Repair of a crack in a container

On January and berthed alongside Algeciras port, TSE diving team proceed with a permanent afloat repair of crack located on nº 1 water ballast on the container vessel of 49.000 DWT.

Close-up underwater cctv-video inspection together with Owners Superintendent and Class DNV Surveyor representatives were taken in order to determine the exact location and dimension of one in number sprung outward longitudinal crack of 1120 mm lenght x 12 mm opened located at 14 meter from the bow front face section and approx 3 meter from starboard side turn of bilge section on flat bottom nº 1 water ballast tank (starboard section) at frame 188.

The shell plating around the damaged area was found to be in an apparent good condition covered with anti-fouling top-coat paint and free of marine fouling. No visible corrosion plates observed. No visible scratch marks of grounding damaged observed, however some minor indentations plates were found on the damaged area probably caused by bad weather conditions. One in number parallel longitudinal weld seam was observed at 350 mm to the crack damaged area and was found to be in an apparent good condition, painted and no visible wastage material observed.

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TSE diving team proceed to placing of one hand-made reinforced aluminium cofferdam of 2200 mm lenght x 1200 mm wide x 300 mm high x 10 mm thickness and 30 mm thick of rubber gasket foam with a total weight of 146 kg provided with two inlet - outlet valves to cover securely the crack section for internal permanent repair. Divers secured the cofferdam to the bottom shell plating by means of wet-welding of a total 4 in number approved steel "rings" and 4 in number chain-blocks of 2 tons each.

Owner´s Superintendent, Class DNV Surveyor, Insurance Surveyor and Diver´s Supervisor inspected internally the extension of the sprung outward longitudinal crack. The extension of the fracture was located between the bottom shell plating and bottom longitudinal stiffener at frame 188.

Following to the TSE approved procedure for welding of "insert" by means of external cofferdam, coded fitters and welders team cropped one section to bottom plating of 1355 mm length x 496 mm wide x 14,5 mm thickness with top rounded corners r.150 in order to place of one certified "insert" plate grade "AH-36" with same dimensions x 18 mm in thickness according to manufacturer S355 J2+N (EN10025-2:2004).

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Due to the differences thickness plates between the original vessel shell plate of 14,5 mm thick and the new insert plate of 18 mm thick, coded fitters proceed to prepare the wide transition of 14,5 / 18 mm as per Class DNV required.

After positioned a new "insert" plate, coded welders proceed to start with the SMAW first pass weld root full penetration welding (without backing strip). An independent NDT tester then carried out a dye-penetrant method to inspect the full penetration welding seam. Minor indications of slags were observed. Welders/fitters proceeded to grinded this anomalies and re-welded again as per NDT Technician required. No others significant indications were observed using the above mentioned method. Welders proceeded to complete the welding permanent repairs using FCAW method. A total of 5th pass weld runs were carried out. On completion of welding repairs, Ultrasonic method to inspect 100% of butts ´welds were carried out. No significant indications or anomalies were observed and was approved by DNV Surveyor who was present during the operations.

Upon completion of the "insert", coded welders carried out welding the top section of the insert with the longitudinal stiffener at each side together with scalloped holes at the ends.

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Internal welding works were agreed by DNV Surveyor, Owner´s Superintendent and Insurance Surveyor.

After finishing the internal permanent repair, divers removed the cofferdam together with chain blocks and steel "rings" and proceeded by close-up cctv-video system to inspected the full penetration weld seams and found agreed by DNV Surveyor. Also divers applied epoxy-cement around the insert weld seams to prevent corrosion.

Internal repairs was concluded and confirmed approval of "permanent" repairs were satisfactorily concluded to a satisfaction of DNV Surveyor and Owner´s Superintendent.

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