Corrugated Hoses

In its classic design as a corrugated hose, a metal hose consists of three core components:

• a corrugated hose as a sealed, pressure-bearing element,
• an outer braided hose designed to absorb the longitudinal force generated by internal pressure,
• as well as the connection fittings, which serve as an interface with the surrounding environment.
  

Optionally, a PTFE liner can be added to increase chemical resistance, along with an inner braid for flow guidance, an outer round wire spiral, or a protective hose for mechanical protection.

The standard material for the corrugated hose is austenitic stainless steel 1.4404, and for the braid, it is 1.4301.

For applications with higher corrosion or temperature requirements, other materials such as 1.4565, 2.4856, 1.4571, and other stainless steel alloys are available.

The maximum allowable operating pressure of a corrugated hose assembly generally depends on the operating temperature. Material-specific derating factors reduce the allowable operating pressure at elevated temperatures.

In the standard version, nominal pressures of up to 250 bar are possible at 4 times the burst pressure for small nominal diameters and at temperatures below room temperature. Various special versions are available for even higher pressure requirements.

The maximum operating temperature for standard stainless steels is 550°C, depending on pressure; with special materials, it can be even higher. In the low-temperature range, temperatures as low as -270°C are possible.

Relevant design parameters are:

• Nominal Diameter (DN) and Inner Diameter
• Operating Pressure (PS) and Operating Temperature (TS)
• Type of motion (stroke, oscillation, thermal expansion) and load cycle count
• Medium (Corrosion Resistance, Chemical Resistance)
• Installation Type (U-bend, 90° elbow, lateral)
• Standards and Certifications (e.g., DVGW, DGRL, DIN EN ISO 10380)

FLEXPERTE (download version) is available for standard-compliant design: After entering the operating conditions, the tool provides suitable product recommendations, including all installation dimensions and sketches.

The most important standards for corrugated hoses are:

• DIN EN ISO 10380: (International Standard: Design, Manufacture, and Testing of Corrugated Metal Hoses)
• DIN EN 14585: Product standard for the EU Pressure Equipment Directive (PED 2014/68/EU)
• DGRL (2014/68/EU): Mandatory EU Directive on Pressure Equipment; metal hoses are classified as “piping”
• DIN 3384: Stainless steel gas hose lines (industrial, up to PN 16)
• DIN 2827: Hose Assemblies for Chemical Substances
• DIN EN 15265 / EN 14800: Gas lines and gas hoses for buildings and household appliances
• DIN EN 16617: Corrugated metal hoses for flammable gases

Witzenmann is certified to ISO 9001, IATF 16949, EN 9100, ISO 14001, PPE Directive 2014/68/EU, EN 15085, EN ISO 3834-2, as well as product-specific approvals from DVGW, SVGW, VdS, FM, and international shipping classification societies (ABS, BV, DNV, LRS).

• Axial expansion cannot be accommodated—corrugated hoses must be installed in a U-bend (180°) or a 90° bend.
• The minimum bending radius must never be exceeded.
• Avoid twisting—first secure the hose on one side only, run through 2–3 movement cycles without pressure, then tighten both sides.
• Position the anchor points immediately behind the end of the hose line.
• The operator should perform visual inspections at regular intervals to check for kinks, breaks in the braiding, and corrosion.
• Insulation must not restrict mobility; corrosive insulation materials are prohibited.
• Perform a pressure test before commissioning; apply the test pressure only at room temperature.