Method for determining amplitude of stick-slip on a valve assembly and implementation thereof
View Patent ↗A method for processing operating data (e.g., position, setpoint, and pressure) for a valve assembly. The method is configured to associate characteristics of operation for the valve assembly with a root cause and/or a contributing factor. In one embodiment, the method can assign a first amplitude with a value that quantifies movement or “jump” of the valve stem that results from stick-slip on the valve assembly. The method can also assign a second amplitude with a value that quantifies a change in the data for the setpoint. The method can further ascertain the relationship or “position” of the first amplitude relative to the second amplitude, or vice versa. The method can use the relationship between the first amplitude and the second amplitude to indicate the root cause of the operation of the valve assembly.
1. A method for quantifying an operating condition on a valve assembly, comprising:
receiving an input with a sample set of data having data samples that correspond with operating parameters for a valve assembly, the operating parameters comprising a position and a setpoint;
determining a first amplitude having a value that quantifies a change in the position from a first position to a second position by
determining a stick-slip condition metric; and
comparing the stick-slip condition metric to a threshold criteria, wherein the threshold criteria has a value that corresponds with stick-slip on the valve assembly and wherein the value for the first amplitude indicates that the stick-slip condition metric exceeds the value for the threshold criteria;
comparing the first amplitude to a second amplitude, the second amplitude having a value that quantifies a change in the setpoint from a first setpoint to a second setpoint; and
generating an output that reflects a relative position of the first amplitude with respect to the second amplitude; and
using the output, triggering an alert that corresponds with either instructions to change process parameters or instructions to perform maintenance on the valve assembly,
wherein the stick-slip condition metric is calculated in accordance with,
M
ST
=
M
P
M
S
,
wherein M ST is the stick-slip condition metric, M P is a position metric, and M S is a setpoint metric,
wherein the position metric M P and the setpoint metric M S are calculated in accordance with,
M
P
=
Σ
(
P
i
-
P
i
-
1
)
X
N
X
,
M
S
=
Σ
(
S
i
-
S
i
-
1
)
X
N
X
,
and
wherein P i-1 is a first data sample for the position, P i is a second data sample for the position that is adjacent the first data sample in the sample set, S i-1 is a first data sample for the setpoint, S i is a second data sample for the setpoint that is adjacent the first data sample in the sample set, N is a number of data samples in the sample set, and X is a p-norm parameter.
2. The method of claim 1 , further comprising:
calculating one or more sample intervals between data samples that are adjacent to one another in the sample set of data; and
comparing each of the sample intervals to a first threshold value that relates to the position,
wherein the first threshold value is calculated in accordance with,
RMP
position
=
Σ
(
P
i
-
P
i
-
1
)
X
N
X
,
wherein RMP position is the first threshold value, P i-1 is a first data sample for the position in the sample set, P i is a second data sample for the position that is adjacent the first data sample in the sample set, N is a number of data samples in the sample set, and X is a p-norm parameter, and
wherein the value for the first amplitude includes the sample intervals that deviate from the first threshold value.
3. The method of claim 2 , further comprising:
adding the one or more sample intervals together to arrive at a total interval value, wherein the value for the first amplitude incorporates the total interval value.
4. The method of claim 3 , wherein the value for the first amplitude includes the sample intervals that are greater than the first threshold value.
5. An apparatus, comprising:
a processor configured to access a memory that has one or more executable instructions stored thereon, the executable instructions comprising one or more instructions that configure the apparatus for
receiving an input with a sample set of data having data samples that correspond with operating parameters for the valve assembly, the operating parameters comprising a position and a set point;
determining a first amplitude having a value that quantifies a change in the position from a first position to a second position by,
determining a stick-slip condition metric; and
comparing the stick-slip condition metric to a threshold criteria, wherein the threshold criteria has a value that corresponds with stick-slip on the valve assembly and wherein the value for the first amplitude indicates that the stick-slip condition metric exceeds the value for the threshold criteria;
comparing the first amplitude to a second amplitude, the second amplitude having a value that quantifies a change in the setpoint from a first setpoint to a second setpoint;
generating an output that reflects a relative position of the first amplitude with respect to the second amplitude; and
using the output, triggering an alert that corresponds with either instructions to change process parameters or instructions to perform maintenance on the valve assembly,
wherein the stick-slip condition metric is calculated in accordance with,
M
ST
=
M
P
M
S
,
wherein M ST is the stick-slip condition metric, M P is a position metric, and M S is a setpoint metric,
wherein the position metric M P and the setpoint metric M S are calculated in accordance with,
M
P
=
Σ
(
P
i
-
P
i
-
1
)
X
N
X
,
M
S
=
Σ
(
S
i
-
S
i
-
1
)
X
N
X
,
and
wherein P i-1 is a first data sample for the position, P i is a second data sample for the position that is adjacent the first data sample in the sample set, S i-1 is a first data sample for the setpoint, S i is a second data sample for the setpoint that is adjacent the first data sample in the sample set, N is a number of data samples in the sample set, and X is a p-norm parameter.
