| 摘要 |
PURPOSE:To enable the proper detection of abnormality in the flow rate without increasing the passage resistance of a fluid when the flow rate thereof falls below the lower limit thereof, by connecting a bypass line having a relief valve in parallel with a detection tube to communicate. CONSTITUTION:A float 10 movable in the direction of a fluid moves is housed in a detection tube 20 and a sensor 24 is provided to detect the position of the float 10 with respect to the detection tube 20 while a control section 26 to discriminate the abnormal condition of the flow rate according to a detection output signal following an abnormal drop in the float level of the detection tube 20. Moreover, a bypass line 32 having a relief valve 30 in parallel with the detection tube 20 is connected to a fluid transfer line 22 to communicate. Then, in a large flow rate area, a valve 30 operates according to the flow rate to bypass the fluid thereby stabilizing the fluid resistance of the detection tube 20. The taper contact area between a seat 48 and a disc 52 of a valve 30 are set as small as possible to improve the sensitivity in the small flow rate area of the fluid thereby enabling proper detection of abnormality in the flow rate.
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