Founder's Archive

Part 1 of this two-part series by Sierra founder, Dr. John G. Olin, describes the principle of operation of a new microprocessor-based thermal dispersion mass flow meter that uses four temperature sensing elements in its flow sensor and has a dry velocity sensor. Part 1 shows how this unique system provides automatic management of changes in gas selection, gas temperature, gas pressure, and outside temperature. This Part 2 describes advances in the installation and flow calibration of thermal dispersion mass flow meters, including a built-in flow conditioner for in line air flow meters that greatly reduces upstream straight-pipe requirements and a high-performance flow calibration facility that accommodates a range of gases, temperatures, and pressures. 

This by Sierra founder, Dr. John G. Olin,paper describes a newly developed microprocessor-based thermal dispersion mass flow meter that uses four temperature sensing elements in its flow sensor instead of the traditional two elements and automatically manages changes in gas selection, gas temperature, gas pressure, and outside temperature. This new mass flow meter is ideally suited for apportionment applications in natural gas distribution systems.

This paper describes capillary tube mass flow meters and mass controllers for use in general purpose industrial and laboratory applications and in the fabrication of semiconductor devices.

It provides a detailed description of the major components---flow body, flow conditioner, bypass, capillary sensor tube, control valve, and electronics. Flow ranges and specifications for which this technology is best suited are presented. The paper explains the principle of operation; describes gas conversion factors that provide multi-gas capability in a single instrument; lists best practices for users, including the selection, installation, and operation of the instruments; and concludes with a discussion of preferred methods of flow calibration.

Interested in learning more? Check out our other digital flow meter resources below.

John Olin, founder and CEO of Sierra Instruments, Inc., in Monterey, California, provides a historical perspective on the development of thermal mass flow.

Thermo-Systems, Inc. (TSI) began in its founder’s basement in 1959, with a cooled-film anemometer designed for transient measurements in high temperature fluid flows. This led to TSI’s hot-film and hot-wire anemometers, the first commercial products of this type. These immersion-type devices were used mainly as research instruments, many related to environmental pollution.

A flow meter quantifies the movement of a fluid including gas, liquid and steam through closed conduits. Flow can be measured by several types of technology. Mechanical flow meters are positive displacement meters such as turbine meters and variable area meters. These flow meters fill with a fixed volume of fluid and then are divided by the time gives the flow rate. Other flow meters are based on measuring the differential pressure like Venturi or orifice plates. Differential pressure devices traditionally have fast response, but measure volumetric flow and must calculate mass flow.

However, thermal mass flow technology is an industry standard for mass flow control of gases because it measures flow directly at the molecular level. In essence, counting and controlling every gas molecule flowing through the instrument to achieve unmatched precision. The molecular mass or weight of the flowing gas is what you really care about when optimizing your flow process. Because thermal mass flow controllers measure gas mass flow rate directly, they remain unaffected by temperature or pressure effects. It doesn’t matter how hot or cold the gas is or what pressure fluctuations may be happening upstream. You always get smooth, steady, accurate and extremely reliable gas mass flow rate delivered where you need it, every time.

Learn more about gas flow measurement and find out more in this in-depth white paper from Sierra CEO & Founder Dr. John G. Olin.

For gas mass flow measurement and control, Sierra offers the broadest selection of thermal mass flow measurement products on the market. This is because our thermal mass flow control products incorporate two types of advanced thermal technologies, each complimentary to the other and each with unique advantages. These two thermal sensing technologies directly measure gas mass flow based on principals of heat transfer and are commonly called Capillary Thermal Sensor Technology and Immersible Thermal Sensor Technology.

Interested in learning more? Browse our other digital flow meter resources below.

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Thermal dispersion (TD) mass flowmeters measure the mass flowrate of fluids (primarily gases) flowing through a closed conduit, such as a pipe. This article describes the operation and installation of TD mass flowmeters, and gives the reader information about what applications these meters are most suited for.

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Thermal flowmeters came onto the market in the mid-1970s, not long after Coriolis flowmeters. While the worldwide market for Coriolis flowmeters now exceeds $1 billion, the market for thermal flowmeters is under $150 million. Faced with such a wide difference in market share, one might wonder why the Coriolis flowmeter market has developed so rapidly, while the thermal flowmeter market has developed more slowly.

To answer this question, it is important to understand some important differences between Coriolis and thermal flowmeters. Coriolis meters, for example, measure both liquids and gases, while the vast majority of thermal flowmeters measure gases.

