Showing posts with label thermal mass flow meter. Show all posts
Showing posts with label thermal mass flow meter. Show all posts

Mass Flow Controllers for Precise Dosing

mass flow controller cutaway view
Mass Flow Controller - Cutaway View
Image courtesy Brooks Instrument 
There are processing applications that require very accurate flow or dosing control of added constituents. The applications are diverse, ranging from controlled gas flow to precise metering of product fluid components. The ability to accurately and reliably measure and regulate mass flow of a fluid into a process is a common task in process measurement and control.

Thermal mass flow measurement, in basic operation, infers mass flow by measuring the heat dissipation from a heated temperature sensor and comparing it to an unheated reference temperature sensor. The heat dissipation is directly proportional to the mass flow of gas or liquid.

Thermal mass flow meters 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.

For a process control application, accuracy and real time delivery of measurement data are key factors. Advanced smart controls with a range of communications options that will interface with a variety of devices across a choice of platforms bring high levels of functionality and ease of use to an application. For gas applications, smart technology allows one device to be applied to multiple gas types and ranges without removing the flow meter from the system. Product selection is enhanced by the availability of instruments targeted at a range of applications.

Share your flow measurement and control challenges with process measurement and control specialists. Leverage your own process knowledge and experience with their product application expertise to develop effective solutions.

Thermal Mass Flow Meter Q&A From Magnetrol

thermal mass flow meter
Thermatel® thermal mass flow meter
Courtesy Magnetrol®
Sometimes you discover that others do something better than you. When that happens, watch and listen.

Tom Kemme, from Magnetrol®, expertly fielded some questions about thermal mass flow meters in a recent blog post. Mr. Kemme's responses were so useful and clear that I decided, with all the credit flowing his way, to share them here for those of you that may not closely follow the Magnetrol® Blog.

Question: What is the difference between the flow units Nm3/h, Sm3/h, and actual m3/h?

Answer: Actual m3/h is a flow rate at operating temperature and pressure. Normal or standard m3/h (Nm3/h = Sm3/h) is a flow rate at standard temperature and pressure (STP). I tend to reference the natural gas industry, where it is not possible to compare flow rates at every operating condition, so it is preferable to reference all flow rates back to a set of base conditions, such as 60°F and 1 atm. STP is not universal so it may be unique based on the region or industry.

Most flow meters output a flow rate at operating conditions and need to correct this measurement. This may be accomplished with a multivariable transmitter or external to the device. A few examples that do not need to correct the measurement are thermal mass flow meters, such as the ones produced by MAGNETROL, and Coriolis flow meters.

Question: Do you have any certified failure rate data on your units to perform an SIL verification?

Answer: A Failure Modes, Effects, and Diagnostics Analysis (FMEDA) is completed during development to determine failure rates and Safe Failure Fraction (SFF). The SFF is utilized to determine Safety Integrity Level (SIL), which is often the published value.

Question: What should my meter be reading with no air flow in the pipe?

Answer: At zero flow and a dry pipe, a thermal mass flow meter should measure zero. Different thermal meters may have varying stability at no flow due to differences in operation.

There are two different types of operation: constant temperature (CT) and constant power (CP). CT devices start with a low power and this power increases with the flow rate to maintain the constant temperature difference (ΔT) between the RTDs. CP devices start with a high ΔT between RTDs at low flow and the ΔT decreases as the flow rate increases. CP may lack stability at zero flow due to possible convection currents associated with the high ΔT. CT will hold zero better, particularly devices that add less heat. For example, the maximum surface temperature of a TA2 probe is 4 C above process temperature. This is extremely low heat, eliminating convection currents due to the sensor. Convection currents could also occur through the pipe due to temperature variations.

It is also possible for a thermal meter to measure above zero during a no flow condition when there is pressure buildup in the line (typically a valve closed downstream). There may be low flow cutoff settings that can be changed to ignore nuisance measurements.


You can easily tap into Magnetrol® expertise to solve your flow measurement challenges. Reach out to a product specialist and combine your process knowledge with their flow measurement expertise to develop effective solutions.

Measuring Flare Gas Mass Flow

Industrial Thermal Mass Flow Meter for flare gas applications
Model TA2 Thermal Dispersion
Mass Flow Meter
Courtesy Magnetrol
Industrial processing of fluids often requires the measurement of mass flow. Whether for purposes of process control or regulatory compliance, accurate measurement of fluid mass flow is an important element of industrial processing.

