PROCESS PARAMETERS…….

~ Viscosity ~ Density ~ Specific Gravity ~ Compressibility ~ Temperature ~ Pressure ~ Fluid Velocity

Measurement Methods………

2. Discrete Quantity Flow Measurement

3. Mass Flow Measurement

1. Inferential Flow Measurement

•Head Type Flow Meters•Variable Area Flow Meters•Magnetic Flow Meter•Turbine Meters•Target Meters•Thermal Flow Meters•Swirl Meters•Sonic Flow Meters

Head Type Flow Meters…...

1. Orifice Plate

The flow measurement by orifice plates is achieved by applying Bernoulli’s theorem.The velocity of the flow stream is altered in a predetermined manner, usually by achange in the cross-sectional area of the stream. Flow rate derives from the velocityand area. The basic equation is

A2

1-(A2/A1)

[(2g/o)(P1-P2)]Q =2

WHERE A1= PIPE CROSS SECTIONAL AREA. A2= ORIFICE BORE AREA. 0 = FLUID DENSITY P1= UP STREAM PR. P2= DOWN STREAM PR.

BERNOULLI EQUATION GIVES IDEAL VOLUME FLOW RATE

DISCHARGE COEFFICIENT =Q actualQ ideal

RESTRICTION TO PIPE DIA RATIO IS B = d/D

THE EMPIRICAL IS MORE SIMPLY STATED AS

Orifice Plate …..

Q = KA 2g P 2K = C 1- B4

0

FOR ACCURATE MEASUREMENT TEMPERATURE COMPENSATION AND IN CASE OF COMPRESSIBLE FLUID PRESSURE COMPENSATION IS REQUITED.

Orifice Plate …..

The orifice plate itself is a circular disc usually stainless steel from 1 / 8 to 1 / 2 thickConstruction:

depending on size and flow velocity with a hole (orifice) in the middle and a tabprojecting out to one side -- data plate. The thickness requirement of the orificeplate is a function of line size, flowing temperature and differential pressure acrossthe plate.

1

2

1

2

MEASURED PR. DROP

PRESSURE LOSS

VENA- CONTRACTA

ORIFICE FLOW METERING….

Advantages of Orifice plates:1. Low cost.2. Can be used in wide range of pipe sizes.3. Can be used with differential pressure devices.4. Well known and predictable character.

Limitations of orifice plates:1. Causes relatively high permanent pressure loss.2. Have a square root characteristics.3. In case of slurry services, it tends to clog .4. Accuracy dependent on care during installation.5. Changing characteristics because of erosion, corrosion and scaling.

Orifice Plate …..Types of Orifice:The orifice is classified depending on the shape of the orifice and selection of anorifice depends on application.1. Concentric2. Eccentric3. Segmental4. Quadrant edge

TRANSMITTER CONNECTION….

VAPOR LIQUID

VAPOR

SEAL POT

LIQUID

CORROSIVE SERVICE

TEMPERATURE AND PRESSURE CORRECTION

Density Calculation for the Saturated Steam

For all the superheated steam flow measurements using orifice meters in Hazira complex(generation, import and export measurements), the following density correlation shall be used inthe compensation equation.

1) For 105K steam: Density (in kg/m3) = [264.19327{(P+1.0329)/(T+273.15)}] - 4.38053.

2) For 40K steam: Density (in kg/m3) = [243.34091(P+1.0329)/(T+273.15)}] - 1.04784.

3) For 17K steam: Density (in kg/m3) = [245.3597(P+1.0329)/(T+273.15)}] - 0.59588.

4) For 5K steam: Density (in kg/m3) = [229.35965(P+1.0329)/(T+273.15)}] - 0.10184.

Where P is the measured pressure (in kg/cm2g) and T is the measured temperature (in degC)both at the upstream of the orifice.

The root mean square deviation of the density values calculated using the above correlations fromthe numerical data of steam tables is as given below:For 105K steam: RMS deviation: 0.1596For 40 K steam: RMS deviation: 0.0476For 17K steam: RMS devaition: 0.0354For 5K steam: RMS deviation: 0.00819

The compensation equation will be as below:

Q(comp) = Q(uncomp)*{sqrt(Density actual/Density design)}

where density design is the density taken for orifice design and density actual is the densitycalculated at flowing temp. and pressure using the above correlations. Q is in mass units (kg/hror MT/hr).

