5 tips for gas flowmeter model selection - SenTec

Gas flowmeter is essential instrument used to measure and monitor the flow rate of gases in various industrial applications. They play a crucial role in ensuring the efficient operation of processes that involve the transportation or control of gases. Selecting the right gas flowmeter is of paramount importance to achieve accurate measurements and optimize system performance. This comprehensive guide aims to provide you with essential tips to consider when choosing a gas flowmeter model that best suits your specific application requirements.

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Importance of selecting the right gas flowmeter

Choosing the appropriate gas flowmeter is crucial because it directly impacts the accuracy and reliability of the flow measurements. A poorly selected flowmeter can result in inaccurate readings, leading to inefficient operation and potential safety hazards. On the other hand, selecting the right gas flowmeter ensures accurate measurements, improves process efficiency, and helps in identifying and rectifying any operational issues promptly.

Additionally, different gases have unique properties and behaviors, which require specific flow measurement techniques. Therefore, selecting the right gas flowmeter entails considering the characteristics of the gas being measured, such as pressure, temperature, viscosity, and composition. By carefully evaluating these factors, you can determine the most suitable gas flowmeter that will provide accurate measurements and meet your application requirements.

Different types of gas flowmeters

Gas flowmeters come in various types, each utilizing different principles to measure gas flow. Understanding the different types of gas flowmeters can help you make an informed decision when selecting the right model for your application. Here are some commonly used types of gas flowmeters:

gas flowmeter

1. Differential Pressure (DP) Flowmeters: These flowmeters measure flow by creating a pressure drop across an obstruction or a flow restriction. The pressure drop is then correlated to the flow rate using calibrated equations. Orifice plates, venturi tubes, and flow nozzles are examples of DP flowmeters.
2. Turbine Flowmeters: Turbine flowmeters employ a spinning rotor mounted in the flow path. As the gas flows through the meter, the rotor rotates at a speed proportional to the flow rate. This rotational speed is then converted into flow rate measurements using electronic or mechanical means.
3. Coriolis Flowmeters: Coriolis flowmeters utilize the Coriolis effect, which is the apparent deflection of moving particles caused by the rotation of the Earth. The gas flows through a vibrating tube, and the Coriolis forces generated are used to measure the mass flow rate directly.
4. Ultrasonic Flowmeters: Ultrasonic flowmeters measure gas flow by utilizing sound waves. Transducers are used to emit and receive ultrasonic signals through the gas flow. By measuring the time it takes for the signals to travel upstream and downstream, the flow rate can be accurately determined.
5. Thermal Mass Flowmeters: These flowmeters measure the flow rate by utilizing the cooling effect of the gas flow on a heated sensor. The temperature difference is proportional to the mass flow rate and is used to calculate the flow rate accurately.

Each type of gas flowmeter has its advantages and limitations, making it suitable for specific applications. Understanding the operating principles and characteristics of these flowmeter types will help you in choosing the most appropriate model for your gas flow measurement needs.

5 tips for gas flowmeter model selection

Before order, you will find 5 tips which you should keep in mind as you select a gas flowmeter technology for uses in a natural gas pipeline or industrial processes. Between the new and traditional meter alternatives, picking the right flow technology is the initial step to achieving precise measurement of gas flow. However, most people over look this consideration since it requires research and they end up selecting flow meters that offer unsatisfactory results. What is vital in choosing the correct meter technology is ensuring merits outweighs its disadvantages since no meter is perfect.

1.Gas flowmeter purpose or application
Why do you require the gas flow meter?
Do you want to know the amount of fuel gas? Are you using it for commercial, industrial or residential purposes? Do you need to monitor gas flow in the industrial process? You should check if you have to measure for the custody transfer because not every flow meter is approved to measure gas for custody transfer uses or for measuring gas in the ownership transferal. You should also comprehend the cost of the meter, maintenance, and installation.

