LHN Metering Systems 25131

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0 2007-05-18 Otto Tomasch O.T. Viorel Vladut V.V. R.G. Hollamby RGH Initial Document

Rev Date Prepared by Initials Checked by Initials Approved by Initials Modifications

Form: A62.1858-ADM-FRM-0303 Cegelec 2006 Page 1 of 18

This document is the property of Cegelec (The Company). Distribution and use of this document are strictly governed by the Companys Document Managemen t Policy and Procedures.The contents and form of the document are the sole property of The Company and may not be reproduced, distributed or used without the express written permission of The Company.

Lesson Handout Notes

25131METERING SYSTEMS

A62.1858-LHN-PRO-25131-01

Effective Date: May 19th2007

Training Program : TECHNICIAN: LEVEL 2 CERTIFICATION

Discipline : PROCESS

System : METERING & GAUGING

Sub-System : METERING SYSTEMS

Training Focus : BASIC KNOWLEDGE

Training Elements : This lesson targets training on the following training elements:Reasons for Metering and MeasuringFiscal - Custody TransferOrifice Plate MeterVenturi Meter

Turbine MeterPositive Displacement MeterCoriolis MeterMulti-Phase MetersMetering SystemsMeter Readings

Training Objectives : At the end of the Lesson the participants will be able to:Define the reasons for metering and measuring process flow streamsDescribe the different uses of metering dataDefine the principle of an orifice plate meterDefine the principle of Venturi meter

Define the principles of a turbine meterDefine the principle of positive displacement metersDefine the principle of Coriolis meterDescribe when the use of a multi-phase meter is requiredDescribe the basic management systems required for meteringDescribe the form of the readings from oil and gas meters


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Lesson Handout Notes25131: Metering Systems

A62.1858-LHN-PRO-25131-01May 19th 2007

25131: Metering Systems Cegelec 2007 Page 2 of 18

DOCUMENT INFORMATION

TABLE OF CONTENTS: Page no.

Technician Level 2 Certification 1

Process 1

Metering & Gauging 1

Metering Systems 1

Basic Knowledge 1

Document information 2

Table of Contents 2Reasons for Metering and Measuring 3

Fiscal-Custody Transfer 3

Meter Readings 5

Flow Meters 7

Orifice Plate Meter 8

Venturi Meter 10

Turbine Meter 13

Positive Displacement Meters 14Coriolis Meter 16

Multi-Phase Meters 18

Purpose

The purpose of this document is to provide the participant study information.

Owner

The owner of this document is the Process Discipline Team of Ogere Training Facility, Ogere Remo,Ogun State Nigeria.

Custodian

The custodian of this document is the Data Administrator and Document Controller of the Ogere TrainingFacility, Nigeria.


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Reasons for Metering and Measuring

An understanding of fluid properties as well as installation requirements for metering devices is needed for correctspecification or design of equipment. Various metering devices produce different flow characteristics - a fact that

provides advantages for intermittent dispensing, batch and continuous processes. To specify and design ametering system correctly, engineers need to understand the requirements for a successful installation. Along withthe properties of the fluid to be metered (flow range, viscosity and temperature) and installation requirements(pressure, power and space constraints), they need to be familiar with the various metering devices and the effectthey have on flow characteristics and the process used.

Metering systems can range from complex pumping systems with fully automated closed loop flow control to simplemanual additions of a certain ingredient during a time period. For the purpose of this article, emphasis will beplaced on metering devices claiming steady state accuracy of 1% or better. This would encompass piston orplunger, diaphragm and precision gear type devices. It should be pointed out, however, that other pumping devicesin conjunction with control systems are being applied with success, especially in higher flow rates (above 1,200gph) and reduced turndown ratios.

While the control example still remains the major justification for a metering system, the age of continuousimprovement (cost reduction and inventory control) has shifted batch processes to continuous processes, furtheringthe argument for lower rate and higher accuracy flow control. When asked to find a metering system for a fluid,develop an understanding of whether the need is for flow control or to conserve raw material costs.In continuous processing where production rates can vary, a metering system's ability to repeat the flow rateaccurately for a given condition is critical to product quality.

