What causes corrosion cracking in elbow fittings?
Thread Content
Our company uses Shell gasifiers to produce methanol. Two months after the system was shut down, during the inspections carried out prior to restarting it, corrosion cracks were found at certain bends in the stainless steel pipes within the shift unit, near the welds. This forced us to delay the restart and carry out repairs on the shift unit; no issues were detected in the pipelines, but the attention focused on the weld areas of the bends, as those bends showed signs of cracking. Was this a corrosion problem? Is there still a problem with welding? Is it still a problem with the material? If it keeps running without stopping, will that reduce corrosion?
It’s related to the scouring by gases; it’s probably caused by the scouring and corrosion exerted by gases. The gas pipelines in the system made of stainless steel should meet the requirements; another issue is the quality of welding during pipeline installation.
:Lol, it’s also possible that it’s a material issue caused during the welding process: L
It is recommended to use an elbow with a larger radius! Reduce resistance!
Use stainless steel, regularly check its thickness, and ensure strict quality control during welding.
The one being used now is 304 stainless steel
I was wondering if your straight pipes are made of stainless steel? Really? It should be changed.
There are problems during the processing of elbows; stainless steel cannot be heated during processing. If heating is used, it will damage the crystal structure of the stainless steel. The hydrogen content in the gas is high and the temperature is high, which leads to leakage at the elbow area
Is it a short-radius elbow? Short-radius elbows are also not very good at absorbing stress
It’s probably still a problem with the installation, such as issues with alignment, preheating, welding, pickling, and other steps. As a result, there are relatively high residual stresses from installation at the elbow and the welds in its vicinity. Erosion and corrosion in such places cause damage particularly easily. The wall thickness can be measured to ensure safety.