1. Mark Murphy, PE Technical Director, Fluor Corp.
Flow Measurement
ISA = International Society of Automation
Mark Murphy, PE
Technical Director, Fluor Corp.

2. COMMONLY USED FLOW DEVICES
Differential Pressure (Head) Type
Orifice Plate - Concentric, Eccentric, Segmental, Quadrant Edge, Integral, Conditioning
Venturi Tube
Flow Nozzles
Elbow
Pitot Tube, Averaging Pitot Tube (Annubar)
Variable Area (Rotameter)
Wedge Meter
V-Cone
Mass Type – measures the mass flow rate directly.
Coriolis
Thermal
Velocity Type
Magnetic
Ultrasonic - Transit Time, Doppler
Turbine
Vortex
Open Channel Type
Weir
Parshall Flume
Other Types
Positive Displacement
Target
The following is a list of commonly used flow devices in the Oil & Gas Industry. A corporate standard in many cases provides guidance on the evaluation criteria for flowmeter selection. There are many types of flowmeters available and each has its own application and advantages & limitations, but should always follow project specifications first and be aware that information can vary for the same type of flowmeter between different manufacturers.
There the Differential Pressure (Head) Type, which is the most common flow measuring system, where flow is inferred from the differential pressure caused by the flow. This type of flow meter is based on Bernoullis Equation. Differential Pressure (Head) Type flowmeters include the following:
Orifice Plate - Concentric, Eccentric, Segmental, Quadrant Edge, Integral, Conditioning
Venturi Tube
Flow Nozzles
Elbow
Pitot Tube, Averaging Pitot Tube (Annubar)
Variable Area (Rotameter)
Wedge Meter
V-Cone
Another type of flowmeter is the Mass Type, which measures the mass flow rate directly. Mass Type flowmeters include the following:
Coriolis
Thermal
Another type of flowmeter is the Velocity Type, where flow is calculated by measuring the speed in one or more points in the flow and integrating the flow speed over the flow area. Velocity Type flowmeters include the following:
Magnetic
Ultrasonic - Transit Time, Doppler
Turbine
Vortex
Other Types of flowmeters commonly used in the oil and gas industry include:
Positive Displacement
Target
Another type of flowmeter is the Open Channel Type, where the common method of measuring flow through an open channel is to measure the height of the liquid as it passes over an obstruction (flume or weir) in the channel. Open Channel Type flowmeters include the following:
Weir
Parshall Flume

3. FLOW MEASUREMENT - TERMS
DENSITY (r)
A Measure Of Mass Per Unit Of Volume (lb/ft3 or kg/M3).
SPECIFIC GRAVITY
The Ratio Of The Density Of A Material To The Density Of Water Or Air Depending On Whether It Is A Liquid Or A Gas.
COMPRESSIBLE FLUID
Fluids (Such As Gasses) Where The Volume Changes With Respect To Changes In The Pressure. These Fluids Experience Large Changes In Density Due To Changes In Pressure.
NON-COMPRESSIBLE FLUID
Fluids (Generally Liquids) Which Resist Changes In Volume As The Pressure Changes. These Fluids Experience Little Change In Density Due To Pressure Changes.

4. FLOW MEASUREMENT - TERMS
Linear
Transmitter output is directly proportional to the flow input.
Square Root
Flow is proportional to the square root of the measured value.
Beta Ratio (d/D)
Ratio of a differential pressure flow device bore (d) divided by internal diameter of pipe (D).
A higher Beta ratio means a larger orifice size. A larger orifice plate bore size means greater flow capacity and a lower permanent pressure loss.
Pressure Head
The Pressure At A Given Point In A Liquid Measured In Terms Of The Vertical Height Of A Column Of The Liquid Needed To Produce The Same Pressure.
The following terminology is normally used in flow measurement, including:
Rangeability (Turndown), the ratio of maximum flow to minimum flow, but not zero flow.
Repeatability, the ability of a flow meter to indicate the same readings each time the same flow conditions exist. These readings may or may not be accurate, but will repeat. This capability is important when a flow meter is used for flow control.
Linear, where the transmitter output is directly proportional to the flow input.
Square Root, where flow is proportional to the square root of the sensed differential pressure (head).
Beta Ratio (d/D), which is the ratio of orifice plate or other differential pressure flow device bore (d) divided by internal diameter of pipe (D). A higher Beta ratio means a larger orifice plate bore size. A larger orifice plate bore size means greater flow capacity and a lower permanent pressure loss.

5. FLOW MEASUREMENT - UNITS
Flow is measured as a quantity (either volume or mass) per unit time
Volumetric units
Liquid
gpm, bbl/day, m3/hr, liters/min, etc.
Gas or Vapor
ft3/hr, m3/hr, etc.
Mass units (either liquid, gas or vapor)
lb/hr, kg/hr, etc.
Flow can be measured in accumulated (totalized) total amounts for a time period
gallons, liters, meters passed in a day, etc.
Flow can be measured as a rate per unit time.
For Liquids, the common units used are: gpm, m3/hr, liters/min, etc.
For Gas, the common units used are: ft3/hr, etc.
Flow can be measured as a mass per unit time.
Common units used are: lb/hr, kg/hr, etc.
Flow can be measured in accumulated (totalized) total amounts for a time period.
Common units used are: gallons, liters, meters passed in a day, etc.

6. LAMINAR FLOW
Laminar Flow - Is Characterized By Concentric Layers Of Fluid Moving In Parallel Down The Length Of A Pipe. The Highest Velocity (Vmax) Is Found In The Center Of The Pipe. The Lowest Velocity (V=0) Is Found Along The Pipe Wall.
Laminar Flow - Is Characterized By Concentric Layers Of Fluid Moving In Parallel Down The Length Of A Pipe. The Highest Velocity (Vmax) Is Found In The Center Of The Pipe. The Lowest Velocity (V=0) Is Found Along The Pipe Wall.

7. TURBULENT FLOW
Turbulent Flow - Is Characterized By A Fluid Motion That Has Local Velocities And Pressures That Fluctuate Randomly. This Causes The Velocity Of The Fluid In The Pipe To Be More Uniform Across A Cross Section.
Turbulent Flow - Is Characterized By A Fluid Motion That Has Local Velocities And Pressures That Fluctuate Randomly. This Causes The Velocity Of The Fluid In The Pipe To Be More Uniform Across A Cross Section.

