| 摘要 |
<p>Cases 5791, 5916, 5917, 5918 EARLY CRACK DETECTION Early detection of cracks in non-permeable, structural members subject to stress is effected before the cracks traverse the member by: (a) forming a cavity in the structural member or adjacent thereto such that a crack forming in the structural member provides a passage for a fluid to flow between the environment and the cavity without passing through the entire structural member, (b) sealing a fluid passageway in fluid communication from the cavity to a source of pressure different than ambient pressure at the structural member and to a pressure sensor, (c) imparting a higher or lower pressure to the cavity and the fluid passageway, and, (d) monitoring the internal pressure in the cavity and fluid passageway 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. 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 guage system may be employed in conjunction with the crack detection system.</p> |