TEMPERATURE AND PRESSURE CORRECTION

FLOW COMPENSATION EQUATION FOR HP ETHYLENE

FLUID EthyleneMolecular weight 28.054Acentric factor 0.0856Critical pressure kg/cm2a 51.311Critical temperature degK 282.38Critical compressibility factor 0.276Pres. range kg/cm2a Temp. range degC K Tr Pr Tr2 Tr*Pr Tr2*Pr Pr2 Pr2*Tr Tr2*Pr2 Applicable for

Lower value

Upper value

Lower value

Upper value

ConstantCoefficients

a b c d e f g h30.07 46.179 6.4 37.46 -77.9026 147.1373 237.8303 -68.5881 -444.485 207.4328 -187.718 348.8422 -162.123 PE&PP48.75 61.57 14.87 37.46 -201.97 369.0773 481.7081 -167.821 -878.447 400.3877 -295.445 538.0561 -245.092 FQ-701

Generalised equation for Z: Z = K + aTr + bPr + cTr2 + dTrPr + eTr2Pr + fPr2 + gPr2Tr + hTr2Pr2Plant Tag no. Td Pd Zd Rhod dP Meter max

degC kg/cm2a kg/m3 mmWC flow TPHPE-I 30FE-4141 20 42.033 0.68634 69.12887 4136 35PE-2 33FE-4141 20 42.033 0.68634 69.12887 12340 35ET FE-701 27 53 0.61458 95.07444 14486 70PP FT100108A 20 42.033 0.68634 69.12887 4937 6.804PP FT100108B 20 42.033 0.68634 69.12887 4951 1.81439

Flow comp= Flow uncomp* SQRT{(Pact/Pdes)*(Tdes/Tact)*(Zdes/Zact)}

P in Kg/cm2a

Venturi Tube…….

Venturi Tube Comprises 3 Section :

1.Up stream Conical 2.Conical Throat

3.Conical Down stream

Advantages of Venturi Tube:1. Causes low permanent pressure loss.2. Widely used for high flow rates.3. Available in very large pipe sizes.4. Has well known characteristics.5. More accurate in wide flow ranges than orifice plates.

Disadvantages:1. High cost compared to orifice plate.2. Generally not useful below 3 pipe size.3. More difficult to inspect due to its construction.

Flow Nozzel…….

Flow nozzle:Flow nozzle is a variation of the Venturi in which the exit section is omitted andconsequently the approach section is bell shaped with a cylindrical throat.

Advantages :Pressure loss lower than orifice plate.Can be used for fluids containing solids that settle.Widely accepted for high pressure and temperature steam.Disadvantages: Cost higher than orifice plate. Limited to moderate pipe sizes.

Pitot Tube…….

It consists of cylindrical probe inserted in to a fluid streamIn this device the velocity head is converted in to an impact pressure

The difference between static pressure and impact pressure is a measure of flow

Advantages :1. No process loss .2. Economical to install.Disadvantages:1. Poor accuracy.2. Unsuitability for dirty or sticky fluids.3. Sensitivity to up stream disturbance

2 P 0V=

0 = FLUID DENSITY

P = PR. DIFF OF STAGNATION AND STATIC PR.

V = FLUID VELOCITY

IMPACT OPENING

STATIC OPENING

P

Variable Area Meters…...

Advantages:1. Relatively low cost.2. Good for metering small flows.3. Good for low pressure drop requirement.

Disadvantages:1. Glass tube subject to breakage.2. Must be mounted vertically.3. Not good in pulsating services.4. Generally limited to small pipe sizes.5. Fair Accuracy (+1 / 2% to 10%).

MAGNETIC FLOW METER….

Magnetic flow meter use Faradays law of electromagnetic induction . The liquid is the conductor which has a length equivalent to the inside diameter of the flow meter. The liquid conductor moves with an average velocity V through the magnetic field of strength B. The induced voltage is E.

E = BDV / C where C is constant to take care of proper units.

EV B

Advantages:

1. It is totally obstructionless and has no moving parts.2. Pressure drop is no greater than piece of pipe of same length.3. Suitable for most acids, bases waters and aqueous.4. Widely used for slurry services.5. Can be used as bi-directional meters.

Disadvantages:1. Fluids should be adequate electrical conductors.2. Electrical installation care is required.3. Pipe should be full.

MAGNETIC FLOW METER….

