Thermal expansion relief valve

摘要: A fluid flow control valve, e.g. a pressure vacuum breaker, includes thermal expansion relief valve for protecting the against damage due to freezing. The has body of rigid material and defines main conduit. mounted conduit in communication with conduit, element moves within between first sealing position engagement seat resist second spaced from allow through spring urging toward predetermined force selected exceed normal operating lie below damaging valve. valves, by retrofit, is also described.