GAS FLOW MEASUREMENT.ppsx

GAS FLOW MEASUREMENT

ByMasood A. Farooqui

Sales Gas Distribution Network

Agenda• Definition of Fluid Flow Measurement• History• Basic Flow Equation• Metering Station• Types of Meters;– Diaphragm Type– Rotary Type– Turbine Type– Orifice Type– Ultra Sonic Type

• Electronic Volume Correctors• Selecting a Proper Meter

FLUID FLOW MEASUREMENTThe definition

‘The measurement of smoothly moving particles that fill and conform to the piping in an uninterrupted stream to determine the amount flowing.’

Fluid Flow Measurement1. Fluid:

1. having particles that easily move and change their relative position without separation of the mass and that easily yield to pressure;

2. a substance (as a liquid or a gas) tending to flow or conform to the outline of its container.

2. Flow:1. to issue or move in a stream;2. to move with a continual change of place among the consistent

particles;3. to proceed smoothly and readily;4. to have a smooth, uninterrupted continuity.

3. Measurement:1. the act or process of measuring;2. a figure, extent, or amount obtained by measuring.

The History• Over 4,000 years ago, the Romans measured water flow from their aqueducts to

each household to control allocation.• In the early 1600s, Castelli and Tonicelli, determined the concept of differential

flow measurement. • In the early 1700s, Professor Poleni, provided additional work on understanding

discharge of an orifice.• Same time, Mr. Bernoulli developed the theorem upon which hydraulic

equations of head meters have been based ever since.• In the 1730s, Mr. Pitot published a paper on a meter he had developed,

commonly known as Pitot Tube, which was based on differential pressure.• In the late 1790s, Mr. Venturi introduced Venturi Meters, which were the

improved and streamed shape of orifice meter.• In the mid-1800s, Positive Displacement Meters were commercially introduced

in USA.• Strain Gauge, Vortex, Rotary, Turbine, Magnetic, Ultra Sonic and Laser

technologies based flow measurement meter were introduced from early to late 1900s.

The Basic Gas Flow Equation

Q=(πR4 /16ηL)x (Pi2-Po

2/Po)Where:Q= Volume Flow RateR= Radius of PipePi= Pressure InletPo =Pressure OutletL= Lengthη= Viscosity

Poiseuille's equation for compressible fluidsFor a compressible fluid in a tube the volumetric flow rate and the linear velocity is not constant along the tube. The flow is usually expressed at outlet pressure. As fluid is compressed or expands, work is done and the fluid is heated and cooled. This means that the flow rate depends on the heat transfer to and from the fluid. For an ideal gas in the isothermal case, where the temperature of the fluid is permitted to equilibrate with its surroundings, and when the pressure difference between ends of the pipe is small, the volumetric flow rate at the pipe outlet is given by;

Gas Flow Equations(Through section of tube)

A Typical Meter Station

Meter RunIsolation Valve

Meter RunOutlet ValveRegulator

Metering Device

Pressure Relief Valve

By Pass Run By-pass RunOutlet Valve

By-pass RunInlet Valve

Gas Main

Service Pipe

Dry Gas Filter

Supply or DistributionMain Pipe

Major Components of Metering Station

• Gas Service LineA pipe connection from Gas Main to Meter Station

• Gas Flow Control ValvesA device that control partial or full flow of gas.

• Pressure Control DeviceA device that control flow pressure of gas

• Metering DeviceA device that register flow, energy or mass delivered to customer

• Pressure Safety DeviceA device that protect downstream devices from over pressure.

• Electronic SensorsAll the devices like Pressure, temperature and other devices used for calculation for the

flow or control equipments electronically.• Accessories • Devices used for access control, audio-video communication, etc,.

Gas MeasurementTypes of Meters

• Positive Displacement Meters– Diaphragm Type– Rotary Type

• Turbine Type• Inferential Type– Pitot Tube– Venturi– Orifice Tube

• Ultra-sonic Meters

Positive Displacement MetersDiaphragm Type

• There were no gas meters in the very early days of the gas business, but about 1815, in England, Clegg began to make positive-displacement, revolving-drum, water-sealed devices to measure gas plant send out. They were huge affairs; some units were 16-18 feet in diameter.

