experimental

GROUP 9GROUP 9

UNIVERSITY OF SALFORDSCHOOL OF COMPUTING, SCIENCE AND

TECHNOLOGYMSC IN PETROLEUM & GAS ENGINEERING

PRESSURE DIFFERENTIAL PRESSURE DIFFERENTIAL DEVICESDEVICES

OSEGHALE OKOH (GROUP LEADER)OSEGHALE OKOH (GROUP LEADER)ABDULFTAH SALEM ALDARZIABDULFTAH SALEM ALDARZI

KAYODE GIWAKAYODE GIWAOKUO FIDELISOKUO FIDELIS

ORIGHOYE TEDEYEORIGHOYE TEDEYEAGBUZA EROMOSELEAGBUZA EROMOSELE

PRESENTATION OUTLINE

Flow Measurement Importance of Flow Measurement

Introduction to Pressure Differential Devices Operational Principle

Types of Pressure Differential Devices Orifice Plate Venture Meter. Nozzles. Pitot Tube. Elbow Meters. Variable Area Meter.

Conclusion

References

FLOW MEASUREMENT

• Flow measurement is an important parameter in any fluid based industrial process, it is a measure of the quantity of fluid passing through a particular medium of known area per unit time. It can be

measured either in volumetric or mass based units.

• It is essential to know flow characteristics of a fluid for appropriate quality control of the equipments that come in contact with this

flowing fluid and for accurate revenue calculation when the fluid is transported via pipelines for sale.

• The need for accurate flow measurement cannot be overemphasized, therefore the knowledge of the devices is indispensable.

• One category of such devices is the pressure differential –flow measurement devices

IMPORTANCE OF FLOW MEASUREMENT

INTRODUCTION TO PRESSURE DIFFERENTIAL DEVICES

• Differential Pressure devices belong to a category of flow measurement devices that obstruct fluid flow extracting energy from the flow regime.

• Energy extracted is the form of a pressure drop which is recorded using pressure measuring devices.

• Pressure drop is related to the linear velocity of the flowing fluid using Bernoulli’s Principle, the linear velocity obtained is then substituted into the Continuity equation and the flow rate obtained.

• Bernouilli’s Principle relates pressure drop to linear velocity using the equation :

Which means:

The Continuity equation is given as;

whereᵖ = density of the fluidP1 = Pressure of fluid at point 1P2 = Pressure of fluid at point 2 ΔP= Pressure difference of fluid between point 1 and 2. V1 = Velocity of fluid at point 1V2 = Velocity of fluid at point 2m = mass flow rate of the fluid in kg/sA1 = Area of the pipe at point 1A2 = Area of the pipe at point 2

INTRODUCTION TO PRESSURE DIFFERENTIAL DEVICES

• Cd is the coefficient of discharge that accounts for losses, temperature, pressure, compresibility, Reynords number and various other effects (Nasr & Connor, 2002)

• It is unique to each pressure differential device.• The formula above holds true for incompressible fluids but compressible fluids need

an additional factor that accounts for variation of density with pressure change and other properties of the fluid this is expansion coefficient, it is dependent on the Isentropic exponent of the fluid.

• Therefore for compressible fluids, flow can be calculated using;

• Where Є = expansibility coefficient.

TYPES OF DIFFERENTIAL PRESSURE DEVICES

ORIFICE PLATE

• An Orifice Plate is a Pressure Differential Device consisting of a thin metal plate with an Orifice located on it.

• The Orifice might vary in shape, location on the metal plate and size.

Fig 1: Orifice Plate (Orifice flow meters, 2014)

Fig 2: Schematics of Orifice Plate(Orifice flow meters, 2014)

ORIFICE PLATE

• There are three main types of orifice plates, classified according to the shape and location of the orifice.

Fig 3: Types of Orifice Plates(Head Flow Meter: Orifice Plate, 2014)

The variation in shape is for improvement of the drainage property of the Orifice plate, the eccentric and segmental variation are ideal for multi phase flows.

TYPES

ORIFICE PLATE

Fig 4: Installation Schematics of an Orifice Plate(Orifice Plate Steam Traps, 2014)

INSTALLATION

ApplicationsFlow rate measurement in Single and Multi phase fluid flowing Regimes in Water pipelines in Water distribution CompaniesOil and Gas pipelines in Petroleum industry

RangeRange of 4:1Coefficient of discharge of 0.6

AdvantagesSimple and CheapCalibration is not requiredIt is applicable to gas and liquid systems

DisadvantagesLow rangeabilityIt is subject poor flow regimes(formation of Eddies)Installation cost for proper installationcan be high

VENTURI METER

A Venturi meter is a device used to measure the flow velocity of a fluid in a pipeline.

