Introduction to Pipe Axonometric Drawing

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A pipe axonometric diagram, commonly known as a single-line diagram, is a drawing of one or part of a pipeline created using the principles of orthographic axonometric projection. Single-line diagrams are characterized by a strong three-dimensional feel and are easy to understand; they are the most practical and convenient type of construction drawing in pipeline construction. Contents of pipeline axonometric drawing: 1. Graphics – Drawings of pipe sections along with associated fittings, valves, etc., created based on the principles of orthographic axonometric projection. 2. Mark the pipeline number, the equipment tag number connected to the pipe, the pipe tag number, elevation, dimensions, etc. 3. Direction indicator: Establishes the installation orientation reference, commonly known as coordinates. 4. Technical requirements: Special requirements that need to be addressed regarding the welding and pressure testing of prefabricated pipes. 5. Material list: Details of the materials used in the pipelines, such as specifications, quantities, and applicable standards. 6. Title bar: image name, image number, etc. Drawing of pipe axonometric views: Generally, for medium and low-pressure carbon steel pipes with a nominal diameter greater than DN50 mm, as well as medium and low-pressure stainless steel pipes with a nominal diameter greater than DN20 mm, it is necessary to draw axonometric views of these pipes. However, in cases where a single pipe system includes two different diameters, such as in valve assemblies or drain systems, the smaller diameter pipes should also be depicted along with the larger ones. Proportional requirements for drawing: The entire diagram does not necessarily need to be drawn to scale, but the proportions between the valve assemblies and pipe fittings must be consistent, as well as their relative positions in the pipe section list. Linear: Pipes in axonometric drawings are drawn with a single line (thick solid line, 0.9–1.2 mm), and pipes parallel to the coordinate axes are also drawn parallel to those axes in the axonometric view. For inclined tubes that are not parallel to the coordinate axes, a thin solid line frame is used to indicate their spatial position; when changes occur in both directions, a cube is drawn to represent them. As shown in the image file:///C:/DOCUME~1/ADMINI~1/LOCALS~1/Temp/ksohtml/wps_clip_image-754.png, flanges, valves, and fittings are represented by symbols drawn with thin solid lines (0.5–0.7 mm), and arrows indicating the flow direction are drawn at appropriate positions along the pipes. Representation of connection types: The circumferential weld of a pipe is indicated by a dot, while threaded connections and socket weld connections are represented by a short line; on horizontal pipes, this short line is vertical, and on vertical pipe sections, it runs parallel to the adjacent horizontal pipe sections. The flange is also indicated with a short line, just like above. The handwheel of the valve is represented by a short line that runs parallel to the pipeline, while the center of the valve stem is drawn in accordance with the design direction. The elbows don’t even have arcs drawn. When a pipe is connected to a device, the pipe outlet of the device is generally indicated with thin double-dashed lines; when one pipe segment is connected to another pipe, that other pipe is also indicated with thin double-dashed lines. Annotations: The axonometric view of the piping system should indicate all the dimensions required for the installation and prefabrication of pipes, fittings, valves, etc. In the drawing, meters are used as the unit for elevations, while millimeters are used for all other dimensions. The indicated dimension consists of a dimension line and dimension boundaries; the dimension line is parallel to the corresponding pipe, while the dimension boundaries are vertical lines that usually start from the centerline of the fitting or the flange surface, with the length indicated above the dimension line. For the dimensioning of bias tubes, for those that are not at 45°, two offset dimensions must be indicated, with the angle being omitted ； For a 45° offset tube, the angle and an offset dimension must be indicated ； For a three-dimensional bias tube, draw a hexahedron with three coordinate axes and indicate the dimensions. file:///C:/DOCUME~1/ADMINI~1/LOCALS~1/Temp/ksohtml/wps_clip_image-24277.png For pipes that pass through walls, platforms, roofs, and floor slabs, the elevation of those platforms, roofs, and floor slabs should be indicated; for walls, the dimensional relationship between the wall and the pipe should be shown. file:///C:/DOCUME~1/ADMINI~1/LOCALS~1/Temp/ksohtml/wps_clip_image-27495.png The pipe number and diameter should be indicated above the pipe ； The elevation “EL” of horizontal pipes is indicated below the pipes ； When it is not necessary to indicate the pipe number and diameter, the elevation can be marked above or below the pipe. Devices connected to the pipeline or another line must be labeled with the device identifier or pipeline number. Sometimes, the distance between the end face of the pipe outlet and the center of the equipment is also indicated, along with the elevation of the center line of the pipe outlet and the drawing number corresponding to the other pipe sections. Orientation markers in axonometric drawings: East, South, West, North, UP, and DN are represented by the English letters E, S, W, N, UP, and DN respectively on the coordinate axes. Generally, the upper left is taken as north, but the upper right can also be used as north. Material list: It is necessary to indicate on the axonometric diagram the quantity, specifications, and applicable standards of all materials used for that pipe section.