Corrosion is the first cause of pipeline incidents, and one of the most important responsibilities
of
a pipeline engineer is to choose the right strategy to protect the pipes from it. In trenchless
installations, this aspect is even more important as interventions are not possible during the
design life of the pipeline and usually such crossings are located in environmentally sensitive
areas.

Currently, pipeline operators and designers choose between very robust versions of three-layer
polyolefin (PE/PP) coatings, hoping the additional thickness will compensate material losses due to
abrasion during installation, and relatively thin coatings with very high adhesion properties. In
such situation, they expect the coating to perform better in combination with a cathodic protection
system in the areas where the steel was exposed due to damages to the coating.

In both cases, practical experience has shown that damages cannot be avoided. Currently,
specifically on pipes that are installed by trenchless processes, the available methods for
identifying where the coating was damaged cannot provide absolute or accurate information on the
location, size and geometry of the damages. Moreover, even though cathodic protection verification
at HDD locations can be validated close to the starting and final points of the crossings; the
region between can only be assumed and thus is a questionable strategy.

This paper gives evidence on why these strategies are not valid and provides a technical comparison
of properties between pipeline coatings used in trenchless installations. It also introduces an
engineered mechanical protection system that has been successfully used by German companies for the
past 20 years with an impeccable track record. Such a solution is of particular importance to allow
the trenchless industry to achieve longer and safer crossings.