8. REYNOLDS NUMBER
The Reynolds number is the ratio of inertial forces (velocity and density that keep the fluid in motion) to viscous forces (frictional forces that slow the fluid down) and is used for determining the dynamic properties of the fluid to allow an equal comparison between different fluids and flows.
Laminar Flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion
Turbulent Flow occurs at high Reynolds numbers and is dominated by inertial forces, producing random eddies, vortices and other flow fluctuations.
The Reynolds number is the most important value used in fluid dymanics as it provides a criterion for determining similarity between different fluids, flowrates and piping configurations.
The Reynolds number is the ratio of inertial forces (velocity and density that keep the fluid in motion) to viscous forces (frictional forces that slow the fluid down) and is used for determining the dynamic properties of the fluid to allow an equal comparison between different fluids and flows.
Laminar Flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion
Turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, producing random eddies, vortices and other flow fluctuations.
The Reynolds number is the most important dimensionless number in fluid dynamics and provides a criterion for determining similarity between different fluids, flowrates and piping configurations.

9. REYNOLDS NUMBER
This is the equation for determining the Reynolds number. You can get the required values from process.

10. IDEAL GAS LAW
An Ideal Gas or perfect gas is a hypothetical gas consisting of identical particles with no intermolecular forces. Additionally, the constituent atoms or molecules undergo perfectly elastic collisions with the walls of the container. Real gases act like ideal gases at low pressures and high temperatures.
Real Gases do not exhibit these exact properties, although the approximation is often good enough to describe real gases. The properties of real gases are influenced by compressibility and other thermodynamic effects.
An ideal gas or perfect gas is a hypothetical gas consisting of identical particles with no intermolecular forces. Additionally, the constituent atoms or molecules undergo perfectly elastic collisions with the walls of the container. Real gases act like ideal gases at low pressures and high temperatures.
Real gases do not exhibit these exact properties, although the approximation is often good enough to describe real gases. The properties of real gases are influenced by compressibility and other thermodynamic effects.

11. PV = nRT IDEAL GAS LAW Where: P = Pressure (psia) V = Volume (FT3)
n = Number of Moles of Gas
(1 mole = 6.02 x 1023 molecules)
R = Gas Constant (10.73 FT3 PSIA / lb-mole oR)
T = Temperature (oR)
This is the equation for an Ideal Gas

12. REAL GASES
Compressibility Factor (Z) - The term "compressibility" is used to describe the deviance in the thermodynamic properties of a real gas from those expected from an ideal gas.
Real Gas Behavior can be calculated as:
PV = nZRT
Compressibility Factor (Z) - The term "compressibility" is used to describe the deviance in the thermodynamic properties of a real gas from those expected from an ideal gas.
This is the equation for an Ideal Gas

13. STANDARD CONDITIONS P = 14.7 PSIA T = 520 deg R (60 deg F)
Behavior of gases in a process can be equally compared by using standard conditions – This is due to the nature of gases.
Standard conditions allow gases and vapors of different compositions to be compared equally.

14. ACTUAL CONDITIONS
Standard conditions can be converted to Actual Conditions using the Ideal Gas Law.
This is the method to convert from standard conditions to actual conditions

15. BERNOULLI’S LAW
Bernoulli's Law Describes The Behavior Of An Ideal Fluid Under Varying Conditions In A Closed System. It States That The Overall Energy Of The Fluid As It Enters The System Is Equal To The Overall Energy As It Leaves.
PE1 + KE1 = PE2 + KE2
PE = Potential Energy
KE = Kinetic Energy
Bernoulli's Law Describes The Behavior Of An Ideal Fluid Under Varying Conditions In A Closed System. It States That The Overall Energy Of The Fluid As It Enters The System Is Equal To The Overall Energy As It Leaves.

16. BERNOULLI’S EQUATION
Bernoulli’s Law Is Described By The Following Equation For An Ideal Fluid.
Bernoulli’s law explains the movement of fluid through an orifice or nozzle. It shows that the total energy upstream of the nozzle is equal to the energy at the nozzle throat. It explains how the potential energy is converted to kinetic energy as the fluid speeds up and the pressure drops at the nozzle throat.

17. HEAD METER THEORY OF OPERATION
This diagram shows how fluids flow through an orifice. The Beta ratio is the ratio of the orifice size to the inside diameter of the pipe. These type of meters require a straight section of pipe both upstream and downstream. This is called the meter run. The length of this is dependent on the piping layout. For most piping systems it is 20 pipe diameters upstream and 5 downstream for an orifice plate. This must be checked for every meter against the P, I, P standard.
Note that increasing the beta ratio provides increased accuracy, but also requires increased straight run.
Beta Ratio b = d/D Should Be 0.3 – 0.75
Meter Run – Dependent On Piping
Normally 20 Diameters Upstream & 5 Diameters Downstream

18. r1 = Density b = d / D dP METER – FLOW PRINCIPLES e = Expansion Factor
Flow is measured by creating a pressure drop and applying the flow equation below.
Basic Flow Equation for single phase compressible and non-compressible fluids:
qm = Flow
C = Constant
e = Expansion Factor
a = Orifice Area
Dp = P1 - P2
r1 = Density
b = d / D
d = Diameter of Orifice
D = Diameter of Pipe
Orifice Plate Flow Principles. The most often used flow sensor is the orifice plate shown to the right. Flow is measured by creating a pressure drop and applying the flow equation below. The basic flow equation for single phase compressible and non-compressible fluids is shown below.

