Basics of Rotameters

Rotameters, also referred to as variable area flow meters, have diverse industrial processing applications that range from simple to sophisticated. The devices are easy to install, require no electrical connection, and provide direct flow rate reading. They provide fail-safe flow rate readings in a wide array of industrial applications.

Rotameters: An Overview 

Developed by German inventor Karl Kueppers in 1908, Rotameters measure the volumetric flow rate of liquids and gases.

Important elements of a rotameter (variable area flow meter) include the tube and the float. Their operation is simple. The tube is fixed vertically and the fluid is fed from the bottom. It travels upward and exits from the top. The float remains at the bottom when no liquid is present and rises upward when fluid enters the tube.

The float inside the tube moves in proportion to the rate of fluid flow and the area between the tube wall and the float. When the float moves upward, the area increases while the differential pressure decreases. A stable position is reached when the upward force exerted by the fluid is equal to the weight of the float. A scale mounted on the tube records the flow rate of the liquid. Usually, the flow can be adjusted manually using a built-in valve.

Types of Rotameter 

Variable area flow meters can be categorized by the type of tube they use, which relates to their ability to withstands various pressures, temperatures, process media, and cost. Process connection size and wetted part materials vary as a function the rotameter type and construction.

Glass Tube Rotameter
(Yokogawa)

Glass Tube Rotameter - The basic glass variable area flow meter consists of borosilicate glass tube while the float is made of either glass, plastic, or stainless steel. The most common combination is a glass tube and metal float. This is suitable for a measure the flow rate of liquid of low to medium temperatures and pressures.

Applications:

• Analytical instrumentation
• Industrial processes
• Chemical production
• Pharmaceutical production
• Oil & gas extraction
• Refining processes
• Fuel cell research
• Water treatment systems

Metal Tube Rotameter
(Yokogawa)

Metal Tube Rotameter - Metal tube variable area flow meters are another type that is suitable for temperatures and pressures beyond the physical and mechanical limits of glass tube versions. They are generally manufactured of stainless steel, aluminum, or brass. The piston position is determined by the mechanical and magnetic followers that can be read from the outside of the tube. They are suitable in situations where applications conditions would damage the glass metering tubes, such as steam applications.

Applications:

• Purge liquid/ gas metering
• Liquid, oil, or gas flow measurement
• Chemical injection
• Rotating equipment flow measurement
• High-pressure flow meters on offshore oil platforms

For more information, contact Classic Controls.
https://classiccontrols.com
863.644.3642

University Campuses Greatly Reduce Energy Costs Retrofitting with Clamp-on Thermal Energy Meters

Flexim Clamp-on Thermal Meter

The cooling and heating of a university campus is one of the primary areas where better energy management, including improved efficiency and energy reduction, brings some of the highest returns.

Every university to some extent is now engaged in this process, and one of the first things that has to be addressed is the metering of distributed thermal energy. To effectively begin energy reduction initiatives, accurate and reliable thermal energy metering has to be in place.

Today, there is high priority for understanding that we need to be better stewards of energy consumption. Poor energy consumption harms the environment and creates much higher operating costs. Universities have become very involved in the move toward greener energy. Many universities began metering long ago while some are just beginning. Most are in the middle of the process.

Installation of clamp-on thermal meter (click for larger view).

Installation in under 4 hrs. (steps from image above):

• Step 1: Cut insulation where transducers and RTD will be located.
• Step 2: Install stainless bands around pipe under insulation.
• Step 3: Install transducers and RTD.
• Step 4: Cover transducers and RTD with insulation and tape.

There are many different types of meters, and often, many of these choices turn out to be unreliable. In order to achieve real accountability for energy usage at campus buildings, energy managers at leading universities are applying a “utility model.” In the utility model, building managers responsible for campus buildings are billed at utility grade costs for the thermal energy consumed. This creates an environment where focus falls to thermal energy conservation. It’s also vital that inefficiencies are identified and corrected through metering.

Many universities have gone through an evolution of trying to meter thermal energy consumption throughout their campus. The success of these ventures can be elusive when the meter chosen for the job doesn’t live up to expectations. Examples include insertion meters that over time will foul and meters that cannot respond to low velocities that are prevalent during off-peak metering.

