Leaking Carbon Steel Weldments in a Sulfur Recovery Unit

2 Leaking Carbon Steel Weldments in a Sulfur Recovery Unit 

Brinell hardness values, obtained by conversion of Knoop micro-hardness readings, were 133 to 160 (pipe base metal), 160 to 230 (weld metal), 182 to 227 (HAZs), and 117 to 198 (elbow base metal). The pipe base metal had an equiaxed fine-grain micro-structure typical of low-carbon steel, and the elbow base metal had a non-equiaxed micro-structure typical of hot-finished fittings. Carbon contents ranged from 0.25 to 0.30% by weight. Cracking was intergranular. 

The refinery operators immediately embarked on a program of visual inspection of all amine lines. As of June 1985, a total of 35 leaks in lean amine piping had been discovered. All leaks were at cracks in or around pipe-to-elbow welds, except for two leaks at welds that connected a tee and a reducer, respectively. Piping size ranged from 76 to 305 mm (3 to 12 inches). 

It is interesting to note that other researchers have also metaUographicaUy examined numerous samples of similar cracks their results can be summarized as follows  

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