2.The type of gas to monitor or measure
You should also consider the kind of gas that you need. Do you want it single or mixed? Is there any composition variation? Ascertain whether you want a dirty or clean gas. Is the gas pipeline, processed, fuel, digester or flare? Check the flow range operation of your gas and its accuracy necessity. All meters are designed for a unique flow range. Some of these
meters have a better rangeability implying they can effectively handle variations in the flow ranges. You should determine what is more important to you, is it the accuracy, repeatability or application?

3.The position of the gas flow meter
Where will you install the gas meter? Ensure the installation place of the gas meter is free from the interference from environmental conditions like heat, electricity or cold. Also, the preferred location has to be coherent with the government regulations. Moreover, check the size of the pipe, the duct materials and if there are environmental conditions that may impact your pipeline and ultimately the meter.

4. Short term and long term meter needs
Check whether you need a gas flow totalizer which will maintain the running of the gas which has passed over a specified time. Consider whether you require a signal output. Additionally, you have to comprehend the meter calibration needs. All gas flow measurement sensors should be calibrated in the factory. However, some of the meters need to be frequently calibrated and therefore have to be removed and taken to the gas flow meter manufacturer or a NIST accredited calibration institution. Some other meters provide calibration features which allow you to check whether the meter is in calibration. You also should check if the meter will enable upgrades. With the presence of PLCs, SCADA systems or advanced electronics, manufacturers provide upgrades to make sure your meter works efficiently, optimally and accurately.

5. Gas mass flow or gas volume flow
For gas volumetric flow measurement, we often refer to gas turbine flow meter, vortex flow meter, DP flow meter and so on, while for mass flow meter measurement, we often use coriolis flow meter or thermal mass flow meter.

Case studies: Successful gas flowmeter model selection

To further illustrate the importance of gas flowmeter model selection and its impact on different applications, let&#;s examine a couple of case studies:

1. Case Study 1: Natural Gas Distribution: A natural gas distribution company was experiencing inaccurate flow measurements and high energy consumption due to the use of an outdated flowmeter technology. By consulting with flowmeter experts and thoroughly evaluating their application requirements, they selected a Coriolis flowmeter model suitable for natural gas flow measurement. The new flowmeter provided highly accurate measurements, resulting in optimized energy consumption and improved system performance.
2. Case Study 2: Chemical Manufacturing: A chemical manufacturing plant needed to accurately measure the flow rate of a corrosive gas mixture. They consulted with flowmeter manufacturers and selected a thermal mass flowmeter specifically designed for corrosive gas applications. The chosen flowmeter provided accurate and reliable measurements, with minimal maintenance requirements, ensuring smooth operations in their manufacturing process.

These case studies highlight the importance of selecting the right gas flowmeter model based on specific application requirements. By considering the unique characteristics of the gas being measured and consulting with experts, these companies were able to overcome their flow measurement challenges and achieve accurate and reliable measurements.

Conclusion: Making an informed decision for gas flowmeter model selection

Selecting the right gas flowmeter is instrumental in achieving accurate flow measurements and optimizing system performance. By considering the factors discussed in this comprehensive guide, including flow rate range, pressure and temperature conditions, gas composition, installation requirements, and budget considerations, you can make an informed decision.

Thoroughly understand your application requirements, consult with flowmeter experts, and evaluate accuracy, reliability, and long-term costs. Take into account challenges and considerations specific to gas flowmeter selection, such as gas composition compatibility, installation constraints, and maintenance requirements.

Consider case studies of successful flowmeter model selection to gain insights into real-world applications. Prioritize regular maintenance and calibration to ensure accurate measurements and optimal performance. Finally, compare popular gas flowmeter brands based on their reputation, reliability, and suitability for your specific application.

By following these essential tips and guidelines, you can confidently select the right gas flowmeter model that meets your requirements, resulting in accurate measurements, improved efficiency, and enhanced operational performance.

