Abstract: A method for monitoring the integrity of a permeable structure that is disposed in an environment containing a fluid at ambient pressure is provided. At least one cavity is formed in or on the permeable structure. A source of first fluid is provided at a first pressure greater than the ambient pressure. The cavity is coupled to the source through a high-fluid-flow impedance to establish a flow of the first fluid through the permeable structure via the cavity. A rate of flow of the first fluid through the permeable structure is allowed to stabilize to a steady-state rate. A change in the steady-state flow rate of the first fluid through the permeable structure is monitored.

Abstract: A method for monitoring the integrity of a permeable structure that is disposed in an environment containing a fluid at ambient pressure is provided. At least one cavity is formed in or on the permeable structure. A source of first fluid is provided at a first pressure greater than the ambient pressure. The cavity is coupled to the source through a high-fluid-flow impedance to establish a flow of the first fluid through the permeable structure via the cavity. A rate of flow of the first fluid through the permeable structure is allowed to stabilize to a steady-state rate. A change in the steady-state flow rate of the first fluid through the permeable structure is monitored.

Abstract: A system for monitoring a structure includes cavities on an outer surface and a fluid source at substantially constant pressure coupled to the cavities through high fluid impedances to create pressure differentials therebetween. A telemetry system has pressure differential switches across each of the high impedances for monitoring differential pressure changes across the impedances and providing a signal indicative of the location of the cavity associated with the high impedance across which the change is monitored. A fluid capacitance is associated with each cavity and the corresponding impedances to facilitate a transient fluid flow through the impedances.

Abstract: A system 10 for continuously monitoring the integrity of a structure 14 includes a sensor pad 16 having a surface 18. The surface 18 is provided with a set of first channels 22 and interspersed second channels 24. Surface 18 is sealed onto the surface 12 of structure 14 so that the channels 22, 24 together with surface 12 form respective sets of first and second cavities 26 and 28. The first cavities 26 are placed in fluid communication with a vacuum source 101 via a third channel 30. The second cavities 28 are vented to the atmosphere via a fourth channel 34, through hole 35, and conduit 36. A high impedance 102 is placed in series between the vacuum source 101 and the first cavities 26. A differential pressure transducer 103 is connected across the high impedance 102 and monitors for change in vacuum condition between the vacuum source 101 and the vacuum in the cavities 26.

Abstract: Apparatus 10 for measuring permeability of a material 12 includes a substantially constant vacuum source 14 coupled via duct 11 to a fluid capacitance vessel 16 which contains pressure transducer 18 coupled by conductors 20 to an amplifier and display 22 for monitoring the source 14. Fluid impervious disc 24 is provided with placement on surface 26 on the material 12 to define, between disc 24 and surface 26 a fluid flow cavity 28. Disc 24 is coupled by conduit 32 to a restriction tube 30 which provides a high impedance to fluid flow. An opposite end of the restriction tube 30 is in fluid communication with vessel 16. A transducer 34 is coupled across restriction tube 30 to provide a measure of fluid flow. Fluid impervious seal 60 forms a seal about the periphery of disc 24 and extends radially outwardly on the surface 26. Assuming the material 12 has some degree of permeability, air will be able to permeate through the material 12 from beyond the periphery of the seal 60 and to the cavity 28.

Abstract: Apparatus 10 for condition monitoring the integrity of a rivet 12 joint holding together sheets 14 and 16 of a structure 18 includes a substantially fluid impervious pad 20 for covering the heads of the rivets 12 and an adjacent surface 24 of the structure 18. The pad 20 has a first surface 26 for placement over the rivets 12 and the surface 24. An inner portion of the surface 26 is formed or otherwise configured to define a fluid flow region 28 between the pad 20 and the rivets 12/surface 24 across which fluid can flow. The region 28 is coupled to a constant vacuum source 30 via a conduit 32 and a series coupled high fluid flow impedance 34. A transducer 38 and display 44 coupled in parallel across the impedance 34 provides an indication of change in differential pressure across the high impedance which in turn provides an indication of the presence or development of a flaw in the rivets joint.

