Plugged impulse line detection
First Claim
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1. A method to diagnose plugging of at least one impulse line carrying a process fluid therethrough;
- said method comprising;
receiving a digital signal from a differential pressure transmitter representative of pressure differential across at least two points of said impulse line;
processing the signal through a filter to provide a filtered noise signal;
calculating an absolute value of the filtered noise signal;
arbitrating a plurality of noise threshold limit and a plurality of cross-over frequency of said absolute value of the filtered noise signal beyond said noise threshold limit to characterize plugging diagnostics of the impulse line corresponding to each of a plurality of predetermined diagnostic states pertaining to said impulse lines;
comparing the absolute value of the filtered noise signal relative to said arbitrated noise threshold limit to obtain plugging diagnostics information; and
discriminating among said plurality of diagnostic states as a function of said plugging diagnostic information.
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Abstract
A digital signal representative of a difference in pressure is received from a differential pressure transmitter. A noise signal is obtained by processing the signal through a band pass filter or otherwise to provide a filtered noise signal. Absolute values of the filtered noise signal are calculated and compared to one or more predetermined threshold values to determine if one or more impulse lines are plugged. A training mode is used to determine the thresholds, which may be a function of flow rate and other flow conditions.
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Citations
20 Claims
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1. A method to diagnose plugging of at least one impulse line carrying a process fluid therethrough;
- said method comprising;
receiving a digital signal from a differential pressure transmitter representative of pressure differential across at least two points of said impulse line; processing the signal through a filter to provide a filtered noise signal; calculating an absolute value of the filtered noise signal; arbitrating a plurality of noise threshold limit and a plurality of cross-over frequency of said absolute value of the filtered noise signal beyond said noise threshold limit to characterize plugging diagnostics of the impulse line corresponding to each of a plurality of predetermined diagnostic states pertaining to said impulse lines; comparing the absolute value of the filtered noise signal relative to said arbitrated noise threshold limit to obtain plugging diagnostics information; and discriminating among said plurality of diagnostic states as a function of said plugging diagnostic information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- said method comprising;
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10. A machine readable medium having instructions stored thereon for causing a machine to execute a method comprising:
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receiving a digital signal representative of a difference in pressure from a differential pressure transmitter; processing the signal through a band pass filter to provide a filtered noise signal; calculating an absolute value of the filtered noise signal; and counting the number of times that the absolute value of the filtered noise signal exceeds a predetermined threshold value to determine if an impulse line is plugged.
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11. A method comprising:
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receiving digital data from a differential pressure transmitter; filtering out a required band of signals and retaining a desired frequency band signal; calculating thresholds based on user confidence limits for detection and false alarms; calculating thresholds based on flow rate variances; calculating thresholds based on different process fluid and process conditions; detecting a plugged impulse line or lines based on the threshold calculated and comparing with the filtered signal; and alarming the condition of the impulse lines with the confidence limits.
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12. A method comprising:
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detecting a difference in pressure via impulse lines coupled to a process being monitored; filtering the detected pressure difference to obtain a noise signal; converting the noise signal to absolute values; comparing the absolute values to predetermined thresholds; and counting the number of times the absolute values exceed predetermined thresholds to determine whether one or both impulse lines are plugged. - View Dependent Claims (13, 14, 15)
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16. A system comprising:
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a differential pressure transmitter for coupling to impulse lines to sense a difference in pressure in a process; and means for discriminating among a plurality of diagnostic states pertaining to said impulse lines as a function of plugging diagnostics information, said diagnostics information being determined as a function of noise, said means comprising; an analog to digital converter that converts sensed pressure to a digital representation; a band pass filter that provides a noise signal from the digital representation; and a detector that counts a number of times an absolute value of the noise signal reaches a predetermined threshold. - View Dependent Claims (17, 18, 19, 20)
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Specification