Some standards allow a metering device to have stated accuracy based on two tests at rated or maximumcapacity. When designing a metering system, be sure to consider accuracy and repeatability over the entireturndown range. It is very important to specify accuracy over the flow range desired to be assured that yourconditions are met.

Fiscal Metering

Fiscal metering systems (see Figure 1) are used on pipelines to check the values of the oil & gas parameters (flowrate, oil/gas composition) when they are subject to change or when the pipeline crosses a border between twocountries.Product is measured to determine how much is being consumed or sold. Where hydrocarbon product is beingmeasured to determine payment from a customer, or the payment of taxes or royalties to a governmentdepartment, the operation is termed fiscal metering.

Often the volumes of hydrocarbons involved in fiscal metering can be very high and even small inaccuracies canresult in large losses in monetary terms to the supplier or the customer. For this reason great care is taken in fiscalmetering and equipment capable of achieving a high degree of accuracy is used. It is common for meteringequipment to be controlled by a Computer Supervisory System (CSS). Many different types of meters are available

to measure the volumetric flow of hydrocarbons, e.g.:

Orifice meters

Positive displacement meters

Venturi meters

Turbine meters

Flow nozzles

Elbow meters

Of these meters, the orifice-type flow meter, is the most commonly used in field service and pipeline systems.Because of their accuracy, however, turbine meters are most widely used in fiscal metering systems.Regulatory authorities approve the use of turbine meters for fiscal metering on condition the meter is regularly

checked for accuracy by a Meter Prover.


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Metering Points

Oil transfer to off-loading vessels

High pressure flare gas

Low pressure flare gas Fuel gas consumption

Figure 1: Fiscal Metering Skid

Custody Transfer

Custody transfer is the simultaneous process of exchanging the ownership of a determined quantity of fluid, suchas a refined petroleum product, while physically moving the fluid from one owner's facility/container to thefacility/container of a different owner.

For example, custody transfer could take place when gasoline is pumped out of a pipeline into a storage tank in atank farm, or again, from the storage tank into a transport truck where the volume of fluid exchanged is determinedby a flow meter.

Flow Meter ReadingSo you want to measure flow? With fluid flow defined as the amount of fluid that travels past a given location, thiswould seem to be straightforward any flow meter would suffice. However, consider the following equationdescribing the flow of a fluid in a pipe.

Q = A x v

Q is flow rate, A is the cross-sectional area of the pipe, and v is the average fluid velocity in the pipe. Putting thisequation into action, the flow of a fluid traveling at an average velocity of a 1 meter per second through a pipe witha 1 square meter cross-sectional area is 1 cubic meter per second. Note that Q is a volume per unit time, so Q iscommonly denoted as the volumetric flow rate.


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Now consider the following equation:

W = rho x Q

Where W is flow rate, and rho is the fluid density. Putting this equation into action, the flow rate will be 1 kilogramper second when 1 cubic meter per second of a fluid with a density of 1 kilogram per cubic meter is flowing. Notethat W is a mass per unit time, so W is commonly denoted as the mass flow rate. Now which flow do you wantto measure? Not sure? In some applications, measuring the volumetric flow is the thing to do.

Consider filling a tank. Volumetric flow may be of interest to avoid overflowing a tank where liquids of differingdensities can be added. (Then again, a level transmitter and high level switch/shutoff may obviate the need for aflow meter.) Consider controlling fluid flow into a process that can only accept a limited volume per unit time.Volumetric flowmeasurement would seem applicable.

In other processes, mass flow is important. Consider chemical reactions where it is desirable to react substances A,

B and C. Of interest is the number of molecules present, not its volume. Similarly, when buying and selling products(custody transfer), the massis important, not its volume.

Having discovered that there are two types of flow rates (volumetric and mass), it should not be a surprise thatsome flow meters measure mass (W) while other flow meters measure volume (Q). However, it is not quite thatsimple. Repeating the equations above, it can be seen that, assuming A is constant, Q can be determined bymeasuring the average fluid velocity v. Further, assuming that rho is constant, W can be determined from Q.

Q = A x v W = rho x Q

Summarizing:

Some flow meters measure Volumetricflow,

Some flow meters measure velocityfrom which the volumetric flow is determined, and

Some flow meters measure massflow.

