Method of Comparison for Calibration of Critical Nozzles

Abstract

The method of comparison for the transmission of the units of volume gas flow from standard critical nozzles to calibratable nozzles is described. A flow laminarizer with flat slitted channels 0.8 mm in height exhibiting a direct proportional relation between the pressure drop in the channel and the volume flow is used as a comparator (modulus of comparison). The flow laminarizer is characterized by high sensitivity to variations in the flow, a broad range of the flows that may be employed, simplicity of the device, and the absence of moving units. Through the use of the present method of comparison in State Primary Standard of the unit of volume flow and mass flow of gas GET 118–2017, it was possible to reduce the load on the expensive bell-type primary bell-type standard plant, decrease the number of standard nozzles required, significantly increase the productivity, and decrease the cost of calibration operations.