The thermal mass flow meter is a well-known tool for measuring gas mass flow. The device is utilized in a variety of sectors, including oil and gas, refining, chemicals, mining, and wastewater treatment. For many applications, the meter is precise, dependable, and cost-effective. However, like any technology, the flow meter's limits may bring issues that the user should address before use. Here are nine limitations or obstacles of thermal mass flow meters by Flow Meter Manufacturer and solutions to them.
Condensed Moisture may Cause Inaccuracies
Angled flow sensors in pipes can assist counteract inaccuracies caused by condensed moisture.
The fundamental thermal mass flow measuring principle is heat transfer generated by gas movement. Condensed moisture in the gas that contacts the heated sensor accelerates heat transfer, causing the instrument to respond with a spike and resulting in erroneous flow measurement.
Diminished Sensitivity at Higher Velocities
There is a nonlinear connection between mass velocity and heat transfer in thermal flow measurement. While thermal flow meters have good sensitivity for low gas flow rates, their sensitivity decreases at large rates. When choosing a mass flow meter for a certain application, the meter is scaled based on mass velocity in relation to STP (Standard Temperature and Pressure) conditions. Other types of flow meters are sized based on velocity under operating circumstances. Gas molecules pack closer together when pressure increases, increasing gas density. The mass velocity reported by thermal mass flow meters made by Flow Meter Manufacturer rises as gas density increases, whereas the real velocity under working circumstances remains constant.
When Unable to Calibrate with the Actual Gas Type
Each gas has unique physical features that influence heat transmission. As a result, a thermal mass flow meter can only reliably measure the gas (or gas mixture) for which it was calibrated. During calibration on a flow bench, a regulated amount of the required gas flows past the meter's sensor, and the signal is monitored. This procedure is done several times across the operating range to establish the link between mass flow and the signal for calibrating gas and the sensor.
Annual Recalibrations are Expensive and Inconvenient
When a thermal mass flow meter is calibrated, the question is when it has to be re-calibrated. Some manufacturers demand that their meters be returned to the factory or a NIST-traceable facility for calibration. This recalibration can be costly, and taking a meter out of operation is cumbersome. Some mass flow meter manufacturers, notably Sage Metering, have created methods to check that the meter stays calibrated as technology advances. These calibration verification techniques differ from one vendor to the next.
Gas Flow Composition Variation
Because a thermal mass flowmeter must be calibrated for the gas being measured, any change in the gas composition will result in inaccurate results (see challenge #3 for calibration). Of course, the degree of inaccuracy will depend on the gas fluctuation.
Undeveloped Flow Profile
The test station delivers a fully developed turbulent flow profile at the sensor during the calibration of the thermal mass flowmeter. The most accurate results will be obtained by replicating this flow profile in the field. However, departures from the required distance will result in mistakes. Most flow systems need a minimum of upstream and downstream straight lines, with an emphasis on the upstream range. To generate the optimal flow profile, the needed straight run is frequently unattainable at the location. As a general rule, a spacing of 15-25 pipe diameters downstream of a single elbow is usually adequate.
Each flow measuring system has its limitations. Difficulties may develop when straining the limits of a thermal mass flowmeter made by a Flow Meter Manufacturer. In all cases, communicating the application and operating environment specifics to the manufacturer allows the solution provider to guarantee the technology under consideration can achieve the expected outcomes. Visit Petron Thermoplast now and buy one!
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