General requirements for the numbering and labeling rules of pipelines

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I. The pipes on the P&ID are numbered based on the process step (main item) and the medium. For pipes of each medium type, within each process step, numbering starts at 01 (or 001), with numbers increasing in sequence according to the order of the pipes in that step. II. The number of pipeline numbers assigned should be as low as possible, provided that the requirements for design, ordering, construction, operation, accident handling, and maintenance are met without causing confusion or errors. III. The pipeline numbering method used for various processes within a single unit should be the same; different units (or those designed by different agencies) may employ different pipeline numbering methods. IV. After the pipelines are numbered, as the engineering design progresses, if some pipelines need to be removed, their original numbers are usually no longer used; these removed numbers are not applied to the newly added pipelines.