Hidden problems with three layer polypropylene pipeline coatings

Abstract

In recent years three layer polyolefin (3LPO) coatings, including three layer polypropylene (3LPP) and three layer polyethylene (3LPE) have become the system of choice for pipeline coatings in many companies worldwide. The main reasons for the growth in popularity of these coatings are their resistance to high temperatures (up to 140°C for 3LPP), good mechanical properties, and increased availability of these coatings and compatible field joint coatings. A series of recent failures, however, have put a question mark over the long term performance and suitability of these coatings, especially for high temperature (>100°C) gas pipelines. Two large scale problems are discussed here and possible reasons for the failures, together with lessons learnt and recommendations for future usage of such coatings are provided. ©2006 by NACE International.