Method for determining an operating position of an open/closed-valve and field device

A field device of a technical process plant, comprising:

• an open/closed-valve;
• a pneumatic actuating drive actuating the open/closed-valve;
• an i/p-converter which during normal operation of the plant pneumatically influences a pneumatic working chamber of the actuating drive in such a way that the open/closed-valve moves to one of the open/closed positions and in the case of a predetermined operating condition the i/p-converter vents the working chamber so that the open/closed-valve moves to the other one of the open/closed positions;
• a pressure sensor capturing continuously over time at least one of the pressures selected from a group consisting of a pneumatic working pressure prevailing in the working chamber and a the pneumatic control pressure output at the i/p-converter;
• and
• an analysis unit determining a physical motion variable of the open/closed-valve.

A method for determining a position of an open/closed-valve positioned by a pneumatic actuating drive and movable to an opened open position and a closed position depending on operating requirements, comprising the steps of:

• during normal operation the actuating drive pneumatically influencing with a controllable pressure converter a pneumatic working chamber of the actuating drive such that the open/closed-valve moves to one of the open/closed positions and, in the case of a predefined operating condition, the controllable pressure converter allowing the working chamber to vent so that the open/closed-valve automatically moves to the other one of the open/closed positions;
• capturing at least one of the pressures selected from a group consisting of pressure prevailing in the working chamber and a pneumatic control pressure output at the controllable pressure converter over time;
• and
• determining a pressure change over time on the basis of which a physical operational variable of the open/closed-valve is determined.

A field device of a technical process plant, comprising:

• an open/closed-valve;
• a pneumatic actuating drive actuating the open/closed-valve;
• a controllable pressure converter which during normal operation of the plant pneumatically influences a pneumatic working chamber of the actuating drive in such a way that the open/closed-valve moves to one of the open/closed positions and in the case of a predetermined operating condition the controllable pressure converter vents the working chamber so that the open/closed-valve moves to the other one of the open/closed positions;
• a pressure sensor capturing continuously over time at least one of the pressures selected from a group consisting of a pneumatic working pressure prevailing in the working chamber and a the pneumatic control pressure output at the controllable pressure converter;
• and
• an analysis unit determining a physical motion variable of the open/closed-valve.