Crack issue in the base material of a buffer tank
Thread Content
The inner diameter is 700 mm; cracks have appeared in the base metal of the fillet weld area at the top head connection (DN25). It is unknown what caused this – any ideas? Material: 16MnR, thickness: 10mm, Class II vessel, medium: propylene gas.
By the way, how should it be handled?
It’s probably not a material issue; it could be a welding quality problem, or perhaps too high a current? The solution is to grind it off, and determine whether welding repair is needed based on the depth of grinding.
There are many issues with takeover, mainly due to the inability to detect them. It’s possible that the equipment hasn’t undergone heat treatment, and the stresses haven’t been addressed; issues generally arise in the heat-affected zone during use. Generally, it is necessary to gas cut down to the bottom of the crack, then perform patch welding, and carry out heat treatment after welding
It is recommended to conduct a failure analysis~ or post a picture for everyone to see.
First of all, is the poster using an existing device or a new one? New equipment is prone to welding defects, which may be caused by welders not following the welding procedures properly or by improper control of the cooling rate. There are various possibilities for the equipment in use; propylene is produced as a downstream product of oil refining. It is important to ensure that the H2S level is properly controlled, otherwise stress corrosion cracking may occur, or perhaps thermal stress? My humble opinion
If nothing unexpected happens, it is usually caused by fatigue. I have conducted failure analyses on similar joints, and a feasible improvement measure is to weld support rods or plates around them in order to reduce the vibration stress on the joint; for more details, refer to the August 2009 issue of \"China Special Equipment Safety\".
The new equipment has been in use for only a short time, maybe a few months; logically speaking, it doesn’t require heat treatment. Later, the head was replaced
We have also encountered similar problems, which are usually caused by welding issues. If not addressed promptly, they can lead to more serious accidents. Using surfacing techniques generally does not yield good results in such cases. Of course, if your welders are skilled enough, polymer composite materials can be considered for repairs; leaks can usually be fixed on-site immediately. My space has information on dealing with leaks; I hope it can be helpful to you
Generally, propylene gas contains a certain amount of hydrogen sulfide, so it is necessary to measure the hydrogen sulfide concentration in the medium.