Flowmeter Selection Guide|Find the Best One for Your ...

Our flowmeter selection guide is designed to help you find the best flow meter for your application. Flow meters are one of the most commonly used instruments in industry.

You will get efficient and thoughtful service from TNMA.

Since flow is a dynamic quantity, the measuring instrument itself is affected by many factors, such as: pipe, diameter size, shape (circular, rectangular), boundary conditions, physical properties of the medium (temperature, pressure, density, viscosity, dirtiness, corrosiveness) etc.), the flow state of the fluid (turbulence state, velocity distribution, etc.) and the influence of installation conditions and levels.

Therefore, in the face of more than a dozen categories and hundreds of varieties of flow meters at home and abroad, how to make reasonable selection is the prerequisite and foundation for the good application of flow meters.

Our flow meter selection guide can help you quickly master the selection and application of flow meters.

Generally speaking, the analysis should mainly be carried out from the following 6 aspects:

1. Measurement purpose;
2. Fluid characteristics;
3. Characteristics of flow meter;
4. Installation requirements;
5. Environmental conditions;
6. Flow meter cost;

Measurement purpose

First of all, clarifying your measurement purpose is the key to choosing a suitable flow meter.

• For example, you need to detect the instantaneous flow of a pipeline and need local flow display.
• Or, if you need to detect the instantaneous flow rate and cumulative flow rate of the pipeline, you need to bring a calculator.
• Or, you need to conduct trade settlement through flow monitoring of pipelines. So high precision is very important.
• Or, you need to detect the flow, pressure and other parameters of the pipeline, and at the same time, you need to output the 4-20mA signal to the monitoring room.
• Or, you need to detect traffic parameters and store data.

Therefore, first you need to clarify the purpose of your traffic measurement and what effect you want to achieve.

Fluid characteristics

Common fluid physical properties include density, viscosity, vapor pressure and other parameters. These parameters can generally be found in the manual, and the suitability of each fluid parameter and the selection of the flowmeter can be evaluated under the conditions of use. But there are also some physical properties that cannot be found. Such as corrosiveness, scaling, clogging, phase change and miscible state, etc.

Detailed enumeration and description are as follows:

1.Fluid types:
The first thing that needs to be clarified is what fluid is being measured. Is the measured medium gas, liquid, or steam? And the measured fluid is single? Or mixed?

2.Density&#;
Density of FluidsFor liquids, the density is relatively constant in most applications. Unless the temperature changes greatly causing major changes, density correction generally does not need to be performed. In gas applications, the range and linearity of the flow meter depend on the gas density. Generally, it is necessary to know the values under standard conditions and working conditions for selection. There is also a method of converting flow state values to certain recognized reference values. This method is commonly used in petroleum storage and transportation. Low-density gases can be difficult for some measurement methods, especially instruments that use the momentum of the gas to push the detection sensor (such as turbine flowmeters).

3.Viscosity:
Required for liquids. The viscosity of various liquids varies greatly and changes significantly due to temperature changes. Gases are different. The difference in viscosity between various gases is small, and their values are generally low. And it will not change significantly due to changes in temperature and pressure. Therefore, the effect of viscosity must be considered for liquids.

4.Electrical conductivity:
Required for electromagnetic type flow meters. If the measured medium is liquid. Then it is best to confirm the conductivity of the fluid.

5.Contaminants:
Air bubbles, mixed-in foreign objects, slurry, etc.

6.Flow range:
It is best to confirm the minimum-normal-maximum flow rate in the pipeline. Can be mass flow rate or volume flow rate.

7.Fluid temperature and pressure:
Carefully analyze the working pressure and temperature of the fluid in the flow meter, especially if the temperature and pressure changes cause excessive density changes when measuring gas, the selected measurement method may need to be changed. For example, when temperature and pressure affect performance such as flow measurement accuracy, temperature or pressure correction must be made. In addition, the structural strength design and material of the flowmeter housing also depend on the temperature and pressure of the fluid. Therefore, the maximum and minimum values of temperature and pressure must be known exactly. Careful selection should be made when temperature and pressure vary greatly. It should also be noted that when measuring gas, it is necessary to confirm whether the volume flow value is the temperature and pressure under working conditions or the temperature and pressure under standard conditions.

8.Chemical corrosion:
The problem of chemical corrosion of fluids sometimes becomes a deciding factor in our choice of measurement method and use of flow meters. For example, certain fluids can corrode parts in contact with the flow meter, cause surface scaling or precipitation of crystals, and produce electrolytic chemical effects on the surface of metal parts. The occurrence of these phenomena will reduce the performance and service life of the flow meter. Therefore, in order to solve the chemical corrosion situation, a flowmeter made of anti-corrosion materials is selected.

