In industrial production (such as chemical, semiconductor, energy, biomedicine), the selection of gas flow meters directly affects process stability, measurement accuracy, and equipment life. But most engineers are prone to getting stuck “Only looking at the range/Accuracy, ignoring the characteristics of the medium”Misunderstandings can lead to equipment corrosion, damage, distorted readings, and even safety accidents. This article focuses onInert gas, corrosive gas, high-temperature gasThree typical media, disassembly and selection of core pain points and adaptation solutions to help you avoid90%The selection trap.

1、 Inert gas: Do not be trapped “harmless”Misleading, these details determine measurement stability

Inert gases (such asN₂TheArTheHeTheNe）Stable chemical properties, non corrosive, non reactive, seemingly“Good choice”However, in actual selection, there may be some issues“Ignore working condition details”Resulting in insufficient accuracy or cost waste, with core avoidance points concentrated in“Range matching”“Installation environment”and“Special scenario adaptation”.

1. Common selection misconceptions

lmisconception 1Blind pursuit“wide range”: Believe that “The wider the range coverage, the more universal it is”For example, using0-1000Nm³/hFlow meter measurement50Nm³/hLow flow inert gas leads to measurement errors exceeding±5%(The range ratio is too large, and the accuracy drops sharply in the low flow range);

lmisconception 2: Ignore“gas purity”influenceHigh purity materials used in the semiconductor industryArGas (purity)99.999%）Using a regular metal tube rotor flowmeter, impurities inside the tube fall off and contaminate the gas, resulting in a decrease in wafer yield;

lmisconception 3: Not considered“Low pressure condition”In a vacuum environment (such as a coating machine)ArIn gas supply, the use of differential pressure flow meters that require high-pressure driving results in no readings or reading drift.

2. Adapt measurement scheme

According to the inert gas “Non corrosive, low-risk”Characteristics, priority selection“High precision, low maintenance, adaptable to working conditions and pressure”The specific scenario matching for the flowmeter type is as follows:

3. Cost optimization suggestions

lNon high precision requirements (such as inert gas purging in the workshop): using a metal tube rotor flowmeter, the cost is only the same as that of a mass flowmeter1/5And it is easy to maintain;

lMulti pipeline centralized monitoring: selection “Multi channel gas mass flow controller”Can measure simultaneously4-8Inert gas is used to reduce the number of equipment and installation costs.

2、 Corrosive gas: What is the correct material selection “lifeline”Be wary of these traps

Corrosive gases (such asCl₂TheHFTheSO₂TheH₂STheNO₂）It's a selection“worst-hit area”If the material is incompatible, it will be short1-3Corrosion and leakage of flow meters within a month can lead to safety accidents in the long run (such asHFGas leakage burns). The core avoidance points are concentrated in“Material adaptation”“sealed structure”and“safety design”Never use it“Universal flowmeter”Sum up the numbers.

1. Common selection misconceptions

lmisconception 1：“stainless steel=corrosion-resistant”: Believe that 304 Stainless steel can withstand all corrosive gases, such as304 Material flow meter measurementCl₂，1 Within months, the sensor has corroded and the readings are completely distorted（Cl₂Hydrochloric acid is generated in humid environments, which corrodes stainless steel;

lmisconception 2: Ignore“Seal material”The flowmeter body is made of Hastelloy alloy, but the sealing component is made of ordinary nitrile rubber, resulting inHFGas leaks from the seal (nitrile rubber resistant)HFPoor sex,3 Swelling and failure within days);

lmisconception 3: Not considered“Gas moisture content”Like measuring wet stateSO₂(Moisture content>5%）Using a differential pressure flowmeter without anti-corrosion coating, sulfuric acid is generated on the sensor surface to accelerate corrosion.

2. Adapt measurement scheme

The core of selecting corrosive gases is “Material compatibility”According to the chemical characteristics of the gas (acidity)/alkaline/Oxidized) matching body, sensor, and sealing material, while strengthening“Security redundancy design”(such as leakage alarm).

3. Maintain pit avoidance reminders

lRegular inspection of seals: The lifespan of seals for corrosive gas flow meters is usually6-12Months, need to be replaced periodically (e.gHFGas useFFKMSeals, each8 Replace once a month);

lavoid “dry state/Wet state mixed use”As measuredCl₂If the gas changes from a dry state to a wet state (with a sudden increase in water content), it needs to be replaced in advance“Moisture resistant and anti-corrosion sensor”To prevent the formation of hydrochloric acid from accelerating corrosion;

lCalibration precautions: When calibrating a corrosive gas flowmeter, do not use air or nitrogen “leak test”Some corrosive gases react when mixed with air, such asH₂SandO₂Mixing is prone to explosion and requires inert gas (such asAr）Try to leak.

3、 High temperature gas: temperature beyond the range=“Waste equipment”Don't miss these parameters

High temperature gas (usually referring to temperature>200℃The selection of materials such as boiler flue gas, chemical cracking gas, and metallurgical high-temperature exhaust gas is easily overlooked“The Influence of Temperature on Sensor Performance”, leading to the flow meter“High temperature failure”(such as sensor drift, circuit burnout). The core avoidance points are concentrated in“Temperature range matching”“thermal design”and“high-temperature stability”.

