Sliding gate valve comprising a carriage

A sliding gate valve for controlling a flow of liquid metal out of a metallurgic vessel, comprising

• a carriage for a sliding gate valve of a metallurgic vessel, comprising a carriage support structure and a plate frame for supporting a first refractory plate, and wherein the plate frame is slideably mounted on the carriage support structure for sliding along a first axis,
• a fixed underframe configured for supporting a second refractory plate in a fixed position with respect to the fixed underframe, wherein said fixed underframe comprises fixing elements for fixing the fixed underframe to a bottom floor of the metallurgic vessel,
• wherein said carriage is coupled to the fixed underframe, wherein said carriage and said fixed underframe are configured such that when first and second refractory plates are supported in the respective plate frame and fixed underframe, a sliding surface of the first refractory plate comprising first aperture can slide within a first stroke ΔX1 against a sliding surface of the second refractory plate comprising a second aperture, thereby allowing to bring the first and second apertures in and out of registry, by sliding the plate frame to respectively an initial position of said plate frame corresponding to the open valve position and to a nominal end-position of said plate frame corresponding to a closed valve position,
• wherein said carriage support structure comprises a permanently attached selecting device for selecting between said first stroke ΔX1 and a second stroke ΔX2 of said plate frame with ΔX2>ΔX1, and wherein the first stroke ΔX1 and the second stroke ΔX2 are defined as maximum plate frame sliding distances measured between the initial position and respectively the nominal end-position and a service end-position, and wherein said selecting device comprises a blocking member reversibly moveable between a blocking position for selecting the first stroke ΔX1 and a non-blocking position for selecting the second stroke ΔX2, wherein said plate frame and said selection device are configured such that when said blocking member is positioned in said blocking position, a first bumper portion of said plate frame is bumping into said blocking member if said plate frame is to slide beyond said nominal end-position, thereby limiting the plate frame to slide within said first stroke ΔX1, and when said blocking member is positioned in said non-blocking position, the plate frame is free to slide within said second stroke ΔX2, and consequently to slide beyond the nominal end-position to the service end-position,
• wherein said carriage comprises resilient pressing elements configured such that when first and second refractory plates are supported in the respective plate frame and fixed underframe then:
• a pressure is exercised by said resilient pressing elements pressing the sliding surface of the first refractory plate against the sliding surface of the second refractory plate when the plate frame is located within the first stroke, and
• no pressure or a reduced pressure is exercised by said resilient pressing elements onto the sliding surfaces when the plate frame is located at the service end-position,
• wherein said selecting device of said carriage support structure comprises a moving mechanism for moving the blocking member with respect to said carriage support structure between said blocking position and said non-blocking position, wherein said moving mechanism of the selecting device is configured such that when the plate frame is being moved from the service end-position towards the initial position, the blocking member automatically moves from said non-blocking position to said blocking position at the moment the plate frame is sliding beyond the first end position.