9.Scaling situation:
Due to scaling or crystallization on the flow meter cavity and flow sensor, the clearance of the moving parts in the flow meter will be reduced, and the sensitivity or measurement performance of the sensitive components in the flow meter will be reduced. For example, in ultrasonic flowmeter applications, the scale layer will hinder the emission of ultrasonic waves. In electromagnetic flowmeter applications, the non-conductive scale layer insulates the electrode surface and makes the flowmeter unable to operate.

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Characteristics of flow meters

Different types of flow meters have different advantages, disadvantages and performance parameters. For details, please refer to: 11 Flow Meter Types and Their Advantages and Disadvantages. Before we choose a flow meter, it is best to understand the performance parameters of various flow meters. Mainly from the following aspects:

There are two types of flow measurement, namely instantaneous flow and cumulative flow.
For example, the crude oil in the distribution station pipeline belongs to the custody transfer, or the continuous proportioning of the petrochemical pipeline, the process control of the production or production process, etc. need to measure the total amount. Occasionally supplemented by observation of instantaneous flow.

In some workplaces, instantaneous flow measurement is required to control flow. Therefore, the selection should be made according to the needs of on-site measurement.

This accuracy class refers to the maximum error of the flow meter.
When calibrating a flow meter, it generally only marks two points: zero point and span. During calibration, five points are generally checked, namely 0%, 25%, 50%, 65% and 100% of the full scale. The error of these five points is less than 1%, which means it is qualified and allowed to leave the factory. The actual errors of these five points may be 0.1%, 0.3%, 0.5%, 0.8%, and 0.4% respectively, but the error of the entire machine is subject to the largest error.

For example: the measuring range of the flow meter is 10m³/h.
Then an accuracy of level 1.0 means that the difference between the measured value of the flow meter at any measuring point and the real flow rate is within plus or minus 1m³/h. For example, when the measured value of the flow meter is 5m³/h, the actual flow rate is between 4-6m³/h.
Therefore, the higher the accuracy of the flow meter, the more accurately it represents the true flow rate. Level 0.5 is definitely more accurate than level 1.0.

Repeatability refers to the ability to produce the same results repeatedly under the same conditions. That is, the flow meter should produce the same reading when operating under the same variables and conditions. This is also expressed as ± percentage.

Generally, the measurement performance requirements in the calibration regulations not only stipulate the accuracy level of the flow meter, but also stipulate the repeatability. The general stipulation is: the repeatability of the flow meter shall not exceed the maximum allowable error specified in the corresponding accuracy level. 1/3&#;1/5.

However, in practical applications, the repeatability of the flow meter is often affected by changes in fluid viscosity and density parameters. Sometimes these parameter changes have not reached the level that requires special correction, and it is mistakenly thought to be poor repeatability of the flow meter. . In view of this situation, a flowmeter that is not sensitive to changes in this parameter should be selected.

The linearity of the flow meter refers to the degree of consistency between the flow characteristic curve and the specified straight line within the flow range.

It can be expressed by the following formula:
δ=±(Kmax-Kmin)/(Kmax+Kmin)*100%

In the formula:
δ&#;linearity;
Kmax&#;the maximum value of the instrument coefficient at each measuring point within the flow range;
Kmin&#;the minimum value of the instrument coefficient at each measuring point within the flow range;

The output of the flow meter mainly includes linear and nonlinear square root.
Generally speaking, the nonlinear error of the flow meter is not listed separately, but is included in the error of the flow meter.

For flowmeters that generally have a wide flow range, have pulse output signals, and are used for total volume accumulation, linearity is an important technical indicator. If a single instrument coefficient is used within the flow range, the linearity difference will be Will reduce the accuracy of the flow meter.

For example, a turbine flowmeter uses an instrument coefficient within the flow range of 10:1. When the linearity is poor, its accuracy will be lower. With the development of computer technology, its flow range can be segmented and fitted using the least squares method. The flow rate-instrument coefficient curve corrects the flow meter, thereby improving the accuracy of the flow meter and expanding the flow range.

The upper limit flow rate is also called the full scale flow rate or maximum flow rate of the flow meter. When we select the diameter of the flow meter, we should configure it according to the flow range used by the pipeline under test and the upper limit flow rate and lower limit flow rate of the selected flow meter. We cannot simply configure it according to the diameter of the pipe.

Generally speaking, the maximum flow rate of fluid in a designed pipeline is determined based on the economic flow rate. If the selection is too low, the pipe diameter will be thick and the investment will be large; if it is too high, the transmission power will be high and operating costs will increase.

