Expansion Joints

Decorative Pipe Expansion Joint: Clean-Looking Expansion Control for Risers

Discover decorative pipe expansion joints that safely absorb thermal expansion in heating and hot water risers of tall buildings and suit visible areas.

ORFA Technical TeamUpdated: Oct 30, 20263 min read

In heating and hot water systems of multi-storey buildings, riser pipes lengthen and shorten as the temperature changes. If this movement is not accommodated, pipes bend, make disturbing noises, joints fail and threads strip. A decorative pipe expansion joint is an axial expansion joint that absorbs this movement safely and, thanks to its aluminium outer cover, can also be used in visible areas.

This article covers the function, benefits, installation rules and technical data of decorative type pipe expansion joints.

What Is a Decorative Pipe Expansion Joint?

It is an axial expansion joint with a stainless steel bellows enclosed in an aesthetic aluminium protective sleeve. The pipeline is divided by fixed points into expansion sections, and the thermal growth of each section is absorbed axially by the joint placed in it. This protects the riser pipe and its connections from excessive stress.

How Much Do Risers Expand?

In 90/70 °C heating risers, expansion of approximately 3 mm occurs per floor. Total movement grows with the number of floors; a 10-storey section, for example, must accommodate about 30 mm. For this reason the manufacturer (Ayvaz) considers expansion joints compulsory in the risers of buildings over 7 floors and recommends repeating the arrangement every 10 floors.

Benefits

Expansion and noise control: Absorbs thermal expansion in risers, preventing pipe stress and expansion noise.
Low pressure drop: The straight flow path adds no significant pressure loss to the system.
Quick, easy installation: Short preparation and installation time lowers labour costs.
Aesthetic appearance: The aluminium cover allows use in rooms, halls, offices and exposed risers.

Installation Rules

The distance between two fixed points should not exceed 30 metres (about 10 floors).
One expansion joint is placed in each fixed-point section, mounted near the ceiling on a floor between the two fixed points.
Fixed points must be strong enough to carry the axial pressure thrust and the bellows spring force.
Guides must be used so that the pipe moves only axially; axial expansion joints are not designed for lateral or angular movement.

Tip: Do not pressurise the expansion joint before fixed points and guides are complete. During a pressure test, an axial joint without anchors can overextend and be damaged.

Technical Data

Property	Value
Bellows material	Stainless steel to DIN 17440
Outer cover	Decorative aluminium
Connection type	Threaded or weld neck
Nominal size	DN15 (1/2″) – DN100 (4″)
Pressure	Max. 16 bar (operating pressure depends on size and temperature)
Temperature range	-20 °C to +90 °C, depending on materials

Frequently Asked Questions

How often should a decorative expansion joint be used on a riser?

It is recommended to use one joint in each fixed-point section, with no more than 30 metres (about 10 floors) between two fixed points.

How does a decorative joint differ from a standard axial expansion joint?

The working principle is the same; in the decorative type the bellows is protected by an aluminium sleeve that looks neat in visible areas.

Can a decorative pipe expansion joint absorb lateral movement?

No. It is an axial joint that absorbs lengthening and shortening along the pipe axis, so it must be used together with pipe guides.

Conclusion

Decorative pipe expansion joints safely absorb expansion in heating and hot water risers of tall buildings while offering a clean look in visible areas. Installed with correct anchors and guides, they help the system run quietly for many years. For other models, see our metal bellows expansion joints page.

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