Abnormality detection/suppression system for a valve apparatus

In a valve apparatus including a valve casing which defines therein a fluid passage having first valve seats mounted therein, a valve body movable between a fully open position and a fully closed position for selectively opening or closing said fluid passage to fluid flow thru said valve apparatus, said valve body having second valve seats mounted thereon and adapted to selectively engage with said first valve seats in a fluid-tight manner in a leak-free valve apparatus, a stem having one end portion coupled to said valve body integrally therewith and the other end portion extending through a gland/packing assembly installed around said valve stem in said valve casing to the exterior thereof, and a driving unit operatively coupled to said stem at a location externally of said valve casing so as to move said valve body between the two extreme, intended modes of said fully open position and said fully closed position, or in the event of a leak condition that said valve body assumes a position only partially fully-open or partially fully-closed, respectively, to move said valve body towards said fully-open position or fully-closed position;

• an abnormality detection and suppression system, characterized in that a vibration sensor, a temperature sensor and a strain sensor are disposed internally of said stem at a portion thereof which is located outside of said valve casing when said valve body is intentionally moved to said fully closed position, and that a mini-computer control unit is disposed externally of said valve casing and adapted to receive output signals from said vibration sensor, said temperature sensor and said strain sensor, wherein when said valve body should occupy the presumed position corresponding to the intended said fully closed position, substantially a partially fully-closed position, said control unit responds to the output signal of said vibration sensor indicating occurrence of vibration brought abut by leakage passing through the presumedly sealingly-engaged said first and second valve seats to thereby actuate and control said driving unit such that said valve body is further urged and driven in the valve closing direction towards the said fully closed position by means of said stem while monitoring simultaneously a load applied to said stem with said strain sensor until substantially no vibration is detected by said vibration sensor, thereby indicating cessation of the prior leak condition at said valve seats;
• and whereas when said temperature sensor detects a temperature change due to leakage flow in the state in which said valve body is disposed to occupy the assumed position corresponding to the intended said fully open position, it releases an output signal that triggers a leakage failure condition in the control unit, whereupon said control unit responds to the output signal of said temperature sensor indicating occurrence of leakage through said gland/packing assembly to thereby actuate said driving unit such that said valve body is further driven in the valve opening direction towards said fully open position by means of said stem while monitoring simultaneously a load applied to said stem with said strain sensor until said temperature change and output signal substantially disappear, thereby also indicating cessation of the prior leak condition in said valve apparatus.