TURBINE METER...

Turbine flow meter consists of a multi-bladed rotor suspended in the fluid stream on a free running bearing. The axis of rotation of the rotor in perpendicular to the flow direction and the rotor blades sweep out virtually to the full bore of the meter. The fluid impinging on the rotor blades causes the rotor to revolve within the linear flow range of the meter. The angular speed of rotation in directly proportional to volumetric flow rate. The speed of rotation in monitored by an electro -magnetic pick up coil

Application:Due to excellent preference characteristics the turbine meter in widely used for high accuracy custody transfer of crude oil refined by hydrocarbons and other valuable liquids.

PICK-UP COILS….

INDUCTANCE

•Permanent magnet in the coil.•Blades are made of a paramagnetic material.•Each blade produces a separate and distinct voltage pulse

•Permanent magnet is embedded in the rotor•It generates a voltage pulse for every complete revolution of the rotor.

RELUCTANCE

RELUCTANCE INDUCTANCE

THERMAL FLOW METERS...

TYPE 1Flow meters that measure the rise in temperature of the fluid after a known amount of heat has been added to it.

TYPE 2Flow meters that measure the effect of the flowing fluid on a hot body.

Q = W c ( T2-T1)

where Q= heat transferred(BTU/hour) W= mass flow rate of fluid (lbm/hour) C= specific heat of fluid (BTU/lbm oF) T1= temperature of the fluid before heat is transferred to it (oF) T2= temperature of the fluid after heat has been transferred to it (oF)

DRAG- FORCE FLOW METER...

A BODY IMMERSED IN A FLOWING FLUID IS SUBJECTED TO A DRAG FORCE IS GIVEN BY

Fd = CAdV2

2C - DRAG COEFFICIENTA - CROSS SECTION AREAd - FLUID MASS DENSITYV - FLUID VELOCITY

FOR A GIVEN DENSITY Fd IS PROPORTIONAL TO SQUARE OF VOLUME FLOW RATE HENCE SQUARE-ROOT ELEMENT IS REQUIRED FOR LINEARIZATION.

THE DRAG FORCE CAN BE MEASURED BY ATTACHING THE DRAG PRODUCING BODY TO A STRAIN GAGE.

VORTEX SHEDDING FLOW METER...

The vortices are shed from the alternate sides of the body. The frequency at which vortices are formed is directly proportional to fluid velocity.

The vortices cause alternating forces or local pressures on the shedder. Piezo electric and strain gauge methods are employed to sense the vortices formed.

Advantages:1. No moving component. 2. Linear digital signal3. Good flow range capability and long term stable calibration.Disadvantages:1. High pressure loss in liquid application.2. High cost

ULTRASONIC FLOW METER...

TYPE-1.Transit time : As the name implies, these devices measure flow by measuring the time taken for the ultrasonic energy to traverse a pipe section, both with and against the flow of liquid with in pipe.

TYPE-2.Doppler flow meters: In this case ultrasonic wave is projected in to the liquid by transmitting crystal in a transducer mounted outside pipe. Part of the energy is reflected by the bubbles or the particles in the liquid and is returned through the pipe wall to a receiving crystal. Since the reflectors are travelling at the fluid velocity the frequency of the reflected wave is shifted according to Doppler principle. The measurement of frequency enables to determine flow rate.

ULTRASONIC FLOW METER...

Positive displacement meters split the flow of liquids in to separate known volume based on the physical dimension of the meter and count them or totalize them.

Different types of PD meters depending on application.1. Impeller, propeller turbine 2. Nutating disc3. Oval gear4. Piston5. Rotating Vane6. Viscous helix

The mass flow meter is based on Coriolis effect and provides mass flow measurement for both liquid and gases.

The mass flow meter is based on Coriolis effect and provides mass flow measurement for both liquid and gases. In mass flow meter a U-shaped sensor tube is vibrated at its natural frequency. The angular velocity of the vibrating tube to be in combination with the mass velocity of the flowing fluid causes the tube to twist. The amount of twist is measured with magnetic position detectors producing signal which is linearly proportional to the mass flow rate of every parcel and particle passing through the u-shaped sensor tube.

Advantages of Mass Flow Meters

• Unaffected by variation in fluid properties.• Can be used for liquids, mixtures,foams,slurries,sticky viscous fluids and liquid containing gases.• Very accurate (0.2%)