19. METER RANGEABILITY METER RANGEABILITY NORMAL RANGE
The square root function’s impact on a differential pressure device limits the measurement turndown (rangeability) to between 4:1 and 6:1.
METER RANGEABILITY
% MAXIMUM METER HEAD
The square root functions impact on a differential pressure device limits the measurement turndown (rangeability).
NORMAL RANGE
% MAXIMUM FLOW RATE

20. ORIFICE PLATE Orifice Plate Orifice Flanges
A simple device, considered a precision instrument. It is simply a piece of flat metal with a flow-restricting bore that is inserted into the pipe between flanges. The orifice meter is well understood, rugged and inexpensive. It’s accuracy under ideal conditions is in the range of %. It can be sensitive to a variety of error-inducing conditions, such as if the plate is eroded or damaged.
The Orifice Plate is a simple device, considered to be a precision instrument. It is simply a piece of flat metal with a flow-restricting bore that is inserted into the pipe between flanges. The orifice meter is well understood, rugged and inexpensive. It’s accuracy under ideal conditions is in the range of 0.75 to 1.5 percent. It can be sensitive to a variety of error-inducing conditions, such as if the plate is eroded or damaged.
Orifice Plate
Orifice Flanges

21. CONCENTRIC ORIFICE PLATE
The most common orifice plate is the square-edged concentric bored orifice plate. The concentric bored orifice plate is the dominant design because of its proven reliability in a variety of applications and the extensive amount of research conducted on this design. It is easily reproduced at a relatively low cost. It is used to measure a wide variety of single phase, liquid and gas products, typically in conjunction with flange taps.
The most common orifice plate is the square-edged concentric bored orifice plate. The concentric bored orifice plate is the dominant design because of its proven reliability in a variety of applications and the extensive amount of research conducted on this design. It is easily reproduced at a relatively low cost. It is used to measure a wide variety of single phase, liquid and gas products, typically in conjunction with flange taps.

22. ECCENTRIC ORIFICE PLATE
Eccentrically bored plates are plates with the orifice off center, or eccentric, as opposed to concentric. This type of plate is most commonly used to measure fluids which carry a small amount of non-abrasive solids, or gases with small amounts of liquid, since with the opening at the bottom of the pipe, the solids and liquids will carry through, rather than collect at the orifice plate. A higher degree of uncertainty as compared to the concentric orifice. Eccentric orifice plates are used in many industries including heavy and light chemicals and petrochemicals.
Eccentrically bored plates are plates with the orifice off center, or eccentric, as opposed to concentric. This type of plate is most commonly used to measure fluids which carry a small amount of non-abrasive solids, or gases with small amounts of liquid, since with the opening at the bottom of the pipe, the solids and liquids will carry through, rather than collect at the orifice plate. A higher degree of uncertainty as compared to the concentric orifice. Eccentric orifice plates are used in many industries including heavy and light chemicals and petrochemicals.

23. QUADRANT EDGE ORIFICE PLATE
The quadrant, quadrant edge or quarter-circle orifice is recommended for measurement of fluids with high viscosity which have pipe Reynolds Numbers below 10,000. The orifice incorporates a rounded edge of definite radius which is a particular function of the orifice diameter.
Quadrant in U.S.
Conical in Europe
The quadrant, quadrant edge or quarter-circle orifice is recommended for measurement of fluids with high viscosity which have pipe Reynolds Numbers below 10,000. The orifice incorporates a rounded edge of definite radius which is a particular function of the orifice diameter.
Quadrant in U.S.
Conical in Europe

24. INTEGRAL ORIFICE PLATE
identical to a square-edged orifice plate installation except that the plate, flanges and DP transmitter are supplied as one unit.
used for small lines (typically under 2”) and is relatively inexpensive to install since it is part of the transmitter
Integral Orifice Plate is identical to a square-edged orifice plate installation except that the plate, flanges and DP transmitter are supplied as one unit. They are used for small lines (typically under 2” or 50mm) and is relatively inexpensive to install since it is part of the transmitter.

25. CONDITIONING ORIFICE PLATE
The Conditioning Orifice Plate is designed to be installed downstream of a variety of disturbances with minimal straight pipe run, providing superior performance.
Requires only two diameters of straight pipe run after an upstream flow disturbance
Reduced installation costs
Easy to use, prove, and troubleshoot
Good for most gas, liquid, and steam as well as high temperature and high pressure applications
Most conditioning orifice plates have the following characteristics:
Recommended Service: Liquids, Gases & Steam
Rangeability: 4 to 1
Pressure Loss: Medium
Accuracy: 0.5%
Straight Run Required: 2D Upstream, 2D Downstream
Viscosity Effect: High
Relative Cost: Low
Size: 2” to 24”
Connection: Between Flanges
Type of Output: Square Root

26. VENT AND WEEP HOLES
There are times when a gas may be have a small amount of liquid or a liquid may have a small amount of gas but not enough in either case to warrant the use of an eccentric orifice. In these cases it is best to simply add a small hole near the edge of the plate, flush with the inside diameter of the pipe, allowing undesired substances to pass through the plate rather than collect on the upstream side. If such a hole is oriented upward to pass vapor bubbles, it is called a vent hole. If the hole is oriented downward to pass liquid droplets, it is called a drain hole.
There are times when a gas may be have a small amount of liquid or a liquid may have a small amount of gas but not enough in either case to warrant the use of an eccentric orifice. In these cases it is best to simply add a small hole near the edge of the plate, flush with the inside diameter of the pipe, allowing undesired substances to pass through the plate rather than collect on the upstream side. If such a hole is oriented upward to pass vapor bubbles, it is called a vent hole. If the hole is oriented downward to pass liquid droplets, it is called a drain hole.

27. ORIFICE PLATE SELECTION CONSIDERATIONS
Quadrant Edge Orifice Plate can be considered if Reynolds number is too low.
Orifice plate must be specified with proper flange rating to account for proper bolt circle.
Typical acceptable beta ratio is .25 to .7 for non commerce meter, .3 to .6 for accounting meter but also check specifications.
Assure that calculation accounts for vent or drain hole, if required.
For dual transmitter installation on a common set of orifice flanges, custom tap locations must be specified.
Quadrant Edge Orifice Plate can be considered if Reynolds number is too low.
Orifice plate must be specified with proper flange rating to account for proper bolt circle.
Typical acceptable beta ratio is .25 to .7 for non commerce meter, .3 to .6 for accounting meter but also check specifications.
Assure that calculation accounts for vent or drain hole, if required.
For dual transmitter installation on a common set of orifice flanges, custom tap locations must be specified.