For example, the economic flow rate of low-viscosity liquids such as water is 1.5 to 3 m/s, and that of high-viscosity liquids is 0.2 to 1 m/s. The upper flow rate of most flow meters is close to or higher than the economic flow rate of pipelines. Therefore, when selecting a flowmeter, its diameter is usually the same as that of the pipe, and installation is more convenient. If they are not the same, there will not be much difference. Generally, the specifications of the upper and lower adjacent gears can be connected by reducing pipes.

The range is the ratio of the upper limit flow and the lower limit flow of the flow meter. The larger the value, the wider the flow range. Linear meters have a wider range, generally 1:10. The range of nonlinear flowmeter is as small as 1:3.

Flow meters are generally used for process control or custody transfer accounting. If a wide flow range is required, do not choose a flow meter with a small range.

At present, in order to promote the wide flow range of their flow meters, some manufacturers have raised the flow rate of the upper limit flow very high in the instruction manual. For example, the liquid speed is raised to 7~10m/s (usually 6m/s), and the gas speed is raised to 50~ 75m/s (usually 40~50) m/s). In fact, such a high flow rate is not used.

In fact, the key to a wide range is to have a lower lower limit flow rate to meet the measurement needs. Therefore, a wide-range flowmeter with a low lower limit flow rate is more practical.

Pressure loss generally refers to the irrecoverable pressure loss that changes with the flow rate due to the static or movable detection element installed in the flow channel or the change of flow direction in the flow sensor.

Therefore, the flowmeter should be selected based on the pumping capacity of the pipeline system and the inlet pressure of the flowmeter to determine the allowable pressure loss of the maximum flow rate.

Improper selection will restrict the fluid flow and cause excessive pressure loss, which will affect the circulation efficiency. For some liquids (high vapor pressure hydrocarbon liquids), it should also be noted that excessive pressure drop may cause cavitation and liquid phase vaporization, reduce measurement accuracy and even damage the flow meter.

For example, for flowmeters used for water delivery with pipe diameters greater than 500mm, the increased pumping costs due to excessive energy loss caused by pressure loss should be considered.

According to relevant reports, the pumping costs paid for measurement by flow meters with large pressure losses in recent years often exceed the purchase cost of more expensive flow meters with low pressure losses.

The output and display volume of the flow meter can be divided into: &#; instantaneous flow (volume flow or mass flow); &#; cumulative flow; &#; average flow rate; &#; point flow rate.

Some flowmeters output analog quantities (current or voltage), others output pulse quantities. Analog output is generally considered suitable for process control, and is more suitable for coupling with control loop units such as regulating valves. Pulse output is more suitable for total volume and high-accuracy flow measurement.

Long-distance signal transmission pulse output has higher transmission accuracy than analog output. The mode and amplitude of the output signal should also be compatible with other devices. Such as control interfaces, data processors, alarm devices, circuit breaker protection circuits and data transmission systems.

When used in pulsating flow situations, attention should be paid to the response of the flowmeter to step changes in flow. Some applications require the flowmeter output to follow the fluid flow, while others require a slower response output to obtain a comprehensive average.

Instantaneous response is often expressed in terms of time constant or response frequency. The former ranges from a few milliseconds to a few seconds, and the latter is below hundreds of Hz. The use of a display instrument may significantly extend the response time.

It is generally believed that when the flow rate of a flow meter increases or decreases, the asymmetric dynamic response will accelerate the flow measurement error.

Flow Meter Installation

Installation issues have different requirements for flow meters with different principles.

When using the flow meter, attention should be paid to the adaptability and requirements of the installation conditions, mainly considering the following aspects. For example, the installation direction of the flow meter, the flow direction of the fluid, the configuration of the upstream and downstream pipelines, valve positions, protective accessories, pulsating flow Impact, vibration, electrical interference and flow meter maintenance, etc.