In addition, when the density is known or assumed, mass flow can be determined from the volumetric flow, and thevolumetric flow can be determined from the mass flow.So you just wanted to measure flow did you now? It all seemed so logical and simple at the time. Stick around it gets worse.Some flow meters use other principles to infer flow. The most common of these measurements measure thevelocity head(1/2 rho v x v) to infer the volumetric flow. Notice that these flow meters do NOT measure volume,do NOT measure mass, and do NOT measure velocity - but rather measure a combination of density and the

square of velocity! Would it surprise you to discover that this is a description of (commonly-applied) head flowmeters, such as orifice plates, Venturis, nozzles...? Further, in many applications, the inferred volumetric flow isused to determine the mass flow.

Summarizing (again):

Some flow meters measure volume,

Some flow meters measuremass,

Some flow meters measure velocity, and

Some flow meters measure inferentially.

Understand the difference, but also understand that careful attention to detail can result in an inferentialmeasurement that is better than the others.

Volumetric flow is expressed in units that reflect a volume per unit time. The example above determines cubicmeters and cubic feet per unit time to be volumetric flow units. Gallons and liters per unit time are also volumetricflow units.


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Mass flow is expressed in units that reflect a mass per unit time. The other example above determines kilogramsand pounds per unit time to be mass flow units. Note that the units of time are independent of whether volumetric ormass flow is measured.

Flow Rate Measurements

In order to check on changing conditions, flow meters are installed in pipelines at various points. Flow meteringsystems provide vital information for export costing, production planning and product quality control. There arethree common flow rate measurements:

Velocity: This indicates how fast the fluid is flowing past the measurement sensor, usually in meters per second

(m/s). This is usually converted to give an indication of volumetric f low rate.

Volumetric flow: This measures either the rate of volume flow or the total volume of fluid that has passed through

the flow meter e.g. m/s, cm/min, gallons/min, liters/min, standard cubic feet/min.

Mass flow: These types of flow meter measure:

Mass flow through the flow meter

Total mass of fluid that has passed through the flow meter

Flow Meter Selection

Flow meter selection is decided upon awareness to the following questions:

Which of the three flow measurements listed above will provide the plant with the most appropriateinformation?

What is the required accuracy? (Increasing the flow meter accuracy; rapidly increases the cost and rulesout some types).

What is the nature of the process fluid? (Temperature, pressure, viscosity, solid content, etc.).

Over what range does the flow need to be measured?

Flow Meters

Flow meters are devices that measure the amount of liquid, gas or vapor that passes through them. Some measureflow as the amount of fluid passing through the flow meter during a time period, i.e. rate of flow e.g. 100 liters perminute. Others measure the totalized amount of fluid that has passed through the flow meter (such as 100 liters).

Measurement principles for liquid and gas vary slightly because gas is compressible and liquid is not. As the gaspressure changes, the amount of gas also changes. Liquids do not change in volume as pressure changes. For thismain reason, the flow measurement methods used for liquid and gas applications differ slightly.

Accurate flow measurement is necessary to ensure that:

The correct volumes of gas and liquid are measured and exported

Process flow is measured and controlled

Factors affecting flow meter selection are:

The units in which the flow needs to be measured

The required accuracy (Increasing flow meter accuracy rapidly increases the cost).

The nature of the process fluid (temperature, pressure, viscosity, solid content)

The range that needs to be measured


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The most common principals for fluid flow metering are:

Differential Pressure Flow meter

Variable Area Flow Meter or Rotameter

Velocity Flow meter Pilot Tube

Calorimetric Flow meter

Turbine Flow meter

Vortex Flow meter

Electromagnetic Flow meter

Ultrasonic Doppler Flow meter

Positive Displacement Flow meter

Mass Flow meter

Thermal Flow meter

Coriolis Flow meter

Open Channel Flow meter

Flow meters consist of a primary device, a transducer and a transmitter:

The Primary Deviceis the actual measuring element

The Transducersenses the fluid that passes through the primary device

TheTransmitterproduces a usable flow signal from the element signal

Differential Pressure Flow Meters

The most common types of differential pressure flow meters are:

Orifice Plates

Flow Nozzles Venturi Tube

Variable Area - Rotameter

Orifice Plate

The orifice plate is the most popular version of the head type flow meter and the most commonly used of all typesof industrial flow meters (see Figure 2). This is because different designs can be used to measure the flow of agreat variety of fluids, under different conditions without any appreciable reduction in accuracy.

