SI-3501 Thermal Mass Flow Meter

by

What is a thermal gas mass flow meter? A thermal gas mass flow meter is an instrument that measures gas flow rate using the principle of thermal diffusion. It requires no temperature or pressure compensation, making it the preferred product for measuring the flow rate of dry gases. It is widely used in fields such as coal gas, natural gas, compressed air, and semiconductor process gases, effectively monitoring gas flow rate in pipelines.

Thermal Mass Flow Meters
DiameterDN15～DN6000mm
Accuracy±1%
Temp. range-20~350℃
PressureMedium pressure≤10MPa
Flow rate0.1-100m/s
ProtectionIP67 (sensor part)

Benefits:

  • No need Temperature and pressure compensation; the measurement process is simple and accurate.
  • Could measure mass flow or standard volume flow rate of gas.
  • Range ratio 100:1, could measure gas flow from 100Nm/s to 0.1Nm/s, and be used for gas leak detection.
  • Good vibration resistance, long service life. No moving parts or pressure detecting parts, accuracy will not be affected by vibration.
  • Easy installation and maintenance.
  • Adopt an overall digitizing circuit measurement to ensure high accuracy.
  • The flow meter is with RS-485 communication, which could be part of the automation and integration of your facilities.

Specifications

MediumAll gases (except acetylene)
Pipe diameterDN10-80 (Flange type)DN50-6000 (Insert type)
Flow rate0.1-100m/s
Accuracy±1%~±2.5%
Operating temp.SensorDefault type: -10~+200℃ High temp. type: -10~350℃
Transmitter-20~+45℃
Operating pressureMedium pressure≤10MPaMedium pressure≤2.5MPa
Power supplyCompact typeDC24V or AC220V≤18W
Remote typeAC220V≤19W
Response time1s
Output4-20mAOptical isolation, max. load 500Ω
RS485Optical isolation
HART
AlarmOption(1-2 alarm、10A/220V/AC 5A/30V/DC)
Pipe materialCarbon steel, stainless steel, plastic, etc.
DisplayCompact type: 4 lines LCD display
Display contentMass flow, standard volume flow, accumulated flow, time, accumulated time, medium temp., standard flow, etc.
Ingress protectionIP67 (sensor part)
Sensor materialStainless steelStainless / carbon steel

Thermal Mass Flow Meter Working Principle

A thermal gas mass flowmeter is a meter that measures the mass flow of gas using the principle of heat conduction. The sensor of the thermal mass flowmeter consists of two reference thermal resistors (platinum RTD). One is the mass speed sensor T1, and the other is the temperature sensor T2 that measures the temperature change of the gas.

When these two RTDs are placed in the measured gas, the sensor T1 is heated to a constant temperature difference above the gas temperature, and the other sensor T2 is used to sense the temperature of the measured gas.

As the mass flow rate of the gas increases, the airflow takes away more heat, and the temperature of the sensor T1 decreases. To maintain a constant temperature difference between T1 and T2, the heating power of T1 must increase.

Check Wikipedia

Thermal Mass Flow Meter working

According to King’s law of thermal effects, there is a certain mathematical relationship between heating power P, temperature difference △ T (T1-T2) and mass flow Q.

P / △ T = K1 + K2 f (Q) K3

K1, K2, and K3 are constants related to the physical properties of the gas. 

Read more about: Thermal Mass Flow Meter Technology

Featured Applications

Thermal gas mass flow meters are widely used in fields and industries where high accuracy and stability in gas flow measurement are required.

Custom internal thread Thermal Mass Flow Meter
  1. Public Utilities

Biogas; coal gas; natural gas; liquefied petroleum gas (LPG); boiler preheating air.

  1. Oil and Gas Industry

Energy exchange; well filler gas recovery; fuel gas metering; gas quality analysis; leak detection; natural gas measurement; flare gas monitoring.

  1. Power Industry

Gas measurement during gas distribution in fuel systems; measurement of various gases in boilers and auxiliary systems; gas measurement in gas-fired furnaces; hydrogen measurement; measurement of primary and secondary air in power plant blast furnaces.

  1. Chemical Industry

Flue gas circulation monitoring; gas flow measurement in sampling systems; gas flow measurement in induced draft fans; ammonia measurement in fertilizer plants; measurement of various gas flow rates in battery factories.

  1. Metallurgical Industry

Gas measurement in steel plants; blast furnace gas measurement in ironmaking plants; coke oven gas measurement in coking plants; measurement and control of fuel gas (blast furnace gas, coking gas, natural gas, etc.) in steel rolling mills; control of hydrogen, oxygen, nitrogen, and other gases in heat treatment quenching furnaces, etc.

  1. Pulp and Paper Industry

Gas measurement in wastewater treatment systems; flue gas flow monitoring; boiler secondary/tertiary air recovery; boiler fuel gas and air supply measurement.

  1. Food and Pharmaceutical Industry

Fresh air introduction during processing operations; carbon dioxide treatment in breweries; hot air flow rate in bottle sterilizers; gas flow rate measurement during thermal oxidation; ventilation systems; boiler intake, exhaust gas, and process control.

  1. Environmental Protection

Gas measurement during biogas utilization; chlorine gas measurement during chlorine treatment; gas measurement in aeration tanks during wastewater treatment; monitoring of SO2 and NOx emissions from chimney exhaust.

  1. Other Industries

Compressed air measurement in factories; pulverized coal combustion process pulverized gas/air ratio control; hot gas flow control from vertical grinding mills in the cement industry.

IndustryApplication DescriptionTypical Case Studies
Chemical Process ControlMonitor the feed flow rate of reaction feedstocks (such as hydrogen, oxygen, methane, and other gases) to ensure precise reaction ratios, preventing raw material waste or uncontrolled reactions.At a petrochemical plant’s hydrocracking unit, thermal mass flow meters control hydrogen injection to ensure crude cracking efficiency while preventing safety risks from excessive hydrogen.
Natural Gas/Gas MeteringUsed for flow measurement in natural gas extraction, transmission, and urban gas distribution networks, particularly suited for low-pressure, high-flow gas monitoring with accuracy up to ±1%.In residential pressure regulating stations operated by urban gas companies, thermal mass flow meters measure household gas consumption, replacing traditional volumetric flow meters and reducing metering errors caused by pressure fluctuations.
Energy Recovery and Exhaust Gas MonitoringMeasures exhaust gas flow (e.g., flue gas, waste heat recovery gas) from boilers and incinerators to calculate thermal efficiency or pollutant emission concentrations (requires integration with component analysis).At a waste incineration plant’s flue gas treatment system, thermal mass flow meters continuously monitor gas flow rates. Combined with sensors, they calculate total dioxin and NOx emissions to meet environmental standards.
Pharmaceutical Fermentation and SynthesisMonitors sterile air and oxygen feed rates in fermentation tanks, which influence microbial growth rates and pharmaceutical yields (e.g., antibiotic and vaccine production).In a vaccine manufacturer’s CHO cell fermentation tanks, sanitary-grade thermal flow meters regulate oxygen flow to maintain stable cell density and ensure vaccine potency compliance.
Food and Beverage ProcessingMeasure flow rates of food-grade gases (e.g., carbon dioxide for carbonated beverages, nitrogen for fruit/vegetable preservation) or liquids (e.g., syrups, fruit juices) to prevent contamination.At a cola factory’s carbonation process, thermal mass flow meters precisely control CO₂ injection to guarantee consistent carbonation levels in every bottle.
Medical Gas DeliveryMonitor oxygen and nitrous oxide (N₂O) flow rates in hospital central oxygen supply systems and anesthetic gas delivery to ensure patient respiratory safety.In the ICU of a tertiary hospital, thermal flow meters embedded in oxygen pipelines display real-time patient oxygen flow rates and trigger automatic alarms during abnormalities.

Energy efficiency is crucial in compressed air systems, and the key to achieving this lies in accurately measuring the compressor’s flow rate.

While there are different types of compressed air flow meters (flow meters), we need to understand which one is the right fit.

Thermal mass flow meters are simply flow meter probes immersed in the pipeline, thus not disturbing the flow in the pipes and causing no pressure loss.

They are also very robust because they have no moving parts like mechanical turbines.

For these reasons, thermal mass flow meters are one of the suitable choices for compressed air flow measurement equipment.

