What is the reason for the different names "A designation" and "B designation" for the same piping? An explanation of the origins of the colloquial terms used on site!

■What does "nominal diameter" in piping mean? The thickness of piping is managed by a value called "nominal diameter." The nominal diameter is not the actual outer diameter of the pipe itself, but a designation defined by JIS standards. If the nominal diameter is the same, the outer diameter will be the same even if the notation differs. ■What is the difference between A designation and B designation? There are "A designation" and "B designation" for nominal diameters. A designation is based on millimeters, such as "10A" and "20A," while B designation is based on inches, represented as "3/8" and "1." Both refer to pipes with the same outer diameter. ■Why are there two different designations? It is said that this is due to Japanese piping standards being influenced by American standards (inch-based), leading to the parallel use of both millimeter and inch standards. ■What should you be careful about regarding the "common names" you hear on-site? In addition to these two designations, a "common name" that fixes the denominator of the B designation to 8 is also used on-site. "1/8" is referred to as "one-bun," and "1/4" as "two-bun," with the "bun" unit said to originate from the shakkanhō measurement system. It is reassuring to confirm the official nominal diameter when placing orders. Please feel free to consult with us first.

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