LNG pipeline flaw detection and inspection reporting
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Dear everyone, I have a question: is 100% flaw detection required for LNG liquid or gas pipelines? Or, under what kind of pressure are there different flaw detection standards for different pipe diameters? If so, what are the specific flaw detection standards? Also, what is the process for submitting applications for LNG pipelines? Is inspection required only for those larger than DN50? Or what? Are there any suitable standards?
100% flaw detection for GC1 pipes, 10% flaw detection for GC2 pipes, with ≥1 flaw detected. It is stated in the design specifications provided by the design institute
According to the classification of inspection grades for pipeline welds specified in Chapter 8, 8.1.1 of GB50184-2011, LNG pipelines with a pressure below 4 MPa are classified as Grade 3. Section 8.2.1 specifies that the proportion of non-destructive testing required for Grade 3 is ≥10%. Under the Construction Quality Acceptance Code for Petrochemical Metal Pipelines GB50517-2010, LNG falls under the SHB2 category; per Section 9.3.1 regarding the quantity of non-destructive testing required for pipeline welding, 20% testing is specified for SHB2. For LNG pipelines in liquid and gas phases, I find that the differences among various standards lie in these specifics. So which one will be implemented in the end? ?
This mainly depends on the design documents, and the regulations for pipeline classification testing also include temperature requirements. Generally, LNG pipelines are at 100%, while at normal temperature the pipelines and venting systems can be at 10–20% after gasification.
Based on the design requirements, for example, with a certain foreign-funded design firm, the pipeline inspection is required to cover 100% of the area above the ceiling, 30% of the area below the ceiling but above the liquid level, while no inspection is needed in the areas below the liquid level.
Usually, 100% flaw detection is carried out. In the FSRU project I worked on, 100% flaw detection was required for all LNG, GNG, and pipelines; the vent pipes also needed to be inspected, as high-speed vent pipes can also be under pressure. Only the air defense ducts that are in communication with the atmosphere during pressure testing can be exempted from such testing
Boring people ask boring questions! You shouldn’t work in engineering design!
It’s a good idea to take a closer look at the standards specified in the technical specifications, and then find the section related to testing within those standards