Read more about: Inline Compressed Air Flow Meters

Industrial nitrogen flow meters are digital flow meters used to measure the flow rate of nitrogen (N2). Nitrogen is an inert gas widely used in various industries. It is required in many processes in the chemical and pharmaceutical industries. It is primarily used as a protective gas to prevent the formation of explosive gas atmospheres, such as when handling dusty products or solvents. In many places, nitrogen, like compressed air, is centrally supplied.

For the measurement of the vast majority of clean nitrogen, the mainstream choice is the thermal mass flow meter. It directly measures mass flow rate without the need for temperature and pressure compensation, simplifying the system. With no moving parts, it has extremely low pressure loss and good energy efficiency (especially suitable for compressed nitrogen).

Read more about: Industrial Nitrogen Gas Flow Meters; Case – Liquid Nitrogen Level Measurement

Natural gas, as a clean energy source, is seeing its usage increase year by year. Accurate flow measurement is crucial during the transportation, distribution, and use of natural gas. Since the composition and physical properties of natural gas can vary depending on its source and processing methods, a measurement tool capable of adapting to these variations is needed.

Advantages of thermal gas mass flow meters in natural gas measurement:

  1. High-precision measurement: Thermal gas mass flow meters directly measure the mass flow rate of a gas, rather than its volumetric flow rate, thus eliminating errors caused by temperature and pressure variations and providing more accurate measurement results.
  2. Wide measurement range: This type of flow meter is suitable for flow rates ranging from extremely low to extremely high, meeting the measurement needs of natural gas in various applications.
  3. Applicable to multiple gases: Because the working principle of thermal gas mass flow meters does not depend on the physical properties of a specific gas, it can accurately measure natural gas with different compositions and densities.
  4. Good stability: Thermal flow meters are insensitive to impurities and particulate matter in the fluid and can maintain stable performance in complex field environments.
  5. In high-pressure natural gas metering, pressure loss is common due to long pipeline distances and the high pressure of natural gas. Thermal gas mass flow meters, with their low pressure loss and wide rangeability, perform exceptionally well in high-pressure metering applications.
  6. Thermal gas mass flow meters feature online plug-and-play functionality, allowing for instrument maintenance while the medium is flowing normally, thus ensuring an uninterrupted natural gas supply.

Read more about: Techniques, Importance, and Challenges of Natural Gas Flow Measurement

Flange installation Thermal Mass Flow Meter

Thermal Mass Flow Meters Types

Thermal mass flow meters are mainly classified into two types: thermally distributed and thermally diffused. They can also be further classified according to installation method and working principle.

Classification by Measurement Principle

  • Thermally Distributed Mass Flow Meter: Utilizes the heat transfer caused by gas flow, measuring gas flow rate by changing the temperature distribution along the measured pipe. Suitable for measuring small flow rates in small-diameter pipes.
  • Thermally Diffusion Mass Flow Meter: Based on thermodynamic principles, often called a King’s flow meter, suitable for measuring larger flow rates. It determines mass flow rate by measuring the heat exchange between the fluid and a heat source.

Classification by Installation Method

  • Insertion Flow Meter: The measuring probe is inserted into the pipe containing the fluid to be measured. Suitable for flow measurement in large and medium-sized pipes.
  • Pipe Section Flow Meter: The measuring probe is fixed within a section of standard pipe. Suitable for applications requiring connection to an actual fluid pipeline.

Order Guide

In addition to regular products, we support customization

SI-3501Thermal mass flow meter
Sensor typeC           Retrench pattern insert type
D           Online pluggable type
E           Flange pipe type
F           Thread pipe type
G           Clamp on type
Pipe diameterC         Round pipe: DN15~DN6000
S         Square pipe: 25*25mm~2000*2000mm
Housing materialA           SUS304
B           SUS316
C           Other material
PressureS            1.6MPa
M           2.5MPa
T            4.0MPa
Temp.I                10~200℃
II              10~400℃
Output1                 4-20mA
2                 RS485
3                 PULSE
4                 Relay contact
5                 HART
PowerDC        24VDC
AC        220VAC
DisplayJ          Integrated display
S         Split display

FAQ

Thermal flow meters and thermal flow switches operate on the same principle. The difference is that thermal flow meters are only suitable for gas measurement, while thermal flow switches are suitable for all fluid measurements, including flow measurement and control of fluids with different thermal properties such as gases, oils, water, slurries, and foams.

