Example of the executed work:

Repair of propeller shaft plating on m/v OCEAN LUCK of Kaalbye SHIPPING by welding.

The vessel OCEAN LUCK of m/v type "Norilsk" project SA-15 was built on shipyard "Valmet" Helsinki, Finland in 1983.

Propeller shaft of 13065 mm long and weighting 66000 kg has external diameter of stern part 1055 mm, plating of shaft stern part 4700 mm long, 35 mm thick, weight of stern plating is 4500 kg. Material of plating is bronze of 10-2 grade.

Because of emergency (failure of propeller shaft water cooling) on vessel OCEAN LUCK, plating material (stern part the most) was overheated, that caused cracks on some areas of plating, in some parts they are reach-through. Plating of stern part was not allowed to be used in such state and required full replacement or development of special technology of its repair.

Replacement of plating was eliminated because there was no practical possibility to cast the work parts both in Ukraine and in the nearest countries; lack of the equipment for press-fitting of plating on shaft because of its length and weight and, at last, because of terms of such work performance (8÷10 months) and its price.

The customer (firm Kaalbye SHIPPING) has decided to repair the plating by welding method. Such work was performed for the first time in all Postsoviet space and was related to a lot of engineering and technical problems.

Chemical analysis and studies of physical and chemical properties of plating material have determined excess of lead content in plating almost in five times, that, proceeding from the experience of welding of tin bronze, showed its bad weldability. A number of practical researchers attributed tin bronze with such lead content to unweldable.

The plating has been in operation for long time, and especially the last overheating led to accumulation of superficial tensions almost up to critical ones.

At last, the plating has been initially installed on the shaft with maximal tightness of 0,56 mm, that also could not provide welding of its defects.

Total volume of defects on plating was equal to 50720cm³ (~10 % of all volume) among them through cracks were 5800m³, single cracks of 4500m³, areas with crack network of 40420m³.

All these defects had to be removed to put the shaft back into operation without restrictions.

As the propeller shaft is one of the most crucial units of the vessel, the work was performed under supervision of Russian sea navigation Register inspection.

The work was performed by forces of the qualified employees and in the following basic directions:

  • Studies of process variables and choice of adding materials and welding regimes;
  • Development and endorsement of propeller shaft repair technology with Russian sea navigation Register inspection and customer;
  • Performance of the work for reconstruction of shaft plating.

As a result of the executed work, technological instruction NAPR 25190.00174 has been developed and tested. To remove pressure in propeller shaft while in service and in emergency, heat treatment of plating has been performed with application of special unit for thermal processing of pipes butt joints of high-strength steel of TERMOCONTROL R 16BT Digit/A type produced by A.E.C TECHNOLOGY S.rl, ITALY. The regimes of thermal processing: heating up to 300° with speed up to 20÷25 degrees / hour, exposure to temperature of 280-320° during 5 hours.

Cooling with speed of 20-25°/hour up to temperature of 60°.

The defects were welded by method of machine welding using the device PS - 5000 of the company KEMPPI (Finland) on regimes: welding current 240-260, voltage on arch 26-28 V, speed of wire feed 14-16 m/minutes with wire diameter of 1,6÷2,0 mm.

Before welding, weld areas of plating were warmed up to temperature 120÷150 by scattered flame of gas burners. After welding, the areas were impregnated by anaerobic composition Anaterm 1 according to the regimes resulted in I 31-994-775-83.

In March 2004. the shaft was installed on its normal place and works without restrictions.

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