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Erosion of B Control Valves in Gas Transmission Lines Containing Black Powder lack powder generated in Saudi Aramco sales gas transmission lines is mostly made of various corrosion products, namely magnetite (Fe3O4), with minor amounts of iron oxide (FeOOH) and iron carbonate (FeCO3).1 Fe3O4 particles are very hard (average Rockwell C 53) with sharp edges.2 This combination of high hardness and sharp edges coupled with the high velocities of gas encountered in control valves makes many engineering materials used in pressure control valves prone to erosion failures from black powder particle impingement. Figure 1(a) shows a 1-in (25.4-mm) thick carbon steel (CS) control valve cage that was perforated after only 45 days of service due to black powder erosion. In addition, black powder can have a serious impact on pipeline operations and customer complaints, such as contamination of gas supplies, delays in inline inspection (ILI) runs, and lower accuracy of the data gathered by the ILI tools.3 Black powder can be found in several forms, including wet with a tar-like appearance or dry AbdelmounAm Sherik And ehAb el-SAAdAwy, in the form of a very fine powder. Figures 1(b) and (c) show typical dry black Research and Development Center, Saudi Aramco, Saudi Arabia powder. Experimental Procedures To aid in the materials selection of various components of pipeline pressure control valves, the solid particle erosion behavior of seven ferrous metals typically used in these valves was investigated using impinging jets of magnetite particles. Te erosion rates were measured at two diferent particle sizes, two diferent velocities, and six diferent impingement angles. 70 MATERIALS PERFORMANCE May 2013 The erosion experiments were performed on the seven ferrous metals listed in Table 1, which were identified as candidate materials for gas pipeline pressure control valve components. Target samples were cut to 50 by 100 mm and were between 1.5 and 2 mm thick. They were polished as per ASTM G76-074 specifcations to a surface roughness of <1 μm (rms). The as-received hardness was measured using loads between 200 and 1,000 gf (Table 1). For all materials in Table 1, the erosion rate was measured using two different particle sizes, 6.9 and 30.4 μm (d in Figures 3 through 6), at two velocities NACE International, Vol. 52, No. 5