1. On-site pipeline wiring: When wiring on-site pipelines, attention should be paid to the installation direction of the flow meter. Since the installation direction of the flow meter is generally divided into vertical installation and horizontal installation, there is a difference in flow measurement performance between these two installation methods. of.
2. Fluid flow direction: This problem is similar to the installation direction of the flow meter. Since some flow meters are stipulated to only work in one direction, reverse flow will damage the flow meter.
3. Straight pipe sections upstream and downstream of the flow meter.
4. Pipe diameter and pipe vibration: Some types of flow meters do not have a very wide range of pipe diameters, so being too large or too small will limit the choice of flow meter varieties.
5. Installation position of the valve: Control valves and isolation valves are installed in the pipelines where the flow meters are installed. In order to avoid some flow velocity distribution disturbances and cavitations caused by the valves that affect the flow meter measurement, the control valve should generally be installed downstream of the flow meter. Installing the control valve downstream of the flow meter can also increase the back pressure of the flow meter and reduce the possibility of air pockets inside the flow meter.
6. Protective accessories: Installing protective accessories is a protective measure to ensure the normal operation of the flow meter. For example, positive displacement flowmeters and turbine flowmeters generally need to install some necessary equipment such as filters upstream. All these equipment must be installed so as not to affect the use of the flowmeter.
7. Electrical connection and electromagnetic interference: Most of the current flow measurement systems, whether the flow meter itself or its accessory connections, have electronic equipment, so the power supply used must be matched with the flow meter. &#;
8. Pulsating flow and unsteady flow: Pay attention to keep all installed flow meters away from the source of pulsation. The most common sources of pulsation include hydraulic oscillations such as fixed displacement pumps, reciprocating compressors, oscillating valves or regulators, and vortex columns. Generally, differential pressure flowmeters have pulsating flow errors, and turbine flowmeters and vortex flowmeters also produce pulsating flow errors. Unsteady flow refers to flow that changes with time and slow pulsation is a special case of unsteady flow. Such as the slow pulsation caused by the operation of an oversized control valve.

Environmental conditions

In the process of selecting a flow meter, surrounding conditions and related changes should not be ignored, such as ambient temperature, humidity, safety and electrical interference, etc.:

1) Ambient temperature
Changes in ambient temperature can affect the electronics and flow sensor portions of the flow meter. For example, temperature changes will affect changes in sensor size, and heat transfer through the flowmeter housing will change fluid density and viscosity. When the ambient temperature affects the electronic components of the display instrument, the component parameters will change.

2) Ambient humidity
The atmospheric humidity in the environment is also one of the problems that affects the use of flow meters. For example, high humidity will accelerate atmospheric corrosion and electrolytic corrosion and reduce electrical insulation, while low humidity will induce static electricity.

3) Security
The flowmeter should be selected in accordance with relevant specifications and standards to adapt to use in explosive hazardous environments, and on-site requirements should be carried out in accordance with explosion-proof standards.

4) Electrical interference
Power cables, motors and electrical switches will all produce electromagnetic interference. If relevant measures are not taken, it will become the cause of errors in flow measurement.

Flow meter cost

1. Purchase cost of flow meter.
   When purchasing a flowmeter, the economic impact of different types of flowmeters on the entire measurement system should be compared. For example, measuring water pipe flow, DN300 large diameter. Then the external clamp ultrasonic flowmeter will cost less than other flowmeters.
2. Installation and maintenance costs
   When purchasing a flow meter, you must consider not only the purchase cost of the flow meter, but also other costs, such as accessory purchase fees, installation and commissioning fees, maintenance and regular testing fees, operating fees and spare parts fees.

Reference application guidance

Below is a summary of flow meter options for some common application types. For your preliminary reference:

 LiquidsClean LiquidDirty LiquidAbrasive /SlurryCorrosiveHigh PressureDensity, ConcentrationCryogenicHigh TempMass FlowLow Flow Rates <0.1m³/hr (0.44gpm)Low ConductivityCoriolis Flow Meter&#;&#;OO&#;&#;&#;&#;&#;&#;&#;Magnetic Flow Meter (4-wire)&#;&#;&#;&#;OOoOMagnetic Flow Meter (2-wire)&#;O&#;OOOO  Capacitance Magnetic Flow Meter&#;&#;&#;&#;OOO&#;Vortex Flow Meter&#;OO&#;O&#;&#;&#;&#;Variable Area Flow Meter&#;O&#;O&#;&#;O&#;&#;Differential Pressure (DP)Flow&#;OOO&#;OO&#;&#;&#;Gas and SteamClean GasDirty GasCorrosiveLow PressureSaturated SteamSuperheated SteamCryogenicHigh TempMass FlowLow Flow RatesCoriolis Flow Meter&#;&#;OO&#;&#;&#;&#;&#;Vortex Flow Meter&#;OO&#;&#;&#;&#;&#;&#;Variable Area Flow Meter&#;OO&#;&#;&#;&#;&#;&#;Differential Pressure (DP)Flow Meter&#;OO&#;&#;&#;OOO&#;&#; Designed for this service  ;   O Applicable for this service under certain conditions -consult manufacturer

Selection examples

Refrigerant Flow Measurement for HVAC System

A customer from the United States was looking to purchase a flow meter to measure the flow rate of liquid R134A in their HVAC system. The system requirements and fluid properties were as follows:

• Fluid: Liquid R134A
• Connection tube size: 1/4&#;
• Flow rate: 5-250 L/h
• Operating temperature: -30°C to 150°C (-22°F to 302°F)
• Operating pressure: 0 to 600 psig
• Preferred output signal: 0-5V DC (alternative options: 0-10V DC, 4-20mA)

