PURPOSE: To control function of an alarm by detecting difference between output signal of temperature sensors arranged on the inner circumference and the outer circumference of a packing pressing member.
CONSTITUTION: A valve plug 3 is inserted slidably through a packing 23 into a plug insertion hole 22 made through an upper cover 12 fixed to a valve body. A member 27 for pressing the packing 23 is arranged on the upper cover 12, and temperature sensors 51, 52 for detecting temperatures at the outer circumference and the inner circumference are arranged on the pressing member 27. Then the difference between output signals fed from the sensors 51, 52 is amplified through a comparison amplifier 56, and an alarm 57 is operated when the difference exceeds over a preset level. Upon occurrence of leakage of fluid to be controlled, temperatures at the inner and outer circumference of the pressing 27 vary, and the alarm 57 is operated through the temperature difference thus information leakage.
TOKI YOSHIKUNI
TANAKA MIKIO
