Angular Expansion Joints
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General information - Angular expansion joints 1 - Anchors, pipe supports / guides, - Expansion joint systems 3 Pipe supports and guides 21 operating pressure, Expansion joint data sheet 25

General information Angular expansion joints are suited for the compensation of both long pipe sections of district heating systems as well as short boiler and turbine room pipelines in one or more planes. For installations with very limited space one should also check the possibility of the installation of tied universal or pressure balanced expansion joints. Contrary to axial and universal expansion joints that are suited to compensate for movements independently, angular expansion joints are only elements of an expansion system. A minimum of two and a maximum of three angular expansion...

General information Anchors, pipe supports / guides Angular expansion joints make no special demands on pipe supports or guides in contrast to axial expansion joints. Even swing hangers can be sufficient. Additional supports are unnecessary for short turbine house pipelines. The weight of the pipe sections between the angular expansion joints must be supported by supports or hangers which must not hinder the movements of the angular expansion joints. Pipe guides placed before and after each expansion system are necessary in long pipelines. Pipe guides which have been fitted too tightly may...

General information The following expansion joint arrangements are most common in the planning of angular expansion systems: Expansion joint systems Two pin Z-system for pipelines of any length under utilization of a given route. Three pin L-system suited for the compensation of transfer pipelines between two tanks for example. Two pin gimbal system for the compensation of perpendicular movements in short pipeline sections. Three pin U-system preferably for the compensation of long pipelines.

General information Expansion joint systems Three pin W-system for the compensation of longest and shortest pipelines with concurrent movements from two directions. Three pin gimbal W-system for the compensation of three dimensional systems, for example boiler and turbine house pipelines. Three pin Z-system for the compensation of pipelines under utilization of given pipeline routings including the compensation of the vertical pipeline section.

Calculations In the following example, the three pin Wsystem is used to explain the basic procedure for the design of expansion systems. First of all, one has to choose a suitable expansion system under consideration of the given routing and the anticipated expansion of the pipeline. Note that both ends of the line must be limited by pipe anchors. For our example, we assume an L-shaped pipe routing of which the thermal expansion Δ1 and Δ2 from the pipe sections L01 and L02 will be optimally compensated for by a system of three hinged expansion joints in the three pin W arrangement. In order...

= anchor = pipe support / guide System calculation Required hinge distance Under consideration of the permissible angular rotation [␣zul] and a 50% prestressing, the minimum required distance between the hinges L1 is: Resulting arc height At the maximum effective angular rotation (␣e) the vertical distance between the hinges is reduced by the dimension h due to the circular motion of the expansion joints. The height of the arc and the thermal expansion of the pipe section L1 must be compensated for by the pipe section (2.5 · L1) or a sufficient clearance in the pipe guide must be available....

Calculations Bending moments of angular expansion joints In order to calculate the bending moments and forces, the absolute values of the effective angular rotations (without signs) must be used in the following equation. Bending moments at the connection points My1 = MB + Fx · Anchor / connection point forces Forces at the connection points If the system ist pre-stressed at 50%, the moments and forces have different signs in the pre-stressed position and operating position of the system. Center to center distance between bellows and connection point [mm] Bending spring rate [Nm/degr.]...

= anchor = pipe support/guide System calculation Required hinge distance Under consideration of the permissible angular rotation [␣zul] and 50% pre-stressing, the minimum required distance between the hinges L1 is: Resulting arc height At the maximum effective angular rotation (␣e) the vertical distance between the hinges is reduced by the dimension h due to the circular motion of the expansion joints: h = L1 · (1-cos␣e) [mm] The height of the arc and the thermal expansion of the pipe section L1 must be compensated for by the pipe section (2.5 · L1) or a sufficient clearance in the pipe...

Calculations Bending moments of angular expansion joints In order to calculate the bending moments and forces, the absolute values of the effective angular rotations (without signs) are used in the following formulae: Bending moments at the connection points My1 = MBy + Fx · Anchor / connection point forces Forces at the connection points Fx = 2000 · MBy [N] L1 If the system ist pre-stressed at 50%, the moments and forces have different signs in the pre-stressed position and operating position of the system. Center to center distance between bellows and connection point [mm] Bending spring...

Calculations Three pin U-system 3U = anchor System calculation Required hinge distance If the permissible angular rotation [␣zul] of all three expansion joints is the same and the system is pre-stressed at 50%, then the minimum distance between the hinges is determined as follows L1: Effective angular rotation If the pin distance L1 is given, the effective angular rotation of the angular expansion joints (B1, B2) is calculated as follows if the system is pre-stressed at 50%: ␣e1 = ± arcsin Δ L1 = [mm] 2 · sin␣zul. L2 should be chosen as short as possible. Bending moments of angular...