With hundreds of flow meters available, how do you choose the right one? This article addresses the challenges users face when purchasing flow meters, introducing key considerations and summarizing the usage conditions of different types in a table. This will help you select the flow meter that best fits your needs. If you want to understand how flow meters work, please refer to Understanding How Different Flow Meters Work in 5 Minutes

(This table is for preliminary selection reference only. Due to varying characteristics of flow meters from different manufacturers, it is recommended to refer to catalogs or consult manufacturers when purchasing to confirm whether the temperature and pressure resistance meet your usage conditions.)

&#; Reference Table for Flow Meter Pressure Range and Operating Temperature: Compiled from the official websites of flow meter manufacturers like Emerson, Endress+Hauser, and Doweston: Pressure is measured in MPa: Low Pressure: &#; 1.0 MPa Medium Pressure: 1.0 MPa to 10 MPa High Pressure: > 10 MPa Fluid temperature inside the pipe is measured in degrees Celsius (°C): Low Temperature: -40°C to 0°C Medium Temperature: 0°C to 100°C High Temperature: > 100°C

Moreover, pipe pressure and temperature are crucial. Different flow meters have varying tolerances to pressure and temperature. Even the same type of flow meter may have different resistance levels due to material differences or special design requirements. In engineering design, it's recommended to have a safety margin exceeding 10 degrees. For example, with a pipe pressure of 20 kg and sodium hydroxide solution at 50 degrees inside the pipe, using Lorric flow meters as an example, although the liquid temperature tolerance is greater than 50+10, the pipe pressure tolerance should be greater than 20+10.

(This table is for preliminary selection reference only. Due to varying characteristics of flow meters from different manufacturers, it's recommended to refer to catalogs or consult manufacturers to confirm if the flow meter's measurement range meets your usage conditions.)

&#; Reference Table for Measuring Ranges of Various Flow Meters:The following data is compiled from flow meter product information published on the official websites of manufacturers like Emerson, Endress+Hauser, and Doweston, based on the turndown ratio:

We can refer to the measuring range to select a flow meter that meets our needs. If the measurement range of the equipment is between 10-150 lpm, dividing 150 by 10 equals 15. It is recommended to choose a flow meter with a turndown ratio greater than 1:15. Additionally, it's advisable that the minimum measurable flow of the flow meter is less than 10 lpm, and the maximum flow is greater than 150 lpm. For example, you can choose a flow meter with a measuring range of 5~180 lpm or 3~300 lpm. The minimum value of the measuring range (lower limit) affects the zero point (boundary value); the upper limit affects the accuracy of the flow meter. Since errors are usually calculated as a percentage of the upper limit value (full scale), if there's a large gap between the minimum and maximum measurement values, the accuracy at low flow rates will be poorer.

The measurable range of the flow meter should be greater than the variation range of the liquid flow in the equipment pipeline:

While flow meter accuracy is important, higher accuracy often means a higher price. It's advisable to balance accuracy and cost based on your needs. For instance, if you just need to know the approximate flow in a pipeline, high accuracy isn't essential. However, for precise chemical monitoring in manufacturing processes, higher accuracy is crucial. Let's understand some related terms:

| Flow Meter Accuracy

1. Repeatability and Measurement Accuracy

Repeatability

Definition: The consistency or closeness of measurement results when the same quantity is measured multiple times under identical conditions. Repeatability reflects the short-term stability of the measuring device or system.
For example, if you use a flow meter to measure the same flow rate (e.g., 10 liters per second) and repeat the measurement 10 times under the same conditions, a flow meter with high repeatability will yield results very close to each other, such as 9.98, 9.99, 10.01 liters. Higher repeatability means less data dispersion.

Measurement Accuracy
Definition: The closeness of the measured value to the true value (or reference standard). Measurement accuracy reflects the correctness of the measuring device.
If you aim to measure a liquid flow of 10 liters per second, ideally, the flow meter should display 10.0 liters per second. If it shows 9.8 liters per second, it indicates lower measurement accuracy. The higher the measurement accuracy, the closer the measured value is to the true value of 10.0 liters per second.

