Understanding the Behavior of Surface Hardness Hard Spots of Plate and Pipe :Extensive Test Program

Abstract

Recent use of thick wall pipelines for the transmission of extreme sour hydrocar bons in deep and ultra- deep water has required the confirmation of resistance to environmental cracking. This paper presents a comprehensive test program conducted on 30 inch outside diameter and 38.7 mm wall thickness, ISO 3183 L415MS / L415MO PSL2 line pipe to establish the contribution of plate and pipe properties and process parameters on the environmental cracking resistance. The JCOE forming technology was used to prepare the test pipes for evaluating the influence of isolated surface hardness zones on the initiation and propagation of Hydrogen Induced Cracking (HIC) and Sulfide Stress Corrosion Cracking (SSCC). Detailed technical requirements for plate supply included but was not limited to the development of alloy design, steel melting and continuous casting parameters as well as plate rolling and accelerated cooling process control limits. The test program covered the contribution of various stages of pipe production such as forming, welding, and mechanical cold expansion, on fracture toughness (KIC, KISSC and CTOD), HIC and SSCC resistance. The pipe was tested in the as-manufactured, aged, and aged+1% strained conditions. Pipe dimension conformance was verified using the Automatic Pipe Dimension Measurement System (APDMS). The reliability of eddy current inspection for the detection of isolated hard zones was included in the program.