Abstract: A system for monitoring a structure includes cavities on an outer surface and a fluid source at substantially constant pressure coupled to the cavities through high fluid impedances to create pressure differentials therebetween. A telemetry system has pressure differential switches across each of the high impedances for monitoring differential pressure changes across the impedances and providing a signal indicative of the location of the cavity associated with the high impedance across which the change is monitored. A fluid capacitance is associated with each cavity and the corresponding impedances to facilitate a transient fluid flow through the impedances.

Abstract: Apparatus 10 for condition monitoring the integrity of a rivet 12 joint holding together sheets 14 and 16 of a structure 18 includes a substantially fluid impervious pad 20 for covering the heads of the rivets 12 and an adjacent surface 24 of the structure 18. The pad 20 has a first surface 26 for placement over the rivets 12 and the surface 24. An inner portion of the surface 26 is formed or otherwise configured to define a fluid flow region 28 between the pad 20 and the rivets 12/surface 24 across which fluid can flow. The region 28 is coupled to a constant vacuum source 30 via a conduit 32 and a series coupled high fluid flow impedance 34. A transducer 38 and display 44 coupled in parallel across the impedance 34 provides an indication of change in differential pressure across the high impedance which in turn provides an indication of the presence or development of a flaw in the rivets joint.

Abstract: Apparatus 10 for measuring permeability of a material 12 includes a substantially constant vacuum source 14 coupled via duct 11 to a fluid capacitance vessel 16 which contains pressure transducer 18 coupled by conductors 20 to an amplifier and display 22 for monitoring the source 14. Fluid impervious disc 24 is provided with placement on surface 26 on the material 12 to define, between disc 24 and surface 26 a fluid flow cavity 28. Disc 24 is coupled by conduit 32 to a restriction tube 30 which provides a high impedance to fluid flow. An opposite end of the restriction tube 30 is in fluid communication with vessel 16. A transducer 34 is coupled across restriction tube 30 to provide a measure of fluid flow. Fluid impervious seal 60 forms a seal about the periphery of disc 24 and extends radially outwardly on the surface 26. Assuming the material 12 has some degree of permeability, air will be able to permeate through the material 12 from beyond the periphery of the seal 60 and to the cavity 28.

Abstract: A method and apparatus provided for monitoring the integrity of a structure 10 disposed in an environment containing a fluid F at an ambient pressure. The structure 10 includes a skin 12 and a plurality of internal cavities 14. The method involves applying a further fluid to the cavities 14, the applied fluid being at a pressure which is marginally greater than the atmospheric ambient pressure F. The flow rate of the applied fluid is monitored for detection in a change in the flow rate. The change in flow rate is indicative of additional fluid seepage through the structure 10 providing advance warning of a failure in the integrity of the structure 10. Monitoring is achieved by passing the applied fluid through a high fluid flow impedance 28 and monitoring for a change in pressure across the impedance 28 using a transducer 30.

Abstract: A system 10 for continuously monitoring the integrity of a structure 14 includes a sensor pad 16 having a surface 18. The surface 18 is provided with a set of first channels 22 and interspersed second channels 24. Surface 18 is sealed onto the surface 12 of structure 14 so that the channels 22, 24 together with surface 12 form respective sets of first and second cavities 26 and 28. The first cavities 26 are placed in fluid communication with a vacuum source 101 via a third channel 30. The second cavities 28 are vented to the atmosphere via a fourth channel 34, through hole 35, and conduit 36. A high impedance 102 is placed in series between the vacuum source 101 and the first cavities 26. A differential pressure transducer 103 is connected across the high impedance 102 and monitors for change in vacuum condition between the vacuum source 101 and the vacuum in the cavities 26.

Abstract: A monitoring apparatus for monitoring impending faults in the integrity of a component or structure in static or dynamic application. The apparatus includes a sealed cavity on or within the component or structure connected to a source of constant vacuum. The connection between the cavity and the source incorporates a device of high impedance fluid flow and a monitor for monitoring the change in pressure between the cavity and the source.