Apparatus for adjusting shape memory alloy transition temperatures to track slowly changing ambient temperature

A valve, comprising:

• a valve body;
• an orifice within the valve body;
• a fluid flow restraining member located at a first location of the orifice, the fluid flow restraining member movable between a closed position and an open position;
• a shape memory alloy element connected to the fluid flow restraining member, the shape memory alloy element causing pivotal movement of the fluid flow restraining member between open and closed positions responsive to at least a threshold amount of temperature change of the shape memory alloy element;
• and
• an expansion element attached to the shape memory alloy element, the expansion element responsive to temperature changes at a rate lower than a rate of change of temperature indicative of a valve leak, the expansion element adjusting tension on the shape memory alloy element, thereby changing the threshold amount of temperature change.

A method of actuating a valve from an open position to a closed position, the method comprising:

• experiencing a first temperature change from a first temperature to a second temperature at the valve over a first amount of time;
• adjusting a tensile stress on a shape memory alloy element used to actuate the valve in response to the first temperature change, thereby adjusting a threshold temperature at which the shape memory alloy element actuates;
• experiencing a second temperature change at a valve actuator including the shape memory alloy element over a second amount of time;
• actuating the valve between the open position and the closed position in response to the second temperature change, wherein the second temperature change is greater than the threshold temperature and the second amount of time is shorter than the first amount of time.