Metal Hoses

Manufacturing corrugated hoses

The first step in creating a corrugated hose is to shape the starting metal strip from the coil into a smooth, longitudinally welded tube. The strip is continuously welded using the highly precise shielding gas welding method. Then the tube is corrugated by one of the following procedures:

The first step in creating a corrugated hose is to shape the starting metal strip from the coil into a smooth, longitudinally welded tube. The strip is continuously welded using the highly precise shielding gas welding method. Then the tube is corrugated by one of the following procedures:

The mechanical corrugation method, on the other hand, is used to produce both annular and helical corrugated hoses. Usually, multiple profiled pressure rollers are positioned around the tube with an offset that enables them to roll the desired corrugation profile into the tube from the outside to the inside. Both corrugation methods cause material hardening and thus increase the pressure and fatigue resistance of the corrugated hoses.

In addition, corrugated hoses can be manufactured by a special method that is closely related to the manufacture of stripwound hoses. In this procedure, the starting strip is given a corrugated profile in a longitudinal direction. This profile strip is then wound helically and the overlapping coils are tightly welded along the helical seam. After corrugation, the hose may be equipped with a braided sheath (see below). In this case, the hose then passes through a braiding machine that has circumferential wire coil holders, or so-called bobbins.

The wire bundles are wrapped helically around the hose while also being alternately layered one over the other. This creates a tubular braid with the characteristic crisscross pattern. After the fittings are mounted, the hose line is complete. Production-related testing is an integral part of the manufacturing process. It encompasses incoming tests of the starting material as well as dimensional, leakage and pressure testing of the finished conduit.

Flexibility

Bellows

The flexibility of the hose is achieved by means of the elastic behaviour of the corrugation profile. When the hose is bent, the outer corrugations separate while the inner corrugations are squeezed together. The flexibility, bending behaviour and pressure stability of corrugated hoses depend on the selected profile shape. While flexibility increases with an increase in profile height and a decrease in corrugation spacing, pressure resistance decreases. The frequently required semi-flexible bending behaviour is achieved by flat profiles. Depending on the use of the hose, special application-specific profile shapes can be implemented Pressure resistance and flexibility can also be altered by varying the wall thickness. A reduction in the wall thickness increases the bending capacity but reduces the pressure resistance of the hose.