• In the 1840s, Croll, Richards, and Glover invented and perfected a satisfactory dry, two-diaphragm, sliding-valve, four-chamber, positive-displacement meter for measuring customer consumption.

• In 1903, Sprague invented a two-diaphragm, oscillating-valve meter with three-chambers. The principles of operation and basic construction of these devices remain essentially the same today.

• These meters are constructed in such a way that gas entered in to a known volume chamber and pushes out exist chamber, the lateral to circular motion mechanism rotates number index to register the quantity of gas passed through.

Diaphragm Meter(Circular Reading Index)

Diaphragm Meter(Cutaway Drawing)

Diaphragm MeterMeter Index & Volume Corrector

Diaphragm Meter Mechanism

Diaphragm MeterFlow Equation

Q=2.18xCx(0.6/G)0.5 x(520/T+460) 0.5 x(Ps+Pa/14.73) 0.75

Where;• Q = Recommended meter capacity, scfh, gas• 2.18 = Differential pressure correction factor = (1.9/0.4)0. 5

• C = Meter capacity at 0.5 inches w.c. pressure drop• G = Specific gravity of gas (air = 1.0)• T = Operating temperature, °F• PS = Service pressure, psig• Pa = Actual atmospheric pressure, psia

Standards & Classification(Small Diaphragm Meters)

ANSI Standard B109.1-1992 is identified by its title as applying to “Gas Displacement Meters (Under 500 Cubic Feet per Hour Capacity).” The major parts of this standard address:

• Construction requirements• Performance requirements for new-type meters• In-service performance• Meter installation requirements• Auxiliary devices• Test methods and equipment

The standard divides small meters into four classes based on their capacity expressed in standard cubic feet per hour (scfh) of 0.6-specific-gravity gas at a pressure drop of 0.5 inch water column (w.c.) gauge across the meter:

– Class Capacity– 50 Between 50 and 174 cfh– 175 Between 175 and 249 cfh– 250 Between 250 and 399 cfh– 400 Between 400 and 499 cfh

Standards & Classification(Large Diaphragm Meters)

• ANSI Standard B109.2-1992 addresses “Diaphragm Type Gas Displacement Meters (500 Cubic Feet per Hour Capacity and Over).” This standard is organized in similar fashion to B109.1. Again, the meters are divided into classes based on capacity at 0.5 inch w.c. differential pressure for 0.6-specific-gravity gas:

– Class Capacity– 500 Between 500 and 899 cfh– 900 Between 900 and 1,399 cfh– 1400 Between 1,400 and 2,299 cfh– 2300 Between 2,300 and 3,499 cfh– 3500 More than 3,500 cfh

Diaphragm Meters(Make, Model & Specification)

Make Model MAOPPSIG

CAP. SCFH at 8 PSI

CAP. SCFH at 30 PSI

CAP. SCFH at 40 PSI

CAP. SCFH at 50 PSI Weight Lb Const.

Material INLET OUTLET

ROCKWELL MR - 09 10 0 0 0 0 14.0 Al 1.25" 1.25"

ROCKWELL MR - 12 10 0 0 0 0 21.0 Al 1.25" 1.25"

ROCKWELL RW - 750 20 2,300 51.0 Al 1.50" 1.50"

ROCKWELL RW - 1,600 100 2,300 3,860 4,500 5,000 70.0 Al 1.50" 1.50"

ROCKWELL RW - 3,000 100 4,350 7,370 8,700 9,370 120.0 Al 2" 2"

ROCKWELL RW - 5,000 100 6,960 12,000 13,900 15,600 233.0 Al 3" 3"

ROCKWELL RW - 10,000 100 15,000 24,100 27,800 31,200 360.0 Al 3" 3"

AMERICAN AL - 425 10 1,200 22.0 Al 1.25" 1.25"

AMERICAN AL - 425 25 1,200 22.0 Al 1.25" 1.25"

AMERICAN AL - 800 30 2,400 50.0 Al 1.50" 1.50"

AMERICAN AL - 1400 100 4,240 6,800 7,900 9,000 175.0 Al 2" 3" Flg.



