Kawaki INF-MA Flow Switch and INF-M Area Flow Meter for Liquid and Gas

A compact area flow meter and switch for liquid and gas in horizontal lines

The Kawaki INF-MA flow switch and its INF-M flow meter are described by Kawaki as the NF type with indicator: a compact area flow meter for liquid and gas that works in horizontal piping. According to the instruction manual, the INF-M measures both liquids and gases, and for liquids it handles water, oil and corrosive liquids; the INF-MA detects an increase or decrease in flow and switches an electrical contact on or off. The manual also names an INF-MA(A) version.

The principle is the shuttle type of area flow meter. Flow passing the float produces a pressure difference that lifts the float until the growing flow area between float and slit reduces the velocity and balances the weight, so the float position is proportional to flow. A magnet inside the float top is coupled through a non-magnetic tube to an external magnet that turns a pointer on the scale, and the process fluid is completely sealed by the tube, so Kawaki states that leakage does not occur.

Technical specifications

Switch function and installation limits

In the INF-MA the external magnet shaft carries a cam that operates a micro switch. The switch mount can slide through 90 degrees about the main shaft, so the set point can be placed over the full scale, but the manual warns that below 20 percent of full scale the micro switch operation is unstable and the set point should not be placed there. Wiring uses colour-marked leads: NC (blue), COM (white) and NO (red), with NC to COM for the lower limit and NO to COM for the upper limit.

The manual is explicit that the instrument can be used only on horizontal pipework, with the body mounted level and in the direction of the flow arrow cast in the body. A tilted centre axis causes friction on the float shaft and reading errors. No straight pipe run is required before or after the meter, but the valve must be on the outlet side. Mount it where vibration is low and flush the line first, because seal-tape and weld debris collect easily.

Selecting an INF unit

Provide the bore (3/8B to 3B flange or RC3/8 to RC2 screw), whether the fluid is liquid or gas, its density, temperature and pressure, the flow range for the scale, whether a contact is needed and the material. The standard working pressure is 1.0 MPa and the temperature 80 degrees C or less, with accuracy of plus or minus 3 percent of each indication scale. Because gas and liquid scales differ, state the medium and operating conditions so the scale can be matched.

Documents and quotation

The Kawaki instruction manual is attached; it is in Japanese. Seven Star LLC is an independent supplier in Muscat; send the model, bore, connection, fluid or gas, conditions and contact requirement and we will request a quotation. Related items are in Flow Indicators and Switches.