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Ask the Expert

This page contains questions and answers on all topics related to flow and flowmeters.

Published expert and Flow Research founder Jesse Yoder has over 20 years experience researching and writing market studies and participating in and influencing the industry with over 200 published trade articles. 

If you'd like to submit your own question, please email Dr. Yoder at jesse@flowresearch.com.


What is the difference between "traditional" and "new technology" flowmeters?


In studying flowmeter markets, we found most flowmeters fell into one of two groups: the “traditional,” that have been around and studied for 50+ years, and the “new-technology” flowmeters introduced in the second half of the 20th century. We later added an “emerging technology” category for flowmeters developed in the past 20 years.


Traditional technology flowmeters share the following characteristics:

1.     As a group, these meters were introduced before the end of World War II.

2.     They are less the focus of new product development than new-technology meters.

3.     Their performance, including criteria such as accuracy, is not at the same level as the performance of

         new-technology flowmeters. 

4.     They generally have higher maintenance requirements than new-technology flowmeters.

5.     They are slow to incorporate recent advances in communication protocols, such as HART, Foundation

         Fieldbus, and Profibus.

Traditional technology flowmeters include differential pressure, positive displacement, turbine, open channel, and variable area. Despite the inherent advantages of many new-technology meters, end-user demand for traditional meter types remains strong.

New-technology flowmeters are defined by the following characteristics:

1.   The core technology was introduced after the end of World War II.
2.   They incorporate technological ad-vances that avoid some of the problems in earlier flowmeters.
They receive more focus in terms of new product development than older technologies.
Their performance, including criteria such as accuracy, is at a higher level than that of traditional technology

5  .
They are quicker to incorporate recent advances in communication protocols such as HART, Foundation
       Fieldbus, and Profibus than traditional technology meters.

Generally, flowmeters that fit in the "new technology" category include Coriolis, magnetic, ultrasonic, vortex, and thermal.

Learn More: 
Part I: Flow Trend Watch. A Look at Recent Developments in New-Technology Flowmeters - Flow Control, May 2013
Part II: Trend Watch. A Look at Recent Developments in Traditional Technology Flowmeters - Flow Control, June 2013


Which types of flowmeters are most typically used for gas flow measurement?

The main types of flowmeters used for gas flow measurement include: 
 - Ultrasonic 
 - Coriolis 
 - Vortex 
 - Thermal 
 - Differential Pressure 
 - Positive Displacement, and 
 - Turbine
Learn More:
Part 2: The Role of Oil & Natural Gas - Digging Down on the Pros and Cons of Each and Every Possible Solution - Flow Control, February 2013

What is the status of vortex flowmeters? Have there been any technological improvements over the last several years?

One perennial problem with vortex flowmeters has been susceptibility to vibration error. Vibrations in the line can cause a vortex flowmeter to falsely generate a vortex signal, or to incorrectly read an existing vortex. Suppliers have responded by implementing software and electronics, including digital signal processing, that have reduced the susceptibility of vortex meters to interference from vibration.

Another important product enhancement is the introduction of reducer vortex meters. Reducer vortex flowmeters have a reduced diameter in the center of the pipe, where the bluff body generates vortices. This reduced diameter results in a speeded up flowstream where the pipe narrows. The introduction of reducer vortex models has simplified vortex flowmeter installation and has improved the ability of vortex flowmeters to provide accurate measurement at low flowrates.

The growing availability of multivariable vortex flowmeters is also helping boost sales of vortex flowmeters. Sierra Instruments (www.sierrainstruments.com) introduced the first multivariable vortex flowmeter in 1997. This flowmeter included an RTD temperature sensor and a pressure transducer. By using information from these sensors, together with detection of vortices generated, the flowmeter can output volumetric flow, temperature, pressure, fluid density, and mass flow. Multivariable flowmeters measure more than one process variable, and typically use this information to compute mass flow. This makes the flowmeter measurement more accurate in changing temperature and pressure conditions.
Learn More:
Vortex Flowmeters - Positioned Well for More Widespread Use Going Forward - Flow Control, December 2012

We've always installed turbine meters. What product enhancements are offered for these traditional meters?

Turbine meter suppliers have made technology improvements to enhance reliability. Many of these improvements have involved making the moving parts—a traditional source of concern regarding maintenance and repair—more reliable. By making the ball bearings out of more durable material, such as newly developed ceramics and synthetic sapphires, turbine suppliers have been able to add significantly to the life of the bearings. This is important, since some customers select new-technology meters over turbine meters simply because turbine meters have moving parts that are subject to wear.

