Tankers are a composition in duplex stainless.
Duplex stainless steel is finding an increasing uptake in the shipbuilding sector, mainly due to its higher strength and corrosion resistance properties. Ing. Fred Neessen, EWE and Piet Bandsma, EWT from Lincoln Smitweld illustrate the trend with a report of a current chemical tanker project.
Shipyard K. DAMEN has been situated on the banks of the Merwede river, close to the Worldport of Rotterdam, since 1927. It is a company with approximately 100 employees and has gained national and international fame due to its excellent craftsmanship.
K. Damen gained its national fame undertaking large contracts for the Dutch Government and its international fame through the supply of ships to governments in addition to harbour and coast authorities in the Middle-East, Africa and Western Europe.
Included in the many varied types of vessels produced are tug boats, supply vessels, high-speed boats, tankers, fishing vessels and chemical tankers. The tankers recently built are advanced double hull chemical tankers for inland navigation as well as sea going.
GERMAN ORDERS
The German ship owner GEFO (Gesellschaft für Öltransport) from Hamburg awarded the Shipyard K.DAMEN a huge contract for the construction of ships with cargo tanks made out of duplex stainless steel. Each ship is named after world famous composers. The first ship was named after Gioacchino Antonio ROSSINI (1792 – 1868) and the second ship after Giacomo PUCCINI (1858 – 1924), two famous Italian opera composers. Verdi, Bellini, Mozart and Donizetti are the chosen names for the last four tankers. Fig. 1 shows an aerial view of the chemical tanker Verdi.
The 95m long seagoing ships have a 12.5m beam and are 6.35m high. The double hull cargo tanks are designed to transport up to 2,750 tonnes or 3,250m3 liquid in 12 separate tanks. The cargo tanks are completely separated and can be loaded and emptied fully independently of the other cargo tanks. This enables different chemicals to be carried and transported simultaneously.
Table 1: Chemical composition of duplex stainless steel (W.Nr. 1.4462) for application in chemical tankers.
The cargo tanks are constructed from a duplex stainless steel (WNr 1.4462) which is a higher grade of stainless steel as opposed to austenitic AISI 316L(N) grade that is often used for inland navigation tankers. Duplex stainless steel has a higher strength combined with a favourable corrosion resistance, two properties that have governed the choice of this material as a way of increasing the number of chemical products that can be loaded and transported by these chemical tankers.
An overview is provided of the welding procedures and the consumables selection for the numerous welding joints between duplex stainless steel and dissimilar metals as applied in chemical tankers.
Depending on the required welding positions during construction, as well as the various base material combinations, the selection of welding processes and welding consumables have been made and tested in accordance with the Germanischer Lloyd (GL) rules. Lincoln Smitweld’s involvement in the huge project has been considerable. It has involved providing technical support and assistance with the:
Table 2. Mechanical properties of duplex stainless steel (1.4462) plate.
• development of the welding procedures,
• consumables selection,
• welding process selection,
• welding qualifications and
• testing according to GL,
• supplying the welding consumables as well as
• the training of the welders
The welders needed training and qualification (t & q) on duplex stainless steel in addition to t & q on welding of dissimilar materials joints.
During the construction phase Lincoln Smitweld remained closely involved with the welding execution and provided continuous technical support.
DUPLEX STAINLESS STEEL
Duplex stainless steel has a number of different properties in comparison with AlSI 316L(N) including chemical composition (table 1), microstructure, corrosion behaviour and mechanical properties (table 2). The higher yield strength combined with the excellent stress and pitting corrosion resistance of duplex stainless steel has increased the popularity and usage of the material considerably over recent years. When the yield strength is increased, the plate thickness can be reduced. The corrosion resistance can be calculated and expressed by the Pitting Resistance Equivalent (PRE), adjusted for N-containing stainless steels: PREN = %Cr + 3,3* %Mo + 16* %N.
The duplex stainless steel (Werkstoff Nr. 1.4462) also has excellent weldability.
Actual view of the layout of the tanks.
WELDED JOINTS
The various joint configurations and material combinations are illustrated in figure 2 and listed in table 3. The cross section of figure 2 shows where the various welding processes can be applied. The corresponding welding consumables are listed in table 4. The various selections welding processes and consumables involved a total of 12 welding procedures, developed and successfully applied in practice for the welding of the duplex stainless steel cargo tanks.
Table 3. Overview of welding methods.Figure 2. Schematic cross section of a chemical tanker.
Table 4. Typical mechanical properties of the welding consumable that have been applied.
Lincoln Smitweld would like to express its thanks to Mr van As and the management of Shipyard K. Damen in Hardinxveld-Giessendam for its assistance in preparing this article and for its permission to publish.