On proven alternative is FLEXIM’s Thermal Energy / BTU Flow Meter. The technology, based upon FLEXIM's ultrasonic clamp-on meters, do not require shutdown and are very cost effective to install.

Clamp-on ultrasonic meters have been doing the job of BTU-metering for decades and the Flexim thermal energy meters are leading the effort towards more energy efficient buildings and facilities.

More than 150 colleges and universities throughout the country are using the FLEXIM product as their preferred thermal energy meter and attest to FLEXIM’s performance, reliability and support.

For more information on Flexim thermal energy products, contact Classic Controls by visiting https://classiccontrols.com or by calling 863-644-3642.

Fox Thermal Instruments Releases New Gas Flowmeter Targeted at Oil and Gas Operations

The FT4X thermal mass flow meter accommodates
inline, insertion, and retractor installations.
Image courtesy Fox Thermal Instruments, Inc.

Keeping up to date on the latest product information....

Fox Thermal Instruments, an acknowledged innovator in thermal mass flow technology and instruments, has released a flow meter targeted for gas flow measurement in the oil and gas industry. The FT4X delivers a long list of advanced and useful features for flare and waste gas monitoring, gas studies, royalty and allocation, and general gas flow research.

The instrument utilizes a constant temperature differential technology to measure gas or air mass flow, employing two precision RTD sensors. One temperature sensor follows the media temperature, while the other is heated by the instrument electronics to maintain a constant temperature differential between the two sensors. The amount of applied heat to maintain the differential is proportional to the mass flow rate. A linearized 4-20mA output signal is the final output of the transmitter.

The flow meter is available for inline or insertion installation, along with another variant that features retraction of the instrument from the line without flow interruption. Various probe lengths accommodate line sizes to 70 inches. Flow bodies, flow conditioners, and other accessories are available to customize the instrument assembly to fit each application.

There is a wealth of additional information provided in the brochure included below. Share your flow measurement challenges and requirements for process measurement specialists. Leverage your own knowledge and experience with their product application expertise to develop effective solutions.

Thermal Mass Flow Meter for Oil & Gas Applications from Classic Controls, Inc.

Ultrasonic Clamp-On Flowmeter with SIL 2 Rating

FLUXUS F/G70X and F/G80X series meters
Image Courtesy Flexim

Measuring the flow quantity of gases and liquids is a common industrial processing task. There are numerous technologies available for measuring fluid flow, each with its own set of advantages and drawbacks for any particular application. Some of the technologies and methods have been in use for a very long time, with recent enhancements provided by electronics or smart sensor designs.

Ultrasonic flow measurement devices employ a comparatively recent technology to measure gaseous or liquid flow. Whether the transit time differential or Doppler method is utilized, ultrasonic flow meters have a distinctive characteristic in that they can be deployed in a form factor that does not require contact with the the process fluid, nor insertion in the fluid flow path. A common installation method is to clamp the ultrasonic transducer assembly onto the exterior of a process pipe. This makes the technology attractive for applications that involve adding a flow measurement point to an existing piping system.

Flexim, a globally recognized leader in ultrasonic flow measurement, offers a number of permanent and portable units for measuring liquid and gaseous flow rates. Some of their instruments have been certified as SIL 2 capable, along with a host of other third party certifications. The product range includes simple and accurate instruments designed for general industrial use, and extends to multi-beam units intended for applications, such as custody transfer of fluids, that require the highest accuracy and overall performance levels.

Share your flow measurement challenges and requirements with instrumentation specialists, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Ultrasonic Gas Flow Measurement from Classic Controls, Inc.

Flexim Wins Recognition for Innovative Flow Measurement

Flexim F704 Ultrasonic Flow Meter
Image courtesy Flexim Americas

Flow Control Magazine, which targets solutions for fluid movement, measurement and containment, handed out its annual Innovation Awards recently. Among those receiving honorable mention was Flexim Americas Corporation, for the Fluxus Cryo that provides noninvasive measurement of cryogenic fluids. Special design adaptations prevent ice build up on the measurement apparatus that that can plague other technologies.