Diaphragm MetersAdvantages/ Disadvantages

Advantages •Very high range-ability• Meters are reliable and durable• Accuracy not affected by rapidly fluctuating flows• Small pressures drop across the meters• Meter can be housed in a small enclosure.

Disadvantages• Not practical for high volume/ high pressure applications• Meters are relatively large compared to other types with equivalent capacity• Liquid accumulation in the meter causes measurement errors.

Rotary Meters(History)

• The first recorded use of a rotary gas meter was in 1920 at the Michigan Light Company, Jackson, Michigan. At that time, two 10 × 24 rotary gas meters were used to measure unpurified gas. In 1924, a study was made at the Peoples’ Gas Light and Coke Company, Chicago, by a joint committee representing the American Gas Association and the National Bureau of Standards. The favorable results of this study and good field experience led to greater use of these meters. By 1950, some 5,000 rotary gas meters had been built; 400 of them were being used at the Peoples’ Gas Light and Coke Company.

• Until the 1960s, Roots-Connersville was the only U.S. manufacturer of rotary gas meters, but, as the meters became more popular, additional manufacturers began to introduce their own designs. Today, the use of rotary positive-displacement meters continues to expand as their design and production incorporate advances in technology.

Rotary Meters(Principle of Operation)

• Rotary meters receive their name from the rotating vanes—also called impellers-that sweep the measuring chambers of the meter. They are true positive-displacement meters, in that each cycle causes a fixed volume of gas to be displaced from the inlet of the meter to the outlet. Gas volume is measured by actual displacement, not inferred from the rotational velocity of the impellers.

• The volume displaced by each meter cycle is determined by the size of the swept area of the meter. Unlike the diaphragm meter, there are no adjustments that affect the volume displaced per cycle. The primary causes of any deterioration in accuracy are internal leakage and friction.

• The pressure differential resulting from gas usage downstream of the meter drives the meter’s impellers and associated devices such as integrating instruments and chart recorders or electronic volume correctors.

Rotary Meterwith Electronic Volume Corrector (EVC)

Rotary Gas MeterEVC with Data logger

Rotary Meters Mechanism

Rotary Meters(Make, Model & Specification)

ModelMAOP. PSIG

CAP. SCFH at 8 PSI

CAP. SCFH at 30 PSI

CAP. SCFH at 40 PSI

CAP. SCFH at 50 PSI

Weight LbConst.

MaterialINLET OUTLET

ROOTS 5 C 175 750 Al 1.50" 1.50"

ROOTS 8 C 175 1,220 2,410 2,350 3,500 4.5 Al 1.50" 1.50"

ROOTS 11 C 175 1,700 Al 1.50" 1.50"

ROOTS 1.5 M 175 2,300 4,500 5,500 6,600 26.0 Al 1.50" 1.50"

ROOTS 2 M 175 3,000 Al 2" Flg. 2" Flg.

ROOTS 3 M 175 4,100 9,000 11,100 13,100 32.0 Al 2" Flg. 2" Flg.

ROOTS 5 M 175 7,630 15,100 18,500 21,900 42.0 Al 3" Flg. 3" Flg.

ROOTS 7 M 175 10,640 21,100 25,900 30,600 54.0 Al 3" Flg. 3" Flg.

ROOTS 11 M 175 16,720 33,200 40,600 48,100 70.0 Al 4" Flg. 4" Flg.

ROOTS 16 M 175 21,310 48,200 59,100 70,000 90.0 Al 4" Flg. 4" Flg.

ROOTS 23 M 175 35,900 69,300 84,900 100,000 475.0 Cast Iron 6" Flg. 6" Flg.

ROOTS 38 M 175 57,700 114,500 140,300 166,100 675.0 Cast Iron 6" Flg. 6" Flg.

