System and method for detecting a stick-slip

1. A method of performing online diagnostics for a valve, said method comprising:

receiving valve information while the valve is in operation, the valve information including setpoint data and position data associated with the valve;

defining a plurality of regions, wherein each region is defined by points in time at which a setpoint of the valve intersects a position of the valve;

calculating, for each of the plurality of regions, an area between the setpoint and the position of the valve;

processing the setpoint data by calculating a setpoint value based on the setpoint data at each of the plurality of time intervals, wherein the setpoint value is based on a p-norm of a first difference of setpoint;

processing the position data at a plurality of time intervals by calculating a position value based on the position data at each of the plurality of time intervals, wherein the position value is based on a p-norm of a first difference of position; and

detecting an occurrence of a stick-slip based on the processing.

2. The method of claim 1 , wherein:

processing the setpoint data and the position data at the plurality of time intervals comprises:

comparing the calculated areas with an area threshold level; and

identifying each calculated area that exceeds the area threshold level; and

detecting the occurrence of the stick-slip based on the processing comprises detecting an occurrence of a stick-slip cycle when a defined consecutive number of identified calculated areas exceeds the area threshold level.

3. The method of claim 1 , wherein:

processing the setpoint data and the position data at the plurality of time intervals comprises:

identifying a lowest calculated area from the calculated areas; and

detecting the occurrence of the stick-slip based on the processing comprises detecting the occurrence of the stick-slip when the lowest calculated area exceeds an area threshold level.

4. The method of claim 1 further comprising, prior to detecting an occurrence of the stick-slip, determining at least one of the following:

shutoff cycling is not detected;

if tight shutoff is enabled, the position of the valve exceeds a position threshold;

if a tight shutoff is enabled, the setpoint of the valve exceeds a setpoint threshold; and

an unexpected movement in the position of the valve is detected.

5. The method of claim 1 further comprising providing a recommendation to correct the stick-slip, wherein the recommendation comprises one or more of the following:

adjusting a valve packing;

applying a packing lubricant to the valve packing;

replacing the valve packing; and

replacing a stem of the valve.

6. The method of claim 1 , wherein:

detecting the occurrence of the stick-slip based on the processing comprises:

comparing a ratio of the position value over the setpoint value to a stick-slip threshold value; and

detecting the occurrence of the stick-slip when the ratio is greater than the stick-slip threshold value.

7. A system for performing online diagnostics for a valve, said system comprising:

a process controller generating a plurality of setpoints for operating the valve through a series of gradual movements;

a positioner component receiving the plurality of setpoints and generating a signal for positioning the valve based on the plurality of setpoints; and

a processor programmed to:

receive valve information from the positioner component, the valve information including setpoint data and position data associated with the valve;

define a plurality of regions, wherein each region is defined by points in time at which a setpoint of the valve intersects a position of the valve;

calculate, for each of the plurality of regions, an area between the setpoint and the position of the valve;

process the setpoint data by calculating a setpoint value based on the setpoint data at each of the plurality of time intervals, wherein the setpoint value is based on a p-norm of a first difference of setpoint;

process the position data at a plurality of time intervals by calculating a position value based on the position data at each of the plurality of time intervals, wherein the position value is based on a p-norm of a first difference of position; and

detect an occurrence of a stick-slip based on the processing.

8. The system of claim 7 , wherein:

processing the setpoint data and the position data at the plurality of time intervals comprises:

comparing the calculated areas with an area threshold level; and

identifying each calculated area that exceeds the area threshold level; and

detecting the occurrence of the stick-slip based on the processing comprises detecting an occurrence of a stick-slip cycle when a defined consecutive number of identified calculated areas exceeds the area threshold level.

9. The system of claim 7 , wherein:

processing the setpoint data and the position data at the plurality of time intervals comprises:

identifying a lowest calculated area from the calculated areas; and

detecting the occurrence of the stick-slip based on the processing comprises detecting the occurrence of the stick-slip when the lowest calculated area exceeds an area threshold level.

10. The system of claim 7 , wherein the processor is further programmed to, prior to detecting an occurrence of the stick-slip, determine at least one of the following:

shutoff cycling is not detected;

if tight shutoff is enabled, the position of the valve exceeds a position threshold;

if a tight shutoff is enabled, the setpoint of the valve exceeds a setpoint threshold; and

an unexpected movement in a position of the valve is detected.

11. The system of claim 7 , wherein the processor is further programmed to provide a recommendation to correct the stick-slip, wherein the recommendation comprises one or more of the following:

adjusting a valve packing;

applying a packing lubricant to the valve packing;

replacing the valve packing; and

replacing a stem of the valve.

12. The system of claim 7 , wherein:

detecting the occurrence of the stick-slip based on the processing comprises:

comparing a ratio of the position value over the setpoint value to a stick-slip threshold value; and

detecting the occurrence of the stick-slip when the ratio is greater than the stick-slip threshold value.

13. One or more non-transitory computer-readable media comprising computer-executable instructions for performing online diagnostics for a valve, the computer-executable instructions causing at least one processor to:

receive valve information while the valve is in operation, the valve information including setpoint data and position data associated with the valve;

process the setpoint data and the position data at a plurality of time intervals by:

calculating a setpoint value based on the setpoint data at each of a plurality of time intervals, wherein the setpoint value is based on a p-norm of a first difference of setpoint; and

calculating a position value based on the position data at each of the plurality of time intervals, wherein the position value is based on a p-norm of a first difference of position; and

detect an occurrence of a stick-slip based on the processing.

14. The non-transitory computer-readable media of claim 13 , wherein the computer-executable instructions further cause the at least one processor to define a plurality of regions, wherein:

each region is defined by points in time at which a setpoint of the valve intersects a position of the valve;

processing the setpoint data and the position data at the plurality of time intervals comprises:

for each of the plurality of regions, calculating an area between the setpoint and the position of the valve;

comparing the calculated areas with an area threshold level; and

identifying each calculated area that exceeds the area threshold level; and

detecting the occurrence of the stick-slip based on the processing comprises detecting an occurrence of a stick-slip cycle when a defined consecutive number of identified calculated areas exceeds the area threshold level.

15. The non-transitory computer-readable media of claim 13 , wherein the computer-executable instructions further cause the at least one processor to define a plurality of regions, wherein:

each region is defined by points in time at which a setpoint of the valve intersects a position of the valve; and

processing the setpoint data and the position data at the plurality of time intervals comprises:

for each of the plurality of regions, calculating an area between the setpoint and the position of the valve;

identifying a lowest calculated area from the calculated areas; and

detecting the occurrence of the stick-slip based on the processing comprises detecting an occurrence of the stick-slip when the lowest calculated area exceeds an area threshold level.

16. The non-transitory computer-readable media of claim 13 , wherein the computer-executable instructions further cause the at least one processor to provide a recommendation to correct the stick-slip, wherein the recommendation comprises one or more of the following:

adjusting a valve packing;

applying a packing lubricant to the valve packing;

replacing the valve packing; and

replacing a stem of the valve.

17. The non-transitory computer-readable media of claim 13 , wherein:

detecting the occurrence of the stick-slip based on the processing comprises:

comparing a ratio of the position value over the setpoint value to a stick-slip threshold value; and

detecting the occurrence of the stick-slip when the ratio is greater than the stick-slip threshold value.