Ultrasonic flow measurement offers some distinct advantages over other available methods, with high accuracy, no intrusion into the media, and no moving parts. While the award was specifically for a cryogenic application, Flexim ultrasonic flow measurement instruments are available for an extensive array of applications.

For more information, share your flow measurement requirements and challenges with process instrumentation experts, leveraging your own process knowledge and experience with their product application expertise to develop effective solutions.

Magnetic Flow Meters: Principles and Applications

Magnetic flowmeters are well suited for flow measurement

with conductive fluids.

Image courtesy Yokogawa

Fluid process control operations rely on the operator's ability to accurately determine qualities and quantities of liquid or gaseous materials. In terms of appraising and working with fluids (such as liquids, steam, and gases) the flow meter is a staple tool, with the simple goal of expressing the delivery of a subject fluid in a quantified manner. Measurement of media flow velocity can be used, along with other inputs, to determine volumetric or mass flow. The magnetic flow meter, also called a magmeter, is one of several technologies used to measure fluid flow.

In general, magnetic flow meters are sturdy, reliable devices able to withstand hazardous environments while returning accurate measurements to operators of a wide variety of processes. The magnetic flow meter has no moving parts. The operational principle of the device is powered by Faraday’s Law, a fundamental scientific principle stating that a voltage will be induced across any conductor moving at a right angle through a magnetic field, with the voltage being proportional to the velocity of the conductor. The principle allows for an inherently hard-to-measure quality of a substance to be expressed via the magmeter. In a magmeter application, the meter produces the magnetic field referred to in Faraday’s Law. The conductor is the fluid. The actual measurement of a magnetic flow meter is the induced voltage corresponding to fluid velocity. This can be used to determine volumetric flow and mass flow when combined with other measurements.

The magnetic flow meter technology is not impacted by temperature, pressure, or density of the subject fluid. It is however, necessary to fill the entire cross section of the pipe in order to derive useful volumetric flow measurements. Faraday’s Law relies on conductivity, so the fluid being measured has to be electrically conductive. Many hydrocarbons are not sufficiently conductive for a flow measurement using this method, nor are gases. On the other hand, water and aqueous solutions tend to exhibit sufficient conductivity to apply magmeter technology.

Magmeters apply Faraday’s law by using two charged magnetic coils; fluid passes through the magnetic field produced by the coils. A precise measurement of the voltage generated in the fluid will be proportional to fluid velocity. The relationship between voltage and flow is theoretically a linear expression, yet some outside factors may present barriers and complications in the interaction of the instrument with the subject fluid. These complications include a higher amount of voltage in the liquid being processed, and coupling issues between the signal circuit, power source, and/or connective leads of both an inductive and capacitive nature.

In addition to salient factors such as price, accuracy, ease of use, and the size-scale of the flow meter in relation to the fluid system, there are multiple reasons why magmeters are the unit of choice for certain applications. They are resistant to corrosion, and can provide accurate measurement of dirty fluids – making them suitable for wastewater measurement. As mentioned, there are no moving parts in a magmeter, keeping maintenance to a minimum. Power requirements are also low. Instruments are available in a wide range of configurations, sizes, and construction materials to accommodate various process installation requirements.

As with all process measurement instruments, proper selection, configuration, and installation are the real keys to a successful project. Share your flow measurement challenges of all types with a process measurement specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Thermal Mass Flow Meters for Combustion Efficiency Control and Monitoring

Example of inline thermal mass flow meter
Image Courtesy Fox Thermal Instruments

Fox Thermal Instruments, a recognized leader in the manufacture of thermal mass flow meters, has authored a white paper entitled "Reduce Energy Costs and Enhance Emissions Monitoring Systems" which provides a technical view of how the use of thermal mass flow measuring technology can be effectively employed on combustion based systems to provide efficient energy usage. Combustion efficiency contributes to the financial benefit of an operation, as well as enabling compliance with emission requirements.

Thermal mass flow measurement is a well regarded mature technology in industrial process measurement and control applications. The instrument returns a mass flow reading by measuring the heat dissipating effect of the media flow on a temperature sensor. Heat transfer is proportional to the mass flow.