Other product enhancements that are available today include the new “dual-rotor design” being promoted by Cox Instruments (http://www.cox-instruments.com/) and other manufacturers. The dual-rotor design increases the effective operating range of turbine meters in the smaller line sizes. This innovation specifies that the two rotors turn in opposite direction, with the first rotor being upstream from the second and acting as a flow conditioner. Flow is then directed back to the second rotor. The rotors are hydraulically connected, and will continue to turn as the flow decreases even at very low flowrates. This innovation has enhanced turbine flowmeters’ suitability in low-flow applications. Other recently introduced improvements include bi-directional flow, self-lubrication, and significantly reduced pressure drop.
Learn More: 
Turbine Flowmeters - Technology Upgrades Enhance Turbine Flowmeter Reliability - Flow Control, December 2012

What is the main application for an insertion-mounted ultrasonic meter?

Ultrasonic meters can also be differentiated by mounting type, of which there are three commonly applied to ultrasonic meters:

 - Insertion
 - Clamp-on
 - Inline (spool piece)

Insertion flowmeters are widely used for flare and stack gas monitoring, as well as for measuring exhaust emissions. Insertion meters are a good choice in these applications because the stacks and chimneys are often too large in diameter to make an inline meter practical. Insertion ultrasonic flowmeters compete with averaging Pitot tubes and thermal meters in these applications. They can also be hot-tapped or cold-tapped into a pipe to make a measurement when meter cost is a consideration and high accuracy is not required.
Learn More: 
Ultrasonic Flowmeters - Measurement Methods & Mounting Options Support a Range of Applications - Flow Control, December 2012

What type of flowmeter is the most accurate?

Coriolis flowmeters remain the most accurate flowmeter, and they are highly reliable with little need for maintenance. Coriolis meters do not place any obstruction in the flowstream, although bent-tube meters can slow down flow velocity. Straight-tube meters have been developed to address this effect and to suit the needs of sanitary applications, which pose an issue for bent-tube meters, which can accumulate material building at their bending points.
Learn More:  

Part I: Flow Trend Watch. A Look at Recent Developments in New-Technology Flowmeters - Flow Control, May 2013

What is the "paradigm case" method of selecting flowmeters?


The "paradigm case" method is a step-by-step method which helps you to analyze your flowmeter choices, taking into account factors such as operating principles, advantages, and limitations of each technology. The steps are as follows:

1.   Every type of flowmeter is based on a physical principle that correlates flow with some set of conditions.  This principle determines the paradigm case application for this type of flowmeter. When selecting a flowmeter, begin by selecting the types of flowmeters whose paradigm case applications are closest to your own.

2.   Make a list of application criteria that relate to the flow measurement you wish to make.  These conditions may include type of fluid (liquid, steam, gas, slurry), type of measurement (volumetric or mass flow), pipe size, process pressure, process temperature, condition of fluid (clean or dirty), flow profile considerations, fluid viscosity, fluid density, Reynolds number constraints, range, and others.  From those types of flowmeters selected in Step 1, select those that best meet these application criteria.

3.   Make a list of performance criteria that apply to the flowmeter you wish to select. These include reliability, accuracy, repeatability, range, and others.  From those types of flowmeters selected in step 2, select the ones that meet these performance criteria.

4.   Make a list of cost criteria that apply to your flowmeter selection.  These include initial cost, cost of ownership, installation cost, maintenance cost, and others.  From the types of flowmeters chosen in step 3, select the types that meet your cost conditions.

5.   Make a list of supplier criteria that govern your selection of a flowmeter supplier.  These include type of flowmeter, company location, service, responsiveness, training, internal requirements, and others.  From the types of flowmeters listed in step 4, select the suppliers that meet your criteria.

6.   For the final step, review the meters that are left as a result of step 4 and the suppliers listed as a result of step 5.  Review the application, performance, and cost conditions for the remaining flowmeter types, and select the one that best meets all these conditions. Now select the best supplier for this flowmeter from those suppliers listed as a result of step 5.

Learn More: Each of our research reports discusses in detail the applications, performances, approximated costs and suppliers of each flowmeter technology. Please see www.FlowResearch.com for information on available reports.












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