Automation Business
Flow Measurement
Some Basic Terms and Concepts
 Fluid - The state of a substance in which its particles easily move and change their
relative position without a separation of the mass and that easily yield to pressure.
A fluid can be a liquid (generally considered incompressible) or a gas.
 Mass - Quantity of matter that causes it to have weight in a gravitational field.
Mass flow is expressed in weight/time, ie kilograms/hr.
 Volume - Space occupied or enclosed by cubic units. Volumetric flow is expressed
in cubic measure/time i.e. cubic feet/minute or gallons/hour.
 Density - Mass of a substance per unit volume.
 Specific Gravity - The ratio of the density of a substance to the density of some
some substance taken as a standard. For flow of liquids, specific gravity of fluid is
compared against that of water, for gases against that of air.
 Mole - grams/molecular weight
 SCFM - Standard Cubic Feet per Minute.
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Automation Business
Flow Measurement
Some Basic Terms and Concepts
 Liquids are generally considered incompressible
 Ideal Gas Law - The pressure, temperature and volume of a gas are all
interrelated.
• PV = nRT
– P = pressure of the gas
– V = the volume that the gas occupies(ie ft3)
– n = number of moles
– R = ideal gas constant (a universal constant)
– T = temperature of the gas in absolute units
 For the gas industry flow is most commonly measured as volumetric flow
and expressed at base conditions
• volume is dependant on temperature and pressure and composition
• volumetric measurement must be corrected back to base conditions
– usually 60 - 700F and 1 atmosphere (14.73 psia) pressure
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Automation Business
The Object of Flow Measurement
How much went from one place to another?
 Volumetric
• corrected to base pressure and temperature
 Mass
• Mass is mass. It doesn’t change with changes in
temperature or pressure.
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Automation Business
A Variety of Flow Measurement Methods
 Orifice plate meter
•
Most common in the gas industry
•
Relatively low rangeability
•
Least accurate of all popular methods
•
High installation cost
•
No moving parts low (or no) maintenance
•
No calibration little maintenance
•
Intrusive device
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Automation Business
Orifice Plate Meter
Static Pressure
Temperature
Differential Pressure
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Automation Business
A Variety of Flow Measurement Methods
 Turbine Meter
• Most common meter type across all industries
– Second most common in the gas industry
• Much more accurate than orifice plate
• Wide flow rangeability
• Low relative cost to purchase but comparatively high cost to
maintain
• Has moving parts that can fail but is easily field repaired
– Requires calibration
• Intrusive device
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Automation Business
Turbine meters
 Use a vaned rotor engaged by the flowing
fluid
• the fluid spins the rotor at an angular
velocity proportional to the flow rate
 As the turbine rotates, an AC voltage is
induced in a magnetic pickup
• mounted externally to the fluid process
 As each turbine blade passes the pickup the total magnetic flux density is changed
• induces a single voltage pulse
 Each pulse represents a finite volume of fluid that has been displaced through 2
adjacent rotor blades.
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Automation Business
A Variety of Flow Measurement Methods
 Positive displacement meter
• Most accurate
• Uses standard low speed digital input on PLC
 Other less common types
• Venturi meter
• Ultrasonic meter
• Vortex meter
• Lots more
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Automation Business
Flow Measurement by the Orifice Plate Method
Origins of the fluid flow “Laws”
 More than 300 years ago, Charles and Boyle discovered that
Uf1 = (P *h)1/2
 The formula looks deceptively simple
Qb =(218.573Cd(FT)EvY1d2Tb/Pb)(Pf1Zb Zb air*hw/GiZf1Tf) ½
 And it would be,
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Automation Business
Flow Measurement by the Orifice Plate Method
Origins of the fluid flow “Laws”
 More than 300 years ago, Charles and Boyle discovered that
Uf1 = (P *h)1/2
 The formula looks deceptively simple
Qb =(218.573Cd(FT)EvY1d2Tb/Pb)(Pf1Zb Zb air*hw/GiZf1Tf) ½
 And it would be, except each component of the equation,
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Automation Business
Flow Measurement by the Orifice Plate Method
Origins of the fluid flow “Laws”
 More than 300 years ago, Charles and Boyle discovered that
Uf1 = (P *h)1/2
 The formula looks deceptively simple
Qb =(218.573Cd(FT)EvY1d2Tb/Pb)(Pf1Zb Zb air*hw/GiZf1Tf) ½
 And it would be, except each component of the equation, for example the
Coefficient of discharge term, relies on solving an equation like this:
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Automation Business
Flow Measurement by the Orifice Plate Method
Origins of the fluid flow “Laws”
 More than 300 years ago, Charles and Boyle discovered that
Uf1 = (P *h)1/2
 The formula looks deceptively simple
Qb =(218.573Cd(FT)EvY1d2Tb/Pb)(Pf1Zb Zb air*hw/GiZf1Tf) ½
 And it would be, except each component of the equation, for example the
Coefficient of discharge term, relies on solving an equation like this:
Cd(FT) =Ci(FT)+.000511(106 β/Red)0.7+((0.0210+.0049(19,000β/ Red)0.8) β4(106/
Red)0.35
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Automation Business
Flow Measurement
The Names and Numbers to Know
 For measuring flow there are 3 equations that are the
most common
• For orifice plate meters, AGA 3
– 1992 version
– 1985 version
– ISO 5167 is equivalent and is very similar
– ISO is currently upgrading and will probably come into
lock step with AGA
• For turbine meters AGA 7
– AGA 7 is a relatively simple equation compared to AGA 3
Uf1 = (f/K)*M
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Automation Business
Flow Measurement
The Names and Numbers to Know(cont’d)
