More than a box of metal sheet!

Liquid natural gas tanks in are high-tech monsters inside a Tanker. They need to handle huge temperature differences from -160°C to +40°C or more, if still empty. Also the volume changes during transportation, as liquid gas continuously evaporates. To compensate these severe environmental impacts, the walls are engineered to compensate for these changes.

Curled steel sheets are welded together, not an easy task for automated processing. The weld seam needs to be gas tight. Specially designed plasma welding systems from SBI are used to master this challenge in an extremely high precision. In the process the primary metal membrane with a thickness of only 1mm is welded onto the secondary layer, that is integrating the cooling channels for insulation.

Rocket Science?

Although its not rocket science it has the potential to make things easier in the Thermosphere and above. The talk is about Plasma Metal Deposition (PMD) for space applications.

Because space is an uncomfortable place it is essential to use materials with high toughness, one of those is titanium. Due its excellent corrosion resistance compared with its specific strength it is a superior material for such applications. One of its drawbacks is its high price and that’s the point where PMD is entering the game.

With its near-net-shape manufacturing style, titanium parts can be made with much less material than traditional machining methods like milling or lathing resulting in a more economic production.

Joint welding of satellite propellant tank

Satellite propellant tanks are often made of titanium due two reasons.
First titanium offers a great specific strength and second it has good corrosion resistance.

Lifting a mass of 1kg into the orbit is not a bargain - starting at 2,500€ and rising up to several 10,000€ depending on the orbit height. To save weight and therefore money for the rocket start, propellant tanks of satellites are made of thin titanium sheets with a thickness between 0.8-1.2mm. This thin titanium skin acts as a tight membrane. To withstand the enormous pressure resulting due the gauge pressure and the evacuated space, the titanium membrane is wrapped by carbon or glass fibre reinforced plastic layers.

The welding of the titanium sheets can be done by Plasma Welding with or without a filler wire. Argon, which is used for shielding gas, trailing gas and forming gas, protects the liquid weld pool during the Plasma Welding process from atmospheric conditions and keeps the seam safe and clean.

Welding of tanks for wine storage and transportation

In the processing & handling of beverages, stainless steels are the favoured materials to use. Thanks to their good durability against corrosion and their low affinity to release alloying elements, stainless steels are a superb choice for this task. Plasma Spot Welding is used to join stainless steels in an economic way, the focused plasma arc and the additional shielding gas enable fast and safe welding procedures.