I have a customer that is using 316L and 304L flanged valves in the process piping process. These are much longer lead times and specially manufactured and as a result much more expensive. I understand the benefit when welding is involved but is there a reason to require L grade material from a safety or reliability standpoint for a flanged valve? The plant is a nitrogen facility.
Topic: Is there a reason to require L grade material from a safety or reliability standpoint for a flanged valve?19 July 2010
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Brian Dalder Forum Moderator 175 Posts
Re: Is there a reason to require L grade material from a safety or reliability standpoint for a flanged valve?19 July 2010 at 1:29pmThe difference in composition between 316 and 316L stainless steel is that 316L has lower carbon content (< 0.03%). As you pointed out, the lower carbon content is only important to corrosion resistance if welding is involved. Because of the higher carbon levels, welding 316 (or 304) can lead to sensitization and precipitation of chromium carbide at the grain boundaries making it more susceptible to intergranular corrosion. Beyond better welded corrosion resistance, I am not aware of any reason that 316L should be superior to 316 (or 304L to 304). It would seem that the low carbon versions of stainless steel would not be necessary for valve flanges unless welding is somehow involved in the valve manufacturing process.