Acoustic emission monitoring system

• US 4,033,179 A
• Filed: 03/07/1975
• Issued: 07/05/1977
• Est. Priority Date: 03/07/1975
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Romrell, Delwin M.
• Primary Examiner(s): Tubbesing, T.H.
• Assistant Examiner(s): Blum, T. M.
• Application Number:
  US05/556,354
• Time in Patent Office: 851 Days
• Field of Search: 340/15, 73/67 R, 73/67.3, 73/69, 73/88 R, 73/88.3, 73/71.4
• US Class Current: 73/587
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01S 3/808 using transducers spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01V 1/00 Seismology; Seismic or acoustic prospecting or detecting

Abstract

Methods and apparatus for identifying the source location of acoustic emissions generated within an acoustically conductive medium. A plurality of acoustic receivers are communicably coupled to the surface of the medium at a corresponding number of spaced locations. The differences in the reception time of the respective sensors in response to a given acoustic event are measured among various sensor combinations prescribed by the monitoring mode employed. Acoustic reception response encountered subsequent to the reception by a predetermined number of the prescribed sensor combinations are inhibited from being communicated to the processing circuitry, while the time measurements obtained from the prescribed sensor combinations are translated into a position measurement representative of the location on the surface most proximate the source of the emission. The apparatus is programmable to function in six separate and five distinct operating modes employing either two, three or four sensory locations. In its preferred arrangement the apparatus of this invention will re-initiate a monitoring interval if the predetermined number of sensors do not respond to a particular emission within a given time period.

Claims

1. A method of monitoring the presence and source location of acoustic emissions generated within or on a tubular, acoustically conductive medium comprising the steps of:

monitoring acoustic emissions respectively at a plurality of at least three separate spaced locations around the girth of the tubular surface;

measuring the time difference between the first reception at one of the monitoring locations of a particular acoustic emission and the next reception of the same emission at a second of the monitoring locations;

automatically blocking for a given period of time all further acoustic reception responses from the monitoring locations subsequent to the reception at the second monitoring location;

translating the time measurement into a position measurement around the tubular girth representative of the girth location most proximate the source of the emission; and

registering the position measurement.

2. The method of claim 1 wherein the blocking time is adjusted to at least the time required to register the position measurement.

3. The method of claim 2 wherein the measuring step is automatically re-initiated when the blocking time has passed.

4. The method of claim 1 wherein the translating step includes the step of identifying the two monitoring locations first receiving the acoustic emission.

5. The method of claim 4 including the step of identifying the monitoring location first receiving the acoustic emission.

6. The method of claim 1 wherein the measuring step is automatically re-initiated if the time difference exceeds a preset time interval.

7. The method of claim 6 wherein the preset time interval is selected to be less than the time required for the acoustic emission to travel a distance equal to the surface spatial separation between the monitoring location first receiving the emission and the next most proximate monitoring location.

8. The method of claim 1 wherein the time difference is measured in time increments respectively equal to the time required for the acoustic emission to traverse a one-tenth inch spatial separation on the tubular surface.

9. The method of claim 8 wherein the time difference is clocked by an oscillator having a cycle duration corresponding to one time increment.

10. The method of claim 1 wherein the monitoring locations are substantially equally spaced around the girth of the tubular surface.

11. Apparatus for monitoring the presence and source location of acoustic emissions generated within or on an acoustically conductive medium comprising:

a plurality of acoustic sensors communicably coupled to the surface of the medium and respectively positioned at a corresponding plurality of spaced locations;

means for respectively measuring the difference in time between the reception of a given acoustic event at a pre-established combination of sensors;

means for blocking further acoustic reception reponses from the monitoring locations subsequent to the reception by a predetermined number of the pre-established sensor combinations;

means for programming the measuring means and blocking means to re-establish the sensor combinational groupings and corresponding predetermined number of responses required before blocking in accordance with a plurality of given acoustical monitoring functions; and

means for translating the time measurement into a position measurement on the surface representative of the location of the source of the emission; and

means for registering the location of the emission source.

12. The apparatus of claim 11 including means for resetting the measuring means in the event an acoustic event is not received by a set number of sensors governed by the acoustic monitoring function programmed, within a given time interval.

13. The apparatus of claim 11 wherein said program means adjusts said measuring means to clock the difference in time between the first reception of a given acoustic emission at a sensor location and the next reception of the same emission at a sensor location and adjusts said blocking means to block subsequent acoustic responses.

14. The apparatus of claim 11 wherein the blocking means functions to block further receptions for a selected time interval.

15. The apparatus of claim 14 wherein the blocking time is adjusted to at least the time required to register the source location.

16. The apparatus of claim 14 wherein the measuring means is reset for a new measurement when the blocking time has passed.

17. The apparatus of claim 11 wherein said program means adjusts said measuring means to clock the difference in acoustic reception time respectively between the sensors in two separate sensor pairs and adjusts said blocking means to block subsequent acoustic response after reception at the four sensor locations which are a part of the paired groupings.

18. The apparatus of claim 11 wherein said program means adjusts said measuring means to clock the difference in acoustic reception time respectively between first and second, second and third, and third and fourth sensor locations and adjusts said blocking means to block subsequent acoustic responses after reception at the four sensor locations.

19. The apparatus of claim 11 wherein said program means adjusts said measuring means to monitor acoustic receptions by the sensors of two separate sensor pairs and clock the difference in acoustic reception time between the sensors in the first pair having an acoustic response, and adjusts the blocking means to block subsequent acoustic response after reception by both sensors of the pair being clocked.