2. Full Scale (FS) vs. Reading (Rd)

When you see the accuracy specifications of a flow meter, pay attention to whether it's expressed as a percentage of Full Scale (FS) or Reading (Rd or RD).

1) What is Full Scale (FS)?

Using FS to express error means the error is calculated based on the maximum range of the scale. The absolute error remains constant, but the relative error percentage changes with the flow rate.

For example: Suppose a flow meter has a range of 3&#;300 LPM with an accuracy of ±3.0% FS.
Then, Absolute Error = 300 LPM × 3.0% = 9 LPM

If the displayed flow is 250 LPM, the actual flow could be 250 LPM ±9 LPM (241&#;259 LPM). The relative error is 9 LPM / 250 LPM = ±3.6%.

If the displayed flow is 100 LPM, the actual flow could be 100 LPM ±9 LPM (91&#;109 LPM). The relative error is ±9%.

The advantage of FS is that it's simple to calculate since the absolute error doesn't change. It's suitable for indicating errors at high flow rates. However, at lower flow rates, the absolute error constitutes a larger percentage of the flow rate, leading to poorer measurement accuracy.

 

2) What is Reading (Rd or RD)?
When using Rd to express error, the error is calculated based on the actual measured value. The percentage remains constant regardless of where the flow rate is within the range.

For example: Suppose a flow meter has an accuracy of ±0.3% Rd.

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When the actual measured value is 100 LPM, the absolute error is 100 LPM × 0.3% = 0.3 LPM.

When the actual measured value is 50 LPM, the absolute error is 50 LPM × 0.3% = 0.15 LPM.

The advantage of Rd is that the error varies with the measured value, offering more precise measurements at low flow rates and stable relative errors. It's suitable for applications with varying flow rates, maintaining accuracy across different ranges. The downside is that calculations are more complex, requiring dynamic computation for each reading. At high flow rates, the error might increase, affecting measurement accuracy.

Based on data from manufacturers like Emerson, Endress+Hauser, and Doweston, using Full Scale (FS) error as the standard:

• High Accuracy: FS &#; ±0.5%, suitable for laboratory measurements or high-precision industrial applications.
• Medium Accuracy: FS between ±0.5% and ±2%, suitable for most industrial applications and daily measurement needs.
• Low Accuracy: FS > ±2%, suitable for applications with large flow variations or lower accuracy requirements.

&#; Flow Meter Accuracy Reference Table:Based on data from manufacturers like Emerson, Endress+Hauser, and Doweston, using Full Scale (FS) error as the standard:

Flow Meter Type

Accuracy Range

1. Ultrasonic Flow Meter

High

2. Paddle Wheel Flow Meter

Low

3. Variable Area Flow Meter (Rotameter)

Low

4. Coriolis Flow Meter

High

5. Positive Displacement Flow Meter (Gear Flow Meter)

Medium to High

6. Vortex Flow Meter

Medium

7. Turbine Flow Meter

Medium

8. Differential Pressure Flow Meter

High

9. Electromagnetic Flow Meter

High

10. Thermal Mass Flow Meter

High

(This table is for preliminary selection reference only. Due to varying characteristics of flow meters from different manufacturers, it is recommended to refer to catalogs or consult manufacturers to confirm if the flow meter's accuracy meets your usage conditions.)

V. Installation Environment

Whether the equipment can be shut down, whether pipe cutting is necessary, and the installation location must be considered when selecting a flow meter:

• Determine if the equipment can be shut down and pipes cut for flow meter installation: When the pipeline cannot be stopped or cut, it's recommended to use non-intrusive flow meters like ultrasonic flow meters, although installing without cutting the pipeline usually requires a higher budget.
• Select the connection method based on the pipe material: Choosing an appropriate connection method can enhance the sealing of the flow meter. Metal pipes (such as stainless steel, copper) usually require welding or flange connections, while plastic pipes (such as PVC, PPH) often use adhesive bonding or threaded connections.
• Pay attention to corrosion resistance requirements: When the fluid is corrosive, you need to choose flow meter materials with good chemical resistance, such as engineering plastics (PVC, PPH, PVDF, PFA).
• Note whether the installation position is horizontal or vertical?