After evaluating various flow meter technologies, the customer selected our gear flow meter due to its suitability for their specific application. The gear flow meter provided accurate measurement for the refrigerant and met the temperature and pressure requirements. The selected gear flow meter had the following specifications:

• Model: GF-04
• Measuring range: 5-250 L/h
• Material: Stainless steel
• Connection: G3/8 thread
• Operating temperature and pressure: -30°C to 150°C (-22°F to 302°F), 0 to 600 psig
• Output signal: 0-5V DC

By choosing the gear flow meter, the customer was able to accurately measure and control the flow rate of liquid R134A in their HVAC system, ensuring optimal performance and energy efficiency.

More Flow Measurement Solutions

Choosing the right flow meter for your application is critical to achieving accurate, efficient flow measurement. By considering the factors discussed in this Flowmeter Selection Guide and understanding the different flow meter technologies available, you can make an informed decision and find the product that best suits your specific needs.

As an experienced manufacturer and supplier, Sino-Inst offers a variety of flow meters and supports customization to meet your unique requirements.

Contact us today to discuss your flow meter needs and learn how our expertise can help you improve process control and efficiency.

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Flow meters are some of the most versatile and integral components in any fluid handling system. From agriculture chemical production to water treatment facilities, meters offer a reliable means to monitor how efficient your operation is and provide a tangible reading to identify potential issues within the plumbing system. This makes choosing the right flow meter for your application even more important. Selecting the wrong meter causes inaccuracies within your flow monitoring processes and creates inefficiencies throughout the rest of the system, not to mention significant unintended costs.

Dultmeier Sales is here to ensure that doesn't happen.

In this guide to flow meter selection, we'll take a look at several common meter types and the various applications in which they are used. We will also highlight some key considerations to keep in mind so that you always choose the best flow meter for your application needs. So, without further ado, let's get started.

 

Understanding What a Flow Meter Does

Simply put, a flow meter is a device that measures the flow of material-typically either liquids or gases-through a pipe. It determines how much material passes through the pipe (or hose) in a given period. It typically provides this measurement in units like gallons per minute (GPM), liters per second (L/s), or cubic feet per minute (CFM).

While this concept is straightforward, selecting the right flow meter for your specific task, however, can be more complicated.

 

Fill-Rite mechanical flow meters & digital flow meters

 

How to Choose the Right Flow Meter

First off, It is important to note that no two meters are exactly alike. Depending on application and metering needs, you may have several meter options or a single very specific one from which to choose. Complicating things further are the many external considerations your meter must satisfy in order to accomplish its intended purpose. As they say, the "devil is in the details," and the same goes for choosing the best flow meter for your application.

Below are some key characteristics to keep in mind when selecting the proper flow meter:

• Accuracy & Repeatability
• Type of Fluid (liquid, gas, slurry, steam)
• Density
• Viscosity
• Conductivity
• Temperature
• Pressure
• Flammable/Oxidizer
• Corrosiveness/Toxicity
• Flow Range/Turndown
• Materials of Construction
• Environment/Location & System Configuration
• Hygiene Requirements (pharmaceutical, food processing, etc.)
• Costs
  • Initial Investment
  • Installation
  • Long-term Maintenance

While the meter you ultimately select should ideally meet every factor above, ensuring it meets the most important ones for your operation will help guarantee you receive the best results. Let's dive into a few of the main ones on which you should focus.

Contact us to discuss your requirements of Gas Flow Measurement Instruments. Our experienced sales team can help you identify the options that best suit your needs.

Accuracy & Repeatability

Near the top of the list when evaluating flow meter specs is flow meter accuracy. Accuracy is how close a measurement is to the actual true value passing through a system. Expressed as a percentage (i.e. +/- 1%) accuracy represents how close the meter's output is to its calibrated parameters. Generally, the lower the percentage, the more accurate a meter is.

However, accuracy is not the only side of the coin. Repeatability, or the production of like outcomes under the same conditions, is perhaps even more important when evaluating which flow meter to choose. This is because accuracy is only reliable so far as its consistency. As you can see below, repeatability is possible without high accuracy, but high accuracy is not achievable without repeatability.

Flow meter accuracy & repeatability

If your flow readouts are unreliable-meaning you receive inconsistent results despite the same conditions-then you aren't gaining any value. Likewise, if your flow volume falls short of or exceeds your meter's rated flow range (also known as turndown), you won't receive accurate readings either.

Precision readings go hand in hand with any well-tuned operation. Choosing the best flow meter accuracy and repeatability percentages that meet your application requirements ensures your system maintains the precision readings you desire.