Fig 5: Venturi Effect (Venturi Effect, 2014)

ApplicationTo measure the flow rate of oil and gas in a pipeFor fire engine pump flowFor water and waste water applications

Range

AdvantagesHigh efficiency and good pressure recovery

Less sensitive to upstream disturbances

Good performance at high β ratios

DisadvantagesOccupies much longer length in the line

More expensive to manufacture and install

Larger size difficult to handle

NOZZLE METER

• A Nozzle meter, also a pressure differential device is formed when the size of a classical Venturi is reduced by replacing the upstream cone with a nozzle. This size can be still further reduced by discarding the

diffuser, the result being a nozzle. Nozzles therefore, are a compromise design between the compact orifice plate and a good pressure drop

characteristics of the Venturi. These are two standard designs, the ISA Nozzle and the ASME long radius nozzle. Discharge Coefficient is

about 0.9 to 0.99.

INTRODUCTION

NOZZLE METER

Openings are provided at two places 1 and 2 for attaching a differential pressure sensor (u-tube manometer, differential pressure gauge etc.,) as show in the diagram. A flow nozzle is held between flanges of pipes carrying the fluid

whose flow rate is being measured. The flow nozzle’s area is minimum at its throat.

Fig 6: Types of Orifice Plates (Head Flow Meter: Nozzle Meter, 2014)

Applications It is used to measure flow rates of the

liquid discharged into the atmosphere. It is usually used in situation where

suspended solids have the property of settling.

It is widely used for high pressure and temperature steam flows.

Advantages Installation is easy and is cheaper

when compared venturi-meter It is very compact Has high coefficient of discharge

DisadvantagesPressure recovery is lowMaintenance is highInstallation is difficult when compared to orifice flow meter.

Range

PITOT TUBE

Fig 7: Pitot tube.(Bernoulli’s Equation 1: Pitot tube Velocity, 2014)

The impending fluid is brought to rest as the tube is placed with its open end facing the stream of fluid and its kinetic energy converted to pressure energy.

It measures the velocity at a point but by traversing the pipe and measuring the velocity at several points possible to obtain the average velocity hence the volume flowing

PRINCIPLE OF OPERATION

PITOT TUBE

Fig 8: Single-hole Pitot Tube (BSRIA,2014) Fig 9: NPL hemispherical head pitot staticTube. (Hemispherical head Pitot head, quarter section view, 2014)

TYPES OF PITOT TUBE

ApplicationsUsed to monitor gas flow in gas network.They are essentially exploratory devices and are rarely used permanently in industry.They are of more interest to industrial gas engineers for velocity and direction measurements in combustion studies and heat transfer work in industrial furnaces.

AccuracyAccuracy of the device is dependent on the position of the sewing holes on the velocity profile

AdvantagesPresents little resistance to flow inexpensive to buysimple types can be used on different diameter pipes

DisadvantagesTurndown is limited to approximately 4:1 by the square root relationship between pressure and velocityIf stem is wet, the bottom holes can become effectively blocked.

ELBOW METERS

This type of flow meter generates a differential pressure due to the centrifugal forces created by the fluid flowing through the elbow. As the fluid flows through the elbow high pressure area appears on the outer radii of the elbow and the lower at the inner. The sensing elements are installed on the inner and the outer faces of the elbow.

Fig 10: Elbow Meter (Elbow Meter, 2014)

ELBOW METERS

For gases, the differential pressure created is very low, so an Venturi section could be incorporated to increase the pressure as show on the figure bellow.

Fig 11: Venturi-Elbow Meter.(Venturi-Elbow Meter, 2014) Fig 12: Sketch of an Elbow Meter( Nasr&Connor, 2002)

Applications

This type of meters is mostly used in areas with space limitations such as :

Compressor Stations.

Steam Flow From Boilers.

Range

Advantages Low Cost.

Less pressure losses Suitable where there is space limitation

Disadvantages Higher sensitivity to upstream conditions than other meter types. Poor accuracy

Noisy operation

VARIABLE AREA METERS (ROTAMETERS)

DESCRIPTIONA variable area meter is a meter that

measures fluid flow by allowing the cross sectional area of the device to vary in response

to the flow, causing some measurable effect that indicates the rate.

A typical example is the rotameter.A rotameter consists of a tapered tube,

typically made of glass with a 'float', actually a shaped weight, inside that is pushed up by

the drag force of the flow and pulled down by gravity. The fluid flow raises a float in a tapered

tube, increasing the area for passage of the fluid. The greater the flow, the higher the float

is raised. The height of the float is directly proportional to the flowrate.

