Flexible and Metal Hoses

Flexible Metal Hoses: Vibration Damping and Correct Installation

Corrugated, braided stainless steel flexible metal hoses damp vibration and compensate misalignment in pipework. Correct installation is essential for a long service life.

ORFA Technical TeamUpdated: Oct 30, 20263 min read

In industrial installations, rigid pipework is stressed by vibration, misalignment and temperature changes, and fatigue cracks and leaks can develop at the connections over time. Flexible metal hoses, made of a corrugated stainless steel inner hose surrounded by a steel braid, eliminate these weak points as leak-tight, durable connectors.

This article covers the construction of a flexible metal hose, the role of the braid, which movements a hose can and cannot absorb, and the rules for correct installation.

Corrugated Hose and the Role of the Braid

The heart of a flexible metal hose is the corrugated inner hose made of AISI 304 or AISI 316L stainless steel. The corrugations allow it to bend. Under internal pressure, however, the corrugated hose tries to extend lengthwise like a bellows. The stainless steel braid around it prevents this elongation, carries the pressure thrust and determines the hose’s pressure rating.

Single braid: For medium-pressure applications.
Double braid: For higher working pressures.

Braid layers and hose size should be selected from the manufacturer’s data according to the working pressure and temperature. Remember that the permissible working pressure decreases as temperature rises.

Which Movements Can Flexible Metal Hoses Absorb?

Type of movement	Suitability
Vibration (pumps, compressors, engines)	Suitable – best when the hose is installed perpendicular to the direction of vibration
Lateral offset (misalignment)	Suitable
Movement by bending (loop installation)	Suitable
Axial extension or compression	Not suitable – the braid prevents axial movement; use an expansion joint or a hose loop instead
Torsion (twisting)	Never acceptable – drastically shortens hose life

Thermal expansion can only be absorbed by flexible hoses when they are installed perpendicular to the direction of expansion (lateral movement) or as U- or V-shaped loops.

Operational Benefits

Vibration isolation: Damps vibration transmitted from machines to the pipework, protecting pipes, valves, meters and sensitive instruments.
Installation flexibility: Easy fitting in tight spaces or where connection points are not perfectly aligned.
Corrosion and chemical resistance: The AISI 316L option offers greater resistance to aggressive media and harsh environments.
Wide temperature range: The all-metal construction suits applications from cryogenic to high temperatures; the actual limit depends on the end connection, gasket and welding/brazing method.

Correct Installation Rules

Never twist the hose; use a back-up spanner when tightening unions.
Do not bend below the manufacturer’s minimum bend radius, and do not bend the hose immediately behind the end fitting.
Provide supports where needed so the weight of the hose and medium does not load the connections.
At pump outlets, install the hose perpendicular to the direction of vibration.

Tip: Most flexible metal hose failures are caused by torsion and over-bending. After installation, check that the hose is not under tension and that no spiral line has formed along the braid.

Industrial Applications

Pump and chiller connections in HVAC systems
Refineries and petrochemical plants
Food and chemical process lines
Shipbuilding, engine and auxiliary machinery connections
Thermal oil and steam lines

ORFA offers flexible metal hoses with flanged, union or weld-end connections to suit your project requirements.

Frequently Asked Questions

What does the braid on a metal hose do?

The braid stops the corrugated hose from extending lengthwise under internal pressure and carries the pressure thrust. It largely determines the hose’s pressure rating.

Can a flexible metal hose absorb axial expansion?

No. A braided hose cannot extend or compress axially. Use an expansion joint for axial expansion, or install the hose as a loop that converts the movement into lateral movement.

What is the difference between AISI 304 and AISI 316L?

Thanks to its molybdenum content, AISI 316L offers higher corrosion resistance, especially in chloride-containing environments and with aggressive media.

Conclusion

When correctly selected and installed, flexible metal hoses isolate vibration, compensate misalignment and help prevent unplanned shutdowns. For product options, see our Braided Flexible and Metal Hoses page.

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