Cargo Tank Corrugated Bulkhead Damages of Double Hull Tankers

Corrugated bulkheads are generally utilised as the boundary between cargo tanks of small and medium sized product or chemical tankers. The corrugation provides benefits such as simplified cleaning which is highly desirable due to the operational profile of these vessel types. Properly designed, constructed and maintained corrugated bulkhead structures can give many years of safe and satisfactory service. On the other hand the complexity of structural configuration and difficulties of manufacture can lead to significant defects occurring which may be costly to repair. The following information is an extract from a Tanker Structure Co-operative Forum (TSCF) paper which reviews corrugated bulkhead design practice and provides details of damage experience from TSCF members.

2013.10.08 - Cargo Tank Corrugated Bulkhead Damages of Double Hull Tankers Figure 1

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Typical Cracks in Deck of Oil Tankers

Cracks in deck plating in way of deck penetrations of oil tankers has been an increasing problem and is typical on vessels with high strength steel in deck and most typically found on Buoy loading Oil Tankers trading in the North Sea. The damaged areas (as shown in this post) were limited to cracks in the upper deck plating in way of the pipe penetrations resulting in small leaks, but could easily have resulted in more serious damage to the deck structure and the safety of the ship if left unattended over time.

2013.05.17 - Typical Cracks in Deck of Oil Tankers Figure 1

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Electrocution of Fitter During Welding Repair – Investigation Report

On January 2010, the Hong Kong registered general cargo vessel Suntec departed the port of Huangpu, China after loading 19 300 tonnes of river sand to be discharged at the port of Keelung, Taiwan. On the next morning the deck fitter was assigned to carry out electric arc welding repair on the bulwark on the main deck at the port side near a cargo hold. While the fitter was carrying out the welding repair, seawater suddenly rushed up the deck through the opening between the deck and the bulwark plate and dampened his body. He screamed after suffering from electric shock and fell unconscious on the deck.

2013.01.14 - Electrocution of Fitter During Welding Repair Figure 1

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Weld Defects in Ships

A welding structure in order to have the required reliability, during her lifetime, it should have satisfactory quality. This means that it should:

  1. Be designed in a way that is appropriate for its sought use during its forecasting lifetime.
  2. Be manufactured from materials and welding methods according to the requirements.
  3. Be used and maintained rightly.

Welding quality is a relative term and this means that it is not necessary a construction to have better quality from what is needed according to the requirements. When the requirements are strict, that has as consequence the cost of production to be extremely high. On the other hand when the requirements are loose, that has as consequence the cost of maintenance to be high and the forecasting lifetime to be reduced.

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Aluminum Alloys MIG Welding Procedure Instructions

1. Base-metal preparation:

To weld aluminum alloys, operators must take care to clean the base material and remove any aluminum oxide and hydrocarbon contamination from oils or cutting solvents or NC machines coolants. Aluminum oxide on the surface of the material melts at about 2035o C while the base-material aluminum underneath will melt at 650o C. Therefore, leaving any oxide on the surface of the base material will inhibit penetration of the filler metal into the work piece. To remove aluminum oxides, use a stainless-steel bristle wire brush (and/or grinding) or solvents and etching solutions. If grinding is used for cleaning/preparing weld areas it should be paid attention to the brand used since some grinding wheels use an organic binder that leaves a residue behind, that will possibly cause weld porosity. Thus, it is recommended to test the particular brand of grinding wheels before actual use, in a welding test work piece

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