Steel pipe manufacturers, pay attention! Regarding Series Ia and Ib pipes
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Dear manufacturers, those in charge of procurement, or anyone with expertise in this field: In actual production, are pipes from the Ib series more commonly used? ? Why not use the Ia series? Is it because it’s easier to produce after rounding it off, or something like that? For example, in the large outer diameter series, model Ⅰa has an outer diameter of 323.9 for DN300 pipes, while model Ⅰb has an outer diameter of 325, which is the same as that of the small outer diameter series; there is a difference of 0.55 in outer diameter. There is concern that welding in such conditions may make it difficult to pass flaw detection tests. I hope experts in this field can help answer it. Thank you
@boyirensheng
There are differences in the standards; those with significant differences are manufactured according to the requirements of each series, while those with minor differences are generally set at an intermediate value. For example, for the DN300 specification, 323.9 is close to 324, whereas the B series uses 325. By taking an intermediate value along with the tolerance range, it becomes possible to use it in both cases. However, this does not apply to specifications like DN500, where the values are 508 and 530. Attention must also be paid to the issue of flaw detection, as this can be complicated due to tolerance ranges, as well as the possibility of ellipticity in the pipes themselves. If all pipes belong to the same batch, it’s simpler; but if they don’t, extreme errors can occur, such as older pipes having higher values and newer pipes having lower values, or vice versa. In such cases, edge damage may occur, though this situation tends to happen less frequently
In the market, which has greater demand: the large outer diameter series or the rounded-type pipes?
In reality, the former is used in the largest quantities, while the latter usually has specific requirements
It is widely used in the petrochemical industry, after all, to keep up with international standards
The Ia series of pipes are weekly and British-system pipes; they have a great influence worldwide and belong to internationally standard dimensions； Ib belongs to the former Soviet Union standards; China adopted it quite early on and has continued to use it, but it is gradually being phased out. After all, since the Soviet Union no longer exists, there is no one to maintain these standards anymore
The Ia series belongs to the American standard series. The Ib series came into existence because version 96 of SH/T 3405 was formulated based on the American standards; the Ib series was created to accommodate pipes that Meets the requirements those standards. Version 2012 of SH/T 3405 is no longer based on such standardized formats, and therefore the Ib series is intended for modifying pipes from version 96 of SH/T 3405 – its scope of application is quite limited. As for Soviet standards, it is likely that they correspond to the II series