ROOTS 56 M 175 85,100 168,400 206,800 244,800 1,050.0 Cast Iron 8" Flg. 8" Flg.

ROOTS 102 M 175 153,000 Cast Iron 8" Flg. 8" Flg.

DELTA - 10 175 1,330 2,620 3,200 3,780 21.0 Al 1.50" 1.50"

DELTA - 25 175 2,130 4,180 5,100 6,050 21.0 Al 1.50" 1.50"

DELTA - 40 175 3,450 6,800 8,320 9,840 21.0 Al 2" Flg. 2" Flg.

DELTA - 65 175 5,320 10,460 12,800 15,140 21.0 Al 3" Flg. 3" Flg.

DELTA - 100 175 8,500 16,730 20,480 24,230 66.0 Al 3" Flg. 3" Flg.

DELTA - 160 175 13,280 26,150 32,000 37,860 95.0 Cast Iron 4" Flg. 4" Flg.




Rotary MetersAdvantages/ Disadvantages

Advantages• Compatible with Electronic Flow Measurement devices• Range ability greater that 100:1 at high pressures• Meter piping requirements allow for a small metering facility

Disadvantages• Gas flow completely shut off it meter seizes• Requires an upstream strainer• Continuous high rates result in excessive wear• Leakage at very low flow rates causes measurement errors

Turbine Meter(History)

• The concept of turbine-meter measurement of fluid flow is not new. For many years, turbine meters have accurately measured liquid flows. Patents on turbine meters for air and gas measurement existed in the late 1800s.

• However, turbine devices were not applied practically to natural gas measurement until the 1950s. Improvements in the turbine meter’s design included externally lubricated ball bearing systems, low-friction magnetic coupling mechanical output drives, advanced rotor designs, electronic outputs, calibration facilities, and techniques and auxiliary instrumentation such as on-line gas flow computers. The A.G.A. Transmission Measurement Committee Report No.7, entitled Measurement of Gas by Turbine Meters, published in 1985, provides a basis for design, operation, and maintenance activities associated with turbine-meter measurement.

Turbine Meters(Principle of Operation)

• The principle of operation of the turbine meter is as follows: gas entering the turbine meter increases velocity as it flows through the annular passage formed by the nose cone or upstream stator and the interior wall of the body.

• Movement of this gas over angled rotor blades causes rotation of the rotor. The speed of the rotor is directly proportional to the average velocity of the gas through the meter. From the rotor rotation through a gear train and/or an electronic signal, a volumetric output is provided that is linear within specified error limits over the range of operation specified by the meter manufacturer.

Turbine MeterFlow Equation AGA #7

• Flow rate at Base Conditions, Qb

Qb = (Qf)(Fpm)(Fpb)(Ftm)(Ftb)(s)

Where;Qf : Flow rate at flowing condition

Fpm: Pressure Factor

Fpb : Pressure Base Factor

Ftm : Flowing Temperature Factor

Ftb : Pressure Base Factor

s : Compressibility Factor

Turbine MeterRecommended Installation Arrangement as per AGA#7

Advantages• Compatible with Electronic Flow Measurement devices• Range-ability greater that 100:1 at high pressure• Accuracy (error less than 0.65%)• Small pressure drop across the meter

Disadvantages• Susceptible to damage from liquids and solids• Requires upstream strainer• Rotor friction at low flow rates can cause measurement errors• Not cost effective at low pressure• Requires over range protection

Turbine MetersAdvantages/ Disadvantages

Orifice Meter(History)

• The orifice has been in commercial use since the early 1900’s. The device is used to create a differential pressure that relates to the velocity of the gas from which a flow rate can be calculated.

• Orifice measurement is a mature technology. Orifice flow coefficients were published in 1903, while the first

• documented installation of an orifice meter with a recorder was in 1911, and the first commercially available orifice

• meter was offered in 1915.• Orifice measurement is guided by the standards of several

organizations. Primary among these is the American Gas Association and the American Petroleum Institute.

• The AGA #3 report is the standard that provides guidelines for the construction and installation of orifice meters.

