Hello,
I have read the forums for a while. This is my first post, so please bear with me. Hopefully I won't require too much hand holding.
We ran into an issue recently at the plant I work at. The equipment involved are two 304 SS vessels, two pumps, and an assortment of 2"-6" 304 SS piping. Without getting into too much detail of the chemicals involved, they are all compatible with stainless. The equipment has been in service for about two years. Around six months ago, the first leaks appeared. We fixed the leak, and in the following months, more and more leaks started. We have shut down the equipment and are in the process of replacing all the piping. The existing piping is 304 seamed pipe. We are replacing with 316 seamless pipe.
During investigation, we found that the welds were being corroded away. As I said, all chemicals involved are compatible with stainless. None of the pipe walls or plates in the vessels have any indication of corrosion. However, some of the welds seams in the pipe were so corroded that it looked like someone literally took a grinder to the weld. Most of the weld seams in the pipe has varying levels of corrosion, but some have none at all. The radial welds around flanges and fittings were better. Some had serious corrosion, but most had none at all. The system seemingly randomly decided to corrode certain welds and not touch others. We were able to get inside the tank yesterday. It is in much better shape, but a few of the welds in there appear to be beginning to be eaten away at the edges. There is zero pitting throughout the entire system. The welds just seem to be disappearing.
After talking to some people about it, one person said he had seen something like that before. He seems to remember that the issue came from something to do with grounding. It had been a while, so he was not sure of the details. As far as lightning/fire protection, the tanks are grounded as far as I know. We are going to be testing it soon.
My question is, has anyone here seen anything like this before, or have an idea to what may be the cause? It is a strange phenomenon that currently has everyone stumped. We are replacing piping with seamless, which eliminates those welds. It does not solve the issue though, so it will come back eventually unless we do.
As I said, it's my first time here, so let me know what other info I should include or if my formatting needs to change.
Thanks for the help!
I have read the forums for a while. This is my first post, so please bear with me. Hopefully I won't require too much hand holding.
We ran into an issue recently at the plant I work at. The equipment involved are two 304 SS vessels, two pumps, and an assortment of 2"-6" 304 SS piping. Without getting into too much detail of the chemicals involved, they are all compatible with stainless. The equipment has been in service for about two years. Around six months ago, the first leaks appeared. We fixed the leak, and in the following months, more and more leaks started. We have shut down the equipment and are in the process of replacing all the piping. The existing piping is 304 seamed pipe. We are replacing with 316 seamless pipe.
During investigation, we found that the welds were being corroded away. As I said, all chemicals involved are compatible with stainless. None of the pipe walls or plates in the vessels have any indication of corrosion. However, some of the welds seams in the pipe were so corroded that it looked like someone literally took a grinder to the weld. Most of the weld seams in the pipe has varying levels of corrosion, but some have none at all. The radial welds around flanges and fittings were better. Some had serious corrosion, but most had none at all. The system seemingly randomly decided to corrode certain welds and not touch others. We were able to get inside the tank yesterday. It is in much better shape, but a few of the welds in there appear to be beginning to be eaten away at the edges. There is zero pitting throughout the entire system. The welds just seem to be disappearing.
After talking to some people about it, one person said he had seen something like that before. He seems to remember that the issue came from something to do with grounding. It had been a while, so he was not sure of the details. As far as lightning/fire protection, the tanks are grounded as far as I know. We are going to be testing it soon.
My question is, has anyone here seen anything like this before, or have an idea to what may be the cause? It is a strange phenomenon that currently has everyone stumped. We are replacing piping with seamless, which eliminates those welds. It does not solve the issue though, so it will come back eventually unless we do.
As I said, it's my first time here, so let me know what other info I should include or if my formatting needs to change.
Thanks for the help!
