ABOVE-GROUND INSTALLATION GUIDELINES

Pexgol pipes withstand exposure to sunlight for pipe lifetime. Above-ground installation of Pexgol pipes is advantageous in the following cases:

• Slurry lines which are frequently relocated
• Installation through marshes or areas with difficult access
• Quick installation of temporary pipelines

The coefficient of expansion of Pexgol pipes is high compared to steel pipes, but the forces generated by thermal stresses are much lower for Pexgol pipes. The reason is the low modulus of elasticity and the fact that the Pexgol pipes feature stress relaxation.

Pexgol pipes installed above ground might increase in length as a result of temperature increases and tend to undergo “snaking”. Longitudinal elongation and contraction of the pipe is not uniform due to the coefficient of friction between the pipe and the ground varies. However, the toughness and the exceptional abrasion resistance of Pexgol pipes enable the pipes to move across the soil without affecting strength or service life.

When the design temperature is lower than the installation temp. The pipe tends to contract. The contraction creates axial stresses in the pipes which tend to pullout the pipes from the fittings.

Installing Pexgol pipes above the ground with a calculated slack rather than in a straight line, is a way to reduce thermal stresses. This procedure reduces the tendency of the pipe to pullout of its fittings.

The slack (calculated according to the Pexgol coefficient of thermal contraction) is 0.2% or 2mm for every meter per 10°C. The actual value depends on the temperature difference between the installation temperature and the lowest temperature. The slack can be maintained by pushing the mid span of the pipe slightly sidewise during the installation.

Axially unrestrained fittings should be secured and protected from pull out.

If a straight pipeline is required, guiding the pipeline at intervals is a good method of limiting and controlling thermal expansion and contraction of the pipeline. The smaller the distance between the guides, the smaller the theoretic increase in pipe length. As a result, lateral deflections decrease and the pipeline remains straight.

The distance between two adjacent guides is calculated according to the following formula:

L = F x D where:
L is the distance (in m) between the guides.
D = outside pipe diameter (in mm).
F is a coefficient which depends on the temperature.

Increase ΔT between the installation temperature and the design temperature.

The formula allows for a maximum sidewise deflection of 50 mm between two adjacent guides.

Example:

Pipe diameter: 200 mm
Installation temperature: 20°C
Maximum ambient temperature: 40°C
Design temperature: 20 + 40 = 60°C
ΔT= 60° – 20° = 40° F = 0.064  L= 0.064 X 200 = 12.8 m

Coefficients F:

Correction Factors: