Welding steel and coating
Delta Marine Scandinavia AB combines decades of experience in the industry with the integration of the most modern technologies and latest designs adapted to the needs of customers. Tugboats, fishing surveillance vessels, salvage vessels, dredgers, oceanographic vessels and, of course, fishing vessels, have left their slipways with the best results in terms of quality and efficiency, meeting the deadlines and exceeding the high expectations that are already presupposed for Scandinavian shipbuilding.
At Delta Marine Scandinavia AB, we offer a design completely adapted to the needs of our customers, being flexible to changes and trying to provide the greatest possible value to the user. We work with the best engineering companies in the sector and have a modern internal technical office, as well as a project team with extensive experience and preparation to bring any challenge to fruition.
The construction of a ship is a complicated and highly technical process, requiring the coordination of numerous permanent and temporary workers under the control of the main contractor. Shipbuilding can be civil or military in nature. This is an international sector in which shipyards around the world compete for a rather limited market.
Since the 1980s, shipbuilding has changed dramatically. In the past, most shipbuilding work took place in the buildings or on the slipways of a shipyard, where the ship was lifted and built almost piece by piece. Technological progress and more detailed planning now make it possible to build ships from subunits or modules incorporating integrated facilities and systems. This makes it relatively easy to connect the modules. This process is faster, less costly and ensures stricter quality control. In addition, this type of construction lends itself to automation and robotization, which saves money and reduces exposure to chemical and physical hazards.
The shipyard’s “assembly line” begins in the steel storage area. Huge steel plates of different sizes, thicknesses and strengths are stored there ready for use. The steel is then sandblasted and primed to protect it during the various stages of the construction process. The prepared plates are then transferred to the construction workshops, where they are cut to the desired size with automatic torches. These cut pieces are welded together to form the structural components of the vessel.
The structure of most ships is a composite of mild steel and high-strength steel elements. This material has excellent properties of ductility and suitability for machining and welding, as well as the strength required for transoceanic vessels. The basic material used in shipbuilding is steel of various grades, but aluminum and other non-ferrous materials are also used in the assembly of some superstructures (e.g. deck accommodation) and in certain areas of the ship. Special materials such as stainless and galvanized steels or copper and nickel alloys are used for corrosion protection and to improve the structural integrity of the vessel. In any case, non-ferrous materials are used in much smaller quantities than steel. Onboard systems (ventilation, combat, navigation, piping) are almost always the ones that consume the largest amount of these “exotic” materials. They are required to perform a variety of functions: ship propulsion, standby power, galleys, fuel pumping units, combat systems, etc.
Steel is an excellent material for shipbuilding, and the choice of welding electrodes is critical in all welding applications throughout construction. The objective is always that the weld should have strength characteristics similar to those of the starting metal. As some minor imperfections are likely to occur in industrial welding work, it is common practice to choose welding techniques and electrodes so that the joint obtained is stronger than the starting metal.
Painting and finishing
It is painted almost everywhere in the shipyard. The nature of shipbuilding and repair work requires the use of various types of paint for different applications, from waterborne products to high-performance epoxy coatings. The type of paint suitable for a given application depends on the conditions to which it will be exposed. Paint application tools range from simple rollers and brushes to airless sprayers and automatic machines. In general, there are special painting standards in the following areas of the vessels:
– underwater (hull bottom)
– upper superstructures
– internal enclosures and warehouses
– outdoor covers
– loose equipment.
Pre-assembly outfitting of building blocks is the shipbuilding method currently employed worldwide by competitive shipyards. The installation of various components and sub-assemblies (piping systems, ventilation equipment, electrical components) in the blocks before they are joined together in the assembly phase is called equipping. The equipment of the blocks in the shipyard lends itself to the organization in the form of an assembly line.
Equipment throughout construction is planned so that work progresses without interruption throughout the shipyard. Once the steel structure of the block is assembled, and for simplicity, the equipment can be divided into three main construction stages:
- unit equipment
- block equipment
- equipment on board.
During the operation and testing phase, the functionality of all installed systems and components is evaluated. It is at this stage that all systems are operated, tested and overhauled. Any system that for any reason does not pass the tests will be removed, repaired and checked again until it is fully operational. All on-board piping systems are pressurized to easily locate the possible presence of leaks. Likewise, the tanks must pass the corresponding structural tests by filling with liquid (fresh or sea water) and the subsequent examination of their structural stability. Electrical and ventilation systems, among many others, are also checked. Most of the operational tests and system checks take place with the ship moored at the shipyard’s dock. However, there is an increasing tendency to carry out these tests at earlier stages of construction (preliminary tests in production workshops).
Performing these tests at earlier stages of construction facilitates troubleshooting due to greater accessibility to all systems, although tests on complete systems must always be performed on board the ship. Once all tests have been completed with the vessel moored, it is put to sea and undergoes further sea trials before it is considered fully operational for seaworthiness purposes and handed over to its owner.