 

There are considerations when installing on horizontal or vertical pipes; choose the flow meter based on site conditions. If installed on a horizontal pipe, it's best to install at a low point or the bottom of a U-shaped pipe, because insufficient pressure at higher points and incomplete filling of the pipe can lead to inaccurate flow measurements.

If installed on a vertical pipe, it's recommended to install the flow meter where the liquid flows upward from bottom to top. If the liquid flows from top to bottom, it may create segmented falling flow, causing unstable flow rates. Therefore, install the flow meter on a pipe section where the liquid flows upward.

| Flow meter installed on a vertical pipe

VI. Purchase Cost and Special Certifications

When purchasing a flow meter, besides the price of the flow meter itself, you also need to consider installation, maintenance, and operating costs. For example, electronic flow meters have a long service life but may require periodic calibration.
Additionally, consider whether you have special certification requirements for the flow meter, especially in industrial environments with high safety and explosion-proof demands. Special certifications include:
CE: The European Union's safety, health, and environmental standards; all equipment sold in the EU must comply with these regulations.  
UL: U.S. safety certification, mainly for electrical safety and fire protection, widely used in the North American market.  
ATEX: European explosion-proof certification for explosive environments, applicable to high-risk areas like chemical and petroleum industries.  
Measurement Certification: Certification for flow meter accuracy and measurement compliance to ensure the accuracy of commercial measurements.

Based on price ranges of flow meters found on Amazon and Alibaba, using DN25 (1 inch) as the standard:

• High Cost: Above 15,000 TWD
• Medium Cost: 5,000~15,000 TWD
• Low Cost: Below 5,000 TWD

&#; Flow Meter Cost Reference Table:Based on price ranges of flow meters found on Amazon and Alibaba, using DN25 (1 inch) as the standard:

Flow Meter Type

Purchase Cost

1. Ultrasonic Flow Meter Medium to High 2. Paddle Wheel Flow Meter Medium 3. Variable Area Flow Meter (Rotameter) Low 4. Coriolis Flow Meter Medium 5. Positive Displacement Flow Meter (Gear Flow Meter) Medium 6. Vortex Flow Meter High 7. Turbine Flow Meter Medium 8. Differential Pressure Flow Meter Low 9. Electromagnetic Flow Meter High 10. Thermal Mass Flow Meter High

(This table is for initial selection reference only. Due to varying characteristics of flow meters from different manufacturers, it is recommended to consult catalogs or contact manufacturers to confirm whether the flow meter price meets your cost considerations.)

VII. Signal Transmission

For example, recent "Energy Management Act" regulations require equipment in buildings and workplaces to submit annual energy reports. This necessitates flow meters with data collection capabilities. When purchasing flow meters, pay attention to whether the communication interfaces and protocols are compatible.
Learn more:
&#; Ultrasonic Flow Meters Simplify Energy Reporting
&#; What Is Analog Current Output?
&#; What Is RS485?
&#; What Is a Switch Signal?

In some cases, there is a need for flow data storage and transmission. You should ensure that the signal transmission method is compatible with other equipment, such as Pulse, 4-20mA, RS485, I/O LINK, etc.For example, recent "Energy Management Act" regulations require equipment in buildings and workplaces to submit annual energy reports. This necessitates flow meters with data collection capabilities. When purchasing flow meters, pay attention to whether the communication interfaces and protocols are compatible.Learn more:

If you are looking for more details, kindly visit Piston Type Circulating Real Gas Flow Standard Device.

VIII. Summary of Various Flow Meter Features