Regarding pipeline material grades
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This is my first time creating a table of pipeline material grades. I would like to ask: when there are flanges of different grades on the same pipeline (with valves rated at 10 kilograms and others rated at 16 kilograms, the design pressure of the pipeline being 6 kilograms, and the operating pressure of the fluid being 5.2 kilograms), what is the general approach to handling this situation?
Taking both cost-effectiveness and safety into consideration: all fittings and valves are selected with a pressure rating of PN1.6MPa, and the design pressure for the pipes is also set at PN1.6MPa. Valves generally should not use grades below 1.6, so fittings should also not be chosen of a lower grade; moreover, even if a lower grade is selected, it won’t save much money on procurement costs.
First of all, thank you. However, since the pipes are quite large and have multiple diameter changes, there is a significant price difference between pipes over 1 meter in length when using 1.6-inch and 1.0-inch pipes; for smaller pipes, the price difference isn’t much. The current situation is that it has become unavoidable to have different grades on a single pipeline; the large valves on this pipeline use D37A1X5-10ZB1, while the small valves use J41H-16C. I’m really stuck as to how to determine the pipeline grades so that they can be entered into the software for use.
In this case, it is recommended to increase the pipeline grade and handle the larger pipelines separately. It is indicated with hierarchical symbols in PID.
As a designer, when considering pipeline design, the primary concern should be the safety of the pipelines during operation, followed by their economic viability； Most valves available on the market are of PN1.6MPa standard; in fact, the price of valves of lower grades is more or less the same as that of valves of their corresponding grade ； As for the choice of pipes, it’s fine to consider options as long as the design constraints permit it, after all, a considerable amount will be used!
Different valve grades can be selected based on various pipe diameter ranges
Mainly, since we use software for drawing, it’s difficult to handle multiple material grades for a single pipe.
"The design pressure of the pipeline is 6 kilograms, while the operating pressure of the medium is 5.2 kilograms; your design pressure is too low! I don’t know the properties of your medium and the design temperature, but it is recommended that you set the design pressure at 1.0 MPa. Depending on the characteristics of the medium, valves with a PN1.0 or PN1.6 rating can be used
It can’t be simply said that the choice was too low; the 10kg you mentioned seems like a waste. Of course, savings should be achieved while ensuring safety
Putting aside whether the design is correct or not, economic calculations are generally carried out alongside HAZOP assessments.
You forgot about the compression test; a pressure of 1.5 PN still needs to be applied. There’s an issue with writing to the pipeline
A pressure test at 1.15 times is sufficient.
The design pressure of a pipe and the pipe grade are two different concepts; someone upstairs confused them. The design pressure of a pipe can be relatively low, and there are many possible values – no fixed value exists. The pipe grade, on the other hand, is usually a fixed value, such as 1.0, 1.6, 2.0, 2.5, 5.0. . .
It won’t be difficult; you just need to identify the boundaries on the PID diagram, and you won’t go wrong! What that gentleman said just now is also correct; for larger quantities at different levels, it’s possible to set up several material levels