Orifice Meters(Principle of Operation)

• An orifice meter is an inferential meter in which the fluid velocity and flowrate are inferred from the pressure drop occurring through the known area of an orifice plate.

• Specifically, orifice meter flow is calculated from the flowing;– gas pressure and temperature,– differential pressure drop occurring across the restriction

of the meter’s orifice plate, – the meter geometry including the meter tube’s inside

diameter and orifice plate bore,– and the gas composition.

Orifice MeterFlow Equation AGA #3

• Flow rate at Base Conditions, Qb

Qb = (Qf)(Fpm)(Fpb)(Ftm)(Ftb)(s)

Where;Qf : Flow rate at flowing condition

Fpm: Pressure Factor

Fpb : Pressure Base Factor

Ftm : Flowing Temperature Factor

Ftb : Pressure Base Factor

s : Compressibility Factor

Orifice MeterRecommended Installation Arrangement as per AGA#3

Orifice MeterComponents of Orifice Meters

Orifice MeterAdvantages/ Disadvantages

Advantages• Compatible with Electronic Flow Measurement devices• Accurate, repeatable, and proven• Simple device• Minimal operating costsDisadvantages• Low range-ability• Susceptible to errors if liquids presents in the gas streams• High installation cost• Pressure drop is relatively higher than other meter types

Ultra-Sonic MetersHistory

• The original patent for an ultrasonic meter was issued in 1928, and development of the meter continued from the 1950’s through the 1980’s.

• The application of ultrasonic meters has increased steadily since the 1990’s.

Ultra-Sonic MetersPrinciple of Operation

• An ultrasonic meter measures gas velocity by measuring the transit times of ultrasonic pulses sent between two transducers in the gas flow direction and against the gas flow direction.

• Custody transfer ultrasonic meters typically contain multiple pairs of transducers.

• Gas velocity and flow rate are then calculated using ;– the transit time differences,– gas composition, – gas temperature, gas pressure, and– meter geometry (path length between transducer pairs).

• Ultrasonic meter calculations are based on AGA Report No. 9, Measurement of Gas by Multipath Ultrasonic Meters,

• 1998, and AGA Report No. 10, Speed of Sound in Natural Gas and Other Related Hydrocarbon Gases.

Ultra-Sonic Flow Meter RunA Typical Installation Scheme

Ultra-Sonic Flow MeterFunctional Diagram

Ultra-Sonic Flow MeterTransmitters Arrangement

Ultra-Sonic Flow MeterFlow Equation

• BF70 Ultrasonic flow meters measure the velocity of liquid or gaseous material by taking advantage of the travel time of the ultrasonic in a pipe. The medium flow rate can be achieved based on flow velocity, pipe sectional area and Reynolds number. There will be a pair of ultrasonic transducers A and B on the pipe, and the distance between A and B is the ultrasonic travel distance in the pipe. There are equations as follows:

Ts=L/ C+VCosθ and Tn=L/ C-Vcosθ

V= L/2Cosθ (1/Ts-1/Tn)

• where:C: ultrasonic traveling velocity in static fluid, and it varies with the fluid property,V: fluid velocity, θ : the included angle between ultrasonic travel route L and axes of the pipe.With ts and tn, mean velocity of the fluid can be counted out.

Ultra-sonic MeterAdvantages/ Disadvantages

Advantages• Compatible with Electronic Flow Measurement devices• Accurate, repeatable, and proven• Simple device• Minimal operating costsDisadvantages• Low range-ability• Susceptible to errors if liquids presents in the gas streams• High installation cost• Pressure drop is relatively higher than other meter types

SELECTING A METERGENERAL CONSIDERATIONS

• There are several basic considerations that should always be kept in mind when designing a gas metering station. These include: – Desired flow measurement accuracy,– Range of flow rate or load,– Quality and cleanliness of the gas,– Limits on available space for the meter station installation, – Available Service Utilities,– Environmental or atmospheric conditions,– Long-term maintenance requirements for the selected

measurement equipment.

GAS FLOW MEASUREMENT.ppsx

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