More about: Industrial Flow Switches

The accuracy of thermal mass flow meters is not a fixed value, but is affected by multiple factors such as the measurement principle (thermal dispersion/thermal accumulation), medium type (gas/liquid), measurement range, operating conditions (temperature/pressure), and equipment model, resulting in significant variations in accuracy.

Sino-Inst’s gas thermal mass flow meters generally have an accuracy of ±1.0% ~ ±2.5% FS, which can meet the measurement needs of most operating conditions.

A mass flow transmitter (MFM) is an instrument that accurately measures gas flow rate. Its measurement value is not affected by fluctuations in temperature or pressure and does not require temperature or pressure compensation.

A mass flow controller (MFC) not only has the functions of a mass flow meter, but more importantly, it can automatically control the gas flow rate. The user can set the flow rate as needed, and the MFC automatically maintains the flow rate at the set value. Even if the system pressure fluctuates or the ambient temperature changes, it will not deviate from the set value. Simply put, a mass flow controller is a flow stabilizing device; it is a gas flow measuring device that can be manually set or connected to a computer for automatic control.

Flare gas flow measurement is crucial for environmental protection, safety, and energy recovery. Flare gas may contain impurities such as dust, solid particles, oil, and moisture, placing high demands on the flow meter’s corrosion resistance, resistance to media corrosion, and insensitivity to the media.

Thermal mass flow meters excel in these aspects. Their sensors have no moving parts or pressure-sensing components, are unaffected by vibration on measurement accuracy, and are insensitive to impurities in the media. Furthermore, thermal mass flow meters offer advantages such as good shock resistance, long service life, and stable operation in harsh industrial environments.

Thermal mass flow meters are the preferred choice for flow monitoring in flare systems. Flow signals are acquired by installing a thermal mass flow meter on the main gas inlet pipe of the ground flare. This allows for tiered control of the ground flare, ensuring stable pressure in the main gas inlet pipe and avoiding “saw-like” pressure fluctuations, thus guaranteeing the safe operation of the ground flare.

More Flow Measurement Solutions

  • Case Study: Custom Thermal Mass Flow Meter For Nitrogen Flow Measurement

    Thermal mass flow meters are widely used to measure gas flow in industrial processes. They determine the mass flow rate by measuring the thermal changes in the fluid as it flows through the sensor. Sino-Inst’s thermal mass flow meters utilize a unique temperature differential measurement method to overcome the drawback of traditional thermal mass flow … Read more

  • Brine Flow Meter Guide

    Brine, as used in industrial production, refers to aqueous solutions containing high concentrations of inorganic salts (not just sodium chloride), such as calcium chloride and sodium bromide. Brine has a wide range of industrial applications, primarily leveraging its physical and chemical properties. These include a low freezing point, high boiling point, excellent electrical conductivity, and … Read more

  • Variable Area Flow Meter Case: Oxygen Flow Measurement

    Oxygen is an important gas in the industrial process and is widely used in various industrial sectors as an oxidant and combustion aid. Reasonable oxygen flow measurement can further improve production efficiency, reduce energy consumption, protect the environment, and achieve a win-win situation of economic and social benefits. We, Sino-Inst, supply various types of oxygen … Read more

  • Everything You Need To Know About Propane Gas Flow Meters

    In its gaseous form, Propane has numerous applications. Propane is usually used for residential heating, cooking, and powering small appliances. Industrially, propane can be separated from oilfield gas and cracking gas. It can be used as a raw material for the production of ethylene and propylene or as a solvent in the oil refining industry. … Read more

  • Gas Mass Flow Meters: Applications, Benefits, And Top Manufacturers

    Ascertaining accurate and reliable measurement of gas flow rates is critical for a variety of industrial processes. The ability to measure gas mass flow accurately, rather than simply volumetric flow, provides insights into the true behavior of gases under varying conditions of temperature, pressure, and composition. In this blog post, we will explore the fundamentals … Read more

