A fluid flow control valve includes a valve body having a bore configured to convey fluid from an inlet port to an outlet port. The inlet and outlet ports, and the bore therebetween, define a fluid flow path through the valve body. A gate element is disposed in the bore. The gate element is positionable in the bore from a first position, which allows fluid flow through the bore, to a second position which restricts fluid flow through the bore. An actuator is coupled to the gate element and is configured to urge the gate element from the first position toward the second position. A fuse consisting of a transformable retainer is configured to retain the gate element in the first position, while the retainer is in a first condition, and to allow the gate element to move toward the second position when the retainer transforms to a second condition. The transformable retainer may be configured to transform from the first condition to the second condition responsive to a signal, e.g., a signal indicative of a thermal change or a fluid leak. The innovative valves are especially but not exclusively suited for governing flow in a heat transfer system, particularly a heat transfer system for dissipating heat from a plurality of computer servers. The innovative valves may be embodied in systems, methods, apparatuses, and components.