With an orifice plate, the fluid flow is measured through the difference in pressure from the upstream side to thedownstream side of a partially obstructed pipe. The plate obstructing the flow offers a precisely measuredobstruction that narrows the pipe and forces the flowing fluid to constrict.

The orifice meter consists of a flat orifice plate with a circular hole drilled in it. There is a pressure tap upstreamfrom the orifice plate and another just downstream. There are in general three methods of placing the taps. Thecoefficient of the meter depends upon the position of taps.

Flange location- Tap location 1 inch upstream and 1 inch downstream from face of orifice

Vena contracta location- Tap location 1 pipe diameter (actual inside) upstream and 0.3 to 0.8 pipediameter downstream from face of orifice

Pipe location- Tap location 2.5 times nominal pipe diameter upstream and 8 times nominal pipe diameterdownstream from face of orifice

Theturndown ratefor orifice plates is less than 5:1. Their accuracy is poor at low flow rates. A high accuracydepends on an orifice plate in good shape, with a sharp edge to the upstream side. Wear reduces the accuracy.
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The orifice meter is recommended for clean and dirty liquids

and some slurry services The rangeability is 4 to 1

The pressure loss is medium

Typical accuracy is 2-4% of full scale

The required upstream diameter is 10 to 30 diameters

The viscosity effect is high

The relative cost is low

Figure 2: Orifice Plate

An orifice plate is simply a plate inserted into the process line with a hole (or orifice) machined through it. Thepressure profile generated in the flowing fluid as it passes through the orifice is shown in Fig. 3.Orifice plates have to be installed correctly according to flow direction.The orifice is sharp-edged on the inlet and chamfered on the outlet.The diameter of the orifice is calculated to produce the desired pressure drop, as per design conditions.

Vena Contracta

After passing the orifice plate, the Cross Sectional Areaof the flow (CSA) continues to contract before

expanding again.

The point of minimum CSA lies between 0.4 and 0.8pipe diameters downstream of the orifice plate.

Figure 3: Flow through an Orifice (showing VenaContracta)

Concentric Orifice Plate

The conventional concentric, sharp edged orifice plate shown in Fig. 4 has several major advantages:

It is relatively easy and economical to manufacture to close tolerances.

It is simple to install and replace.

It is well established and supported by a great deal of tried and tested calibration and usage information.However, the orifice plate has some disadvantages:

It cannot handle dirty fluids

There is a permanent pressure loss

Has a relatively low accuracy


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Eccentric & Segmental Orifice Plates

The eccentric orifice plate is similar to the concentricplate except that the eccentric hole is located towards

the bottom of the pipe.

It must be installed so that no portion of the flange orgasket covers the hole.

Figure 4: (a) Eccentric and (b) Segmental Orifice Plates

Eccentric and segmental orifice plates are used for the measurement of slurries, dirty liquids and for gas or vapour

where liquids may be present.

Orifice Plate Installation

The orifice plate is usually installed between two flanges; either with a carrier assembly or in a housing to allow in-line removal of the plate (Fig.5). The differential pressure pick-up points (tappings) can be located either in theflanges (flange tappings or corner tappings) or in the upstream and downstream pipe work.

Figure 5: Orifice Plate Installation

The DanielOrifice Fitting is the most widely used device in gas measurement. Operated by one person, this

differential technology meter saves time and money in many ways. It permits plate-changing under flowingconditions, which means no operation shutdown. By maintaining flow during plate changes, the fitting also avoidsthe burden of bypass piping.


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Venturi Tube

Venturi tubes are head-type flow elements that introduce a restriction into the flow path to create a differentialpressure. A section of tube forms a relatively long passage with smooth entry and exit (Fig. 6).

