Basic knowledge of flexible metal hose

Convoluted stainless steel hose - two braids, annular profile
A standard flexible metal hose constructional detail

Components of a typical flexible metal hose

A flexible metal hose roughly consists of three parts - inner convoluted hose, braid layer, braid sleeve and end fittings. The hose body is usually made of stainless steel, such as 304, 321 or 316L. The corrugated structure makes the flexure maximize. It can withstand cryogenic or high temperature while maintaining flexibility.

The braid, made of stainless steel, bronze or other materials, is designed to provide higher pressure capability.

Braid sleeve is the area where hose body and braid are welded to. However, the properties of the hose and braid materials will change during welding. The area where the properties are changed is called "heat-affected zone" and should be taken care to insure the braid sleeve or ferrule has a proper fit.

End fittings are strongly recommended on the applications where sharp bends or extreme flexure occurs near the end of the hose.

Bore configuration

Annular Corrugation
Annular metal hose refers to a series of complete circles or rings located at right angles to the longitudinal axis of the hose. It is characterized by high flexibility, good elasticity, and small rigidity. Annular flexible metal hose can withstand normal pressure and often be used in places where need good flexibility.

 Annular metal hose, completed circles or rings Helical corrugation hose likes a continuous spiral thread
Annular metal hose broadly used in flexible metal hoses for great flexibility Helical corrugation hose for high strength and pressures

Helical Corrugation
Helical corrugation is similar to a continuous spiral or screw thread. Small or medium hoses often use helical construction. Compared with annular hose, helical metal hose is not so flexible. It is mainly used in places where needs high strength and medium and high pressures.

Braid Function

Included angle of braid, usually 75 degree to 85 degree depending on applications
Braid is interwoven in angles for diverse applications

Corrugated metal hoses are usually braided to withstand internal pressure. Flexible metal hoses used under high pressure often have two or more braids to strengthen their capabilities of extremely high pressures. When internal pressure occurs, braid(s) prevent elongation at the same time allowing flexing in the axial direction. As it transforms into braid tension, the internal pressure on the corrugated hose is effectively dissipated and decreasing.
Below are the frequently-used terms of braid which will assist you with knowing our flexible metal hose easily and quickly.

Braid construction
Braid is fabricated by weaving a couple of carriers which are formed by multiple strands or braided strands. The former is called tubular and the latter braided braid.
Barding angle is major parameters for the diverse angles determine the applications. For general applications, the braiding angles are between 75 degree to 85 degree (see the figure below). Other angles are for special orders.

Braid coverage
Optimal braid coverage should achieve three tasks: reduce the hose squirm, minimize braid wear on the crown of the corrugation; ensure pressure ability while maintaining flexing requirements.

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