Flanged bellows expansion joint

Metal bellows expansion joint (Metal Expansion Joint)

The metal bellows expansion joint (Metal Expansion Joint) is a high-tech, flexible industrial device designed to absorb (compensate) thermal changes in piping systems (thermal expansion and contraction), mechanical oscillations (vibration) and axial movements. It keeps the system intact and prevents pipes from deforming and bursting.

Diameter: DN25 – DN3000
Pressure: PN6 – PN64
Temperature: -20…+400 °C
Bellows: AISI 304 / 316 / 321

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Bellows expansion joint types

AxialFitted on straight pipe runs between fixed supports to absorb axial movement; installed by welding.
FlangedThe most common type: a detachable flanged pipe joint that takes up axial loads.
AngularFitted at pipe bends; a hinged design moves in one plane and protects the bellows from twisting.
GimbalTwo hinged elements allow movement in any plane as well as axially.
LateralTwo-section (two bellows): protects the pipeline from lateral offset, most often where it enters a building.

Installation sequence

1. InspectionCheck the joint and the pipe section for defects.
2. PreparationIf needed, secure the joint by its pipe ends and remove the factory preservative.
3. DocumentationRead the data sheet to see whether pre-stretching is required.
4. Fix the pipe endsFix the pipe ends at the distance set by the joint's length.
5. AlignmentCheck that the pipes are axially aligned.
6. Fit-upBring the pipes and the joint together.
7. ConnectionConnect to the pipeline one end at a time.
8. Protective coverFor open installation fit the cover to protect the bellows from the weather and damage. Install without twisting or bending loads.

Technical specifications

Products can also be manufactured to the customer's drawings and technical requirements, including larger diameters.

Flanged bellows expansion joint — Technical specifications
Parameter	Description / Standard values
Product type	Axial metal bellows expansion joint
Connection type	Flanged connection (Fixed/Loose Flanged)
Bellows material	Stainless steel (AISI 304, AISI 316, AISI 321)
Flange material	Carbon steel (Carbon Steel St37.2 / A105) or stainless steel
Nominal diameter (DN)	From DN25 to DN3000 mm (to order)
Nominal pressure (PN)	PN6, PN10, PN16, PN25, PN40, PN64 (or Class 150/300 Lbs)
Working temperature range	From -20 °C to +400 °C (higher for special designs)
Working medium	Hot and cold water, steam, natural gas, petroleum products, chemicals
Design standard	EJMA (Expansion Joint Manufacturers Association) and EN 1092-1

Parts and materials

1First flange — St37.2 / A105 steel or stainless steel
2Neck rings — to be confirmed
3Bellows — Stainless steel AISI 304 / 316 / 321
4Inner sleeve — to be confirmed
5Polished ring — to be confirmed
6Second flange — St37.2 / A105 steel or stainless steel

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Key advantages and functions

Complete absorption of thermal expansion
Fully neutralises the longitudinal (axial) elongation and contraction of pipes caused by high and low temperatures.
Lower vibration and noise
Absorbs vibration from pumps, compressors and other dynamic equipment, extending the service life of the system.
High durability
The corrugated stainless-steel section is highly resistant to corrosion and high pressure.
Easy installation
Standard flange holes let it be bolted to the pipeline quickly and securely.

Field of application

Widely used on the main pipelines of combined heat and power plants, district heating systems, oil and gas refineries, chemical plants, metallurgical works and large pumping stations.