28. ORIFICE PLATE TAP LOCATIONS
Differential pressure is measured through pressure taps located on each side of the orifice plate. Pressure taps can be positioned at a variety of different locations.
Flange Taps
Corner Taps
Radius Taps
Vena-Contracta Taps
Pipe Taps
Orifice taps in horizontal lines should be as follows:
Differential pressure is measured through pressure taps located on each side of the orifice plate. Pressure taps can be positioned at a variety of different locations. The most common are flange taps. They are located 1 inch from the upstream face of orifice plate and 1 inch from downstream face. They are used for all standard orifice onfigurations.
Corner Taps are used for honed meter runs like an integral orifice. They are located immediately adjacent to plate faces both upstream and downstream.
Radius Taps are located 1 pipe diameter upstream of orifice plate and one half pipe diameter downstream of orifice plate. They are not commonly used.
Vena-Contracta Taps are located 1 pipe diameter upstream of orifice plate and at the point of minimum pressure downstream, this point is called the vena-contracta. This point varies with Beta ratio and are seldom used other than for plant measurement where the flows are relatively constant and plates are not changed. Exact dimensions for the downstream tap are given in appropriate tables.
Pipe Taps are located two and one half pipe diameters upstream of orifice plate and eight pipe diameters downstream of orifice plate this puts the downstream tap at the point of maximum pressure recovery.
Orifice taps in horizontal lines for gas service should be from the top of the pipe or no more than 45 degrees from vertical as shown.
Orifice taps in horizontal lines for liquid or steam should be at horizontal or 45 degrees down from horizontal as shown. For pipe racks, it is recommended that horizontal taps not be used in order to maximize pipe rack space.
Liquid or Steam
Gas

29. VENTURI TUBE
In a Venturi tube, the fluid is accelerated through a converging cone, inducing a local pressure drop. An expanding section of the meter then returns the flow to near its original pressure. These instruments are often selected where it is important not to create a significant pressure drop and where good accuracy is required.
Used when higher velocity and pressure recovery is required.
May be used when a small, constant percentage of solids is present.
In a Venturi tube, the fluid is accelerated through a converging cone, inducing a local pressure drop. An expanding section of the meter then returns the flow to near its original pressure. These instruments are often selected where it is important not to create a significant pressure drop and where good accuracy is required.
Used when higher velocity and pressure recovery is required.
May be used when a small, constant percentage of solids is present.

30. FLOW NOZZLE DP Type Flowmeter
Used when higher velocity & pressure recovery are required
Better suited for gas service than for liquid
Another DP Type Flowmeter is the Flow Nozzle. It is used when higher velocity & pressure recovery are required and are better suited for gas service than for liquid.

31. WEDGE METER
Wedge flow meters can be used on just about any liquid or gas, just like orifice plates. However they are generally chosen for dirty service applications, or high viscosity applications such as slurry or heavy oil, or where solids are present. For regular service applications consider other types of meters first unless wedge meters are specified by customer as preferred.
Since they are a differential pressure device their sizing calculation is similar to that of other dP flowmeters. P1 Q H D LP HP
Seal fluid
Transmitter
Seal pots P2
Wedge flow meters can be used on just about any liquid or gas, just like orifice plates. However they are generally chosen for dirty service, or high viscosity applications such as slurry or heavy oil, or where solids are present. For regular service applications consider other types of meters first unless wedge meters are specified by customer as preferred.
Since they are a differential pressure device their sizing calculation is similar to that of other d, P flowmeters.

32. V-CONE
The V-Cone is similar to other differential pressure (Dp) meters in the equations of flow that it uses. V-Cone geometry, however, is quite different from traditional Dp meters. The V-Cone constricts the flow by positioning a cone in the center of the pipe. This forces the flow in the center of the pipe to flow around the cone. V-cones can be used with viscous fluids and require little straight run.
V-Cone is another differential pressure type flowmeter.
The V-Cone is similar to other differential pressure (Dp) meters in the equations of flow that it uses. V-Cone geometry, however, is quite different from traditional Dp meters. The V-Cone constricts the flow by positioning a cone in the center of the pipe. This forces the flow in the center of the pipe to flow around the cone.

33. Multivariable Pressure Transmitter
A Multivariable pressure transmitter provides gauge pressure, differential pressure, and temperature measurement in a single instrument.
Uses Smart digital HART communications for multiple measurements.
Minimizes the number of transmitters and process connections
Basic information of a multivariable transmitter.

34. PITOT TUBE
In a pitot tube (insertion DP meter), a probe consisting of two parts senses two pressures: impact (dynamic) and static. The impact pressure is sensed by one impact tube bent toward the flow (dynamic head). The averaging-type pitot tube has four or more pressure taps located at mathematically defined locations, averaging the velocity profile across the pipe or flow area, to measure the dynamic pressure. The static pressure is sensed through a small hole on the side (static head). They develop low differential pressure and like all head meters they use a differential pressure transmitter to convert the flow to an electrical transmission signal.
In a pitot tube (insertion DP meter), a probe consisting of two parts senses two pressures: impact (dynamic) and static. The impact pressure is sensed by one impact tube bent toward the flow (dynamic head). The averaging-type pitot tube has four or more pressure taps located at mathematically defined locations, averaging the velocity profile across the pipe or flow area, to measure the dynamic pressure. The static pressure is sensed through a small hole on the side (static head). They develop low differential pressure and like all head meters they use a differential pressure transmitter to convert the flow to an electrical transmission signal.

35. PITOT TUBE FLOW PRINCIPLES
Pitot tubes make use of dynamic pressure difference. Orifices in the leading face register total head pressure, dynamic + static, while the hole in the trailing face only conveys static pressure. Pressure difference between the two gives dynamic pressure in pipe, from which flow can be calculated.
Basic Mass rate of flow equation for single phase compressible and non-compressible fluids:
Pitot tubes make use of dynamic pressure difference. Orifices in the leading face register total head pressure, dynamic + static, while the hole in the trailing face only conveys static pressure. Pressure difference between the two gives dynamic pressure in pipe, from which flow can be calculated.
Basic Mass rate of flow equation for single phase compressible and non-compressible fluids is shown below.

36. PIP PCCFL001 STRAIGHT RUN REQUIREMENTS
PIP PCCFL001 includes tables for minimum straight run lengths with various upstream disturbances, providing upstream requirements for different beta ratios and downstream requirements per beta ratios regardless of upstream disturbance type.
PIP PCCFL001 includes tables for minimum straight run lengths with various upstream disturbances, providing upstream requirements for different beta ratios and downstream requirements per beta ratios regardless of upstream disturbance type.

