Regarding the corrosion-induced leakage that occurred in the 316L reboiler within a short period of time
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In my company, corrosion of the tubes in 316L stainless steel heat exchangers has occurred frequently over the past year and this year... The process conditions are: 80°C to 85°C, LLP steam on the shell side, and organic acids on the tube side. After spending tens of thousands of yuan on sending the corroded tubes for external analysis, it was determined to be sulfur corrosion. A typical example of such a heat exchanger functioned perfectly for several years, but last year the tube sheet suffered severe corrosion and developed pitting; the tubes also corroded and thinned out, leading to leaks. The walls of the tower bottom were severely corroded as well, and even the manhole rings were damaged. After installing a new 316L heat exchanger this year, and after 180 days of operation, multiple tubes began to leak again, and the other tubes also showed signs of thinning. Now a few of the leaking ones have been replaced and it’s back in use; it’s still unknown how long it will last this time… The tubes are 316L steel tubes with dimensions of 25*2.5, and they get corroded through after just half a year – that corrosion rate is really alarming. I did some research and found that sulfur corrosion occurs at high temperatures around 300°C; therefore, I feel the analysis results are not credible. Based on a rough estimate, the sulfur concentration in the tower bottom is around 230 ppm. Excuse me, is the sulfur corrosion that severe? Are there any other substances that could cause such an astonishing corrosion rate? I would appreciate some advice. It should be noted that there were no issues over the previous few years, but a leak was detected during maintenance at the end of last year; the degree of corrosion was significantly different from that observed during maintenance in the previous cycle, even though the process conditions remained essentially unchanged during that time.
Is there a leak somewhere that has created an acidic environment?
Or use a metal detector to check whether it’s made of another material; there are many cases these days of passing off inferior products as good ones
Change the material; 316 is not suitable for these operating conditions
The shell side of the heat exchanger is originally made of organic acids……
We also suspected a material issue, but the previous heat exchanger was used for several years without any signs of corrosion, yet it became severely damaged in just one year last year
The 316L material has been in use for over a decade; corrosion does occur, but leaks in one or two components usually only appear after 3 or 4 years of use
This is because, after being in use for a few years, or due to potential issues with the welding of the tube sheet, leaks at the tube ends occurred, causing the media in the shell and tube sides to mix together and resulting in corrosion by dilute sulfuric acid. It accelerated the corrosion rate.
But this doesn’t explain the reason for the corrosion of the newly manufactured heat exchangers. Could it be that there’s again fraud regarding the material quality?
Furthermore, mixing of the media in the tube side and shell side can affect the water quality in steam boilers or the moisture content at the bottom of the tower; of course, minor leaks cannot be ruled out
Check whether the metal material truly meets the requirements; moreover, if it’s an organic acid, the corrosion resistance of 316L is only average!