6. The apparatus of claim 5 , wherein the executable instructions include instructions that configure the apparatus for,
calculating one or more sample intervals between data samples that are adjacent to one another in the sample set of data, and
comparing each of the sample intervals to a first threshold value that relates to the position,
wherein the value for the first amplitude includes the sample intervals that deviate from the first threshold value.
7. The apparatus of claim 6 , wherein the executable instruction include instructions that configure the apparatus for,
calculating the first threshold value in accordance with,
RMP
position
=
Σ
(
P
i
-
P
i
-
1
)
X
N
X
,
wherein RMP position is the first threshold value, P i-1 is a first data sample for the position in the sample set, P i is a second data sample for the position that is adjacent the first data sample in the sample set, N is a number of data samples in the sample set, and X is a p-norm parameter.
8. The apparatus of claim 6 , wherein the executable instructions include instructions that configure the apparatus for,
adding the one or more sample intervals together to arrive at a total interval value, wherein the value for the first amplitude incorporates the total interval value.
9. The apparatus of claim 8 , wherein the value for the first amplitude includes the sample intervals that are greater than the first threshold value.
10. A valve positioner for use on a valve assembly having a closure member that moves relative to a seat, said valve positioner comprising:
a processor;
a memory coupled with the processor; and
one or more executable instructions stored on the memory and configured to be executed by the processor, the executable instructions comprising one or more instructions for,
receiving an input with a sample set of data having data samples that correspond with operating parameters for the valve assembly, the operating parameters comprising a position and a setpoint;
determining a first amplitude having a value that quantifies a change in the position from a first position to a second position by,
determining a stick-slip condition metric; and
comparing the stick-slip condition metric to a threshold criteria, wherein the threshold criteria has a value that corresponds with stick-slip on the valve assembly and wherein the value for the first amplitude indicates that the stick-slip condition metric exceeds the value for the threshold criteria;
comparing the first amplitude to a second amplitude, the second amplitude having a value that quantifies a change in the setpoint from a first setpoint to a second set point; and
generating an output that reflects a relative position of the first amplitude with respect to the second amplitude; and
using the output, triggering an alert that corresponds with either instructions to change process parameters or instructions to perform maintenance on the valve assembly, wherein the stick-slip condition metric is calculated in accordance with,
M
ST
=
M
P
M
S
,
wherein M ST is the stick-slip condition metric, M P is a position metric, and M S is a setpoint metric,
wherein the position metric M P and the setpoint metric M S are calculated in accordance with,
M
P
=
E
(
P
i
-
P
i
-
1
)
X
N
X
,
M
S
=
E
(
S
i
-
S
i
-
1
)
X
N
X
,
and
wherein P i-1 is a first data sample for the position, P i is a second data sample for the position that is adjacent the first data sample in the sample set, S 1-1 is a first data sample for the setpoint, S i is a second data sample for the setpoint that is adjacent the first data sample in the sample set, N is a number of data samples in the sample set, and X is a p-norm parameter.
11. The valve positioner of claim 10 , wherein the executable instructions include instructions for,
calculating one or more sample intervals between data samples that are adjacent to one another in the sample set of data, and
comparing each of the sample intervals to a first threshold value that relates to the position,
wherein the first amplitude includes the sample intervals that deviate from the first threshold value.
12. The valve positioner of claim 11 , wherein the executable instructions include instructions for,
adding the one or more sample intervals together to arrive at a total interval value, wherein the value for the first amplitude incorporates the total interval value.
13. The valve positioner of claim 11 , wherein the executable instruction include instructions for,
calculating the first threshold value in accordance with,
RMP
position
=
Σ
(
P
i
-
P
i
-
1
)
X
N
X
,
wherein RMP position is the first threshold value, P i-1 is a first data sample for the position in the sample set, P i is a second data sample for the position that is adjacent the first data sample in the sample set, N is a number of data samples in the sample set, and X is a p-norm parameter, and
wherein the value for the first amplitude includes the sample intervals that are greater than the first threshold value.