Cairo Marine Service, Inc. is accredited by the Department of Labor (Occupational Safety and Health Administration) to perform Non-Destructive Examinations. CMS utilizes both dry particle and continuous wet bath methods employing a DC type Parker probe energized with a 120 VAC supply. Additionally, we use the dye penetrate check method where a DC magnetic field generating probe is not practical.
Magnetic particle testing is generally more advantageous as it allows better detection of hairline fractures in crane hook throat openings, hairline weld fractures, and provides for more exacting evidence of positive indications. It is also beneficial in distinguishing between surface flaws and actual fractures.
Dye penetrate is utilized in areas where it is difficult to place a DC type robe, such as no availability of a 120 VAC power source, and where lighting conditions are particularly poor. While dye penetrate does have its value, it requires greater attention to surface preparation and takes somewhat more time to give evidence of a potential indication. Also, surface flaws, especially in crane hook throat openings, may give the technician false evidence of indications.
CMS also provides ultra sonic testing or audio gauging for determination of actual steel thickness, such as on a boat or barge’s bottom plating, to determine a percent value of steel wastage from the natural elements of hull aging. The ultra sonic meter, coupled with its probe and a conductive agent, gives the technician a “readout” of actual steel thickness present to within three decimal points of inches or millimeters.
To obtain an accurate thickness measurement the area or “shot” to be taken is ideally ground flush with a portable grinder to provide a smooth surface for probe contact. In the case of a hull bottom plate that has significant wastage areas, more specifically “pock marks” or extreme plate irregularities, both the smooth steel and the “pock mark” areas are equally ground smooth to facilitate probe contact and multiple readings are taken and averaged.
The employment of audio gauging, while beneficial in giving a relative indication of plate condition, should not be construed as an “exact science” as respects the plate susceptibility in allowing for the ingress of water through a severe waste hole. This is even more so when the hull is displacing water and generating hydrostatic forces upon the plate in question
CMS can, in the case of extremely sensitive or critical welds, engage in utilizing the “X-Ray” method of determining a welds’ possible imperfections or irregularities. While this type of examination is not usual in marine application (other than a nuclear reactor type shipboard power plant), we are capable of arranging for this service under our strict supervision.