Table 1: Faults to be detected and isolated.

Fault Description f1 Valve clogging f2 Valve or valve seat sedimentation f3 Valve or valve seat erosion f4 Increasing of valve or bushing friction f5 External leakage f6 Internal leakage (valve tightness) f7 Medium evaporation or critical flow f8 Twisted servomotor's piston rod f9 Servomotor's housing or terminals tightness f10 Servomotor's diaphragm perforation f11 Servomotor's spring fault f12 Electropneumatic transducer fault f13 Rod displacement sensor fault f14 Pressure sensor fault f15 Positioner feedback fault f16 Positioner supply pressure drop f17 Unexpected pressure change across the valve f18 Fully or partly opened bypass valves f19 Flow rate sensor fault