headdifference ,h between inlet and

throat as shown.


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oOrifice Meter An orifice plate has a sharped edged concentriccircular hole.Normally it is made from stainless steel from 3mm to 12.5mm thick. Orifice plate has manyvarieties.

Advantages:(1) Chear in cost.(2) Occupies less space.

Disadvantages:(1) High pressure drop.

(2) Slurry or solid particles damage the hole.


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Advantages:(1) Less pressure drop(2) Usedfor large flow rate

(3) The divergent part helps tolower the permanent pressure loss.

Disadvantages:(1) Occupies more space

(2) Not suitable for pipediameter less then 76.2mm.

(3) Costly.


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Flow Nozzle The fiow nozzle is fabricated from stainlesssteel,gun metal etc.It is fitted either in pipe orin tank.

Advantages:(1) Suffer less pressure drop compared to

orifice meter(2) Occupies less space.

Disadvantages:(1) Costly compared to orifice

(2) Suiteble upon medium sized pipes.


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ElectromagneticMeter It works an Faradayselectromagneticinduction principal. Amagnetic field is produced within thepipe,in which fluid flowis to be mesured,by the

magnets place outsidethe pipe..

Advantages:(1)No obstruction,no

pressure drop.(2)No moving parts,no maintenance.(3)Can function even if the flow is reversed.

Disadvantages:(1)Fluid must be electrical conductor.(2)Air trap must be avoided.(3)Costly.


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Ultrasonic Meter Here altrasonictransdusars are usedeither parallel to pipewall or placed atsome angle.Whenultrasonic waves are

passed through the fluid,the velocity ofwaves increasesor decreases depending upon thedirection of fluid flow.Piezo-electrictransducers A and B generateultrasonic waves and transmits themthrough the fluid.The fluid velocity is sayV.

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