Seamlessly Happy Shelf Life

Especially in the area of ​​stainless steel, many metal bellows manufacturers use welded pipe constructions. In order to produce small quantities and large bellows diameters, mechanical single shaft deformation is often used. In contrast, the internal high-pressure process (hydroforming) has proven itself for the economical production of large series. The sleeve is embedded in a special cassette. This moves in the axial direction during the forming process, while depending on the size of the bellows and the wall thickness, water is pressed in at a pressure of 40 bar to 500 bar. Mera Bellows specializes in this methodology and bellows with relatively small inner diameters. For bellows in the precision area, the company only uses seamless sleeves.

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The reason is that seamless metal bellows can be manufactured with far lower tolerances compared to longitudinally welded constructions. With regard to their wall thickness in particular, their empirical scatter is significantly reduced. As a result, the pressure and spring properties of the bellows are more precise and reliable because a weld seam is usually the weak point of a hollow metal body.

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Cover milling machine elements securely over a large area

If the metal bellows breaks in a life cycle test, it is very likely to happen at the seam. In order to achieve maximum lifetimes and whenever you are looking for metal bellows for highly sensitive applications such as automotive engineering, aviation or vacuum applications, the seamless design should be the first choice. In addition, this is superior in other aspects: Due to the deep-drawing of the sleeves, they all have a bottom, which offers considerable advantages in automated handling and checking for leaks. In addition, depending on the customer's preference, the sleeve base can be individually designed, e.g. B. with inner curvature or as an inclined shape to act as a trigger.This means that the power can be transferred later without additional soldering or welding.

Without built-in vulnerability

So let us summarize: Seamless constructions convince by very high accuracy, sustainable durability and a large design scope. The situation is different in the area of ​​metallic compensators. In any case, a construction that is open on both sides is sought here, the advantage of the sleeve base is eliminated. If the focus is on the movement recording in a pipeline or the passage of a medium, the selection of a welded bellows can make sense as long as it fully meets the specific requirements. No exact regulation or measurement is required as a compensator, so the lower variance of seamless bellows does not necessarily mean an added value that would justify the increased manufacturing effort in any case. For welded pipes can be cleaned several times,Annealing and deep drawing can be dispensed with. This cost saving ultimately makes itself felt in the price.

Material suitable for the application

In addition to choosing a manufacturing process, great attention should be paid to the choice of materials. Bronze and brass are widely used for precision bellows, often used in measurement and control technology. These can also be designed as an extra-flexible version to react to the slightest changes in temperature or pressure. In contrast, corrosion-resistant stainless steel is advisable for power transmission, or if very high temperatures occur with possibly large temperature gradients. Bellows in Monel are a popular choice for contacting particularly aggressive media such as salt water. Depending on the application, for example as a stainless steel compensator, the installation of an inner tube for the passage of liquids or gases can provide additional protection for the bellows. (br)