Method and system for rub detection in a steam turbine

Abstract

A method for detecting rubbing between components in a steam turbine, the method includes: sensing a temperature at a plurality of locations on a casing of the steam turbine; comparing the sensed temperatures of the plurality of locations; detecting the rubbing between the components if one of the plurality of locations has a higher sensed temperature than the sensed temperature at the other plurality of locations, and reporting the rub as being at a location near the one of the plurality of locations having the higher sensed temperature.

1 . A method for detecting rubbing between components in a steam turbine, the method comprising:
 sensing a temperature at a plurality of locations on a casing of the steam turbine;   comparing the sensed temperatures of the plurality of locations;   detecting the rubbing between the components if one of the plurality of locations has a higher sensed temperature than the sensed temperature at the other plurality of locations, and   reporting the rub as being at a location near the one of the plurality of locations having the higher sensed temperature.   
   
   
       2 . A method as in  claim 1  wherein the plurality of locations are in an annular array perpendicular to a rotor axis. 
   
   
       3 . A method as in  claim 1  wherein the plurality of locations are four locations arranged symmetrically around the casing in a plane perpendicular to a rotor in the turbine. 
   
   
       4 . A method as in  claim 3  wherein the four locations arranged along vertical and horizontal lines extending through the plane. 
   
   
       5 . A method as in  claim 1  wherein the detection of the rubbing includes comparing each of the sensed temperatures to at least one of an average of sensed temperatures, a mean of sensed temperatures and to each of the other sensed temperatures in the array. 
   
   
       6 . A method as in  claim 1  wherein the plurality of locations are arranged in an annular array in the casing and around a row of steam turbine buckets on a rotor of the turbine. 
   
   
       7 . A method as in  claim 1  wherein the plurality of locations are near an inlet to the turbine. 
   
   
       8 . A method as in  claim 1  wherein the plurality of locations are in a middle of the turbine and substantially mid-way between rotor bearings supporting a rotor to the turbine. 
   
   
       9 . A method to detect rubbing in a steam turbine comprising:
 monitoring temperature sensors in at least one sensor array in a casing for the turbine;   comparing temperature measurements of all sensors in array;   identifying a hottest temperature in array from the comparison;   determine if the hottest temperature is beyond a threshold level;   identifying a sensor reporting the hottest temperature beyond the threshold, and   issuing a warning of rubbing potentially occurring at a position near the identified temperature sensor.   
   
   
       10 . The method of  claim 9  further comprising periodically repeating the steps of the method. 
   
   
       11 . A method as in  claim 9  wherein the sensor array includes a plurality of sensors arranged in a plane perpendicular to an axis of a rotor in the turbine. 
   
   
       12 . A method as in  claim 9  wherein the array of plurality of locations are four locations arranged symmetrically around the casing in a plane perpendicular to a rotor in the turbine. 
   
   
       13 . A method as in  claim 12  wherein the array includes four sensors arranged along vertical and horizontal lines extending through the plane. 
   
   
       14 . A method as in  claim 9  wherein the comparison includes comparing the measurements of each of the sensors to at least one of an average of sensed temperatures, a mean of sensed temperatures and each of the other temperature measurements in the array. 
   
   
       15 . A method as in  claim 9  wherein the sensors include sensors arranged in an annular array in the casing and around a row of steam turbine blades on a rotor of the turbine. 
   
   
       16 . A system to detect rubbing in a steam turbine having a casing around a rotor, the system comprising:
 at least one array of temperature sensors mounted in the casing proximate to an inside casing surface facing the rotor, and   a controller monitoring temperature signals from each of the temperature sensors in the array, wherein said controller issues a rubbing warning if one of the temperature signals reports a temperature substantially hotter than other temperatures reported by the array.   
   
   
       17 . A system as in  claim 16  wherein the at least one array is arranged in a plane perpendicular to a rotational axis of the rotor. 
   
   
       18 . A system as in  claim 17  wherein the at least one array includes four sensors arranged along vertical and horizontal lines extending through the plane. 
   
   
       19 . A system as in  claim 16  wherein the controller compares each of the sensed temperatures to at least one of an average of sensed temperatures, a mean of sensed temperatures and to each of the other sensed temperatures in the array. 
   
   
       20 . A system as in  claim 16  wherein the at least one array is positioned at least at one of proximate to a row of turbine buckets at an inlet to the turbine and a row of turbine buckets between a pair of bearings supporting a rotor of the turbine.