1DN stands for the nominal diameter, which is a standardized size used in piping systems, particularly in water supply and drainage applications. It is often associated with a 100 mm galvanized steel pipe. However, it's important to note that DN (Nominal Diameter) is not the actual inner or outer diameter of the pipe. Instead, it is an approximate value that represents the average of the inner and outer diameters. This standardization ensures that pipes and fittings of the same nominal diameter can be connected and interchanged easily.
The concept of nominal diameter was introduced to simplify the design and manufacturing of pipes and their accessories. Although the actual inner diameter may vary depending on the wall thickness, the nominal diameter remains consistent, making it easier to match components across different systems. DN is commonly expressed in millimeters (mm) or inches, depending on the region and application.
2. The term "G" has multiple meanings in the context of piping. First, "G" stands for "Galvanized Steel Pipe for Water Gas," also known as a gas tube. It is widely used in engineering projects. In the past, when designing pipelines for petroleum and chemical plants, wall thicknesses were classified based on nominal pressure. However, this approach sometimes led to inefficient designs because the allowable stress at higher temperatures was lower than at room temperature. As a result, the wall thickness calculated from nominal pressure wasn't always optimal.
To improve efficiency and reduce material waste, the classification system shifted from nominal pressure to a pipe number system. The letter "G" comes from the first letter of the Chinese pinyin for "pipe" (guan), followed by a number indicating the pipe’s strength class. For example, G6, G10, G20, G30, G45, G60, G100, G120, and G140 are common classifications.
The formula for determining the pipe number is:
**Pipe Number = P / [σ] × 10**,
where **P** is the operating pressure in kg/cm², and **[σ]** is the allowable stress at the operating temperature in kg/mm².
When selecting pipe wall thickness, engineers first determine the allowable stress at the operating temperature, then refer to the corresponding pipe number table to find the appropriate thickness. This ensures safe and efficient performance under various conditions.
In summary, the "100" mentioned here is not an actual diameter but a designation. G100 refers to a specific type of steel pipe with a designated wall thickness, tailored for particular applications. Understanding these terms is essential for proper piping design and installation.
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