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Gases & Instrumentation had the opportunity to speak with Dr. John G. Olin, Founder and Chairman of the Board of Sierra Instruments about the evolution of thermal mass flow meters and his latest product in this technology.

Read More: The Quest for the Perfect Flowmeter

A mass flow controller (MFC) is used to control the flow of gases in a wide range of microelectronic processes. A well designed MFC maintains a constant flow within 1 percent of the full-scale flow, has a repeatabil­ity of 0.2 percent of full scale, and has a response time of 1 second to reach within 2 per­cent of the desired (command) flow; all of this is in response to any changes in command flow, upstream pressure, downstream pressure, gas temperature, or any other variations imposed on the instrument. For enhanced accuracy, simplicity, and cost-effectiveness the MFG should directly monitor gas mass (molecular) flow without the separate measurement of tem­perature and pressure.

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Monterey, CA — July 8, 2015 — For the first time, oil/gas engineers can field adjust their gas composition on thermal mass flow meters in the field for flare, Vapor Recovery Unit (VRU), and storage vessels without sending the meter back to the factory for recalibration with Sierra’s QuadraTherm 640i/780i with qMix gas mixing software.

Sierra’s new gas mixing software package included with every QuadraTherm 640i/780i thermal mass flow meter on a beta trial basis is a unique feature of the Smart Interface Program (SIP), unlike anything available on the market for industrial mass flow meters.

qMix is a user-customizable gas mix feature that allows oil/gas engineers and operators to create custom gases or gas mixtures to compensate for gas compositional changes in the field without accuracy loss. This means oil/gas engineers can easily meet US EPA Directive 40 CFR Part 98 for shale gas upstream production operations since they can use qMix when the gas composition changes in the pipe, or when moving the meter to another location with a different gas composition.

Check out how the qMix creates custom gas mixtures for the QuadraTherm 640i/780i.
 

Customer Benefits
QuadraTherm with qMix Gas Mixing Software allows end users to:

• Field adjust and maintain flow meter accuracy if gas composition changes
• Avoid costly recalibration; once qMix has been installed, no need to send unit back to the factory if gas composition changes
• Quickly create and upload unlimited gas mixtures onto one meter–free of charge 
• Save custom gas mixtures onto your personal “My Gases Database” for later use  
• Benefit from Sierra’s proprietary, ever-improving qTherm “Gas Database” to download more accurate gases

Traditionally, thermal mass flow meters are calibrated using the exact gas mixture they are intended to measure, or a surrogate mixture with very similar properties. In many industrial applications, like oil & gas and biogas measurement, the gas composition changes from the original calibration. When changes in gas composition occur in the field, the accuracy of the flow meter is adversely affected. In the past, the only way to correct for a change in gas composition was to return the meter to the factory for gas recalibration. QuadraTherm with qMix provides a dynamic solution to this problem by allowing end users to manage gas composition changes in the field right from the Smart Interface Program (SIP)—without ever sending the flow meter back to the factory to recalibrate the meter for the new gas composition.

Sierra’s QuadraTherm 640i/780i with qMix is the perfect solution for challenging shale gas upstream production applications.

The QuadraTherm provides the best accuracy +/- 0.5% of reading above 50% of full scale for flow meter air measurement and other gases; built-in flow conditioning (inline version); has high turndown to handle low flows to high flows during upset conditions; multivariable outputs; flow ranges up to 60,000 sfpm (305 smps); qTherm®, Dial-A-Gas®, Dial-A-Pipe™; accurately measures very low pressure vapors with no pressure loss; and has Hazardous Area approvals (ATEX, IECEx, CE, cFMus). The QuadraTherm is available in two models: the 640i insertion and 780i inline.

The QuadraTherm family has a no-drift sensor with lifetime warranty; has multivariable output: mass flow, temperature, pressure (optional); measures all inert and all non-condensing clean gases; flammable gases (methane, propane, hydrogen, and digester gas); repeatability for mass flow rate is +/- 0.15% ; ValidCal™ Diagnostics to validate calibration in the field; gas accuracy is +/- 1°C (1.8°F); and includes above-mentioned qMix.



About Sierra
A global leader in flow measurement and control for over 40 years, Sierra instruments designs and manufactures high performance flow instrumentation for gas, liquid and steam applications commonly found in the pharmaceutical, scientific research, health, energy and semi-conductor industries. With over 150 offices in 50 countries, Sierra is uniquely positioned to provide their innovative products and lifetime support for the leading companies of today and the growth enterprises of tomorrow and lifetime support for the leading companies of today and the growth enterprises of tomorrow.