Method and means for monitoring a control apparatus

A method for monitoring a control apparatus having at least one pneumatic actuating drive, a valve body, a spindle connected to the valve body, and a positioner, the method comprising the following steps:

• a) determining a first valve position (h1) at a first time (t1);
• b) producing a force with the actuating drive, on the basis of changes in at least one manipulated variable, resulting in a well-defined, reproducible, uniform movement of the spindle and valve body in a first direction;
• c1) modifying the manipulated variable at the output of the positioner in such a way that a resulting force acts on the spindle that reverses the direction of movement of the spindle for the first time, whereby the changes in the variable are likewise well-defined, reproducible and uniform, but act in an opposing, second direction;
• c2) determining a second valve position (h2) at a second time (t2), when a first reversal of direction is triggered as a result of step c1;
• d) determining a third valve position (h2) at a third time (t3) at which, due to unavoidable delays, the spindle reaches after the first reversal of direction, the third position (h2) having a first defined relationship to the second valve position (h2);
• e) defining and determining the first time period (from t1 to t11) between the second time (t2) and the third time (t3);
• and
• f) comparing the first time period (from t1 to t11) with a corresponding first target value for a determination of the operativeness of the control apparatus;
• g) maintaining the movement of the spindle after the first time period (from t1 to t11) and determining a fourth valve position (h4) at a fourth time (t4), as well as of a fifth valve position (h5) at a fifth time (t5);
• h) calculating a first speed of the movement of the spindle from the fourth valve position to the fifth valve position (h4 and h5) over the period from the fourth time to the fifth time (t4 and t5);
• and
• i) comparing the first speed with a corresponding second target value, in order to determine the operativeness of the control apparatus.