Pipeline toughness

There has been renewed interest in pipeline toughness in recent years. Pipeline flaws have caused failures, and increased toughness makes pipelines more tolerant of flaws thus helping to prevent or mitigate ruptures. 

Predicting the appropriate level of duetile fraeture resistance involves an analysis of fluid properties, operating conditions, and material properties. For natural gas pipelines containing mostly methane with very 

So = Maximum operating hoop stress level as determined by the Barlow formula using the maximum operating pressure. 

Kiefner, J. F. and W, A. Maxey, Specifying Fracture Toughness Ranks High In Line Pipe Selection, Oil and Gas Journal, Oct. 9,1995. 

Kirby gives sound advice for designers who are not experts in metallurgy. He gives seven pitfalls to avoid  

---

High strength, low alloy (HSLA) steels often contain 0.10—0.30% molybdenum. These steels exhibit toughness at low temperatures and good weldabiHty. They are used extensively for undersea pipelines (qv) transporting gas and oil from offshore weUs to pumping stations on shore, and are also used extensively in remote Arctic environments. 

In contrast, the burst pressure or the required fracture toughness of steel or weld can be estimated when the maximum flaw size or the desired MAOP are given, respectively. The pipeline parameters used for the calculation are shown in Table 10.2. The flaws for the calculation are assumed to be semiellipse with the depth-to-length ratio of 1 10. 

Pipeline with the higher fracture toughness fCIH can tolerate larger flaw size (depth). 

Thicker wall than for natural gas pipeline to allow mild HE to the inside surface region while retaining the overall pipe strength and toughness... 

EFFECT OF REMOTE HYDROGEN BOUNDARY CONDITIONS ON THE NEAR CRACK-TIP HYDROGEN CONCENTRATION PROFILES IN A CRACKED PIPELINE FRACTURE TOUGHNESS ASSESSMENT... 

---