Issues with sand accumulation in pipelines and valves after the introduction of medium-pressure steam
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Dear sea friends, good evening! I would like to ask about the corrosion mechanism that causes erosion in the form of pitting on pipelines and valves after 4.1 MPa superheated steam is put into use Is it electrochemical corrosion? What factors are related to it? Is the main influencing factor chloride ions? Not long after we started using this 4.1 MPa superheated steam, a sand hole appeared in the body of one check valve; simultaneously, a sand hole appeared in the superheated steam pipeline leading to the refrigeration unit (the sand hole in the pipeline appeared after steam purging and testing).
What is the material of the valve body? ? What is the material of the pipe? ? Isn’t the sand in the pipeline caused by improper welding at the beginning?
It is a problem with the material quality or welding quality.
Pipes corroded by chloride ions – no need to be shocked! ! Problems such as sand holes in the valve body and sand holes in pipe welds are often caused by issues during the valve body’s casting process and the pipe welding process. That is, it’s a quality issue.
The sand holes in the valve body are likely to be casting defects, that is, caused by quality issues.
1 The material used for medium-pressure steam pipes is generally low-CrMo alloy steel, which is not sensitive to chloride ions. Is corrosion in superheated steam pipes caused by a lack of control over the drum liquid level or water quality during operation? 2 Unless high-pressure, small-size valves are made of forgings, they are generally cast; cast materials contain tiny voids, and their presence is allowed even during inspections, just as radiographic testing has a threshold for volumetric defects – defects below that threshold are permitted. During factory inspection, the valves are tested under cold conditions; as the temperature rises during operation, any defects present will be exacerbated, and in severe cases, leakage may occur. I hope there won’t be widespread loosening; that would be dangerous. Pray. 4. Targeting of steam pipelines: Even at the moment of explosion, the energy of the high-speed steam stream is not sufficient to wear through the metal; it seems there is no inherent connection, and accidental factors are a more plausible explanation. 5. However, valve leaks and pipeline leaks lead one to question whether the origin of these materials is reliable, and whether this constitutes another inevitable consequence
Valve quality issues Welding quality issues
It’s likely a casting issue; it depends on what material your pipes are made of. The material requirements for valves should be higher than those for the pipes