 For high accuracy gas measurement a compressibility and
sometimes supercompressibility equation is needed
• AGA 8 Most common
– 2 versions
– 1985
– 1992(ISO12213)
– Multiple methods
– Gross methods
– 2 for 1992 (recommended method for use between 32
to 130 oF and less than 1,200 psia, provided the gas
composition is within the normal range)
– 4 for 1985
– Detailed methods
– 1992 is the most accurate and most common
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Automation Business
Flow Measurement
The Names and Numbers to Know(cont’d)
 Other compressibility equations(in order of popularity)
• NX-19 (developed in 1962)
– Still used frequently in high C02 applications
• Compressibility equations used for special gas compositions
– Soave Redlich Kwong (SRK)
– Wichert Aziz
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Automation Business
Flow Measurement
The Names and Numbers to Know(cont’d)
 API 2540
• Used for liquid measurement with turbine or rotary displacement
meters
• Provides temperature and pressure compensation
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Automation Business
Flow Measurement
Putting it all Together
 For measuring gas with an orifice plate meter use one of these
• AGA 3 alone
• AGA 3 with AGA 8
• AGA 3 with NX-19
• AGA 3 with other
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Automation Business
Flow Measurement
Putting it all Together (Cont’d)
 For measuring gas with a turbine meter
• AGA 7 alone
• AGA7 with AGA 8
• AGA7 with NX-19
• AGA7 with other
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Automation Business
Flow Measurement
Putting it all Together (Cont’d)
 For measuring liquid with an orifice plate meter
• AGA 3 alone
 For measuring liquid with a turbine meter
• AGA 7 alone
• AGA 7 with API 2540
 For measuring liquid with a rotary displacement meter
• API 2540
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Automation Business
Flow Measurement
API 21.1 Audit Trail and Event Log
 Custody transfer applications are those where the fluid being
measured changes ownership at the meter point
 If the measurement application is not custody transfer it is
• Allocation (often requires API 21.1 for convenience)
• Control
 For custody transfer applications a detailed audit trail and event log
are required
 The Industry expects a minimum of
• 7 days of hourly averages of specified variables
• 35 days of daily averages of the same variables
• A copy of the configuration of the meter parameters
• A 100 entry time stamped log of events
– All parameter changes
– Alarms
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Automation Business
Flow Measurement
If You Don’t Know for Sure, Just Ask
 If a customer says he needs an RTU that does AGA that doesn’t
mean anything!
 Ask the customer some basic questions and consult your notes.
• What is being measured?
• What kind of meter do they have?
• How accurate does the measurement need to be?
• Is the customer doing custody transfer?
 If a customer is just doing control based on flow measurement
• AGA 3 or 7 alone are often accurate enough.
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Automation Business
What does Schneider offer?
Orifice plate meters
 Starling Associates Gas Flow Loadable Function Block Library
• To run loadables on a continuous basis you must use the proper enabler, 130
HEK 301 01 or 130 HEK 301 02
– Fits in the bus expansion port of a Compact or Micro PLC.
– Disallows the use of the AS HDTA 202 2 slot rack.
– Must be used with a IA WBXT 204 cable if an AS WBXT 201 is used.
– Loadables can be run, without an enabler, in demo mode for 48 hours
after program load.
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Automation Business
What does Schneider offer?
Orifice plate meters (continued)
 Starling Associates Gas Flow Loadable Function Block Library
• consists of 5 blocks that cover the different calculation combinations
• G392 - up to 8 meters of AGA 3 1992 alone. API 21.1 audit trail
130 HEK 301 02
• GD92 - meter of AGA 3 1992 and AGA 8 detailed method.
• GFNX - up to 8 meters of AGA3 1985 and NX-19. API 21.1 audit trail
130 HEK 301 01
• GG92 - up to 8 meters of AGA 3 1992 and AGA 8 both gross methods. API 21.1
audit trail
• GM92 - up to 8 meters of AGA 3 1992 and AGA 8 detailed method. API 21.1
audit trail
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Automation Business
What does Schneider offer?
Orifice plate meters (continued)
 Flow calculations run only on Compact and Micro 612 04 CPUs
 Except for the 612 04 you must have a minimum of 16K 984 LL capable
CPU to run GG92, GFNX or GM92
• The 612 04 is a special case which can run any of the flow loadables
and have a large amount of program space left.
 GD92 and G392 may be run in as small as a Compact 141 CPU
• Using these loadables in an 8 K controller leaves little space for other
programming.
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Automation Business
What does Schneider offer?
Turbine meters
 AS BVRC 200, AS BCTR 205 and AS BCTR 224
• High speed counter input cards, for the Compact and Modicon Micro,
that perform the AGA 7 Calculation in the module
• “K” and “M” factors are configured in the module and a corrected count
or rate is delivered to the CPU.
• BVRC 200 takes direct turbine meter sine frequency input signal
• BCTR 205 and 224 take square wave DC input signals, 5 VDC and
24VDC respectively.
 API 2540 temperature compensation and pressure compensation is
currently not supported as a solution but can be programmed by the end
user.
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Automation Business
What does Schneider offer?
Orifice plate meters (continued)
 Flow calculations run only on Compact and Micro 612 04 CPUs
 Except for the 612 04 you must have a minimum of 16K 984 LL capable
CPU to run GG92, GFNX or GM92
• The 612 04 is a special case which can run any of the flow loadables
and have a large amount of program space left.
 GD92 and G392 may be run in as small as a Compact 141 CPU
• Using these loadables in an 8 K controller leaves little space for other
programming.
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