A Venturi tube is connected to the existing pipe, first narrowing down in diameter then opening up back to theoriginal pipe diameter. The changes in cross section area cause changes in velocity and pressure of the flow. Thepressure loss created in the pipe is much less compared to an orifice plate so they do not disrupt the process asmuch.

The flow restriction point is known as the throat

Inlet pressure is measured at the entrance

Static pressure in the throat section

A pressure drop transmitter measures the difference in pressure across the tapping points

The greater the flow, the greater the difference in pressure measured by the transmitter.

Differential pressure is converted to a proportional flow rate

Figure 6: Venturi FlowMeter

With properinstrumentation and flowcalibrating, the VenturiTubeflow rate can bereduced to about 10% ofits full scale range withproper accuracy. This

provides aTurndown Rate10:1.

Due to its simplicity and dependability, the Venturi tube flow meter is often used in applications where it isnecessary with higherturndown rates,or lower pressure drops, than the orifice plate can provide. The pressurerecovery is much better for the Venturi meter than for the orifice plate.

The Venturi tube is suitable for clean, dirty and viscous liquid and some slurry services

The rangeability is 4 to 1

Pressure loss is low

Typical accuracy is 1% of full range

Required upstream pipe length 5 to 20 diameters

Viscosity effect is high

Relative cost is medium

A Venturi is used to overcome problems of erosion or blockages caused by:

Slurry

Solids build-up

Where net pressure loss across the meter must be minimum.

Venturi tubes are available in sizes up to 2 meters diameter and can pass 25 to 50% more flow than an orifice withthe same pressure drop. The initial cost of Venturi tubes is high, so they are used on larger flows or on moredifficult or demanding flow applications.
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Figure 7: Typical Venturi Flow Meter

Advantages

Venturi tubes produce a small permanent pressure loss. Venturi tubes are capable of measuring dirty fluids containing particles such as crude oil.

Disadvantages

Expensive to manufacture and install

Flow meter length is longer than most other meters.

The differential pressure created is lower than that of a typical orifice plate.


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Bernoullis Theorem

Bernoulli's Theorem describes the relationship between pressure, velocity and elevation in a moving fluid (liquid or

gas). The theorem states that the total mechanical energy of a flowing fluid in a pipe comprises of three energyforms:

Pressure Energy

Kinetic Energy

Potential Energy

These energy forms remain constant providing there are no frictional losses.Bernoulli's theorem implies that if a fluid flows horizontally so that no change in gravitational potential energyoccurs, then a decrease in fluid pressure is associated with an increase in fluid velocity.

Hence:

Where there is slow flow, pressure increases.

Where there is faster flow, pressure decreases.

In a real flow, friction plays a large role - large pressure drops occur due to friction in pipes, fittings and equipment.

Figure 8: Venturi Flow Element Connected to a Transmitter

Applying Bernoullis Theorem:

At A, fluid flow is at a certain velocity with fixed pressure drop.

At B, fluid velocity increases as the cross sectional area reduces

At C, (throat) fluid velocity is at a maximum, pressure is at a minimum

At D, fluid velocity decreases and pressure increases.

At E, the fluid velocity is almost the same as at A but:

There is never a full recovery of upstream system pressure. There is always some permanent pressure loss due tofriction depending on the type of restriction device, velocity, viscosity and other parameter.


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Turbine Flow Meter

There are many different manufacturing designs of turbine flow meters, but in general they are all based on the same

simple principle (see Figure 9).If a fluid moves through a pipe and acts on the vanes of a turbine, the turbine will start to spin and rotate. The rate of spinis measured to calculate the flow.

The turndown ratios may be more than 100:1 if the turbine meter is calibrated for a single fluid and used at constantconditions. Accuracy may be better than +/-0.1%.

The turbine meter uses a small turbine situated in the flow stream. The flow causes the turbine to rotate.

1. The bearings support the multi-bladedrotor

2. The rotor supports the turbine blades

3. A magnetic field is set up by the magneticpick-up. As the turbine blades pass themagnetic pick-up they cut the magneticcoils magnetic lines of flux

4. The magnetic pick-up produces a voltagepulse as each blade passes

Figure 9: Turbine Meter

The Speed of blade rotation is proportional to thevolumetric flow rate

The higher the velocityof flow, the faster the turbine spins. The speed of the turbine and the cross sectional areaof the meter, gives a measure of flow rate.

