Measuring Natural Gas Consumption: A Thermal Alternative to Turbine Wheel Meters and Quantometers

Author: Florian Buchner
Position: Product Manager, Flow Measurement Technology
Area of Expertise: Thermal flow measurement, industrial gas measurement, and energy monitoring
Last updated on October 14, 2026

At a Glance: Thermal mass flow meters from CS INSTRUMENTS measure natural gas consumption without moving parts and directly output the standarized volume flow—for consumption monitoring, cost center tracking, and energy management. The VA 550 and VA 570 are available, depending on the model, with ATEX approval or DVGW approval for natural gas (up to 16 bar).

When is it worthwhile to use a thermal mass flow meter?

Industrial natural gas networks typically use turbine meters, piston gas meters, and quantometers; users sometimes refer to them generally as impeller meters. If low flow rates are not measured accurately, moving parts require maintenance, or digital consumption data is lacking, a thermal mass flow meter for natural gas is an alternative worth considering.

How turbine-wheel and rotary-piston gas meters work—and where their limitations lie. In a turbine-wheel gas meter, the gas flow strikes a mechanically mounted turbine wheel and drives it; the rotational speed is proportional to the flow velocity and, given the known pipe cross-section, to the volume flow. In a rotary piston gas meter, the pressure difference drives rotors in a measuring chamber, each of which encloses a precisely defined volume of gas and conveys it to the consumer. The usable measuring range of mechanical gas meters depends heavily on the design, size, operating pressure, and model: Simple quantometers often operate with significantly lower dynamic range than a thermal sensor.

The inherent limitations of both designs stem from their moving parts: Bearings age due to dirt or abrasion and cause measurement deviations; exceeding the measurement range can cause bearing damage; some bearings must be lubricated regularly—which is easily neglected in practice—contaminated gas leads to greater deviations, and cleaning is virtually impossible; in the case of rotary piston gas meters, there is also a design-related pressure loss.

Measuring partial load and peak flow: The VA 550 and VA 570 offer a measuring span of up to 1:1000. The actual minimum and maximum flow rates (Qmin/Qmax) remain the decisive factors. With the VA 550 and VA 570, the measuring range can be selected to suit the application (Low Speed, Standard, Max, and High Speed). Additional advantages of the thermal principle include negligible pressure loss and the ability to measure extremely low consumption rates: The VA 550 and VA 570 are very often used in large pipe cross-sections with low gas consumption, where mechanical gas meters reach their limits.

Prevent rotor wear: The thermal principle measures based on the heat dissipation of a heated sensor—without rotor bearings and with minimal additional pressure loss. The sensors (heater and temperature sensor) are designed for harsh industrial environments and housed in a thin, robust stainless steel tube: no bearings, no wear, easily accessible, and simple to clean if contaminated. The devices are very robust and virtually maintenance-free.

Output standard volume directly: Mechanical gas meters are typically operating volume meters; conversion to standard volume is performed by external volume converters equipped with additional pressure and temperature sensors. To achieve the required accuracy, these sensors must be highly precise and located inside or near the meter—their measurement errors are added to the meter’s accuracy, which is typically specified in operating volume. The VA 550 and VA 570 measure the thermal mass flow rate and, with appropriate gas parameterization and specified reference conditions, directly output the standarized volume flow; a separate volume converter with additional pressure and temperature measurement is not required for this. For comparisons, the reference conditions must match (e.g., 0 °C; 1,013.25 mbar (a) per DIN 1343—also referred to as standard m³/Nm³); for kWh calculations, the calorific value is added.

Operating Volume vs. Standard Volume: Why the Difference Is Crucial for Natural Gas

At elevated operating pressure, the standard volume is greater than the operating volume—in proportion to the absolute pressures, with an additional correction for temperature. If an operating volume is incorrectly reported as a standard volume or processed as such, the actual gas consumption is systematically underestimated, and the kWh balance mirrors this error exactly because it depends linearly on volume:

In addition, there is the temperature factor: there is a difference of approximately 7% between a gas temperature of 20 °C and the standard reference temperature of 0 °C. These values are provided for illustrative purposes using an ideal gas; for billing or highly accurate state conversion, factors such as temperature, gas composition, and compressibility must be taken into account (DVGW Regulation G 685). The most common source of error in energy balances is not measurement precision, but an unnoticed incorrect volume reference.

Where is thermal natural gas measurement particularly worthwhile?

In main and distribution lines, a point of measurement continuously monitors the total consumption of a building, area, or boiler room—for larger existing pipelines, the VA 550 is a good option as an insertion type sensor because it eliminates the need to install a complete inline measuring section in the nominal diameter. Directly upstream of individual consumers (boilers, burners, production facilities), it becomes clear which consumer requires how much natural gas and when—the basis for load profiles and cost centers. The most informative approach is the combination: main measurement plus submeters shows total consumption and its distribution.

How do the measured values get into the energy management system?

With many installed mechanical meters, consumption data is transmitted solely via a pulse output; modern electronic meters can also offer digital interfaces. Depending on the ordered configuration, the VA 550 and VA 570 can be integrated directly into the central control system or energy monitoring software via Modbus TCP interface over Ethernet (flow, total consumption, gas temperature); an RTU/TCP gateway is not required. Optional Power over Ethernet combines data transmission and power supply in a single network cable—this reduces installation effort, especially when multiple points of measurement are involved. Alternatively, Modbus RTU, 4…20 mA, pulse, M-Bus, IO-Link, or HART are available.

Advantages for Installation, Maintenance, and Recalibration

Retrofitting the VA 550 as an insertion type sensor: The sensor is installed via a suitable process access point or ball valve. A depth scale and defined orientation ensure a reproducible sensor position. The VA 550 is designed for operating pressures up to 50 bar (DVGW version up to 16 bar); installation and removal under pressure are performed via a ½" ball valve with a retaining ring.

VA 570 as an inline solution: During cleaning or recalibration, the measuring section remains in the line—only the sensor unit is removed. For recalibration, the sensor is sent in; replacement sensors can be installed for the duration of the calibration, ensuring no interruption in operation.

Operation: On the VA 550 and VA 570, optical keys allow settings to be adjusted without opening the housing—the operation of both devices is identical. Digital device and status information (Modbus registers) support troubleshooting and handover documentation.

Practical Example: From Consumption Value to Process Parameter

In a boiler application, 330 Nm³/h of natural gas and 5,000 kg/h of vapor are measured. The boiler efficiency is calculated from gas consumption, heating value, and steam data—84% in the documented example. In this way, a simple consumption measurement is transformed into a reliable metric for efficiency and maintenance. (→ Steam Boiler Application Report)

Which natural gas flow meter is right for the application?

What are the requirements for ATEX and gas installations?

The VA 550 and VA 570 are available with ATEX approval/IECEx approval depending on the variant; the Ex marking for these variants, according to the data sheet, is: ATEX II 2G Ex db IIC T4 Gb (gas) and II 2D Ex tb IIIC T90 °C Db (dust); IECEx Ex db IIC T4 Gb / Ex tb IIIC T90 °C Db. The Ex version is rated for a medium temperature of up to 120 °C and has an IP 65 protection rating. The EU-type examination certificate is available in the download section. It is the operator’s responsibility to verify suitability for the specific explosion-protected area. CS INSTRUMENTS provides technical data sheets and Ex certificates for this purpose but does not assume any advisory role regarding zone classification or suitability for a specific facility.