Stop valve for installation in a pipeline, in particular in a pipeline of a nuclear facility

A stop valve for installation in a pipeline to stop a fluid flow through the pipeline in the event of an operational failure, the stop valve comprising:

• a valve housing including a flow channel passing through the valve housing,
• a closure member arranged at least partially in the flow channel and reversibly transferrable between an open position and a closed position such as to open or close the flow channel through the valve housing,
• a non-electrically driven actuator mechanism operatively coupled to the closure member for transferring the closure member at least from the open position in the closed position, wherein the actuator mechanism is configured to be activated by a fluid flow through the flow channel reaching or exceeding a switching temperature and/or switching flow rate during operation, and
• at least one position indicator to indicate whether the closure member is in the open position or in the closed position,
• wherein the position indicator comprises at least one indicator member movably arranged in or at the valve housing between a first position and a second position, wherein the indicator member is magnetically coupled to the closure member such that the indicator member is magnetically transferred into the first position when the closure member is transferred into the open position, and into the second position when the closure member is transferred into the closed position,
• wherein the non-electrically driven actuator mechanism comprises an actuator spring assembly operatively coupled to the closure member and arranged in the flow channel such as to be in direct contact with a fluid flowing through the flow channel during operation, wherein the spring assembly comprises a shape-memory material and is configured to change its shape upon reaching or exceeding a switching temperature due to heating by the fluid, thereby transferring the closure member from the open position in the closed position, and
• wherein the actuator spring assembly comprises a stack of star washers each of which comprises a washer ring and at least three spring arms extending in a star-shaped manner radially outward from the washer ring, wherein upon reaching or exceeding the switching temperature each star washer experiences a specific axial expansion along a length axis of the stack due to its arms bending in a direction transverse to a plane defined by the washer ring.