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10002 Failure Analysis of Three Layer Polypropylene Pipeline Coatings

Three layer polypropylene (3LPP) pipeline coatings failed prematurely in the oilfields of Abu Dhabi in the United Arab Emirates (UAE). A failure investigation and analysis into this phenomenon was instigated. The coating disbondment has been found to be due to high residual stress concentration and adhesion loss.

Product Number: 51300-10002-SG
ISBN: 10002 2010 CP
Author: Ali Noor Moosavi, Benjamin T. A. Chang and Kamal Mohamed Morsi
Publication Date: 2010
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Three layer polypropylene (3LPP) pipeline coatings failed prematurely in the oilfields of Abu Dhabi in the United Arab Emirates (UAE). A failure investigation and analysis into this phenomenon was instigated. Two major failure modes were found: (i) PP cracking at field joint coating (FJC) and mainline pipe coatings, and (ii) 3LPP coating disbondment from fusion bonded epoxy (FBE) -steel interface. The PP cracking is attributed to thermo-oxidative degradation and high residual stresses in PP. The coating disbondment has been found to be due to high residual stress concentration and adhesion loss after moisture interaction or thermo-oxidative degradation of the FBE primer.

The failure analysis results will assist us in our future external pipeline coating selection. The new high temperature external gas pipeline coatings can be either single layer FBE, multi-layer FBE, or 3LPP. But any candidate coating system must demonstrate its thermal stability and adhesion durability in UAE Sabkha environment. We hope that FBE and PP manufacturers will do more research to improve PP and FBE formulations to mitigate PP cracking, to improve FBE thermal stability and adhesion durability in the high temperature Sabkha wet and dry sandy soil environment.

Keywords: 3LPP, polypropylene, fusion-bonded epoxy, thermal stability, residual stress, adhesion, Sabkha

Three layer polypropylene (3LPP) pipeline coatings failed prematurely in the oilfields of Abu Dhabi in the United Arab Emirates (UAE). A failure investigation and analysis into this phenomenon was instigated. Two major failure modes were found: (i) PP cracking at field joint coating (FJC) and mainline pipe coatings, and (ii) 3LPP coating disbondment from fusion bonded epoxy (FBE) -steel interface. The PP cracking is attributed to thermo-oxidative degradation and high residual stresses in PP. The coating disbondment has been found to be due to high residual stress concentration and adhesion loss after moisture interaction or thermo-oxidative degradation of the FBE primer.

The failure analysis results will assist us in our future external pipeline coating selection. The new high temperature external gas pipeline coatings can be either single layer FBE, multi-layer FBE, or 3LPP. But any candidate coating system must demonstrate its thermal stability and adhesion durability in UAE Sabkha environment. We hope that FBE and PP manufacturers will do more research to improve PP and FBE formulations to mitigate PP cracking, to improve FBE thermal stability and adhesion durability in the high temperature Sabkha wet and dry sandy soil environment.

Keywords: 3LPP, polypropylene, fusion-bonded epoxy, thermal stability, residual stress, adhesion, Sabkha

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