Expansion Joints

Braided Expansion Joint: Design and Use of Stainless Braided Bellows

Explore the construction of braided expansion joints, what the stainless steel braid does, their specifications and their use at pump connections.

ORFA Technical TeamUpdated: Oct 30, 20262 min read

Braided expansion joint with stainless steel braided metal bellows

Pipework connected to pumps, compressors and similar machines can be damaged over time by operating vibration and installation stresses, leading to leaks at connections and equipment failures. A braided expansion joint is a flexible metal connector made of an annularly corrugated stainless steel bellows covered by a high-strength stainless steel wire braid.

This article explains how braided expansion joints are built, what the braid does, and their benefits and specifications.

Construction

Bellows: annular (ring-type) corrugated stainless steel bellows providing flexibility and tightness.
Braid: stainless steel wire braid around the bellows; it protects the bellows from external damage and restrains the axial elongation caused by internal pressure, preventing the bellows from stretching under pressure.
End connections: fixed or rotating flanges, or weld ends.

Because the braid carries the pressure thrust, braided joints are not intended for large axial thermal expansion. They are used to dampen vibration, tolerate small misalignments and installation tolerances, and reduce stress at equipment connections.

Benefits

Protects pumps: reduces stresses transferred from the pipework to pump nozzles, minimising pump damage.
Vibration and noise damping: limits the transmission of vibration and noise from pump connections into the pipework.
Quick installation: compact design for easy fitting.
Space-saving: requires minimal installation space.
Durable: stainless steel bellows and braid give a long service life.
Tolerates misalignment: adds flexibility and reduces the effect of small offsets and stresses.

Technical Specifications

Property	Value
Bellows material	Stainless steel AISI 304 (optional AISI 309, 316L, 316Ti, 321)
Braid material	Stainless steel AISI 304
Rod material	Carbon steel St 37-2 as standard (other materials on request)
Connection	Fixed flanges, rotating flanges, weld ends
Operating temperature	-80 °C / +600 °C
Pressure rating	PN16 / PN25
Nominal size	DN32 – DN250

Tip: Install the braided joint as close as possible to the pump suction and discharge nozzles, and always anchor the pipe on the far side of the joint. Never subject the joint to torsion.

Applications

Pump suction and discharge connections
Compressor and fan connections
Mechanical piping in industrial plants and power stations
Equipment connections in heating, cooling and process lines

Frequently Asked Questions

Can a braided expansion joint absorb thermal expansion?

It is not suitable for large axial thermal expansion, because the braid restrains axial elongation. Axial or double-bellows expansion joints should be used for thermal expansion.

What does the braid do?

The braid stops internal pressure from stretching the bellows, carries the pressure thrust and protects the bellows from external damage.

Which sizes and pressures are available?

DN32 to DN250, PN16 and PN25, for temperatures from -80 °C to +600 °C.

Conclusion

Braided expansion joints are compact, durable components that reduce vibration and stress at pump and machine connections, improving pipework safety and equipment life. For other bellows solutions, see our Metal Bellows Expansion Joints page.

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