Liquid, Gas, or Semi-Liquid?

The type of fluid you work with is another big factor when choosing which flow meter best fits your application. Fluid type breaks into four categories: gas, liquid, slurry, and vapor-each with its own unique characteristics.

Properties such as fluid density, temperature, viscosity, and corrosiveness/acidity all must be determined before a final selection. This ensures you avoid choosing a flow meter incompatible with the fluid type you are attempting to measure. Electromagnetic flow meters, for example, won't work with non-conductive fluids like hydrocarbons. Likewise, few meter types are capable of measuring slurries because of their unique semi-liquid characteristics.

Illustration of how slurry particles behave between homogenous & heterogeneous mixtures

Here is a short list of flow meter types commonly used for the four fluid categories:

• Gas: Coriolis, Thermal Mass, Positive Displacement, Turbine, Variable Differential Pressure, Ultrasonic
• Liquid: Coriolis. Thermal Mass, Positive Displacement, Variable Flow, Paddlewheel, Turbine, Variable Differential Pressure, Ultrasonic, Electromagnetic
• Slurry: Coriolis, Electromagnetic, some subsets of Differential Pressure
• Vapor: Vortex, Ultrasonic, Floating Element

While not comprehensive, this list should offer a good starting point. That said, not every meter listed may work for your specific setup or needs. For instance, if your operation handles multiple fluids, you'll want to ensure that the meter you go with is compatible with all fluids-not just one. Otherwise, you likely spend valuable time calibrating your flow meter each time you handle a different product or troubleshooting why your inventories are off from your readouts.

Location & System Configuration

Meter location, as in real estate, is another major consideration. Will the flow meter be installed inside a controlled environment or outdoors in the elements? Is space a non-factor, or must size be considered? Certain flow meters even require stretches of straight pipe before and after the meter to generate accurate flow readings.

As a rule of thumb, pipe lengths of 10X (where X = pipe diameter) are needed before and after a meter for straight runs of pipe. So, if your plumbing's diameter is 2" you would need 20" or approximately 2 feet of pipe before and after the flow meter. This goes for just about any meter type, but it is always best to check the manufacturer's specs.

Also, keep in mind horizontal or vertical mounting. Some meters can be mounted in either orientation while others must be in one orientation or the other. Variable flow meters, for example, rely primarily on gravity in order to measure flow rate. Thus, they must be installed vertically to work. Determining how and where a meter will be installed while choosing a meter saves installation time and avoids costs related to unintended system reconfiguring.

Differentiating Between Volumetric vs. Mass Flow

Before we break down various flow meters, it is important to say a word on flow measurement. While there are many types of flow meters, most used today fall under two primary categories according to how they calculate flow: volumetric and mass.

As their name suggests, volumetric flow meters measure flow by calculating the volume of a fluid. Flow is often directed through an intrusion metering device such as a turbine or orifice plate, which then measures fluid velocity proportionally to the volume of matter passing by. Volumetric flowmeters make up the majority of meter types today and include turbine, magnetic, positive displacement, ultrasonic, and vortex meters to name a few.

Volume flow vs. mass flow within a cylinder

Mass flow meters, meanwhile, calculate flow rate by measuring the mass of a fluid. Mass meters have become increasingly popular due to their precision performance and truer reading of product flow compared to older metering technologies. In the diagram above, for instance, the product volume significantly changes depending on the position of the piston-even as mass remains the same. Today, mass meters have more or less become synonymous with Coriolis mass meters, but other types do exist. We'll discuss how mass meters work later in the article.

Whether you choose volumetric meters and mass meters depends on your application and metering needs, as well as your operational preferences and cost differences. In the end, you can still calculate volume to mass or mass to volume so long as the fluid density, surrounding temperature effects, and other conversion factors are all understood.

Comparing Flow Meter Types

There is, unfortunately, no such thing as a universal flow meter. Each flow meter type has fluids and applications for which it is well suited, and similarly, ones for which they are not. The following is a breakdown of some of the most common types of flow meters and the pros and cons of using each one.

Positive Displacement Flow Meters

Pros

• Accurate across wide flow ranges
• *Can handle very viscous fluids
• Versatile applications-simple, reliable design
• Require no power supply
• Cost-effective

*Thicker viscosity fluids create larger pressure losses & reductions in flow rates

Cons

• Requires medium to high-flow applications
• Experience greater pressure drops
• Larger/heavier than other meters
• Not recommended for dirty fluids or gases
• Some subsets require constant lubrication
• Many moving components need regular maintenance and replacement

Positive displacement (PD) meters consist of chambers featuring mechanical components that rotate in relation to volume flow. As fluid passes through, the reciprocating components-generally a type of gear, vane, or diaphragm-divides the fluid into fixed, metered volumetric units. The number of units rotated through within a specified time frame directly correlates to flow rate. Subtypes include screw meters, rotary vane meters, diaphragm meters, reciprocating or oscillating piston meters, and helical or oval gear meters.

