A fan, in particular axial fan and preferably backward-curved radial fan, having an impeller equipped with blades, an electric motor for rotating the impeller and a device for determining the airflow when the impeller is rotating. The device for determining the airflow includes a volume flow measuring wheel arranged in the air flow, which is arranged upstream of the impeller on the inflow side. The air volume flow is calculated or derived from the rotational speed of the volume flow measuring wheel.

A fan, in particular axial fan and preferably backward-curved radial fan, having an impeller equipped with blades, an electric motor for rotating the impeller and a device for determining the airflow when the impeller is rotating. The device for determining the airflow includes a volume flow measuring wheel arranged in the air flow, which is arranged upstream of the impeller on the inflow side. The air volume flow is calculated or derived from the rotational speed of the volume flow measuring wheel.

A method includes registering a first mass flow rate portion measurement value ṁ.sub.1 of a first flow portion through measuring tubes of a first oscillator and a second mass flow rate portion measurement value ṁ.sub.2 of a second flow portion through measuring tubes of the second oscillator. A sum of the two mass flow rate portion measurement values gives a mass flow rate total measurement value. The method also includes registering first and second density portion measurement values ρ.sub.1, ρ.sub.2 of the medium in the flow portions and calculating the effective density measurement value ρ.sub.eff as a function of the density portion measurement values ρ.sub.1, ρ.sub.2 with weightings dependent on the mass flow rate portion measurement values ṁ.sub.1, ṁ.sub.2. The different weighting functions are applied for ascertaining the weightings as a function of the mass flow rate portion measurement values.

An apparatus having a shaft, a bearing sleeve for rotatably supporting the shaft, a housing, in which at least one part of the bearing sleeve is arranged, and a sealing element, which seals a gap between a wall of the housing and the bearing sleeve. The sealing element divides the gap gas-tight into a first partial space adjacent to the front side of the sealing element and a second partial space adjacent to the back side of the sealing element, the sealing element having a flexible part, which is in contact with the wall of the housing and/or the bearing sleeve, and the housing having a first barrier gas inlet for introducing barrier gas into the first partial space as well as a second barrier gas inlet for introducing barrier gas into the second partial space.

A measuring transducer includes: a measuring tube arrangement having at least one measuring tube for conveying a flowable medium; at least a first exciter component of an oscillation exciter for exciting the at least one measuring tube to execute oscillations; at least a first sensor component of an oscillation sensor for registering oscillations of the at least one measuring tube; a fixing body arrangement, which is connected with the at least one measuring tube and via which a releasable connection with a support apparatus can be made; a connecting apparatus for releasable connecting of the measuring tube arrangement with a process line; and a fastener apparatus for forming a shape-interlocking and/or force-interlocking connection between the connecting apparatus and the fixing body arrangement.

An apparatus having a shaft, a bearing sleeve for rotatably supporting the shaft, a housing, in which at least one part of the bearing sleeve is arranged, and a sealing element, which seals a gap between a wall of the housing and the bearing sleeve. The sealing element divides the gap gas-tight into a first partial space adjacent to the front side of the sealing element and a second partial space adjacent to the back side of the sealing element, the sealing element having a flexible part, which is in contact with the wall of the housing and/or the bearing sleeve, and the housing having a first barrier gas inlet for introducing barrier gas into the first partial space as well as a second barrier gas inlet for introducing barrier gas into the second partial space.

A method includes registering a first mass flow rate portion measurement value {dot over (m)}.sub.1 of a first flow portion through measuring tubes of a first oscillator and a second mass flow rate portion measurement value {dot over (m)}.sub.2 of a second flow portion through measuring tubes of the second oscillator. A sum of the two mass flow rate portion measurement values gives a mass flow rate total measurement value. The method also includes registering first and second density portion measurement values .sub.1, .sub.2 of the medium in the flow portions and calculating the effective density measurement value p.sub.eff as a function of the density portion measurement values .sub.1, .sub.2 with weightings dependent on the mass flow rate portion measurement values {dot over (m)}.sub.1, {dot over (m)}.sub.2. The different weighting functions are applied for ascertaining the weightings as a function of the mass flow rate portion measurement values.