The mass flow measurement instruments are very popular for several reasons. They have no moving parts, have a fairly unobstructed flow path, are accurate over a wide range of flow rates, calculate mass flow rather than volume, measure flow in large or small piping systems, and do not need temperature or pressure compensation.

The white paper is provided below for you to read. It is informative and will prove a good investment of time to read. Share your flow measurement challenges of all types with process instrumentation specialists, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Thermal Mass Flow Meters Reduce Energy Costs and Enhance Emissions Monitoring from Classic Controls, Inc.

Flow Measurement - Sometimes the Simple Solution is Best

These variable area flow meters also permit visible
inspection of flowing media
Courtesy ERDCO Engineering Corp.

For process control and commercial or industrial applications, there are numerous methods of flow measurement from which to choose. Technologies range from very simple applications of physical principles to deployment of very specialized electronics and sensors. The available range of accuracy, response, and cost is quite broad, with a general expectation that higher cost will deliver better performance and accuracy.

Making the best instrument selection for a flow measurement application should include an assessment of what the operators really need in order to safely and effectively run the process or perform the task related to the measurement of fluid flow. Installing instrumentation with capabilities far beyond what is required is almost certainly a waste of financial resources, but may also have an unexpected impact on operators. Through the generation of data that, while accurate, does not provide any actionable information about process condition, operators can be misled, similar to the occurrence of a false or nuisance alarm. Some applications call for high accuracy, some do not. Define your informational needs and select instruments that will meet those needs.

There is a large array of applications that can be satisfied with simpler, less costly measurement technology. These devices often employ turbines or vanes to produce an indication of flow rate. Incorporated into some of the instruments is a means to visually observe the flowing liquid to verify color and clarity. Simple devices sometimes are intended only to indicate the presence of fluid flow, and whether the flow rate is high or low. Configurations are available that allow insertion into lines under pressure (hot tap) through a full port ball valve. Other variants with combinations of features and capabilities abound.

The selection range is enormous, so define your minimum needs first, then search for a compatible product. Your search can be enhanced by contacting an instrumentation specialist. Combining your process expertise with their broad product knowledge will produce effective solutions.

Variable Area Flow Meter - SeeFlo from Classic Controls, Inc.

New Thermal Mass Flow Meter

The new model FT4A thermal mass flowmeter, shown
inserted in process pipe.
Courtesy Fox Thermal Instruments

Fox Thermal Instruments, manufacturer of thermal technology based mass flow instruments for industrial process measurement, has introduced a new more advanced product providing the accuracy and reliability users expect from Fox, along with some new features extending the ease of use and applicability of the instrument.

The basic operation involves measuring flow in relation to its heat dissipating effect on a temperature sensor. Higher mass flow produces a higher rate of heat transfer.

The mass flow measurement instruments are very popular for several reasons. They have no moving parts, have a fairly unobstructed flow path, are accurate over a wide range of flow rates, calculate mass flow rather than volume, measure flow in large or small piping systems, and do not need temperature or pressure compensation. While most thermal flow meters are used to measure flowing gas, some also measure flowing liquids.

The new model FT4A incorporates the latest feature updates and technology advancements. More information can be found in the datasheet provided below. Share your gas flow measurement challenges with instrumentation specialists. Combine your own process experience and knowledge with their product application expertise to develop effective solutions.

New Thermal Mass Flow Meter From Fox Instruments from Classic Controls, Inc.

Operating Principles and Application of Vortex Flowmeters

Vortex Flowmeter
Courtesy Yokogawa

To an untrained ear, the term “vortex flowmeter” may conjure futuristic, potentially Star Wars inspired images of a hugely advanced machine meant for opening channels in warp-space. In reality, vortex flowmeters are application specific, industrial grade instruments designed to measure an important element of a fluid process control operation: flow rate.

