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Corrosion-resistant plastic pipes with barrier layers to prevent permeation of hydrocarbons

Safe transport of contaminated fluids from industrial processes or exploration
: Späth, Thorsten; Rühl, Wolfgang; Gunschera, Jan

Oil gas. European magazine 135 (2019), Nr.3, S.112-119
ISSN: 0342-5622
Fraunhofer WKI ()

Corrosion-resistant plastic pipe systems are a good option for transporting aqueous solutions resulting from industrial separation processes or separation processes involved in oil or natural gas exploration, which are potentially environmentally hazardous, since they are contaminated with volatile organic hydrocarbons and frequently also with brines. Safe containment of these environmentally relevant components in the pipe systems over many years of operation is the concern of every responsible operator. In the past, leakages caused by corrosion damage on steel pipes or by permeation of hydrocarbons through pipes made of polyethylene (PE) have resulted in environmental damages, which required extensive remediation measures. In view of proven permeation losses with plain polyethylene pipes of the kind also used for drinking water, the suitability of pressure pipes made of polyethylene (PE 100-RC) and equipped with an external aluminium barrier layer (SLA® barrier pipe) as well as an outer protective sheath was to be demonstrated. Since permeation is a slow process involving transport of substances through a solid body, pipes with such a barrier layer were tested and compared to the same pipes which did not have a barrier layer over a 4-year time period in the context of field- and laboratory trials. For tests performed during real operation of a crude oil production facility, the composition of the fluid was given by the real case. For systematic laboratory tests, clearly specified test liquids which came as close as possible to providing a representative sample were used. In order to simulate drastic conditions, test liquids were saturated solutions consisting of various volatile hydrocarbons, some of them also chlorinated. A further test liquid was a mixture of pure volatile hydrocarbons with a 10% share of aromatic toluene. In contrast to single-layer polyethylene pipes, the PE pipes featuring a barrier layer (SLA) were shown to be resistant to permeation of all of the dissolved volatile organic ingredients examined. Even under tougher test conditions in the laboratory (which involved pure volatile hydrocarbons), analytic measurements after two years showed some traces of hydrocarbons in the protective sheath beyond the aluminium barrier layer of the SLA pipes only, though not in the gaseous phase outside the barrier layer pipe (SLA). Thus, PE pipes equipped with an aluminium barrier layer can be recommended for loss-free transport of aqueous liquids containing hydrocarbons, such as production water in crude oil and natural gas facilities, and are an alternative for pipes exclusively made of polyethylene. Combined with permanent monitoring for the purpose of damage detection, they comply with the strictest environmental requirements in effect, thus reliablyprotecting the environment.