OVERVIEW

Pipe larger than approximately 16 inches in diameter is commonly manufactured by cold forming of long plates through the UOE process (or the JCO process). The various steps of the process, and in particular its four cold forming steps, are outlined in Section 3.6 (see Figures 3.11 and 3.12).

UOE pipe has been widely used for land pipelines, including the Trans-Alaska and Trans-Siberia pipelines. In the last 15 years, it has also been increasingly used in offshore applications where collapse under external pressure is a primary design consideration, therefore requiring therefore high circularity (see Chapter 4). Modern UOE pipe mills are capable of delivering this demand for higher circularity pipe. Figure 3.15 shows the inside and outside shapes of a 24 in UOE pipe measured and reproduced as described in Section 4.5. For each surface, the radial deviation from the best-fit circular shape ( w) is amplified 20. The ovality of this pipe is 0.175%, while typical values range between 0.10% and 0.35%. Despite their low ovalities, experiments have demonstrated that the collapse pressure of UOE pipes can be significantly lower than that of seamless pipes of the same D/ t and the same grade steel. For typical pipe geometries and plate material properties, the degradation in collapse pressure of UOE pipe can be higher than 30%. Because of the importance of UOE pipe to offshore applications, this chapter examines the causes of this degradation, and outlines remedies to it.

The degradation in collapse performance...