Microscopic residual stress measurements were performed using an unflawed spiral welded pipe section and straight seam pipe using ASTM E-837 Blind Hole Drilling technique at Stress Engineering Services in Houston. It should be noted that no SOHIC cracks were observed in the vicinity of the girth welds. Figure 19.3 shows the metallurgical examination that revealed a stacked array of short HIC-like cracks parallel to the rolling direction linked by cracks perpendicular to the overall resultant stress, a characteristic of SOHIC. The locations of cracks, as seen in Figure 19.2, were 0.2-0.5 in. long crack ran parallel to the weld seam. The ring was split axially showing a circumferential gap of more than 1-in., indicative of compressive macroscopic residual stress. Figure 19.1 shows a ring that was cut from the failed pipe. wall thickness spiral pipe was neither cold expanded nor stress relieved to reduce fabrication and welding residual stresses. The calculated pH was 3.4, and the operating pressure and temperature were 390 psig and 52 ☏, respectively. Spiral welded pipe fabricated from HIC-resistant coil failed after 7 months of service by SOHIC in wet sour hydrocarbon gas containing 10 mole% of H 2S with the same amount of carbon dioxide (CO 2). There is no industry or international standard that prohibits the use of spiral pipe in wet sour applications. Line pipe that may be employed in sour service is usually subject to testing in a simulated environment: either seawater saturated with H 2S or a similar solution acidified with acetic acid. To avoid such segregation, manganese and phosphorus contents are reduced and the liquid steel is subject to electromagnetic stirring during the continuous casting operation. This may be subject to hydrogen cracking even in the absence of laminar inclusions. In continuous casting, manganese and phosphorus segregate to the central region, which results in a hard band in the rolled product. Subsequently steelmakers have offered sulphur contents down to 0.002% (20 ppm) together with rare earth treatment. The steel was strip containing a substantial amount of Type II manganese sulphide inclusions and was therefore particularly susceptible to delamination. The failures, which occurred preferentially adjacent to the welds, were due to H 2S corrosion, which saturated the metal with hydrogen and produced the step-like cracking described in the previous section, but not necessarily restricted to the weld region. A spiral-welded pipe carrying sour gas ruptured only a few weeks after commissioning. This is a problem that arose in The Gulf in the 1970s. Lancaster, in Metallurgy of Welding (Sixth Edition), 1999 Hydrogen pressure-induced cracking Permeationsuntersuchungen an Kunststoffrohren. states that with plastic pipelines as currently used as standard for low pressures in the distribution of natural gas, hydrogen emissions of up to 13.83 m 3/km per year can occur with line pressure of 7.5 bar at room temperature. This guarantees a long service life and leads to low-maintenance operation.Īccording to scientific literature excerpts, hydrogen permeation through steel pipes (and thus the loss of media) is negligible. A carbon equivalent that has also been further reduced ensures excellent weldability of our pipe material. Furthermore, internal points which are vulnerable in relation to hydrogen are reduced to a minimum by the phosphorus and sulphur content levels being guaranteed to remain below those specified in the EIGA guideline. For lasting durability in hydrogen transport, the inner surface is free of any discontinuity (in accordance with ISO 3183).
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