| 摘要 |
A protective device that isolates part of a plumbing or fluid flow system by stopping supply of fluid in the event of freezing conditions comprises a valve 1 and a spring actuator (4, Fig. 4) for actuating the valve. The actuator biases the valve to a closed position but is restrained from doing so by restraining means in above freezing conditions, so that the valve remains normally open. The restraining means comprises a frangible vessel 3 that contains a trapped volume of liquid that may be the same as that which flows in the system (e.g. water for a plumbing system). The vessel will break on freezing expansion of the liquid and allow the actuator to close the valve. |
