What are the failure modes of 5bar, 20bar, 45bar steam pipelines?
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Have you encountered any damage to the aforementioned steam pipelines? What usually causes it to be damaged? Water hammer? Corrosion? Or something else? Thank you!
At 0.5 Mpa, steam corrosion has caused sand holes here
The material used for pipes transporting steam at 0.5MPa, 2.5MPa, and 4.5MPa is generally carbon steel (Grade 20 steel). Carbon steel undergoes uniform corrosion under these steam conditions, and it remains within a controllable range. The sand hole defect mentioned on the 2nd floor falls under the category of installation quality issues ； As for water hammer, it can be avoided during operation and maintenance as long as condensation is removed in a timely manner.
Hello, is this kind of corrosion caused by trachoma actually due to problems with the installation materials?
Sand holes generally refer to slag inclusions in welds; they occur when the welder does not follow the proper welding procedures. These defects can be controlled through radiographic testing of the welded joint – that is, after welding, radiographic inspections are carried out to detect any defects that exceed acceptable limits, and the welds are repaired if necessary
Sand holes are likely due to issues with the quality of welding in the pipes.
Are there any specifications that specify what the acceptable quality grade is for welds in steam pipes at certain pressure and temperature levels? Is it Grade I, Grade II, Grade III, or Grade IV? It seems there are no regulations on this in NB/T 47013, nor in DL/T 869. .
According to GB 50184, there are provisions regarding the inspection grades and acceptance criteria for pressure and media.
I think there are the following issues with damaged steam pipelines: 1. the pH value of the steam, 2. whether there is steam entrainment, 3. whether the steam is stable.
Execution of your question: GB 50184-2011 \"Code for Acceptance of Construction Quality of Industrial Metal Piping Projects\". Specifications and standards related to pressure pipelines: TSG D0001-2009 \"Regulations for the Safety Supervision of Pressure Pipelines – Industrial Pipelines\", GB/T 20801.5-2006 \"Specifications for Pressure Pipelines – Industrial Pipelines, Part 5: Inspection and Testing\", GB 50184-2011 \"Code for Acceptance of Construction Quality of Industrial Metal Piping Projects\", GB 50235-2010 \"Construction Specifications for Industrial Metal Piping Projects\", GB 50316-2000 \"Design Specifications for Industrial Metal Piping\"
The main factor causing damage to steam pipes is liquid entrainment that occurs during the pipe warming process, which generates water hammer and leads to significant displacement of the pipes. Steam pipelines are classified into different grades based on pressure and temperature to determine the inspection ratio, and hydrostatic tests must also be conducted.