37. DP METER CHARACTERISTICS
Recommended Service: Clean & Dirty Liquids, Gases, Some Slurries
Rangeability: 3:1 to 6:1
Maximum Flow: 95% of Range
Pressure Loss: 20 to 60% of Measured Head
Accuracy: 0.5 to 4%
Straight Run Req’d: D Upstream, 2-5D Downstream
Viscosity Effect: High
Size: 2” to 24”
Connection: Dependent on meter type
Type of Output: Square Root
Here are some characteristics of the concentric orifice plate. The unrecovered pressure lost across an orifice plate sized for 100 inches of water is usually in the range of 40 to 60 inches. The amount of upstream straight run required will depend on the piping configuration. The accuracy of an orifice plate depends on a number of factors including piping system design and installation.

38. VARIABLE AREA FLOWMETER (ROTAMETER) FLOW PRINCIPLES
Rotameters are a variable area device. The float moves up and down in proportion to the fluid flow rate and the annular area between the float and the tube wall. As the float rises, the size of the annular opening increases. As this area increases, the differential pressure across the float decreases. The float reaches a stable position when the upward force exerted by the flowing fluid equals the weight of the float. Every float position corresponds to a particular flow rate for a particular fluid's density and viscosity. For this reason, it is necessary to size the rotameter for each application. When sized correctly, the flow rate can be determined by matching the float position to a calibrated scale on the outside of the rotameter. Many rotameters come with a built-in valve for adjusting flow manually.
Rotameters are a variable area flow device. The float moves up and down in proportion to the fluid flow rate and the annular area between the float and the tube wall. As the float rises, the size of the annular opening increases. As this area increases, the differential pressure across the float decreases. The float reaches a stable position when the upward force exerted by the flowing fluid equals the weight of the float. Every float position corresponds to a particular flow rate for a particular fluid's density and viscosity. For this reason, it is necessary to size the rotameter for each application. When sized correctly, the flow rate can be determined by matching the float position to a calibrated scale on the outside of the rotameter. Many rotameters come with a built-in valve for adjusting flow manually.

39. VARIABLE AREA (ROTAMETER) CHARACTERISTICS
Recommended Service: Clean, Dirty & Viscous Liquids
Rangeability: 10 to 1
Pressure Loss: Medium
Accuracy: 1 to 10%
Straight Run Required: None
Viscosity Effect: Medium
Relative Cost: Low
Sizes: <= 4”
Connections: Threaded or Flanged
Type of Output: Linear
Most variable area flowmeters (rotameters) have the following characteristics:
Recommended Service: Clean, Dirty & Viscous Liquids
Rangeability: 10 to 1
Pressure Loss: Medium
Accuracy: 1 to 10%
Straight Run Required: None
Viscosity Effect: Medium
Relative Cost: Low
Sizes: <= 4”
Connections: Threaded or Flanged
Type of Output: Linear

40. CORIOLIS
Direct mass flow measurement is generally chosen for more critical control applications such as the blending of feedstocks or the custody transfer of valuable fluids. Generally chosen for high rangeability and mass flow applications, Coriolis technology is unaffected by changes in temperature, density, viscosity and conductivity. In most flow meters changes in these conditions require monitoring and correction.
Direct mass flow measurement is generally chosen for more critical control applications such as the blending of feedstocks or the custody transfer of valuable fluids. Generally chosen for high rangeability and mass flow applications, Coriolis technology is unaffected by changes in temperature, density, viscosity and conductivity. In most flow meters changes in these conditions require monitoring and correction.

41. CORIOLIS FLOW PRINCIPLES
When the fluid is flowing, it is led through two parallel tubes. An actuator (not shown) induces a vibration of the tubes. The two parallel tubes are counter-vibrating, to make the measuring device less sensitive to outside vibrations. The actual frequency of the vibration depends on the size of the mass flow meter, and ranges from 80 to 1000 vibrations per second.
When no fluid is flowing, the vibration of the two tubes is symmetrical.
Flow is measured by using velocity sensors to detect the twist in the tube and transmit electrical signals having a relative phase shift that is proportional to mass flow.
Coriolis meters also measure density, whereby the resonant frequency of the forced rotation is a function of fluid density.
Fluid is flowing in a tube as shown at a velocity “V”.
The tube is forced to rotate about axis ‘x’ with angular velocity ‘w’.
Due to the rotation of the tube and forward movement of the fluid, forces are created as shown. A Coriolis force (Fcor) is created in opposition to the rotating force F shown.
As a result the tube will twist.
Flow is measured by using velocity sensors to detect the twist in the tube and transmit electrical signals having a relative phase shift that is proportional to mass flow.
Coriolis meters also measure density, whereby the resonant frequency of the forced rotation is a function of fluid density.

42. CORIOLIS CHARACTERISTICS
Recommended Service: Clean, Dirty & Viscous Liquids, Gases, Some Slurries
Rangeability: 10 to 1
Pressure Loss: Medium to High
Accuracy: to 0.1% in liquids & to 0.35% in gas
Straight Run Required: None
Viscosity Effect: None
Relative Cost: High
Sizes: > ½”
Connections: Flanged & Clamp-on Design
Type of Output: Linear
Most coriolis flowmeters have the following characteristics:
Recommended Service: Clean, Dirty & Viscous Liquids, Gases, Some Slurries
Rangeability: 10 to 1
Pressure Loss: Medium to High
Accuracy: to 0.1% in liquids & to 0.35% in gas
Straight Run Required: None
Viscosity Effect: None
Relative Cost: High
Sizes: > ½”
Connections: Flanged & Clamp-on Design
Type of Output: Linear

43. THERMAL MASS FLOWMETER FLOW PRINCIPLES
Thermal mass flow meters introduce heat into the flow stream and measure how much heat dissipates using one or more temperature sensors. This method works best with gas mass flow measurement.
The constant temperature differential method have a heated sensor and another sensor that measures the temperature of the gas. Mass flow rate is computed based on the amount of electrical power required to maintain a constant difference in temperature between the two temperature sensors.
In the constant current method the power to the heated sensor is kept constant. Mass flow is measured as a function of the difference between the temperature of the heated sensor and the temperature of the flow stream.
Both methods are based on the principle that higher velocity flows result in a greater cooling effect. Both measure mass flow based on the measured effects of cooling in the flow stream.
Thermal mass flow meters introduce heat into the flow stream and measure how much heat dissipates using one or more temperature sensors. This method works best with gas mass flow measurement.
The constant temperature differential method have a heated sensor and another sensor that measures the temperature of the gas. Mass flow rate is computed based on the amount of electrical power required to maintain a constant difference in temperature between the two temperature sensors.
In the constant current method the power to the heated sensor is kept constant. Mass flow is measured as a function of the difference between the temperature of the heated sensor and the temperature of the flow stream.
Both methods are based on the principle that higher velocity flows result in a greater cooling effect. Both measure mass flow based on the measured effects of cooling in the flow stream.

