Early crack detection with multi-pressure system
AssigneeContinental Oil Company
InventorDonald H. Oertle
Life of this patent
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Abstract
Early detection of cracks in nonpermeable, structural members subject to stress is effected before the cracks traverse the member by forming a plurality of cavities in the member or adjacent thereto in which a plurality of fluids at differing pressures are confined and monitored, such that a crack in the structural member penetrating between at least two cavities allows passage of fluid between the cavities and is thus detected by a pressure sensor. The apparatus and process is particularly applicable to early detection with vacuum of cracks in the heat affected zone adjacent to welds on critical stressed members of an offshore platform. A strain gauge system may be employed in conjunction with the crack detection system.
Claims44
A process for the early detection 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 first cavity in the structural member or adjacent thereto,
- (b) sealing a first fluid passageway in fluid communication from the first cavity to a first pressure source and to a pressure sensor,
- (c) establishing a fluid pressure in the first cavity and first fluid passageway,
- (d) forming a second cavity in the structural member or adjacent thereto, adjacent to the first cavity but not in fluid communication therewith,
- (e) sealing a second fluid passageway in fluid communication from the second cavity to a second pressure source,
- (f) establishing a fluid pressure in the second fluid passageway and second cavity which differs from the pressure established in the first fluid passageway and first cavity,
- (g) monitoring the pressure in the first cavity and first fluid passageway with the pressure sensor,
- such that a crack in the structural member penetrating between the first cavity and the second cavity allows passage of fluid between the cavities and is thus detected by the pressure sensor.
An apparatus for the early detection of a crack in a non-permeable, structural member subject to stress before the crack traverses the member, the apparatus comprising:
- (a) a first cavity formed into the structural member or adjacent thereto,
- (b) a first fluid passageway sealed in fluid communication from the first cavity to a first pressure source and to a pressure sensor, having a fluid pressure in the first cavity and first fluid passageway,
- (c) a second cavity in the structural member or adjacent thereto, adjacent to the first cavity but not in fluid communication therewith,
- (d) a second fluid passageway sealed in fluid communication from the second cavity to a second pressure source, having a second fluid pressure in the second fluid passageway and second cavity which differs from the first fluid pressure in the first fluid passageway and first cavity.
An apparatus for the early detection of the formation of a crack in a non-permeable, structural member subject to stress before the crack traverses the member, the apparatus comprising:
- (a) a first vacuum source,
- (b) a first vacuum sensor,
- (c) a vacuum tight line connecting the first vacuum source and the vacuum sensor,
- (d) a patch sealed in vacuum tight relationship to the line, the patch comprising a first permeable cavity adjacent to the end of the first vacuum line and to the structural member, the patch further comprising a second cavity adjacent to the structural member but sealed from the first cavity, the second cavity sealed to a line providing fluid communication with a second pressure source.
Dependencies are inferred from the claim text.