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NE 035/07

National Standard for Gas Flow and Volume

Content

The National Standard for Gas Flow and Volume realizes the unit of gas volume and gas flow under near-atmospheric pressure conditions and a temperature of 20°C. The extended flow range of the national standard is (0.01 to 100) m³/h. The standard consists of two technological components:

First Technological Component: "Primary Standard with Inverted Equivalent Quantity"

This system operates on a gravimetric principle, where:

  • Low-viscosity mineral oil with low evaporation properties flows into a sealed chamber containing a weighing scale with a container.
  • The mass of the oil collected in the chamber is converted into volume.
  • The same volume of displaced air flows through the connected calibrated meter.
  • The flow range for this part of the national standard is (0.01 to 3) m³/h.

Second Technological Component: "Primary Bell Prover Standard"

This system operates on a volumetric principle, widely used in national metrology laboratories worldwide:

  • As the bell descends, a defined volume of gas is displaced from the space beneath it through the connected calibrated meter.
  • The displaced volume is determined by the internal surface area of the bell and the height change, measured using an optical ruler with a resolution of 0.004 mm.
  • The basic flow range for this part of the standard is (1 to 65) m³/h, with an extended range of (0.5 to 100) m³/h.

Operational Control and Stability

  • Both systems are centrally controlled from a control room using a unified software interface.
  • The two systems cannot operate simultaneously, as they function as a single metrological unit.
  • Stable microclimate conditions within the facility housing the standard are maintained through climate control.

Metrological Importance

The National Standard for Gas Flow and Volume holds the highest position in the hierarchy of flow and volume measurement in Slovakia. It provides traceability for approximately 1.3 million gas meters installed in households and several thousand industrial meters used by large gas consumers. Additionally, it ensures traceability for gas meters used in healthcare and other industrial sectors beyond heating applications.

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