Advantages:The advantages of turbine meters are that they cause only a small pressure drop and they are accurate over alarge range of flow rates.

Disadvantages:The disadvantages are that the moving parts are subject to wear and corrosion and they are expensive. So, theyshould only be used with clean viscous fluids. Dirty fluids require filtration before metering.

Important Note: There can be a flow below which the turbine fails to respond, i.e. there is a minimum flow rate thatmust be reached before the turbine rotates.

Positive Displacement Meter

Positive displacement flow meters, also known as PD meters, measure volumes of fluid flowing through them bycounting the filling and discharging of a chamber of known fixed volume.Inside the chamber, a rotating/reciprocating mechanical unit is placed to create fixed-volume parcels from thepassing fluid. The volume of the fluid that passes through the chamber is found by counting the number of passingparcels. The volume flow rate can be calculated from the revolution rate of the mechanical device.

It should be noted that displacement meters do not measure flow with any reference to time. If flow rate is required,readings must be taken at the beginning and end of a known time interval.


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Common types of PD flow meter are:

Oval Gear Nutating Disk

Oscillating & Reciprocating Piston

All PD flow meters use the same displacement principle. The only variation is the specific chamber/geararrangement.

Oval Gear PD Flow Meter

There are two oval gears or rotors inside an oval geared flow meter (see Figure 10).

The gears trap fluid in the spaces between the gears and the meter body. These spaces are often referredto as chambers.

Fluid enters the meter via the inlet and applies pressure to the oval gears causing them to rotate.

For every rotation of the oval gears a precise amount of fluid is passed from the inlet to the outlet.

If the velocity of the fluid flow increases, the rotation of the oval gears also increases. The quantity of fluid passingis always the same. Hence the total flow is proportional to the number of rotations. This type of flow meter is oftenused for the measurement of oil flow as this has the effect of lubricating the gears.

A B

C D

E F

Figure 10: Oval Gear Arrangements

Nutating Disk Flow Meter

These meters operate on the same principle of measurement and are of the nutating disc volumetric displacementtype.The liquid enters the meter through the inlet, shown at the left in the sectional view, and passes upward into the top

of the main casing. Here it submerges and lubricates the internal gearing; then moves downward through themeasuring chamber, into the base of the meter, and discharges through the meter outlet.


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Figure 11: Nutating Disk Flow Meter

When the liquid enters the measuring chamber, it drives the single measuring disc, which nutates or rocks, aroundon its central ball (see Figure 11). The roller or positive displacement cam, against which the disc pin bears,controls its movement and compels it to make a complete nutation at each movement. The position of the discdivides the chamber into compartments which are successively filled and emptied, each compartment holding adefinite volume. The movements of the disc are transmitted by a train of gears to the meter register.The edge of the flat portion of the nutating disc is unusually thick. The liquid being measured forms a liquid sealbetween the disc and the chamber wall, minimizing slippage and compelling accuracy at low rates of flow. Works

are made of materials selected for the liquid to be measured. The bearings of the submerged gears carry theweight of the gears on the tops of the gear posts, forming an enclosed, dirt-proof construction.

The amount displaced by a single movement of the disc remains constant for any specified liquid. With the correcttrain of gears, accurate registration on the register is thus assured. Oil meters are tested on oil and the tolerance isnot more than 1%, sometimes much smaller.Like all volumetric meters, nutating disk meters are intended for operation on clean liquids only. Solids such assediment or pipe scale must be removed before metering by a filter or fine mesh strainer.

Oscillating Piston Flow Meter

Oscillating piston flow meters typically are used in viscous fluid services such as oil metering on engine test standswhere turndown is not critical.

Reciprocating Piston Meter

Reciprocating piston meters are probably the oldest PDmeter designs. They are available with multiple pistons,double-acting pistons, or rotary pistons. As in areciprocating piston engine, fluid is drawn into one pistonchamber as it is discharged from the opposed piston in themeter.