 

TCS 700 Series Rotary Fuel Meter with Register

Since PD meters only measure flow while fluid passes through, they're ideal for applications where metering is crucial to calculate fluid usage. The TCS 700 series rotary vane meters, for example, are widely used in oil and gas custody transfer industries, while diaphragm meters are commonly installed on residential or municipal water and gas lines. Their fluid-driven design additionally makes positive displacement flow meters one of the more cost-effective options since they require no outside power supply to operate. However, these meters are ill-suited for impure fluids such as wastewater or slurries, as the suspended soils can clog or slow the reciprocating elements and create inaccurate readings.

Electromagnetic Flow Meters

Pros

• Obstruction-less/No moving components
• Highly accurate-unaffected by density, viscosity, turbulence, or pipe configuration
• Can handle wide flow ranges & multiple fluid types
• Zero pressure drop
• Bi-directional
• Cost-effective

Cons

• Cannot measure gases, vapors, or non-conductive liquids
• Limited fluid temperature range
• Interference possible with certain suspended fluids
• Specialized subsets can be expensive

 

Electromagnetic flow meters, also known as magnetic flow meters or magmeters, are rather unique in the technology they use to measure flow. Magmeters feature two parts, a transmitter and an inline sensor, the latter of which features coils that generate a magnetic field. When a conductive fluid passes through the field, a voltage is produced proportional to flow. This flow principle is known as Faraday's Law.

 

 

Unlike other meters, magnetic flow meters can measure fluids regardless of fluid density, viscosity, or flow turbulence. This makes mag meters highly accurate and reliable across a wide range of solutions. Additionally, their design features no obstructions in the pipe, making these meters ideal for a wide spectrum of applications, from highly sanitary liquids to slurries and highly corrosive fluids. Electromagnetic meters can be found in industries such as pulp and paper, metals and mining, food and beverage, water and wastewater, chemical transfer, and many more.

 

Magnetic meters, however, only work with conductive fluids. This means hydrocarbons such as oils, gasoline, or deionized liquids are not recommended with mag meters. Suspended solids, such as those found in various ag chemicals and fertilizers, can also sometimes pose a problem. The suspended soils, which may not be conductive, can interrupt the magnetic field and throw off the reading's accuracy. Newer, specialized magmeters such as slurry magmeters are engineered to counteract this magnetic interference. However, these units generally feature heftier price tags compared to standard models.

Turbine Flow Meters

Pros

• Highly accurate
• Cost-effective
• Capable of measuring low flow rates
• Versatile applications-simple, reliable design

Cons

• Not recommended for dirty or suspended liquids
• Require straight pipe runs for best results
• Limited to certain pipe sizes
• High flow rates can cause damage or inaccuracies
• Moving components need regular maintenance and replacement

Like paddlewheel or propeller flow meters, turbine meters feature a multi-bladed rotor mounted inline to fluid flow. Sensors attached to one or more of the turbine blades transmit the number of revolutions the turbine makes. The speed at which these revolutions happen is proportional to volumetric flow rate. Similar to positive displacement meters, turbine and paddlewheel meters only measure flow when fluid mechanically acts upon their metering components.

 

 

Because turbine meters provide accurate readouts in relation to linear flow-even at low flow rates-they are widely used in the oil and natural gas, custody transfer, and petrochemical industries. In fact, turbine meters are often used to help verify the accuracy of other meter types.

Turbine meters aren't without their limitations, though. For starters, turbine meters are not well suited to handle dirty or highly viscous fluids, as the turbines can be easily fouled by the soils. These meters also require straight runs of pipe before and after the meter to stabilize flow for the most accurate results. Additionally, larger pipe diameters are incompatible from an engineering standpoint. This limits where and for what applications turbine meters can be installed. Finally, as with any technology with moving components, regular maintenance is necessary to keep these meters in peak-performing condition.

Coriolis Flow Meters

Pros

• Extremely accurate
• Low maintenance
• Can handle a wide spectrum of flow ranges
• Compatible with many dirty, corrosive & difficult to handle fluid types
• Versatile installation-no straight pipe runs required
• Serviceable without removing from the pipeline
• Easy in-field calibration
• Capable of measuring gases

Cons

• Expensive initial investment
• Not suited for low-pressure gases
• Limited to certain pipe sizes

Coriolis meters, more commonly known as mass meters, differ from other meter types in that they measure mass flow instead of volume flow. These meters also feature a unique means of calculating flow rate based upon the Coriolis Principle. Check out the video below for a quick look at Coriolis meter technology.

