US 10,852,224 B2Granted

Method of measuring metal loss from equipment in process systems

AssigneeRoxar Flow Measurement AS

InventorsOlav Espejord, Cristian Mihai Iorga

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Abstract

Method of measuring metal loss from equipment in process systems. Probes installed for monitoring one or both of erosion and corrosion (metal loss) in process equipment use results from resistivity measurements in a measurement element and a reference element to produce a measurement of metal loss in the measurement element exposed to process flow and may trigger an alarm when measured metal loss exceeds a threshold level. Prior art methods produce numerous false alarms hiding true alarms. The present method ignores these false alarms that are common in known methods by calculating confidence measures that are included in the metal loss calculations to attenuate noise that otherwise would produce false alarms or misinterpretation of the corrosion or erosion state in the process equipment being monitored.

Claims11

Dependent claims

Method of measuring metal loss from equipment in process systems in contact with erosive and/or corrosive process fluids, including pipelines and fittings in gas and oil wells exposed to fluids flowing from downhole formations, wherein the method comprises the steps of:

a) providing a monitoring probe in contact with the process fluids, said probe comprising one or more measurement elements exposed to the flow of the process fluids, and a reference element protected from flow of the process fluids,
b) measuring electrical resistance e across said one or more measurement elements,
c) measuring electrical resistance Re across the reference element,
d) calculating the metal loss Δhe from the resistivity measured in accordance with the formula
Δhe=he−hr·(Rr/Re) (1),
where Δhe, Rr and Re are as defined above and he and hr represents the original thickness of said at least one measurement element and the reference element, respectively, characterized in
e) providing a confidence measure of change in resistivity observed, by calculating the stability of the reference element resistance value or stability of temperature of the probe measured by an additional temperature sensor,
f) applying the confidence measure from step e) in a comparison of resistivity changes as a function of time, to provide a trustworthy value for real metal loss in said one or more measurement elements, thus attenuating resistivity changes caused by noise in the process system, and attenuating resistivity changes to a higher degree when the confidence measure is low and attenuating resistivity changes to a lower degree when the confidence measure is high, and
the confidence measure in step e) is calculated in accordance with formula (2)
confidence=(L−Abs(Rt−Ra))/L (2),
where confidence represents calculated confidence with decimal values from ranging from 0 to 1, where the value 0 represents no or low confidence, and the value 1 represents high confidence, Rt represents the latest reference resistance value from a selected range of measurements, Ra represents a weighted average of resistance samples taken at previous points in time, and L represents a noise limit value.

8 more elements

a) providing a monitoring probe in contact with the process fluids, said probe comprising one or more measurement elements exposed to the flow of the process fluids, and a reference element protected from flow of the process fluids,
b) measuring electrical resistance e across said one or more measurement elements,
c) measuring electrical resistance Re across the reference element,
d) calculating the metal loss Δhe from the resistivity measured in accordance with the formula
Δhe=he−hr·(Rr/Re) (1),
where Δhe, Rr and Re are as defined above and he and hr represents the original thickness of said at least one measurement element and the reference element, respectively, characterized in that
e) providing a confidence measure of change in resistivity observed, by calculating the stability of the reference element resistance value or stability of temperature of the probe measured by an additional temperature sensor,
f) applying the confidence measure from step e) in a comparison of resistivity changes as a function of time, to provide a trustworthy value for real metal loss in said one or more measurement elements, thus attenuating resistivity changes caused by noise in the process system, and attenuating resistivity changes to a higher degree when the confidence measure is low and attenuating resistivity changes to a lower degree when the confidence measure is high, and
in step f) the trustworthy value for real metal loss is calculated in accordance with formula (3):
Yt=Xt·confidence+Yt-1·(1−confidence) (3)
where the calculated output value Yt is filtered resistance ratio between the measurement element and the reference element at a point in time t, representing trusted metal loss,
the input value Xt is unfiltered resistance ratio between the measurement element and the reference element at a point in time t, representing untrusted metal loss,
the input value Yt-1 represents calculated filtered resistance ratio between the measurement element and the reference element at a previous point in time t−1, and
the input value confidence represents the confidence measure calculated in step e).

11 more elements

Method of measuring metal loss from equipment in process systems in contact with one or both of erosive and corrosive process fluids, including pipelines and fittings in gas and oil wells exposed to fluids flowing from downhole formations, wherein the method comprises the steps of:

a) providing a monitoring probe in contact with the process fluids, said probe comprising one or more measurement elements exposed to the flow of the process fluids, and a reference element protected from flow of the process fluids,
b) measuring electrical resistance e across said one or more measurement elements,
c) measuring electrical resistance Re across the reference element,
d) calculating the metal loss Δhe from the resistivity measured in accordance with the formula
Δhe=he−hr·(Rr/Re) (1),
where Δhe, Rr, and Re are as defined above and he and hr represents the original thickness of said at least one measurement element and the reference element, respectively, characterized in that
e) providing a confidence measure of change in resistivity observed, by calculating the stability of the reference element resistance value or stability of temperature of the probe measured by an additional temperature sensor,
f) applying the confidence measure from step e) in a comparison of resistivity changes as a function of time, to provide a trustworthy value for real metal loss in said one or more measurement elements, thus attenuating resistivity changes caused by noise in the process system, and attenuating resistivity changes to a higher degree when the confidence measure is low and attenuating resistivity changes to a lower degree when the confidence measure is high, and
in step f) the trustworthy value for real metal loss is calculated in accordance with formula (3):
Yt=Xt·confidence+Yt-1·(1−confidence) (3)
where the calculated output value Yt is a filtered resistance measurement of the measurement element at a point in time t, representing trusted metal loss,
the input value Xt is unfiltered resistance measurement of the measurement element at a point in time t, representing untrusted metal loss,
the input value Yt-1 represents calculated filtered resistance measurement of measurement element at a previous point in time t−1, and
the input value confidence represents the confidence measure calculated in step e),
repeating the calculation above, where Xt represents unfiltered resistance the measurement for reference element, Yt-1 represents calculated filtered resistance for the reference element at a previous point in time t−1, wherein the input value confidence is as defined above, and then
calculating the ratio between filtered resistance values Yt for resistance values for the measurement element and the reference element, respectively, at selected points in time t.

13 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/736,077Filed 15 Jun 2016
Priority: NO 2015079917 Jun 2015
Published: US 2018/0172577 A121 Jun 2018
Granted: 1 Dec 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01N 17/04
Investigating resistance of materials to the weather, to corrosion, or to light: corrosion probes
G01B 7/06
For measuring length, width or thickness: for measuring thickness
G01N 17/006
Investigating resistance of materials to the weather, to corrosion, or to light: of metals
G01N 27/041
By investigating resistance: of a solid body