Figure 12: Reciprocating Piston Meter

:


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Typically, either a crankshaft or a horizontal slide is used to control the opening and closing of the proper orifices inthe meter. These meters are usually smaller (available in sizes down to 1/10-in diameter) and are used formeasuring very low flows of viscous liquids.

Coriolis (or Mass) Flow Meter

Direct mass measurement sets Coriolis flow meters apart from other technologies. Mass measurement is notsensible to changes in pressure, temperature, viscosity and density. With the ability to measure liquids, slurries andgases, Coriolis flow meters are universal meters.For some applications, Coriolis mass-meters offer a technical solution for metering difficult fluids. Oils with highviscosity and solids content can harm more traditional meters

Whether for liquid, gases or slurries, a micro-motion Coriolis flow meter offers many advantages over traditionalvolumetric technologies. By using a multi-variable highly accurate measurement device (+/-0.05%) it providesprecision measurement of:

Mass flow rate

Volumetric flow rate Density

Temperature

There are no special mounting, flow conditioning, or straight pipe runs required and no need to adjust the factoryzero. There are no moving parts and no calibration drift, and the device can be cleaned in place withoutdismantling. Micro-motion flow meters exist in two types: curved-tube and straight-tube.

A Coriolis flow meter consists of a sensor, a transmitterand, in many cases, peripheral devices.

Sensorsdetect flow rate, density and temperature.

Transmittersprovide sensor information asoutputs, acting like the brain of the system toprovide a display, basic menu access, and outputsto interface with other systems.

Peripheralsprovide monitoring, alarm oradditional functionality, such as batch control andenhanced density functions.

Figure 13: Coriolis Flow Meter

Operating Principle

Coriolis Mass Flow meter uses the Coriolis effect to measure the amount of mass moving through the element. Thefluid to be measured runs through a U-shaped tube that is caused to vibrate in an angular harmonic oscillation. Dueto the Coriolis forces, the tubes will deform and an additional vibration component will be added to the oscillation.This additional component causes a phase shift on some places of the tubes which can be measured with sensors.

By vibrating in opposition, the Coriolis flow tubes are balanced and isolated from external vibration or movement ofthe flow meter.In micro-motion flow meters that have dual parallel flow tubes, process fluid entering the sensor is split with half of

the fluid passing through each flow tube. During operation, a drive coil is energized causing the tubes to oscillate inopposition to one another.


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Figure 14: Coriolis Curved-Tube Flow Meter

Figure 15: Vibrating Coriolis Flow Tubes

Figure 16: No-Flow Tube Motion

Figure 17: Flow Tube Motion


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Multiphase (or Wet Gas) Meter

A device that can register individual fluid flow rates of oil and gas when more than one fluid is flowing through a

pipeline.Amultiphasemeter provides accurate readings even when different flow regimes are present in themultiphase flow.

A multiphase meter measures accurately the flow rates of oil, gas and water without separation, mixing or movingparts.

Net oil flow rate accuracy depends on water-cut. All multiphase meters calculate the net oil flow rate from themeasured water-cut and the gross liquid rates. The higher the water-cut and worse the abs. accuracy of the water-cut, the poorer is the net oil flow rate in accuracy.

Multiphase Fluid Flow

Multiphase fluid flow is the commingled flow of differentphase fluids, such as water, oil and gas.Multiphase fluidflow is a complex factor, important in understanding and optimizingproduction hydraulics in both oil and gas wells.

Fourmultiphase fluid flow regimes are recognized when describing flow in oil and gas wells: Bubble flow,

Slug flow,

Transition flow and

Mist flow.

Advantages of Multiphase Meters

Using multiphase meters on wells has the following advantages:

No production loss during testing Extended/increased production from low-pressure wells, due to increased availability of the

test separator for production purposes Immediate detection of water or gas breakthrough Improved recovery, due to continuous well monitoring Multiphase meters cost less, weigh less and require less space

Multiphase meters are more common in deepwater operations, where well-intervention operations are oftenprohibitively expensive.

131: Metering Systems 27 Cegelec 2006

TimeTime--ofof--flight Ultrasonic Flow Meterflight Ultrasonic Flow Meter

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LHN Metering Systems 25131