Method and apparatus for determining the weight of slag on a bath of molten metal

Claim 1

A method of determining the weight of the molten slag covering a bath of molten metal, comprising: (a) determining the surface area of the slag and the pressure head at the slag-metal interface, (b) multiplying said surface area by said pressure head, (c) said pressure head is determined by: (i) inserting a consumable tubular member downwardly into said vessel until said member passes below the interface between said molten slag and said molten metal while passing a gas at a constant flow rate through said member, and (ii) measuring the pressure head at the bottom of said tubular member at about the instant said bottom is at said interface, and (d) the instant the bottom of said tubular member is at said interface is determined by: (i) maintaining constant the downward movement of said tubular member, (ii) measuring the pressure at said bottom at constant intervals, (iii) subtracting the maximum change in pressure that can occur in said slag during said interval from the change in pressure between each successive interval, (iv) subtracting the change in pressure at each (n-1) interval from the change in pressure at each successive interval, (v) in response to a control signal, calculating the pressure head at the bottom of said member, and (vi) producing a control signal when one of the following two conditions exists: (a) the results of the subtractions of both (iii) and (iv) are positive; and (b) a predetermined time interval has elapsed since the pressure head at said bottom exceeded a predetermined value.

Claim 2

A method of determining the weight of the molten slag covering a bath of molten metal, comprising: (a) determining the surface area of the slag and the pressure head at the slag-metal interface, (b) multiplying said surface area by said pressure head, (c) said pressure head is determined by: (i) inserting a consumable tubular member downwardly into said vessel until said member passes below the interface between said molten slag and said molten metal while passing a gas at a constant flow rate through said member, and (ii) measuring the pressure head at the bottom of said tubular member at about the instant said bottom is at said interface, and (d) the instant the bottom of said tubular member is at said interface is determined by: (i) maintaining constant the downward movement of said tubular member, (ii) measuring the pressure at said bottom at constant intervals, (iii) subtracting the maximum change in pressure that can occur in said slag during said interval from the change in pressure between each successive interval, (iv) subtracting the change in pressure at each (n-1) interval from the change in pressure at each successive interval, (v) in response to a control signal, calculating the pressure head at the bottom of said member, and (vi) producing a control signal when one of the following two conditions exists: (a) the results of the subtractions of both (iii) and (iv) are positive; and (b) a predetermined time interval has elapsed since the pressure head at said bottom exceeded a predetermined value.