Linear Expansion

The linear expansion of pipes depends on the difference between the installation temperature and the operating temperature:

T = T_{operating temperature} - T_{installation temperature}

Therefore cold water pipes have practically no linear expansion.

Because of the temperature-dependent expansion of the material, the linear expansion must be specially considered in case of warm water and heating installations. This requires a distinction between the types of installation, i.e.

• Concealed installations with piping insulated
• installation in ducts
• open installation

Concealed installation with insulated piping

Concealed installations generally do not require consideration for the expansion of aquatherm greenpipe pipes. In general, insulation gives enough expansion space for the pipe. In the case where the expansion is greater than the room to move in the insulation, the material absorbs any stress arising from a residual expansion.

The same applies to pipes which do not have to be insulated according to current regulations. Embedding the pipe in concrete or plaster will negate most of the linear expansion. The compressive strain and tensile stress arising from this are no longer critical, as the extra forces are absorbed by the pipe itself.

Open installation

In the case of exposed installation pipes (e.g. in the basement), excellent visual characteristics and form stability are important. Aquatherm greenpipe pipes for cold water and aquatherm greenpipe faser-composite pipes for hot water and heating systems make this possible. The coefficient (?) of linear expansion of aquatherm greenpipe and climatherm fasercomposite pipes is only

faser-composite = 0.035 mm/mK = 2.367•10-4”/ft°F

and comparable to the linear expansion of metal pipes.

The coefficient of linear expansion of aquatherm greenpipe pipes without stabilizing components is

aquatherm greenpipe= 0.150 mm/mK = 1.008•10-3”/ft°F

Aquatherm greenpipe faser-composite pipes must have enough space to expand (see page 4.06). An expansion control must is required for long and straight faser-composite pipes (over 120 ft).

Aquatherm greenpipe pipes without the stabilizing compound should have expansion control on every 30 ft of straight runs. Risers of faser-composite pipes may be installed rigidly without expansion compensation. The following formula, calculation examples, data tables and diagrams help to determine the linear expansion. The difference between working temperature and maximum or minimum installation temperature is essential for the calculation of linear expansion.