 

Advantages of Mass Meters

Mass meters generally hold an NTEP certification and are widely used in legal-for-trade (resale) applications. In the Dultmeier Sales world, this generally means fertilizers or chemicals with respect to the agricultural industry. Back in the s, Dultmeier Sales partnered with Kahler Automation to offer some of the first automated solutions for fertilizer/chemical plant automation.

The mass meter was at the heart of the system because it was new technology that allowed end-users to sell using the real-time density of the product - a truer way to meter liquids. For example, water is known to be 8.34 lbs. per gallon at 70°F. However, as temperature drops, the weight of water increases. Thus, the solution of water becomes denser as the ambient temperature drops. This would mean static volumetric calculations would be off if one pumped gallons of water and converted to 834 lbs. (using 8.34lbs/gal as the constant conversion factor) if the water were only 50°F.

This same principle happens with fertilizer and chemicals - as they are generally water-based solutions. Volumetric meters of the time; however, were unable to account for this change in density in relation to volume flow. Take this scenario for example, which was quite common in the s and early s:

Let's say that it's 40° F. and we're loading a 10,000 gallon tender trailer, running 32% Nitrogen into the vessel. We're using a paddlewheel meter as our measuring device and pumping the product into the vessel. Once we reach our hit point of 10,000 gallons - the automated equipment shuts down and we send our trucker to the scale. The scale breaks in 20 lb. increments.

Our potential for error:

• Paddlewheel meter runs at approx. +/- 2% accuracy (mass meter is +/- .3% accuracy)
• Paddlewheel cannot determine density reading, so we have a static calibration factor that was calibrated at 70° F. (or another temperature) and we are using that static factor to now calibrate pounds to gallons at 40° F.
• Scale breaks in 20 lb. increments vs. mass meter measuring in increments of 1/10th of a pound
• Scale cannot account for "slosh" or movement of liquid as truck stops abruptly on the scale

Considering these many variables and the potential for error, it's no wonder why inventories could, and often would, be way off come year-end. We know that a solution's density changes constantly if in an ambient environment. For this reason alone, mass meter technology is the preferred method of measurement in many instances. By using a mass meter that can continually read this fluctuation in density on the fly, we offer our customers a better method to dispense and record inventory.

Today, Dultmeier works with Easy Automation Inc. to provide automated plant solutions using mass meters in addition to other state-of-the-art meters, controls, and equipment.

Flow Meter Price, Performance & Popularity

Unfortunately, there is no universal flow meter that works for every application. Depending on how diversified your operation is, that could mean multiple types of flow meters are needed. While it is fair to research the most popular meters for your industry, don't buy the first meter you think will work.

Price, quality, and other key factors do play a significant role in a flow meter's overall performance. Simply because everyone else uses a certain meter does not mean you should be. Low purchase cost, for instance, shouldn't be the deciding factor in choosing the best flow meter for your application. When choosing a flow meter, you have to consider not only the initial purchase price, but the overall lifetime costs and long-term returns on investment, too.

 

For instance, while a Coriolis meter boasts a hefty price tag at initial investment, it provides a great ROI because less maintenance and greater product savings are realized over the long run. Mass meters' exceptional accuracy, versatile flow ranges, and fluid compatibilities, minimal wearable parts, and the ability to recalibrate without removing the meter from the pipeline all translate to fewer dollars spent overall. When it comes to the bottom line, spending more money upfront can outweigh years of hemorrhaging dollars spent repairing or replacing inefficient meters.

That said, not every operation needs an expensive, high-end flow meter. It's a good idea to run a cost assessment evaluating application needs against initial investment costs and long-term cost savings. This way you have the best picture of whether a certain meter is practical or worth the price tag over the long haul. If you need help assessing meter options and determining what is best for your application(s), we are always just a call away at 1-888-677-.

Final Words

We hope this article has provided some insight into the world of flow meter solutions. Although we covered some of the most common types, these are by no means the only flow meters out there. Choosing the best type of flow meter for your application all starts with knowing what you need and researching your best options. Compare all associated costs-both short and long-term-and avoid making a decision based on price tags alone. Ultimately; however, the manner in which you choose to meter is entirely up to you.

If you have any questions regarding flowmeter selection, give us a call at 888-667- or dultmeier.com. Dultmeier Sales carries a diverse inventory of chemical and water flow meters, flow meter repair parts, and flow meter accessories. No matter what meter your operation requires, our experience and technical expertise will help make sure you select the right one.

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