Thread Content
1 The meanings of De, DN, d, φ. Generally speaking, the diameter of a pipe can be divided into outer diameter (De), inner diameter (D), and nominal diameter (DN). 1. DN refers to the nominal diameter of a pipe, which is the average of the outer diameter and the inner diameter. The value of DN = the value of De = 0.5 * wall thickness. Note: This is neither the outer diameter nor the inner diameter. Pipes such as water and gas transmission pipes (galvanized or ungalvanized steel pipes), cast iron pipes, steel-plastic composite pipes, and polyvinyl chloride (PVC) pipes should be marked with the nominal diameter “DN” (such as DN15, DN50). 2. De mainly refers to the outer diameter of the pipe; for PPR, PE, and polypropylene pipes, the outer diameter is indicated using De. In such cases, it needs to be specified as outer diameter x wall thickness, for example, De25 x 3. 3. D generally refers to the inner diameter of the pipe. 4. Inner diameter of the d concrete pipe. For pipes made of reinforced concrete (or concrete), clay pipes, acid-resistant ceramic pipes, earthenware pipes, etc., the diameter should be expressed as the inner diameter d (e.g., d230, d380, etc.). 5. φ represents the diameter of a regular circle ； It can also indicate the outer diameter of the pipe, but in that case the wall thickness should be multiplied by it. For example, φ25 x 3 indicates a pipe with an outer diameter of 25 mm and a wall thickness of 3 mm. For seamless steel pipes or non-ferrous metal pipes, “outer diameter x wall thickness” should be indicated. For example, φ108 x 4; the φ can be omitted. Some steel pipe standards in China, ISO, and Japan use wall thickness dimensions to denote the steel pipe wall thickness series. The notation for the specifications of this type of steel pipe is outer diameter x wall thickness. For example, φ60.5 x 3.8. 6. DN stands for Nominal diameter, which means the nominal size. 7. De stands for external diameter, which means the outer diameter. 2 Methods of indicating pipe diameter: 1. For pipes used for transporting water and gas, such as galvanized or ungalvanized steel pipes, cast iron pipes, and plastic pipes, the nominal diameter “DN” should be indicated (e.g., DN15, DN50) ； De can also be used for indicating wall thickness in such cases ； Taking galvanized welded steel pipes as an example, the two notation methods are DN and De, as follows: DN20 De25 x 2.5mm, DN25 De32 x 3mm, DN32 De40 x 4mm, DN40 De50 x 4mm, and so on... 2. For pipes such as seamless steel pipes, welded steel pipes (with straight or spiral seams), copper pipes, and stainless steel pipes, the diameter is preferably expressed as outer diameter x wall thickness (e.g., De108 x 4, De159 x 4.5, etc.) ； For seamless steel pipes or non-ferrous metal pipes, “outer diameter x wall thickness” should be indicated. For example, φ108 x 4; the φ can be omitted. 3. For pipes such as reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic pipes, and cylinder tile pipes, the diameter should be indicated by the inner diameter d (e.g., d230, d380, etc.). 4. For plastic pipes, the pipe diameter should be indicated in accordance with the methods specified in the product standards ； Plastic pipes are usually specified by their outer diameter. The terms 20, 25, 32, etc., which we use informally in actual construction work, refer to De rather than DN; there is thus a difference in specification here. Failing to clarify this can easily lead to losses during the procurement and construction processes. 5. When the pipe diameter is specified using the nominal diameter DN in the design, there should be a table correlating the nominal diameter DN with the corresponding product specifications. 3 The respective range of values for De, DN, d, and φ: 1. De – the outer diameter of PPR, PE, and polypropylene pipes. 2. DN--Nominal diameter of PVC pipes, cast iron pipes, steel-plastic composite pipes, and galvanized steel pipes. 3. φ--For seamless steel pipes or non-ferrous metal pipes, “outer diameter x wall thickness” should be indicated, e.g., φ108X4. 4 Conversion between imperial and metric units: The inch is a unit of length. 1 inch = 2.539999918 centimeters. Inches is a unit of length used in the United Kingdom (UK), that is, Britain (the Commonwealth), and its former colonies. The United States and others **also use it. In **and**, “inch” is usually written as “吋”. The common abbreviations for “inch” are “in” or “吋”. The character “吋” is a recently created character; it is pronounced “inch”. It belongs to the category of Chinese characters that have two pronunciations. Other examples include “浬”, which is pronounced “nautical mile”. This character borrows the traditional Chinese unit of length “寸” and has a “mouth radical” added to it to distinguish it from the original character. 1. Sizes: DN15 (4-inch pipe), DN20 (6-inch pipe), DN25 (1-inch pipe), DN32 (1 1/4-inch pipe), DN40 (1 1/2-inch pipe), DN50 (2-inch pipe), DN65 (2 1/2-inch pipe), DN80 (3-inch pipe), DN100 (4-inch pipe), DN125 (5-inch pipe), DN150 (6-inch pipe), DN200 (8-inch pipe), DN250 (10-inch pipe), etc. 2. Divide 1 inch into 8 equal parts: 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8 inches. (1) This corresponds to what is commonly referred to as 1/8 inch to 7/8 inch; smaller sizes are expressed using 1/16, 1/32, and 1/64, with inches still being the unit of measurement. If the denominator and numerator can be simplified (such as when the numerator is 2, 4, 8, 16, 32), they should be simplified. (2) The inch designation is indicated by two dashes in the upper right corner, such as 1/2". (3) For example, a pipe with a diameter of DN25 (25 mm, the same below) is equivalent to an English 1\" pipe, which was also known as an 8-inch pipe in the past. (4) A DN15 pipe is equivalent to a British 1/2\" pipe, which was also the former 4-mm pipe. (5) A DN20 pipe is equivalent to a British 3/4\" pipe, which was also known as a 6-inch pipe in the past.