Belman developed three customised angular expansion joints using a three-hinge system for a project in Northern Europe.

Recently, one of the Belman’s clients enquired about a combination of an existing condenser with a new one using a piping route.

Expansion joints were necessary to absorb movements. It was also important that both reaction forces and spring rates would be kept low.

The joints will be installed in a pipe routing between two condensers.

In a situation like this, a pressure balanced expansion joint would usually be offered as a solution.

However, the client had sufficient space between the condensers. Therefore, Belman proposed a solution utilising a three-hinge system, also known as U-pipe or 3-pin system.

After further analysis, this proposal was confirmed as the most technically and commercially attractive solution for absorbing the movements.

This solution consisted of three angular expansion joints with hinges. With the selected placement and constellation of the expansion joints in the three-hinge system, the reaction forces and spring rates were maintained at an acceptably low level.

The hinged expansion joints were further designed to carry the weight of the pipes, connecting the expansion joints.

The selection of the expansion joint type, piping constellation and design resulted in the solution and cost optimisation.

Three-hinge system offers a number of benefits. For example, substantial fix points and guides in the piping route are no longer needed. This is due to the pressure thrust force from the bellows being contained by the hinge structure on the expansion joints.

The expansion joints with hinges are able to absorb external forces such as the weight of intermediate pipes and the pressure thrust from the medium.

Three-hinge system also enables larger movements to be absorbed.

To verify that the hinge construction is suitable to carry the load of the intermediate pipes, a finite element analysis of the hinge construction was made.

The angular expansion joints with hinges are a customised solution. They can be adapted to meet the client request.

As the three hinge system is installed horizontally, the gravitational force of the intermediate pipes is perpendicular to the plane of the movements.

The angular expansion joints with hinges have the following design parameters:

  • Dimension: DN 1000
  • Length: 636 mm
  • Medium: steam
  • Design temperature: 120°C
  • Design pressure: full vacuum/0,49 barG
  • AN: +/-11°
  • Bellows: 1.4571
  • Inner sleeve: 1.4541
  • Pipe end, hinge plate: 1.0425

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