Turbine gas meters consist of a pressure-bearing housing made of globular grey cast iron (GGG), cast steel or aluminium. The function-determining components inside the housing are the rectifier, the measuring unit with turbine wheel, the magnetic coupling, the pulse generator and the totalizer. The central unit of a turbine meter is the turbine wheel. The measuring process is simplified as follows:
Gas flows through the inlet duct into the turbine meter. The flow straightener eliminates possible swirl in the gas flow. It equalizes and accelerates the gas flow by reducing the free cross-sectional area to a flow channel. In this flow channel the gas hits the freely rotating turbine wheel. The blades of the turbine wheel are at a precisely defined angle to the gas flow. The incoming gas drives the turbine wheel and sets it in rotation. As the flow rate increases, the speed of the turbine wheel increases. The speed of the wheel is proportional to the flow velocity (instantaneous value), the number of revolutions is proportional to the volume of gas flowing through (indirect volume measurement). Based on this law, the flow rate can be determined. The magnetic coupling transmits the speed of the turbine wheel via a gear to the mechanical totalizer.
Alternatively, special sensors can scan the turbine wheel without contact and the electrical pulses generated in this way can be transmitted to an electronic meter. This totals the quantity of gas flowing through in volume units and transfers the recorded data to a display.
Turbine meters are suitable for measuring the flow rate of various gases, e.g. natural gas, butane, propane, hydrogen, nitrogen, noble gases and others. Depending on the intended use, turbine meters are available in different versions:
- Turbine gas meters subject to calibration and non-custody transfer meters/volumeters
- Meters for low and high operating pressures
- Gas meter for measuring filtered and non-aggressive gases
- Turbine gas meters for corrosive, chemical and aggressive gases such as biogas, sour gas and ethylene. Such meters are made of special materials, are partly coated with Teflon and have a special lubrication
- Meters for use under extreme conditions, such as low temperatures
Turbine meters are also suitable for installation in pipelines with high pressure, since the magnetic coupling for transmitting the speed provides a perfectly sealing connection to the outside. The separate design of the measuring wheel and measuring device also allows the measurement of flammable and aggressive gases. A certain flow rate is necessary for a turbine meter to operate precisely.