Vortex flowmeters operate based on a scientific principle called the von Kármán effect, which generally states that a fluid flow will alternately shed vortices when passing by a solid body. “Vortices” is the plural form of vortex, which is best described as a whirling mass, notably one in which suction forces operate, such as a whirlpool. Detecting the presence of the vortices and determining the frequency of their occurrence is used to provide an indication of fluid velocity. The velocity value can be combined with temperature, pressure, or density information to develop a mass flow calculation. Vortex flowmeters exhibit high reliability, with no moving parts, serving as a useful tool in the measurement of liquid, gas, and steam flow.

While different fluids present unique challenges when applying flowmeters, steam is considered one of the more difficult to measure due to its pressure, temperature, and potential mixture of liquid and vapor in the same line. Multiple types of steam, including wet steam, saturated steam, and superheated steam, are utilized in process plants and commercial installations, and are often related to power or heat transfer. Several of the currently available flow measurement technologies are not well suited for steam flow applications, leaving vortex flowmeters as something of a keystone in steam flow measurement.

Rangeability, defined as a ratio of maximum to minimum flow, is an important consideration for any measurement instrument, indicating its ability to measure over a range of conditions. Vortex flowmeter instruments generally exhibit wide rangeability, one of the positive aspects of the technology and vortex based instruments.

The advantages of the vortex flowmeter, in addition to the aforementioned rangeability and steam-specific implementation, include available accuracy of 1%, a linear output, and a lack of moving parts. It is necessary for the pipe containing the measured fluid to be completely filled in order to obtain useful measurements.

Applications where the technology may face hurdles include flows of slurries or high viscosity liquids. These can prove unsuitable for measurement by the vortex flowmeter because they may not exhibit a suitable degree of the von Kármán effect to facilitate accurate measurement. Measurements can be adversely impacted by pulsating flow, where differences in pressure from the relationship between two or more compressors or pumps in a system results in irregular fluid flow.

When properly applied, the vortex flowmeter is a reliable and low maintenance tool for measuring fluid flow. Frequently, vortex flow velocity measurement will be incorporated with the measurement of temperature and pressure in an instrument referred to as a multivariable flowmeter, used to develop a complete measurement set for calculating mass flow.

Whatever your flow measurement challenges, share them with a flow instrument specialist, combining your process knowledge with their product and technology expertise to develop effective solutions.

Digital Vortex Flowmeters From Yokogawa from Classic Controls, Inc.

Thermal Mass Flowmeters

Thermal dispersion mass flow meters provide an accurate means of mass flow measurement with no moving parts and little or no encroachment on the media flow path. There are a number of different configurations to be found among various manufacturers, but all function in basically the same manner.

Two sensors are exposed to the heat transferring effect of the flowing media. When the media composition is known, the mass flow can be calculated using the meter reading and the pipe cross sectional area. One of the flow meter sensors is heated, the other is allowed to follow the media temperature as a reference. The heat dispersion from the heated sensor is measured and used to calculate mass flow.

Some positive attributes of thermal dispersion flow meters:

• In-line and insertion configurations available to accommodate very small to large pipe sizes
• Rugged Construction
• No moving parts
• Measure liquid or gas in a wide range of applications
• Measurement not adversely impacted by changes in pressure or temperature
• Wide range of process connections 
• In-line versions provide unobstructed flow path
• Wide turndown suitable for extended flow range
• Flow rate and totalized flow
• 4-20 mA output interfaces easily with other instruments and equipment

Share all your process measurement challenges and requirements with product application specialists, combining your process knowledge with their product application expertise to develop effective solutions.

Transit Time Differential Ultrasonic Flow Measurement - How It Works

Ultrasonic flow meter, transducer and control unit
Courtesy Flexim

The measure of flow is a pervasive task in fluid process control. There are several differing technologies employed for measuring fluid flow, each with its own set of performance and application attributes that might make it the advantageous choice for a particular operation.

Ultrasonic flow measurement uses several methods for determining the average velocity of a fluid. One of those methods employs the difference in the transit times of ultrasonic pulses travelling with the flow direction and against the flow direction. The flow velocity of the media will offset the transit times between the flow and counterflow measurements. The measured difference in transit times can be used to determine average flow velocity and, with additional processing, mass flow.

Ultrasonic flow meters are accurate and provide repeatable results, making them suitable for custody transfer operations, as well as many other process control applications. Little maintenance is required and the units have no moving parts. Measurement instruments are available with in-line or clamp-on mounting, providing a high level of installation and application flexibility.

