Notation for cylinder diameter
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I have always wanted to clarify one thing: how exactly should the nominal diameter of a container cylinder be indicated? For example, if the nominal diameter of the cylinder is 1800 and the wall thickness is 6, should the arrow used for indication point to the outer wall? Should it be written as Ф1812x6, Ф1800x6, or DN1800x6? Could any professional please offer some guidance!
F1800: The wall thickness is indicated separately as 6; this is how we mark it, and it’s the same on the drawings I’ve seen. Last edited by GUANGWEI8.26 on 2009-4-20 at 21:16.]
It should be indicated that the inner diameter is 1800 and the wall thickness is 6, with these values specified separately
Generally, the welding of container cylinders is done with the inner walls aligned evenly (probably to reduce stress corrosion or something similar), so the inner diameter should be indicated as Ф1800 and the wall thickness as 6.
Previously, we would make a partial cut of the cylinder and indicate Ф1800 along with a wall thickness of 6; now our reviewers require us to indicate DN1800, with the wall thickness remaining unchanged.
It should be marked as φ1800, with the wall thickness indicated as 6; the way the original poster marked it is suitable for pipes
It should be marked as DN1800x6
Steel tube cylinders are marked as Ф273x6, etc.; the arrow indicates the outer diameter. Cylinder made of steel plates are generally marked as Ф1800, with the arrow indicating the inner diameter; the thickness of the steel plate is indicated separately. In other words, steel tubes are marked in the format of Ф273x6.
It depends on whether your casing is made of tubes or sheet metal; we usually use tubes, in which case the outer diameter is specified, for example: Φ630X10. For sheet metal, the inner diameter Φ600 and wall thickness of 10 are specified, with only these values indicated.
Our company usually specifies an inner diameter of 1800 and a wall thickness of 6；
If the cylinder is made of steel pipe, the nominal diameter indicated is the outer diameter of the cylinder multiplied by the wall thickness, such as ∮426×8； If it is made from steel plates, use the nominal diameter, that is, the inner diameter multiplied by the wall thickness, such as DN500×6.
Generally, DN is used for rolled cylinders, while φ is used for tubes
If the arrow points to the inner diameter, it should be marked as DN1800 S=6; if the arrow points to the outer diameter, it should be marked as Φ1800X6
It should be marked as φ1800×12 or DN1800, δ=12
Indicated inner diameter φ1800; wall thickness specified separately as 6
DN is short for nominal diameter, referring to the nominal diameter of a pipe; note that this is neither the outer diameter nor the inner diameter； It should be related to the imperial units used in the early stages of pipeline engineering development ； It is commonly used to describe galvanized steel pipes, and its correspondence with imperial units is as follows: 4-inch pipe: 4/8 inch: DN15 ； 6-inch pipe: 6/8 inch: DN20 ； 1-inch pipe: 1 inch: DN25 ； 1.5 inch pipe: 1 and 1/4 inches: DN32 ； 1.5-inch pipe: 1 and 1/2 inches: DN40 ； 2-inch pipe: 2 inches: DN50 ； 3-inch pipe: 3 inches: DN80 (often also denoted as DN75) ； Four-inch pipe: 4 inches: DN100 ；
For steel plates, the calculation is usually based on outer diameter × wall thickness, or DN (we use the inner diameter in our calculations) × wall thickness; for pipes, it’s outer diameter × wall thickness
1. The φ*** notation is used only when a tube is used as the cylinder body, and **** refers to the outer diameter; for example, if the nominal diameter is 100, then it will be denoted as φ108X6, 2. If the cylinder is welded from sheet metal, then the nominal diameter refers to the inner diameter; example of notation: DN1800 δ=6
The arrow should point toward the inner wall, indicated as: Ф1800, with the thickness specified separately
For single-layer welded cylindrical shells, the nominal diameter DN refers to the inner diameter. I think it would be appropriate to indicate φ1800, δ6 on the drawings, while using DN1800×6 in the specification table; this way, it meets the requirements of the standard series and at the same time ensures clear representation on the drawings.