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Robust Differential Pressure Flow Meter/Monitor for Liquid and Gas

Kobold, represented locally by Instrotech, has model RCD flow meter, for measuring and monitoring the flow of liquids and gases. Depending on the model, the measuring range of the device is from 0.5 to 2350 l/min for water and 0.5 to 2750 Nm3/h for air with connections G1/2 to G3, ½ “NPT to 3” NPT. It can also be used to measure and/or monitor other liquids and gases.

The functional principle behind this meter is the Venturi tube, developed by Italian physicist Giovanni Battista Venturi (1746-1822). This device consists of a tube that first narrows and then expands; the pressure difference between the inlet of the narrowed area and the narrowest area allows the flow to be determined. Within the housing, passages register the resulting differential pressure and transmit it to a bellows system in the display housing. The bellows system is protected by stop pins whenever the maximum rated flow is exceeded.


With mechanical displays, the flow value measured by the bellows system is transferred to the calibrated display (in l/min for water and N/m3/h for air), and indicated by means of a pointer element. With electronic displays, a Hall sensor converts the mechanical movement into an electrical signal. The strength of this signal varies with the flow. Various electronic systems are available to display or monitor and evaluate the flow volume.

Specific display scales are available for use with any media at any pressure and temperature. This flow meter is appropriate for use in the areas of: machinery, plants, chemical and pharmaceutical industry, heavy industry as well as the beverage and luxury-food industries. Special advantages of the unit are: no moving parts, universal mounting, self-monitoring, and easy operation. Measurement accuracies are 3% of the upper range value, with a reproducibility of 1%, also of the upper range value. The maximum service temperature is 100°C for a needle indicator and 80°C for an electronic display.

For more information on Kobold’s RCD Differential Pressure Flow Meter/Monitor, contact Instrotech on 010 595 1831, sales@instrotech.co.za

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