Published in: Welding & Metal Fabrication, June 2000, Library: LSW-TS-185
Shipyard K. DAMEN has been situated on the banks of the Merwede river, close to the Worldport of Rotterdam, since 1927. It is a company with approximately 100 employees and has gained national and international fame due to its excellent craftsmanship.
K. Damen gained its national fame undertaking large contracts for the Dutch Government and its international fame through the supply of ships to governments in addition to harbour and coast authorities in the Middle-East, Africa and Western Europe.
Included in the many varied types of vessels produced are tug boats, supply vessels, high-speed boats, tankers, fishing vessels and chemical tankers. The tankers recently built are advanced double hull chemical tankers for inland navigation as well as sea going.
GERMAN ORDERS
The German ship owner GEFO (Gesellschaft für Öltransport) from Hamburg awarded the Shipyard K.DAMEN a huge contract for the construction of ships with cargo tanks made out of duplex stainless steel. Each ship is named after world famous composers. The first ship was named after Gioacchino Antonio ROSSINI (1792 – 1868) and the second ship after Giacomo PUCCINI (1858 – 1924), two famous Italian opera composers. Verdi, Bellini, Mozart and Donizetti are the chosen names for the last four tankers. Fig. 1 shows an aerial view of the chemical tanker Verdi.
The 95m long seagoing ships have a 12.5m beam and are 6.35m high. The double hull cargo tanks are designed to transport up to 2,750 tonnes or 3,250m3 liquid in 12 separate tanks. The cargo tanks are completely separated and can be loaded and emptied fully independently of the other cargo tanks. This enables different chemicals to be carried and transported simultaneously.
Table 1: Chemical composition of duplex stainless steel (W.Nr. 1.4462) for application in chemical tankers.
The cargo tanks are constructed from a duplex stainless steel (WNr 1.4462) which is a higher grade of stainless steel as opposed to austenitic AISI 316L(N) grade that is often used for inland navigation tankers. Duplex stainless steel has a higher strength combined with a favourable corrosion resistance, two properties that have governed the choice of this material as a way of increasing the number of chemical products that can be loaded and transported by these chemical tankers.
An overview is provided of the welding procedures and the consumables selection for the numerous welding joints between duplex stainless steel and dissimilar metals as applied in chemical tankers.
Depending on the required welding positions during construction, as well as the various base material combinations, the selection of welding processes and welding consumables have been made and tested in accordance with the Germanischer Lloyd (GL) rules. Lincoln Smitweld’s involvement in the huge project has been considerable. It has involved providing technical support and assistance with the:
Table 2. Mechanical properties of duplex stainless steel (1.4462) plate.
• development of the welding procedures,
• consumables selection,
• welding process selection,
• welding qualifications and
• testing according to GL,
• supplying the welding consumables as well as
• the training of the welders
The welders needed training and qualification (t & q) on duplex stainless steel in addition to t & q on welding of dissimilar materials joints.
During the construction phase Lincoln Smitweld remained closely involved with the welding execution and provided continuous technical support.
DUPLEX STAINLESS STEEL
Duplex stainless steel has a number of different properties in comparison with AlSI 316L(N) including chemical composition (table 1), microstructure, corrosion behaviour and mechanical properties (table 2). The higher yield strength combined with the excellent stress and pitting corrosion resistance of duplex stainless steel has increased the popularity and usage of the material considerably over recent years. When the yield strength is increased, the plate thickness can be reduced. The corrosion resistance can be calculated and expressed by the Pitting Resistance Equivalent (PRE), adjusted for N-containing stainless steels: PREN = %Cr + 3,3* %Mo + 16* %N.
The duplex stainless steel (Werkstoff Nr. 1.4462) also has excellent weldability.
Actual view of the layout of the tanks.
WELDED JOINTS
The various joint configurations and material combinations are illustrated in figure 2 and listed in table 3. The cross section of figure 2 shows where the various welding processes can be applied. The corresponding welding consumables are listed in table 4. The various selections welding processes and consumables involved a total of 12 welding procedures, developed and successfully applied in practice for the welding of the duplex stainless steel cargo tanks.
Table 3. Overview of welding methods.Figure 2. Schematic cross section of a chemical tanker.
Table 4. Typical mechanical properties of the welding consumable that have been applied.
Lincoln Smitweld would like to express its thanks to Mr van As and the management of Shipyard K. Damen in Hardinxveld-Giessendam for its assistance in preparing this article and for its permission to publish.
Published in: Welding & Metal Fabrication, June 2000, Library: LSW-TS-185
