EMERGENCY SHUTDOWN VALVE

PROBLEM TO BE SOLVED: To provide a non-power supply type emergency shutdown valve capable of changing-over between a state in which a flow passage is shutdown when at least any one of occurrence of earthquake and an increased flow speed is detected and a state in which the flow passage is shutdown only when both occurrence of earthquake and an increased flow speed are detected.SOLUTION: An emergency shutdown valve of this invention comprises a biasing mechanism for biasing a valve member to its closed state; a lock mechanism 3 for locking the valve member to an opened state against the biasing by the biasing mechanism; an earthquake detecting mechanism 5 for detecting an occurrence of earthquake under no power supply; a flow speed detecting mechanism for detecting an increased flow speed of fluid flowing in the flow passage under no power supply; a lock releasing mechanism 4 for releasing the locked state of the valve member by the lock mechanism 3; and a changing-over means 9 for changing over the lock releasing mechanism 4 between the first state in which the locked state of the valve member is released when at least any one of detection of occurrence of earthquake and detection of increased flow speed is present and the second state in which the locked state of the valve member is released only when both detection of the occurrence of earthquake and detection of increased flow speed are present.SELECTED DRAWING: Figure 4 【課題】地震の発生及び流速の上昇の少なくともいずれか一方を感知したとき流路を遮断する状態と、双方を感知したときだけ流路を遮断する状態とに切り換え可能な無電源式の緊急遮断弁を提供する。【解決手段】緊急遮断弁は、弁体を閉状態へ付勢する付勢機構と、付勢機構による付勢に抗して弁体を開状態にロックするロック機構３と、地震の発生を無電源で感知する地震感知機構５と、流路を流れる流体の流速の上昇を無電源で感知する流速感知機構と、ロック機構３による弁体のロックを解除するロック解除機構４と、ロック解除機構４を、地震の発生の感知及び流速の上昇の感知の少なくともいずれか一方があるときに弁体のロックを解除する第１状態と、地震の発生の感知及び流速の上昇の感知の双方があるときにだけ弁体のロックを解除する第２状態と、に切り換えるための切換手段９と、を備える。【選択図】図４