Abstract: A device for detecting metal ions in an atmosphere. The device is based on a well known insulated gate-type field-effect transistor (MOSFET). The device includes a metal ion detecting element based on the MOSFET; a means, connected to the metal ion detecting element, for making a current flow through said metal ion detecting element; and a means, connected to the metal ion detecting element, for detecting the change of the strength of the current flowing through the metal ion detecting element, the change being brought by the electric charge of the metal ions which reached the gate oxide film. A metal ion introducing passage for allowing migration of the metal ions to be detected to the gate oxide film is formed in the gate electrode of the metal ion detecting element in the direction of its thickness.

Abstract: Disclosed is a plugging device which comprises a plugging orifice having in a passage for a liquid metal a conical portion spreading out toward the upper-course side and a straight pipe portion extending from a small-diameter part of the conical portion at the lower-course end thereof to the lower-course side, whereby plenty of impurities in the liquid metal flowing supersaturated through the straight pipe portion are precipitated at the straight pipe portion, and a cooler so controlled as to stop a driving motor of a blower for cooling the liquid metal when the flow rate of the liquid metal is below a predetermined level and to rotate the motor in proportion to the deviation between the flow rate by actual measurement and the predetermined level of flow rate when the flow rate of the liquid metal is at the predetermined level or above.

Abstract: A plugging indicator comprises an economizer having concentric outer and inner pipes one ends of which are connected to a main conduit through which liquid metal passes, an electromagnetic pump mounted on the outer pipe for branching the liquid metal into the outer pipe, a device for measuring flow quantity of the liquid metal passing through the outer pipe, and cooling means mounted on the outer pipe. The inner pipe is provided with two openings as a plugging orifice and a by-pass orifice to deposit impurities contained in the liquid metal. The plugging indicator further comprises a thermometer for measuring temperature at the plugging orifice, a blower for supplying cooling air to the cooling means, and a device for controlling the blower in response to the flow quantity at the flow quantity measuring device and the temperature at the plugging orifice.