Thermal expansion and pipe networks
For all the types of pipes constituting a distribution network, the elongations or contractions due to thermal expansions as a result of the increase or decrease of temperature of the conveyed fluid must be evaluated.
Plumbing installations can be subjected to mechanical forces, which can cause damages to the installation in absence of a right solution to face thermal expansions.
To compensate thermal expansion effects, according to the material and to the shape of the network, it is required to provide:
the necessary space for the expansions,
the proper placement of fixed sliding support points,
the realization of any line compensators.
To decide the right solution for each installation, it is necessary to calculate the thermal expansion of the pipe. This number changes according to the pipe material.
The equation used to calculate the extension is:
∆L = L • α • ∆T
∆L: global elongation [m]
L: length of the piping [m]
ΔT: thermal change [°C] or the difference between the maximum and minimum operating temperatures
α: linear expansion coefficient (typical for every material, see the table below)
To obtain the thermal expansion, it is easier to use a default graph, as in the example below:
Small longitudinal changes in piping can be absorbed by the elasticity of the pipe itself while in large pipe networks elongation compensators are required.
Most common compensators are U, L or Z shaped. The U-shaped compensators are called U bend.
L and Z compensators can be obtained by the normal itinerary of the pipes in the network, by using specific collars.
On the contrary, U bends (square or rectangular) have to be purpose-made. Here below, there are two examples:
Square u bend
Rectangular u bend
It is important to pay attention to the positioning of the fixed sliding support points in order to allow the item to compensate the thermal expansion. In this way, the installation can expand correctly with no deformations, which can damage the tightness of the joints.
The consultation of the technical catalogue of each range is advisable to find more about the topic.