Permeation of Chemicals
PE 100 pipes are used to supply both drinking water and gas (and also for conducting municipal wastewater).
These applications have produced very positive operating experiences, especially on account of their resistance to corrosion. The pipes have been standardised in European standards and have been certified for gas and water supply in Germany by the DVGW (German Gas and Water Association).
PE 100 pipes are also used for industrial applications. Tables show whether the polyethylene material is resistant to the medium to be transported (e.g. in supplementary sheet 1 to DIN 8075). It can be seen from this standard that PE-HD (as generic term, PE 100 is a PE HD) is only resistant to technically pure (i.e. almost 100%) benzene to a qualified extent. Over time the benzene can permeate the polyethylene and bring about swelling, and in turn a weakening of the mechanical characteristic values. Therefore a pipe made from PE 100 can only be operated with a reduced internal pressure. The reduction factor for the respective concentration must be determined on a case by case basis.
The impermeability of the pipe material must be taken into consideration in addition to the resistance of the material. Ever since starting to use polyethylene pipes it has been known that these are not permanently diffusion-resistant to benzene. The time at which the first molecules permeate through the pipe wall and the quantities of permeation will depend in each case on the concentrations and operating temperature.
Against this background egeplast developed the SLA® Barrier Pipe SLA® Barrier Pipe in the 1980s. This polyethylene pipe contains an aluminium barrier layer, and is therefore designed like a Tetra Pak. This impermeable PE pipe has been approved in the Dutch KIWA rules and standards for the installation of drinking water pipes in contaminated soils with a concentration of up to 1780 mg/l benzene in the area of the pipe.