44. THERMAL MASS FLOWMETER CHARACTERISTICS
Recommended Service: Clean, Dirty & Viscous Liquids, Some Slurries, Gases
Rangeability: 10 to 1
Pressure Loss: Low
Accuracy: 1%
Straight Run Required: None
Viscosity Effect: None
Relative Cost: High
Sizes: 2” to 24”
Connections: Threaded, Flanged
Type of Output: Exponential
Most thermal mass flowmeters have the following characteristics:
Recommended Service: Clean, Dirty & Viscous Liquids, Some Slurries, Gases
Rangeability: 10 to 1
Pressure Loss: Low
Accuracy: 1%
Straight Run Required: None
Viscosity Effect: None
Relative Cost: High
Sizes: 2” to 24”
Connections: Threaded, Flanged
Type of Output: Exponential

45. MAGNETIC FLOWMETER FLOW PRINCIPLES
A magnetic flow meter (mag flowmeter) is a volumetric flow meter which does not have any moving parts and is ideal for wastewater applications or any dirty liquid which is conductive or water based. Magnetic flowmeters will generally not work with hydrocarbons, distilled water and many non-aqueous solutions). Magnetic flowmeters are also ideal for applications where low pressure drop and low maintenance are required. The operation of a magnetic flowmeter or mag meter is based upon Faraday's Law, which states that the voltage induced across any conductor as it moves at right angles through a magnetic field is proportional to the velocity of that conductor.
A magnetic flow meter or mag meter is a volumetric flow meter which does not have any moving parts and is ideal for any conductive fluid. Typical applications include wastewater, slurries or any dirty liquid which is conductive or water based. Magnetic flowmeters will generally not work with hydrocarbons, distilled water and many non-aqueous solutions. Magnetic flowmeters are also ideal for applications where low pressure drop and low maintenance are required. The operation of a mag meter is based upon Faraday's Law, which states that the voltage induced across any conductor as it moves at right angles through a magnetic field is proportional to the velocity of that conductor. When the fluid moves faster, more voltage is generated. Faraday’s Law states that the voltage generated is proportional to the movement of the flowing liquid. The electronic transmitter processes the voltage signal to determine liquid flow. In contrast with many other flowmeter technologies, magnetic flowmeter technology produces signals that are linear with flow. As such, the turndown associated with magnetic flowmeters can approach 40 to 1 without sacrificing accuracy.

46. MAGNETIC FLOWMETER CHARACTERISTICS
Recommended Service: Clean, Dirty & Viscous Conductive Liquids & Slurries
Rangeability: 40 to 1
Pressure Loss: None
Accuracy: 0.5%
Straight Run Required: 5D Upstream, 2D Downstream
Viscosity Effect: None
Relative Cost: High
Sizes: 1” to 120”
Connections: Flanged
Type of Output: Linear
Most magnetic flowmeters have the following characteristics:
Recommended Service: Clean, Dirty & Viscous Conductive Liquids & Slurries
Rangeability: 40 to 1
Pressure Loss: None
Accuracy: 0.5%
Straight Run Required: 5D Upstream, 2D Downstream
Viscosity Effect: None
Relative Cost: High
Sizes: 1” to 120”
Connections: Flanged
Type of Output: Linear

47. ULTRASONIC METER
Transit time ultrasonic meters employ two transducers located upstream and downstream of each other. Each transmits a sound wave to the other, and the time difference between the receipt of the two signals indicates the fluid velocity. Transit time meters usually require clean fluids and are used where high rangeability is required. Accuracy is within 1% for ideal applications.
Transit time ultrasonic meters employ two transducers located upstream and downstream of each other. Each transmits a sound wave to the other, and the time difference between the receipt of the two signals indicates the fluid velocity. Transit time meters usually require clean fluids and are used where high rangeability is required. Accuracy is within 1% for ideal applications.

48. ULTRASONIC METER FLOW PRINCIPLESB
Transmitter/
Receiver (T/R)
Flow is measured by measuring the difference in transit time for two ultrasonic beams transmitted in a fluid both upstream and downstream.
Ultrasonic Meters are mainly used on large size lines where high rangeability is required.
t dn
FLOW
t up
Frequency pulse A
Transit length L
Transit time difference is proportional to mean velocity Vm, therefore Vm can be calculated as follows:
Vm = (L / 2 * cos ) * [(TAB – TBA) / (TAB . TBA)]
Basic Flow Equation: Q = A * V
Flow is measured by measuring the difference in transit time for two ultrasonic beams transmitted in a fluid both upstream and downstream.
Ultrasonic Meters are mainly used on large size lines where high rangeability is required.
Transit time difference is proportional to mean velocity Vm. Therefore Vm can be calculated as follows:
The Basic Flow Equation is shown below.

49. ULTRASONIC (DOPPLER) FLOW PRINCIPLES
Ultrasonic flowmeters are ideal for wastewater applications or any dirty liquid which is conductive or water based.
The basic principle of operation employs the frequency shift (Doppler Effect) of an ultrasonic signal when it is reflected by suspended particles or gas bubbles (discontinuities) in motion. Current technology requires that the liquid contain at least 100 parts per million (PPM) of 100 micron or larger suspended particles or bubbles.
The basic principle of operation employs the frequency shift (Doppler Effect) of an ultrasonic signal when it is reflected by suspended particles or gas bubbles (discontinuities) in motion. This metering technique utilizes the physical phenomenon of a sound wave that changes frequency when it is reflected by moving discontinuities in a flowing liquid. Ultrasonic sound is transmitted into a pipe with flowing liquids, and the discontinuities reflect the ultrasonic wave with a slightly different frequency that is directly proportional to the rate of flow of the liquid (Figure 1). Current technology requires that the liquid contain at least 100 parts per million (PPM) of 100 micron or larger suspended particles or bubbles.

50. ULTRASONIC CHARACTERISTICS
Recommended Service: Clean & Viscous Liquids, Natural/Flare Gas
Rangeability: 20 to 1
Pressure Loss: None
Accuracy: 0.25% to 5%
Straight Run Required: 5 to 30D Upstream
Viscosity Effect: None
Relative Cost: High
Sizes: > ½”
Connections: Flanged & Clamp-on Design
Type of Output: Linear
Most ultrasonic (Transit Time) flowmeters have the following characteristics:
Recommended Service: Clean & Viscous Liquids, Natural/Flare Gas
Rangeability: 20 to 1
Pressure Loss: None
Accuracy: 1 to 5%
Straight Run Required: 5 to 30D Upstream
Viscosity Effect: None
Relative Cost: High
Sizes: > ½”
Connections: Flanged & Clamp-on Design
Type of Output: Linear

51. TURBINE METER
Turbine meter is kept in rotation by the linear velocity of the stream in which it is immersed. The number of revolutions the device makes is proportional to the rate of flow.
Turbine meter is kept in rotation by the linear velocity of the stream in which it is immersed. The number of revolutions the device makes is proportional to the rate of flow.

52. TURBINE METER CHARACTERISTICS
Recommended Service: Clean & Viscous Liquids, Clean Gases
Rangeability: 20 to 1
Pressure Loss: High
Accuracy: 0.25%
Straight Run Required: 5 to 10D Upstream
Viscosity Effect: High
Relative Cost: High
Sizes: > ¼”
Connections: Flanged
Type of Output: Linear
Most turbine meters have the following characteristics:
Recommended Service: Clean & Viscous Liquids, Clean Gases
Rangeability: 20 to 1
Pressure Loss: High
Accuracy: 0.25%
Straight Run Required: 5 to 10D Upstream
Viscosity Effect: High
Relative Cost: High
Sizes: > ¼”
Connections: Flanged
Type of Output: Linear

53. VORTEX METER
Vortex meters can be used on most clean liquid, vapor or gas. However, they are generally chosen for applications where high flow rangeability is required. Due to break down of vortices at low flow rates, vortex meters will cut off at a low flow limit. Reverse flow measurement is not an option. For regular service applications this meter is the meter of choice by many end users.
Vortex meters can be used on most clean liquid, vapor or gas. However, they are generally chosen for applications where high flow rangeability is required. Due to break down of vortices at low flow rates, vortex meters will cut off at a low flow limit. Reverse flow measurement is not an option. For regular service applications this meter is the meter of choice by many end users.

54. VORTEX METER FLOW PRINCIPLES Basic Flow Equation: Q = A * V
Recovery
Recovery
The Basic Flow Equation for a Vortex Meter is shown below.
Basic Flow Equation: Q = A * V
Flowing Velocity of Fluid: V = (f * d) / St
f = Shedding Frequency
d = Diameter of Bluff Body
St = Stouhal Number (Ratio between Bluff Body Diameter and Vortex Interval)
A = Area of Pipe

55. VORTEX CHARACTERISTICS
Recommended Service: Clean & Dirty Liquids, Gases
Rangeability: 10 to 1
Pressure Loss: Medium
Accuracy: 1%
Straight Run Required: 10 to 20D Upstream, 5D Downstream
Viscosity Effect: Medium
Relative Cost: Medium
Size: ½” to 12”
Connection: Flanged
Type of Output: Linear
Most vortex flowmeters have the following characteristics:
Recommended Service: Clean & Dirty Liquids, Gases
Rangeability: 10 to 1
Pressure Loss: Medium
Accuracy: 1%
Straight Run Required: 10 to 20D Upstream, 5D Downstream
Viscosity Effect: Medium
Relative Cost: Medium
Size: ½” to 12”
Connection: Flanged
Type of Output: Linear

56. POSITIVE DISPLACEMENT (PD) FLOWMETER
PD meters measure flow rate directly by dividing a stream into distinct segments of known volume, counting segments, and multiplying by the volume of each segment. Measured over a specific period, the result is a value expressed in units of volume per unit of time. PD meters frequently report total flow directly on a counter, but they can also generate output pulses with each pulse representing a discrete volume of fluid.
PD meters measure flow rate directly by dividing a stream into distinct segments of known volume, counting segments, and multiplying by the volume of each segment. Measured over a specific period, the result is a value expressed in units of volume per unit of time. PD meters frequently report total flow directly on a counter, but they can also generate output pulses with each pulse representing a discrete volume of fluid.

57. POSITIVE DISPLACEMENT (PD) FLOWMETER FLOW PRINCIPLES
PD meters have 3 parts:
Body
Measuring Unit
Counter Drive Train
Liquid enters the cavity between oval gear B and meter body wall, while an equal volume of liquid passes out of the cavity between oval gear A and meter body wall. Meanwhile, inlet pressure continues to force the two oval gears to rotate to position 3
Quantity of liquid has again filled the cavity between oval gear B and meter body. This pattern is repeated moving four times the liquid capacity of each cavity with each revolution of the rotating gears. Therefore, the flow rate is proportional to the rotational speed of the gears.
Liquids inlet pressure exerts a pressure differential against the lower face of oval gear A, causing the two interlocked oval gears to rotate to position 2.
Positive Displacement Flowmeters have 3 parts: Body, Measuring Unit and Counter Drive Train.
Position 1: Liquids inlet pressure exerts a pressure differential against the lower face of oval gear A, causing the two interlocked oval gears to rotate to position 2.
Position 2: Liquid enters the cavity between oval gear B and meter body wall, while an equal volume of liquid passes out of the cavity between oval gear A and meter body wall. Meanwhile, inlet pressure continues to force the two oval gears to rotate to position 3
Position 3: Quantity of liquid has again filled the cavity between oval gear B and meter body. This pattern is repeated moving four times the liquid capacity of each cavity with each revolution of the rotating gears. Therefore, the flow rate is proportional to the rotational speed of the gears.