The short video below provides a clear explanation of how transit time difference measurement works. Share your flow measurement challenges and requirements with a product application expert, combining your process knowledge with their product expertise to develop effective solutions.

 

Thermal Flowmeters with Constant Temperature Differential (∆T) Technology to Measure Mass Flow Rate of Air and Gases

Thermal Flow Meter
Sensor
Fox Thermal Instruments

Thermal flow meters use a constant temperature differential (∆T) technology to measure mass flow rate of air and gases. The thermal mass flow sensor consists of two Resistance Temperature Detectors (RTD’s). The sensor elements are constructed of a reference grade platinum wire wound around ceramic mandrels that are inserted into stainless steel or Hastelloy tubes.

The reference RTD measures the gas temperature. The instrument electronics
heat the mass flow sensor, or heated element, to a constant temperature and measures the cooling effect of the gas flow. The electrical power required to maintain a constant temperature differential is directly proportional to the gas mass flow rate. The microprocessor then linearizes this signal to deliver a linear 4 to 20mA signal.

One manufacturer, Fox Thermal Instruments, implements a

technology they call the Power Pro™ Sensor. Their sensor operates at a higher power level than other competitive thermal technologies, providing better response time and wider turndown. When compared to a typical differential pressure type flow meter, as shown to the right, the Power Pro™ Sensor offers better low flow or low end sensitivity. The Power Pro™ Sensor also provides exceptional accuracy at high velocities - up to 50,000 SFPM air.

The Fox DDC-Sensor™ is a new state of the art sensor technology used in the Fox Model FT1 Thermal Gas Flow Meter. The DDC-Sensor™, a direct digitally controlled sensor that is interfaced directly to the FT1 microprocessor for more speed and programmability.

Like the Power Pro™ Sensor, the DDC-Sensor™ accurately responds to changes in process variables (gas flow rate, pressure, and temperature) which are used by the microprocessor to determine mass flow rate, totalized flow, and temperature.

In addition to measuring flow, the DDC-Sensor™ provides a technology platform for calculating accurate gas correlations. The FT1 correlation algorithms allow the meter to be calibrated on a single gas in the factory while providing the user the ability to select other gases in the Gas-SelectX® gas menu. Fox’s Model FT1 with its DDC-Sensor™ and state-of-the-art correlation algorithms provide an accurate, multi-gas capable thermal flow meter for gas applications.

Thermal Mass Flowmeter and Temperature Transmitter from Classic Controls, Inc.

Selecting the Right Flow Meter Technology

Vortex Flow Meter
Courtesy Yokogawa Corp.

Magnetic Flow Meter
Courtesy Yokogawa Corp.

Many industrial process control operations require fluid flow measurement as an essential element in the process design. Accurate flow measurement can be obtained with the proper application and installation of a flow meter as part of the fluid transfer system.

Industrial flow meters employ differing technologies to directly or indirectly measure fluid flow rates. Among the many available technologies for fluid flow measurement, vortex flow meters, magnetic flow meters, Coriolis flow meters, and rotameter flow meters are among some of the most common found in industry.

Coriolis Flow Meter
Courtesy Yokogawa Corp.

Rotameter Flow Meters
Courtesy Yokogawa Corp.

Each of the separate technologies have attributes which can make them more suitable to certain applications. Selecting the most appropriate flow measurement technology for an application is one of the initial and crucial steps to designing a well functioning fluid measurement system.

Selection criteria, such as fluid temperature, pressure, and velocity will be part of the selection process. Additional considerations include whether the fluid may be abrasive, corrosive, clean or dirty. The state of the fluid, liquid or gas, must also be considered.

The table below provides quick general guidance on which technologies to consider, based upon the factors outlined above. This will help you better focus further product selection research efforts.

Flow Meter Technology Selection Table
Courtesy Yokogawa Corporation of America

Selecting the right device is not always an easy task, especially since it may be something that you do infrequently. Manufacturers often have knowledgeable local representatives that are experienced in this field and more than willing to contribute their expertise to your selection process.