I am having accelerated corrosion of the top side of 5 Chrome horizontal furnace tubes in a Stripper Heater. The short term corrosion rate is 1.5mm/yr. It was suggested that it may be a "Laminar Flow" problem, where the H2S vapours are sepatating and running at the top of the tubes causing the accalerated corrosion. Has anyone experienced similar problems or have solutions to this problem ?

Mark, The inlet temperature to the heater is 500 F and the outlet 585 F the product is approx. 1.5% wt sulphur. I have deenable to put my hands on a NACE publication 34103 which has shed some light on the corrosion mechanism. Thanks for responding. Ian.

Ian. We already experience sulfidic corrosion in a crude heater tube. After decoking the heater we found a large deep crater located on the half top part section of the tube due to sulfidic corrosion. The remaining thickness on crater zone was 2mm. Nominal tube thickness was 7.2mm. “In furnace tubes and transfer lines, the influence of temperature, velocity and degree of vaporization is very large. Process conditions such as load and steam rate and especially turbulence affect corrosivity. The presence of any naphthenic acid most likely increases sulfidic corrosion. The corrosion mechanism at the furnace tubes, transfer lines, areas of high turbulence such as thermo wells and pumps, is most likely an accelerated corrosion due to the velocity and the two-phase flow.” From NACE publication 34103 Summary on the site bellow www.nace.org/nacestore/assets/freestandardsreports/34103.pdf “Sulfidic corrosion was first encountered in refineries in crude distillation units, thermal and catalytic cracking plants, thermal reforming, and coking units where the crude oil and its fractions were processed at temperatures exceeding 500°F (260°C). 1 Steel alloys containing 5% chromium (Cr) or greater (i.e., 7% Cr, 9% Cr, and 12% Cr, in this order), were found to have increasing resistance to sulfidic corrosion.” “In the 1940s and 1950s, the advent of refining processes that utilized hydrogen, such as catalytic reforming and hydro processing, introduced another facet to sulfidic corrosion. It was observed that for sulfidic services containing hydrogen, steel alloys containing up to 9% Cr were, at best, only slightly more corrosion resistant than carbon steel (CS). 1 Sulfidic corrosion in the presence of H2 is often referred to as H2-H2S corrosion.” If your corrosion related to sulfidic attack is a persistent problem maybe you have to up grade your tube material, I don’t see other solution. Regards Luis Marques