Systems and methods to establish maximum time interval between calibrations of process sensors

A method of deriving a maximum calibration interval value indicating an interval of time after which a calibration check should be made on at least one redundant transmitter in a group of redundant transmitters of an industrial facility, comprising:

• calculating probability that drift is occurring in a same direction for all redundant transmitters in the group of redundant transmitters, based on the number of redundant transmitters in the group of redundant transmitters;
• for each redundant transmitter, calculating a calibration adjustment value for said redundant transmitter;
• for each redundant transmitter, calculating a total number of calibration checks made to each redundant transmitter over the course of its service life to date;
• for each redundant transmitter, calculating a probability of calibration adjustment by dividing a total number of calibration adjustments made to each redundant transmitter by the total number of calibration checks;
• calculating a probability that all redundant transmitters in the group of redundant transmitters will require adjustment at the same time, based on the probabilities of calibration adjustment calculated for each redundant transmitter;
• calculating a probability of common mode drift by multiplying the calculated probability that all redundant transmitters in the group of redundant transmitters will require adjustment at the same time by the calculated probability that drift is occurring in a same direction for all redundant transmitters in the group of redundant transmitters;
• selecting a maximum probability of common-mode drift for the group of redundant transmitters;
• calculating an average time interval between calibrations for each redundant transmitter;
• calculating an average calibration interval by averaging the calculated average time interval between calibrations for each redundant transmitter;
• calculating a maximum interval based on the calculated probability of common mode drift, the calculated average calibration interval, and the maximum probability of common-mode drift for the group of redundant transmitters;
• calculating a maximum calibration interval value from said calculated maximum interval, wherein a calculated maximum calibration interval value is greater than or equal to the average calibration interval, and wherein the calculated maximum calibration interval value is less than or equal to a maximum time span of plant calibration data;
• and
• generating a report identifying transmitters from the group of redundant transmitters that are to be checked for calibration based on a calculated maximum calibration interval value to reduce unnecessary calibrations of the group of redundant transmitters.

A method for monitoring transmitter drift within a group of redundant transmitters in an industrial facility, comprising:

• retrieving redundant output readings from said group of redundant transmitters;
• calculating an average of the retrieved output readings;
• calculating a deviation value for each redundant transmitter based on a differential between the output reading for that redundant transmitter and the calculated average of the retrieved output readings;
• identifying any transmitter with a deviation value in excess of a pre-determined value;
• and
• deriving a maximum calibration interval value indicating an interval of time after which a calibration check should be made on at least one redundant transmitter in the group of redundant transmitters, by:
• calculating probability that drift is occurring in a same direction for all redundant transmitters in the group of redundant transmitters, based on the number of redundant transmitters in the group of redundant transmitters;
• for each redundant transmitter, calculating a calibration adjustment value for said redundant transmitter;
• for each redundant transmitter, calculating a total number of calibration checks made to said redundant transmitter over the course of its service life to date;
• for each redundant transmitter, calculating a probability of calibration adjustment by dividing a total number of calibration adjustments made to each redundant transmitter by the total number of calibration checks;
• calculating a probability that all redundant transmitters in the group of redundant transmitters will require adjustment at the same time, based on the probabilities of calibration adjustment calculated for each redundant transmitter;
• calculating a probability of common mode drift by multiplying the calculated probability that all redundant transmitters in the group of redundant transmitters will require adjustment at the same time by the calculated probability that drift is occurring in a same direction for all redundant transmitters in the group of redundant transmitters;
• selecting a maximum probability of common-mode drift for the group of redundant transmitters;
• calculating an average time interval between calibrations for each redundant transmitter;
• calculating an average calibration interval by averaging the calculated average time interval between calibrations for each redundant transmitter;
• calculating a maximum interval based on the calculated probability of common mode drift, the calculated average calibration interval, and the maximum probability of common-mode drift for the group of redundant transmitters;
• calculating the maximum calibration interval value from said calculated maximum interval, wherein the maximum calibration interval value is processed to be greater than or equal to the average calibration interval and less than or equal to a maximum time span of facility calibration data;
• and
• generating a report identifying transmitters from the group of redundant transmitters that are to be checked for calibration based on a calculated maximum calibration interval value to reduce unnecessary calibrations of the group of redundant transmitters.

A method for monitoring transmitter drift within a group of redundant transmitters in an industrial facility, comprising:

• retrieving redundant output readings from each redundant transmitter;
• calculating an average of retrieved redundant output readings;
• calculating a deviation value for each redundant transmitter based on a differential between the redundant output reading for a respective redundant transmitter and the calculated average of the retrieved redundant output readings;
• identifying any transmitter with a deviation value in excess of a pre-determined value;
• deriving a maximum calibration interval value indicating an interval of time after which a calibration check should be made on at least one redundant transmitter in the group of redundant transmitters, by:
• calculating probability that drift is occurring in a same direction for all redundant transmitters in the group of redundant transmitters, based on a number of redundant transmitters in the group of redundant transmitters;
• for each redundant transmitter, calculating a total number of calibration adjustments made to each redundant transmitter over the course of each respective redundant transmitter's service life to date;
• for each redundant transmitter, calculating a total number of calibration checks made to each redundant transmitter over the course of its service life to date;
• for each redundant transmitter, calculating a probability of calibration adjustment by dividing the total number of calibration adjustments by the total number of calibration checks;
• calculating a probability that all redundant transmitters in the group of redundant transmitters will require adjustment at the same time, based on a calculated probability of calibration adjustment of each redundant transmitter;
• calculating a probability of common mode drift by multiplying the calculated probability that all redundant transmitters in the group of redundant transmitters will require adjustment at the same time by the calculated probability that drift is occurring in a same direction for all redundant transmitters in the group of redundant transmitters;
• selecting a maximum probability of common-mode drift for the group of redundant transmitters;
• calculating an average time interval between calibrations for each redundant transmitter;
• calculating an average calibration interval by averaging the calculated average time interval between calibrations for each redundant transmitter;
• calculating a maximum interval based on the calculated probability of common mode drift, the calculated average calibration interval, and the maximum probability of common-mode drift for the group of redundant transmitters;
• calculating a maximum calibration interval value from said calculated maximum interval, wherein a calculated maximum calibration interval value is greater than or equal to the average calibration interval, and wherein the calculated maximum calibration interval value is less than or equal to a maximum time span of plant calibration data;
• and
• supplying a calculated maximum calibration interval value to an online monitoring (OLM) system;
• and
• generating a report identifying transmitters from the group of redundant transmitters that are to be checked for calibration based on the calculated maximum calibration interval value to reduce unnecessary calibrations of the group of redundant transmitters.