Fig 13: Basic operating principles of a rotameter (Basic operating principles of a rotameter, 2014)


Three main forces act on the floatThe buoyancy A, which is dependent on the density of the medium and the volume of the float. It is constant (at constant density).The weight G, which is dependent on the mass of the float. Floats can be manufactured using stainless steel, aluminum, titanium or hard rubber, for example.The flow force S: The flow force changes transitionally with a change in the flow until a new state of equilibrium has been achieved.

Fig 14: Forces acting on a float.(Rotameters, 2014)


Glass Tube Rotameter : Glass tube rotameters are typically used for simple but reliable indication of flow rate with a high level of repeatability. They provide flow capacities to about 225 L/m, and are manufactured with end fittings of metal or plastic to meet the chemical characteristics of the fluid being metered.

Metal tube rotameter : These devices, also known as armored meters, are designed for applications where the temperature or pressure exceeds the limits of glass tubes.

Plastic tube rotameter : Plastic tubes are also used in some rotameter designs due to their lower cost and high impact strength. Rotameters with all plastic construction are available for applications where metal wetted parts cannot be tolerated, such as with de-ionised water or corrosives

Fig 15: A Rotameter (Variable Area Technology, 2014)

Applications:Simple flow measurementUsed industrially to monitor gas flow rates.Chemical injection (controls flow rate)Boiler control (measures steam flow to a boiler)

Rangeability and AccuracyAccuracies as high as +/- 0.5 percent can be obtained over 10:1 range of flow.

AdvantagesSimple to install and maintain.No external power required.Sustained high repeatability.Can measure very low flowrates.Linear scale.Wide rangeability.They are cost effective

DisadvantagesIt must always be installed vertically due to its use of gravityNot suitable for pulsating flows.Due to the direct flow indication, the resolution is relatively poor compared to other measurement principles.

THANK YOU

GROUP 9

REFERENCES

Basic operating principles of a rotameter .(2014) Basic Rotameters.

Retrieved 9th April 2014 from

http://www.sensorsmag.com/sensors/flow/the-basics-rotameters-1068

Bernoulli’s Equation 1: Pitot Tube Velocity, (2014) Bernoulli’s Equation 1: Pitot Tube Velocity


http://racingtech.wordpress.com/2011/12/17/bernoullis-equation-1-pitot-tube-velocity/

BSRIA.(2014) TSI/Airflow Pitot tubes


https://www.bsria.co.uk/instrument/sales/product/tsi-airflow-pitot-tubes/?tab=downloads

Elbow Meter.(2014) Electronic kits and Instrumental Systems


http://potran09.blogspot.co.uk/

Head Flow Meter: Nozzle Meter,(2014) Head Flow Meter: Nozzle Meter


http://openticle.com/2007/12/09/head-flow-meters-nozzle-meter/

http://www.sensorsmag.com/sensors/flow/the-basics-rotameters-1068

http://racingtech.wordpress.com/2011/12/17/bernoullis-equation-1-pitot-tube-velocity/

https://www.bsria.co.uk/instrument/sales/product/tsi-airflow-pitot-tubes/?tab=downloads

http://potran09.blogspot.co.uk/

http://openticle.com/2007/12/09/head-flow-meters-nozzle-meter/

REFERENCES

Head Flow Meter: Orifice Plate,(2014) Head Flow Meter: Orifice Plate


http://openticle.com/2007/12/09/head-flow-meters-orifice-plate/

Hemispherical head Pitot head, quarter section view, (2014) Basic Air Data: Pitot Tube


http://www.basicairdata.eu/pitot-tube.html

Nasr G. G., and Connor N, E.(2002).

Experimental and Measurement Methods

Orifice Flowmeters.(2014) Types of Steam Flowmeters


http://www.spiraxsarco.com/resources/steam-engineering- tutorials/flowmetering/types-of-steam-flowmeter.asp

Orifice Plate Steam Traps.(2014) Orifice Plate Steam Traps


http://www.wermac.org/steam/steam_venturi.html

REFERENCES

Rotameters.(2014). Flow Meters: Rotameters


http://www.krohne.com/

Variable Area Technology.(2014). Variable Area Technology: Principle of Operation.


http://www.brooksinstrument.com/flow-pressure-level-measurement-technology/variable-area.html

Venturi Effect.(2014) Venturi Effect


http://en.wikipedia.org/wiki/Venturi_effect

Venturi – Elbow Meter,(2014) Venturi – Elbow Meter


http://www.southwellcontrols.com

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