In the oil and gas industry, hydraulic fracturing operations release substantial quantities of natural gas. Gas wells will coincidentally release gas during completion, called flow back. Gas is also a common byproduct of oil wells and a number of other processes unrelated to petroleum production. Some operations lack the equipment and infrastructure to collect the unwanted gas and it is flared off (burned) or vented.

Compliance with state and federal regulations imposes requirements on numerous industry segments to conduct certain measurements of gas quantities flowing to different points of processing, release, or transfer. The regulatory requirements are stringent, and present a challenge to the manufacturers of mass flow measurement instruments and process engineers to achieve a cost effective solution in the face of:
  • Highly Variable Flow Rates - Production can range  from near zero to extreme bursts during upset conditions.
  • Variable Media Temperature - Depth of the gas source, or another factor, can impact temperature
  • Low Process Pressure - The flare headers usually operate near atmospheric pressure
  • Variable Composition - The components and density of the gas can change over time.
  • Difficult Maintenance - Instruments may need to be installed at locations that are hazardous and not easily accessed
The best mass flow measurement solution will effectively accommodate the challenges at each site. Thermal mass flow measurement is one technology that provides a good approach. Examine the paper included below, documenting performance of the TA2 Model manufactured by Magnetrol. Thermal mass flow measuring devices offer cost and other advantages over several competing technologies. 

Share your mass flow measurement challenges with a product application specialist. Combine your process knowledge with their product application expertise to develop the best solution. 

Simple Field Verification of Thermal Mass Flow Meter Calibration

Magnetrol brand industrial thermal mass flow transmitter for measuring mass flow of air and gases
Magnetrol TA2 Thermatel
Thermal Mass Flow Transmitter
Courtesy Magnetrol
In processes that require mass flow measurement of gases or air, thermal dispersion measurement technology is often selected for use. Its direct mass flow measurement and other attributes make this technology a favorable alternative for many applications, including combustion air, compressed air, natural gas, aeration air, vent lines, biogas production, vent lines, hydrogen lines, and more.

schematic of dual sensors on thermal mass flow meter
Schematic depiction of dual
temperature sensors on a
thermal mass flow meter
Courtesy Magnetrol
As it name implies, a thermal mass flow meter calculates flow by using temperature measurements. Two temperature sensors are inserted into the flow path. One measures the media temperature, the other is heated by a measured power source. With a device factory calibrated for a specific medium, the amount of heat transferred away from the heated sensor can be known, and will be proportional to the mass flow rate of the medium.

Some of the key attributes of thermal mass flow measurement devices:

  • Comparatively moderate initial cost
  • Compatible with measurement of low density gases that cannot be achieved with some other methods
  • Provides direct mass flow measurement
  • Most devices have option for output of process temperature
  • High turndown, with strong signal at low flow rates
  • Field calibration verification
Verifying the proper operation of transmitters of any type can be challenging, especially if performed in the field. The video below demonstrates how the Magnetrol TA2, a thermal mass flow transmitter, can have a calibration verification performed on site with a simple procedure.

The video is short and concise, with some valuable technical knowledge to build your understanding of how this technology works. More detailed information about mass flow measurement, or the specific devices shown in the video, is available from a product application specialist. Share your process measurement and control challenges with them and collaborate to develop the best solution.



Thermal Mass Flow Controller - Product Enhancement

Brooks Instrument SLA 5800 Thermal Mass Flow Meter
Newly Enhanced Thermal Mass Flow Meters
And Electronic Pressure Controllers
Courtesy Brooks Instrument
Brooks Instrument, world recognized leader in thermal mass flow controllers and mass flow meters, has improved upon its premier family of smart digital thermal mass flow controllers and meters. The newly enhanced SLA Series features:

Enhanced temperature stability
Upgraded electronics
Improved accuracy
Zero-drift diagnostics
High turndown ratio

Multiple communication protocol support, and more.

The video included below will show you all the latest improvements on this product line that has thousands of units in its installed base throughout many industries and applications.

Application assistance and detailed information is available from product specialists. Combine their product and application knowledge with your own process expertise to generate a positive outcome.