58. POSITIVE DISPLACEMENT (PD) CHARACTERISTICS
Recommended Service: Clean & Viscous Liquids, Clean Gases
Rangeability: 10 to 1
Pressure Loss: High
Accuracy: 0.5%
Straight Run Required: None
Viscosity Effect: High
Relative Cost: Medium
Sizes: >12”
Connections: Flanged
Type of Output: Linear
Most positive displacement (PD) flowmeters have the following characteristics:
Recommended Service: Clean & Viscous Liquids, Clean Gases
Rangeability: 10 to 1
Pressure Loss: High
Accuracy: 0.5%
Straight Run Required: None
Viscosity Effect: High
Relative Cost: Medium
Sizes: >12”
Connections: Flanged
Type of Output: Linear

59. PRACTICES, INDUSTRY STANDARDS & OTHER REFERENCES
Process Industry Practices (PIP)
PIP PCCGN002 – General Instrument Installation Criteria
PIP PCEFL001 – Flow Measurement Guidelines
Industry Codes and Standards
American Gas Association (AGA)
AGA 9 – Measurement of Gas by Multipath Ultrasonic Meters
American National Standards Institute (ANSI)
ANSI-2530/API-14.3/AGA-3/GPA-8185 – Natural Gas Fluids Measurement – Concentric, Square-Edged Orifice Meters
Part 1 General Equations and Uncertainty Guidelines
Part 2 Specification and Installation Requirements
Part 3 Natural Gas Applications
Part 4 Background, Development, Implementation Procedures and Subroutine Documentation
American Petroleum Institute (API)
API RP 551 – Process Measurement Instrumentation
API RP 554 – Process Instrument and Control
API Manual of Petroleum Measurement Standards (MPMS):
Chapter 4 – Proving Systems
Chapter 5 – Metering
Chapter 14 – Natural Gas Fluids Measurement
The following is a list of the Practices, Industry Standards and other references that are commonly used in the oil and gas industry when selecting and specifying flow instruments. References include:
Process Industry Practices (PIP)
PIP PCCGN002 – General Instrument Installation Criteria
Industry Codes and Standards
American Gas Association (AGA)
AGA 9 – Measurement of Gas by Multipath Ultrasonic Meters
American National Standards Institute (ANSI)
ANSI-2530/API-14.3/AGA-3/GPA-8185 – Natural Gas Fluids Measurement – Concentric, Square-Edged Orifice Meters
Part 1 General Equations and Uncertainty Guidelines
Part 2 Specification and Installation Requirements
Part 3 Natural Gas Applications
Part 4 Background, Development, Implementation Procedures and Subroutine Documentation
American Petroleum Institute (API)
API RP 551 – Process Measurement Instrumentation
API RP 554 – Process Instrument and Control
API Manual of Petroleum Measurement Standards (MPMS):
Chapter 4 – Proving Systems
Chapter 5 – Metering
Chapter 14 – Natural Gas Fluids Measurement
American Society of Mechanical Engineers (ASME)
ASME B16.36 – Orifice Flanges
ASME MFC-1M – Glossary of Terms Used in the Measurement of Fluid Flow in Pipes
ASME MFC-2M – Measurement Uncertainty for Fluid Flow in the Closed Conduits
ASME MFC-3M – Measurement of Fluid Flow in Pipes Using Orifice, Nozzle and Venturi
ASME MFC-5M – Measurement of Liquid Flow in Closed Conduits Using Transit-Time Ultrasonic Flowmeters
ASME MFC-6M – Measurement of Fluid Flow in Pipes Using Vortex Flow Meters
ASME MFC-7M – Measurement of Gas Flow by Means of Critical Flow Venturi Nozzles
ASME MFC-11M – Measurement of Fluid Flow by Means of Coriolis Mass Flowmeters
ASME MFC-14M – Measurement of Fluid Flows Using Small Bore Precision Orifice Meters
ASME MFC-16M – Measurement of Fluid Flow in Closed Conduit by Means of Electromagnetic Flowmeter
The International Society for Measurement and Control (ISA)
ISA S20 – Specification Forms for Process Measurement and Control Instruments, Primary Elements and Control Valves
International Organization for Standardization (ISO)
ISO Measurement of Fluid Flow by Means of Pressure Differential Devices Inserted in Circular Cross-Section Conduits Running Full
Part 1: General principles and requirement
Part 2: Orifice Plates
Part 3: Nozzle and Venturi Tubes
Part 4: Venturi Tubes
Other References
Miller, R.W., Flow Measurement Engineering Handbook
ISA – Flow Measurement – Practical Guides for Measurement and Control, Spitzer, D.W., Editor
ASME – Fluid Meters, Their Theory and Application

60. PRACTICES, INDUSTRY STANDARDS & OTHER REFERENCES
American Society of Mechanical Engineers (ASME)
ASME B16.36 – Orifice Flanges
ASME MFC-1M – Glossary of Terms Used in the Measurement of Fluid Flow in Pipes
ASME MFC-2M – Measurement Uncertainty for Fluid Flow in the Closed Conduits
ASME MFC-3M – Measurement of Fluid Flow in Pipes Using Orifice, Nozzle and Venturi
ASME MFC-5M – Measurement of Liquid Flow in Closed Conduits Using Transit-Time Ultrasonic Flowmeters
ASME MFC-6M – Measurement of Fluid Flow in Pipes Using Vortex Flow Meters
ASME MFC-7M – Measurement of Gas Flow by Means of Critical Flow Venturi Nozzles
ASME MFC-11M – Measurement of Fluid Flow by Means of Coriolis Mass Flowmeters
ASME MFC-14M – Measurement of Fluid Flows Using Small Bore Precision Orifice Meters
ASME MFC-16M – Measurement of Fluid Flow in Closed Conduit by Means of Electromagnetic Flowmeter

61. PRACTICES, INDUSTRY STANDARDS & OTHER REFERENCES
The International Society for Measurement and Control (ISA)
ISA S20 – Specification Forms for Process Measurement and Control Instruments, Primary Elements and Control Valves
International Organization for Standardization (ISO)
ISO Measurement of Fluid Flow by Means of Pressure Differential Devices Inserted in Circular Cross-Section Conduits Running Full
Part 1: General principles and requirement
Part 2: Orifice Plates
Part 3: Nozzle and Venturi Tubes
Part 4: Venturi Tubes
Other References
Miller, R.W., Flow Measurement Engineering Handbook
ISA – Flow Measurement – Practical Guides for Measurement and Control, Spitzer, D.W., Editor
ASME – Fluid Meters, Their Theory and Application

62. Any Questions??? QUESTIONS
This completes the Control Systems Training Module CSE156.1 Flow Instruments. Are there any questions?