The main difference between these hoses is their construction and application.
Stripwound hoses („Peschel hoses”) are manufactured by winding profiled, metal strips that overlap each other. They are intended for the extraction of gases and fumes and transfer of bulk materials. Due to their construction, they are not pressure tight. They are usually attached to a stub pipe using a hose clamp (optionally fittings can be welded to the hose to produce a complete hose assembly).
Pressure hoses consist of a corrugated steel tube reinforced with a steel braid from the outside. The corrugated tube is formed mechanically or by hydroforming. They are mainly used as high pressure hose assemblies. Supplied ready-made, with end fittings.
These two types of metal hoses can be combined:
as an external cover (stripwound hose on the outside / pressure hose inside)
as a bend restrictor for the pressure hose (section of a stripwound hose attached to the fittings)
as an internal liner in a pressure hose, e.g. for bulk material transfer
What are the maximum operating parameters, including pressure and temperature, that metal hose assemblies can operate within?
Metal hose assemblies come in countless construction and material options so they can operate at actual operating parameters reaching very high values. The volume of transmitted pressure is determined by: nominal diameter, wall thickness of a source material, geometry of corrugations (pitch and height) and the number of braids.
The same applies to the working temperature, which for stainless steel hoses is normally 600÷700°C, while with some materials such as Inconel alloys it can be as high as +1000°C. However, a correction factor must be always taken into account as the temperature increases. The same applies to dynamic operation (vibration, displacement, type of medium flow). Tables with coefficients are in ourcatalogueor on the website in the section Industrial Hoses –metal hoses.
Fittings are attached to metal hoses and ferrules by a special process such as TIG welding or, less frequently, brazing.
The standard AF… solutions are described in our catalogue/website in the section Industrial Hoses – metal hoses. A bigger/smaller fitting can be joined with a steel hose via an additional reducer. Using seamless pipe elbows, we can also make any fitting angle. In addition to standard fittings, we can supply hoses with special custom fittings, either by adapting standard solutions or, thanks to our Construction Department and machinery, by providing a custom-made solution according to customer specification or a template.
How to prevent the most common failures of metal hoses?
Metal hoses, despite their ‘heavy-duty’ name, are in fact very fragile. The connection point between the corrugated tube and the fitting is particularly vulnerable to all kinds of stress. Therefore, when planning and/or installing the system, it is important to prevent:
a. hose kinking – use a correct bend radius, bend restrictors or use angled fittings b. hose twisting – one of the fittings is a swivel, the plane of movement is in line with the axis of symmetry
Assembly instructions for steel hoses are available in our catalogue, on our website or from a sales representative.