What is an isometric drawing?

The projection

In an isometric projection the three axes are drawn at 120° to each other: one vertical and two at 30° to the horizontal. A pipe that runs north–south, east–west or vertically is drawn along one of these axes. A piping isometric is not to scale: the drawing shows the route and the connections, and the dimensions give the lengths.

What a piping isometric contains

• the route of the line with elbows, tees, reducers, flanges and valves;
• dimensions between the centre lines and to the connections, and elevation marks;
• a north arrow to orient the drawing on site;
• the line number, the specification (piping class), the medium and the insulation;
• weld numbers and spool numbers;
• the bill of materials with quantities, sizes and materials;
• a title block with the project, the drawing number and the revision.

Sloped and skewed pipes

A pipe that does not follow one of the three axes is shown with a hatched triangle or box that indicates the offset in the plane. Slope is given as a ratio or as a difference in elevation.

Isometric drawing per spool

For prefabrication an isometric drawing is often made per spool: one drawing per part that is made in the workshop, with the field welds at the ends.

In FlowCAD3D

Isometric drawings are generated from the 3D model, also per spool, with automatic dimensions, elevation marks, bill of materials and title block. With Isometric drawing, the line is drawn directly on a live isometric while the 3D model is built at the same time. Export to DXF, SVG and PDF, or to PCF for ISOGEN. More: Isometric drawings from the 3D model.