EXPANSION JOINTS VS. ALTERNATIVE FLEXIBLE SOLUTIONS
For the absorption of movements in pipe systems, the pipe designer can choose between the installation of expansion joints, or other flexible solutions such as a pipe loop. Pipe loops also allow movements of the pipe system, but only in the axial direction of the pipe system.
What are pipe loops?
Pipe loops require more material such as pipe bends, pipe support, insulation and NDT. Furthermore, pipe loops consume a lot more space and can generate a greater pressure loss. Due to this, the installation of expansion joints is considered as a reliable and cost effective alternative to the use of pipe loops.
Why are installation of expansions joints better than pipe loops?
The use of expansion joints ensures less material consumption, greater space savings with the reduced number and complexity of fix points and guides. Further, it requires less labour inputs such as those for welding and NDT. Additionally, the selection of expansion joints eliminates the bending stresses in the pipe system, which could cause a fatigue crack of the pipe system. The appropriate type can absorb movement in several planes and is maintenance free. Further, a replacement of a worn-out unit is easier and more efficient in terms of downtime and costs, than replacing a complete pipe loop.
Inverse pipe loops require strong fix points, which can obtain the full pressure thrust force. The advantage of expansion joints versus pipe loops, increases with larger pipe sizes (DN) and increased pipe thicknesses, which is further explained in the table below. In this table, an expansion joint is compared against a pipe loop.
Installation of Expansion joints compared to pipe loops
The table shows that a DN 100 expansion joint is in general approximately 37% cheaper than a pipe loop of the same size. If the pipe size is
DN 400, an expansion joint solution is approximately 82% cheaper than a pipe loop. The data is calculated on the basis of these conditions: PN 10, EN 1.0038/ St. 37-2 welding ends, thermal expansion -0/+ 50 mm.
What about pressure loss?
The pressure loss is significantly lower when installing an expansion joint rather than a pipe loop.
The price index is based on material and working hours. Areas marked with * are not part of this price index. Please note that both solutions will have extra costs such as extra costs for supports/guides for pipe loop and for stronger fix points for expansion joint respectively.
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