  • LPG Gas Flow Meters With Some Prominent Manufacturers And Suppliers

    Liquefied Petroleum Gas (LPG) is an indispensable commodity of domestic and industrial applications. It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer. Choosing the right LPG Gas flow meter is crucial for optimal performance, safety, and efficiency of LPG systems. By … Read more

  • Guide On Industrial Air Flow Measurement Devices

    Air flow measurement is critical in various industrial, automotive, healthcare, and HVAC applications. Many industries call for the measurement of airflow or air velocity. They sometimes ask for some additional requirements like the determination of air temperature, air pressure, or humidity. This is true in electronics and automobile engineering, as well as critical containment applications … Read more

  • Getting to Know The Propane Flow Meters: Better Monitoring of Propane Utilization

    Propane is a common fuel source used in a variety of industries, including manufacturing, agriculture, and transportation. Propane flow meters come in various types and designs, tailored to the specific nature of propane, whether it’s in gaseous or liquid form. Given that propane can exist in both states—depending on temperature and pressure—understanding how to measure … Read more

  • Industrial Refrigerant Flow Meters

    Refrigerant flow meters can accurately measure the refrigerant flow. It is not only related to the stable operation of the refrigeration system but also directly affects the production efficiency and cost control of the enterprise. There are more than 80 substances that can be used as refrigerants, the most commonly used are ammonia, freon, water, … Read more

  • Techniques, Importance, and Challenges of Natural Gas Flow Measurement

    Why Natural Gas Flow Measurement is Pivotal? Natural gas is an essential energy source, supplying power to industries, homes, and businesses globally. High-fidelity “natural gas measurement” is essential for ensuring fair trade, safety, and efficient energy distribution. This blog post will explore the world of natural gas flow measurement, looking into the various techniques used, … Read more

  • Guide To Vortex Flow Meters For Steam Applications: Steam Vortex Flow Meter In detail

    To begin with: Vortex Flow Meters for Steam Applications The requirement for high-fidelity and trustworthy flow measurement has become pivotal across various industries, especially in applications involving steam. Steam is widely used in industries such as power generation, chemical processing, and manufacturing. Where the need to measure the flow of steam accurately is hypercritical for … Read more

  • Featured Gas Turbine Flow Meter for Natural Gas and Other Gases

    Gas turbine flow meter is a precision metering instrument used for gas flow measurement. Especially in natural gas transportation and trade settlement, the gas turbine flow meter is even more popular. Gas Turbine Flow Meter integrates temperature, pressure, and flow sensors. It is also equipped with an electronic volume corrector, which can simultaneously detect and … Read more

  • Approaches To Gas Flow Measurement: Types and Applications Of Gas Flow Meters

    Gas flow measurement is an essential technology in many industrial processes. For example, in the production of chemical products, accurate measurement of the flow of gases such as oxygen and nitrogen can ensure that the reactants are added to the reactor in the appropriate proportion to obtain high-quality products. Introduction: Why Gas Flow Measurement is … Read more

  • Liquid and Gas NH3 Ammonia Flow Meters

    Liquid and Gas ammonia (NH3) is an important industrial raw material. Ammonia flow meters are specially designed to measure the flow of industrial ammonia pipelines. Output pulse signal, 4-20mA, RS485, etc. Help us effectively monitor the flow of liquid or gaseous ammonia! Gas Ammonia properties and industrial applications Ammonia is a commonly used gas widely … Read more

Thermal gas mass flow meters are used in process control. They require no temperature or pressure compensation and directly measure the mass flow rate of fluids.

Sino-Inst’s thermal gas mass flow meters have no moving parts, low pressure loss, wide rangeability, and high accuracy. They are currently widely used in petroleum, chemical, semiconductor, medical instrumentation, bioengineering, combustion gas control and distribution, environmental monitoring, precision instruments, scientific research, metrology, food, metallurgy, and aerospace industries.

If you need gas flow monitoring, please feel free to contact our sales engineers!

    Request For Quote



    Thermal Mass Flow Meter - Best Price from the Manufacturer

    Read more about: Thermal Mass Flow Meter Technology

    Product SKU: Thermal Mass Flow Meter

    Product Brand: Sino-Inst

    Product Currency: USD

    Product Price: 590

    Price Valid Until: 2099-09-09

    Product In-Stock: InStock

    Editor's Rating:
    5