Method and apparatus for detecting a fault of a control valve assembly in a control loop
First Claim
1. A method for determining the cause of a fault in an automatically operated valve assembly of the type having a plurality of elements including at least an actuator, a valve member and positioner controlled by a control signal, comprising the steps of:
- a) defining a mathematical model for operation of the control valve assembly including assigning values to critical parameters including at least the control signal and the position of the valve member,b) deriving data corresponding to a plurality of values of the control signal and corresponding positions of the valve member,c) correlating the mathematical model to the data measured from the control signal and the corresponding positions of the valve member to determine both if an operational deviation from the model exists in the valve assembly and the identity of the critical parameter and control valve element causing the deviation.
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Abstract
A method and apparatus for detecting a fault of an automatically operated control valve assembly. Data consisting of several values of the control signal (i) and corresponding values of the position (h) of the control valve is measured and recorded. A mathematical model for the control valve assembly is defined. The mathematical model is fitted to the data measured from the control signal (i) and the position (h) of the control valve. At least one critical parameter for each component of the valve assembly, that is the valve (2) itself, the actuator (3) and the positioner (5), is chosen. The values and changes of the critical parameters are computed from the mathematical model fitted to the measured data. The component in which the fault is located is detected on the basis of the computed values of the critical parameters.
65 Citations
10 Claims
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1. A method for determining the cause of a fault in an automatically operated valve assembly of the type having a plurality of elements including at least an actuator, a valve member and positioner controlled by a control signal, comprising the steps of:
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a) defining a mathematical model for operation of the control valve assembly including assigning values to critical parameters including at least the control signal and the position of the valve member, b) deriving data corresponding to a plurality of values of the control signal and corresponding positions of the valve member, c) correlating the mathematical model to the data measured from the control signal and the corresponding positions of the valve member to determine both if an operational deviation from the model exists in the valve assembly and the identity of the critical parameter and control valve element causing the deviation. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for determining the cause of a fault in an automatically operated valve assembly of the type having a plurality of elements including at least an actuator, a valve member and positioner controlled by a control signal, comprising the steps of:
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a) defining a mathematical model for operation of the control valve assembly including assigning values to critical parameters including at least the control signal and the position of the valve member, b) deriving data corresponding to a plurality of values of the control signal and corresponding positions of the valve member, c) correlating the mathematical model to the data measured from the control signal and the corresponding positions of the valve member to determine both if an operational deviation from the model exists in the valve assembly and the probable identity of the critical parameter and control valve element causing the deviation, said control valve assembly including a quarter turn valve and a cylinder-piston operated actuator and wherein the following equation is used as the mathematical model;
##EQU2## where x=distance travelled by the actuatorψ
=rotational angle of the valvet=time mred =reduced mass of the actuator J=combined inertia moment of the valve and the actuator b=actuator coefficient M.sub.μ
=friction moment of the valvefm =attenuation coefficient of the actuator fv =attenuation coefficient of the valve Fm =force applied to the actuator piston pA, pB =pressure levels of the actuator cylinder. - View Dependent Claims (8, 9, 10)
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Specification