1. Common selection misconceptions

lmisconception 1：“Over temperature use of normal temperature flowmeter”: Install the ambient temperature vortex flowmeter (with the highest temperature resistance)150℃）Used for250℃Boiler flue gas measurement,1 Circuit module burned out within the week, unable to read;

lmisconception 2: Ignore“Temperature gradient effect”There is a temperature gradient in high-temperature gas pipelines (such as the outer wall of the pipeline)200℃The inner wall300℃）, choose“Average temperature calibration”The flow meter caused measurement errors exceeding±3%；

lmisconception 3: Not considered“Material deformation under high temperature”As measured400℃The metallurgical exhaust gas is treated with an electromagnetic flowmeter lined with plastic, which causes pipeline blockage due to high-temperature softening of the lining.

2. Adapt measurement scheme

High temperature gas selection needs to be prioritized “Temperature upper limit>actual operating temperature20%-30%”(Leave a safety margin), while also paying attention to“Accuracy stability at high temperatures”and“Design of heat dissipation structure”To avoid sensor drift due to high temperature.

3. Installation and calibration to avoid pitfalls

lInstallation position: Avoid installing the flowmeter in the pipeline “dead zone”(such as near bends and valves), high-temperature gases can easily form vortices in dead zones, causing fluctuations in readings;

lHigh temperature calibration: required in “Actual operating temperature”Calibration (such as testing)400℃Cracking gas requires400℃Calibration with standard gas in the environment is prohibited, and direct use in high-temperature scenarios after calibration at room temperature is prohibited (errors will increase)3-5(Multiple times)；

lHeat dissipation protection: The header (display and circuit module) should be kept away from high-temperature pipelines. If it is not possible to keep it away, additional measures should be taken “heat shield”(such as ceramic fiber insulation cover), ensure that the temperature of the meter head is ＜60℃(Upper limit of normal operating temperature for circuit module).

4、 Universal selection to avoid pitfalls:3 Step by step quick matching scheme, avoid repeating traps

Regardless of the type of medium, it must be completed before selection “Sorting of working condition parameters→Material compatibility verification→Scene adaptation verification”3Step by step process to avoid making decisions based on experience:

1. comb, sort out, organize, arrange, streamline“List of operating condition parameters”(One is indispensable)

Before selecting, it is necessary to clarify the following: 6 Record the core parameters in a table (as shown below) to avoid selection bias caused by missing parameters:

2. check“Material compatibility”(Key step)

According to the characteristics of the gas medium, compare “Material Compatibility Table”(can be requested from the supplier), check the flowmeter body, sensors, seals, and lining materials one by one, focusing on:

lAcidic gas: Avoid ordinary stainless steel（304/316）Prioritize the selection of Hastelloy and Monel alloys;

lAlkaline gas: Avoid copper and copper alloys, prioritize316LStainless steel (passivation treatment), titanium alloy；

lHigh temperature gas: Avoid plastic and rubber materials, and prioritize ceramics, high-temperature alloys, and platinum rhodium alloys.

3. Scene adaptation verification (avoiding“empty talk”）

lConsulting industry cases such as measurementHFGas, can inquire with the supplier“Is there a photovoltaic industryHFApplication cases of cleaning”Prioritize selecting models with mature cases;

lSample testing: Important scenarios (such as semiconductors, biomedicine) may require suppliers to provide “Sample flowmeter”Test under actual working conditions1-2Zhou, verify accuracy and stability;

lAfter sales guarantee confirmation: Clear “corrosive/Warranty period of high-temperature gas flowmeter”(Usually shorter than conventional flow meters, please confirm if warranty can be extended), and“Emergency repair response time”(Corrosive gas leakage requires24 Processed within hours).

Conclusion

The core of gas flowmeter selection is not “Choose the most expensive one”But instead“Choose the appropriate one”——Inert gases need to balance accuracy and cost, while corrosive gases need to be maintained“Material Red Line”High temperature gas needs to be kept sufficient“Temperature margin”Each step needs to be based on actual operating parameters rather than empirical judgment to avoid“Selection and scrapping”The trap.

It is recommended to include in the selection process “List of operating condition parameters”and“Material compatibility requirements”Clearly inform the supplier and request them to provide“Selection Plan Description”(Material and adaptation basis of each component should be marked), and reference cases from the same industry should be retained to ensure that the selection plan can be implemented, verified, and ultimately achieved“Accurate measurement, long-term stability, and controllable cost”The goal.

Hangzhou Yushi Technology Co., LtdFocusing on providing technical services and solutions related to flow, pressure, vacuum detection and control for industrial and scientific research customers, the company acts as an agent and distributor in the United StatesALICAT、 Swiss Vogtlin, American MKS, Japanese EBARA and other brands, combined with their agent products, provide customers with high-quality flow and pressure monitoring solutions, aiming to improve customers' research and production efficiency, improve their manufacturing processes, and promote their scientific research and innovation progress.