Early crack detection

An apparatus for the early detecting of a crack in a non-permeable, structural member subject to stress before the crack traverses the member, the apparatus comprising:

• (a) a source of pressure different than ambient,
• (b) a pressure sensor,
• (c) a fluid-tight line connecting the non-ambient pressure source and the pressure sensor,
• (d) a patch sealed in fluid-tight relationship to the line, the patch comprising a permeable material adjacent to the end of the line and to the structural member and sealed thereto with a fluid impermeable sealant.

An apparatus for the early detecting of a crack in a non-permeable, structural member subject to stress before the crack traverses the member, the apparatus comprising:

• (a) a vacuum source,
• (b) a vacuum sensor,
• (c) a vacuum tight line connecting the vacuum source and the vacuum sensor,
• (d) a patch sealed in vacuum tight relationship to the line, the patch comprising a propping member adjacent to the end of the vacuum line, an impermeable sheet material overlying the propping member so as to form a fluid channel extending therefrom, and the sheet and end of vacuum line sealed from the environment with a fluid impermeable sealant.

A process for the early detecting of the formation of a crack in a non-permeable, structural member subject to stress before the crack traverses the member, the process comprising:

• (a) forming a cavity adjacent to the structural member by forming a patch by placing one end of a tubular member adjacent to the structural member and in fluid communication with a permeable material also placed adjacent to the structural member and sealing both from the environment with an impermeable sealant such that a crack forming in the structural member provides a passage for a fluid to flow between the environment and the cavity without traversing the structural member,
• (b) sealing the other end of the tubular member in fluid communication to a source of pressure different than ambient at the structural member and to a pressure sensor,
• (c) imparting pressure other than ambient to the cavity and the interior of the tubular member, and
• (d) monitoring the internal pressure in the cavity and the interior of the tubular member with the pressure sensor;
• such that a crack in the structural member penetrating to the cavity allows passage of fluid between the environment and the cavity and is thus detected by the pressure sensor.