| 摘要 |
PURPOSE:To prevent any pressure drop in an IA system from occurring, by installing a pressure-regulating valve which makes pressure in an instrument compressed air system constant at time of backup operation. CONSTITUTION:In case of backup operation from an SA system 9 to an IA system 1, if an SA backup valve 16 is opened, a pressure regulating valve 101 opens as well. This pressure-regulating valve 101 is controlled of its opening by a pressure controller 102. If pressure in the IA system 1 goes down, opening of the pressure-regulating valve 101 is throttled to some extent whereby pressure in the IA system 1 is kept constant. Consequently, such a situation that pressure in the IA system 1 is abnormally lowered and thereby a plant is scrammed, is surely prevented from occurring.
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