Reboiler Tubes Leak
Background: Leakage in H2S reboiler tubes was experienced with significant pitting observed on the tubes. Reboiler operates under steam pressure and temperatures.
Figure 1: Visual Inspection of As-Received Reboiler Tube and Tubesheet
Figure 2: Scanning Electron Microscopic Examination of Reboiler Tube Sections
Summary: This reboiler tube damage was associated with erosion-corrosion in the presence of wet H2S gas. Presence of moisture accelerates the corrosion attack of H2S on carbon steel type materials. The corrosion products formed are non-adherant and porous which does not provide protection against corrosion attack.
Bubble formation associated with boiling erodes the material at a faster rate locally causing pinholes. Process related steam flow also played a significant role in this reboiler damage. Pinhole and severe erosion-corrosion was observed at the hottest region and near the liquid level where pressure was lower than at the surface. The combined effect of high temperature, lower pressure, and less dense heavies promoted localized vigorous bubbling.
Take Away: Presence of water/water vapor in the H2S environment can cause accelerated corrosion of carbon steel type material. The process conditions viz. flow induced turbulence and creation of localized hot spot can cause severe erosion-corrosion.
Bubble formation associated with boiling erodes the material at a faster rate locally causing pinholes. Process related steam flow also played a significant role in this reboiler damage. Pinhole and severe erosion-corrosion was observed at the hottest region and near the liquid level where pressure was lower than at the surface. The combined effect of high temperature, lower pressure, and less dense heavies promoted localized vigorous bubbling.
Take Away: Presence of water/water vapor in the H2S environment can cause accelerated corrosion of carbon steel type material. The process conditions viz. flow induced turbulence and creation of localized hot spot can cause severe erosion-corrosion.