How To Read Isometric Drawing

In a piping isometrics drawing, pipe is drawn according to it’s length, width and depth, and often shown in a single view. The Isometrics drawing are created from information found on a plan and elevation views.

Symbols like fittings, Valves and flanges are modified to adapt to the isometric grid. Piping isometrics are usually drawn on a pre-printed paper, with lines of equilateral triangles form of 60°.

The isometric drawing is oriented on the grid relative to the north arrow found on plan drawings and not drawn to scale. Therefore, dimensions are required to specify exact lengths of piping runs.

Pipe lengths are measured using coordinates and elevations. Vertical pipe lengths are calculated using elevations, while horizontal lengths are calculated using north-south and east-west coordinates.

Piping isometrics are generally produced from orthographic drawings and essential to design and manufacturing phase of a very complex or large piping systems. It is often used by designers prior to a stress analysis and used by draftsmen to produce shop fabrication spool drawings. Isometrics drawing is also the most important drawings for installation contractors during the field portion of the project.

How to Read the Isometric Drawing?

There are a few information that can be derived from an isometric drawing. Let’s use the isometric below as an example;

Refering to the above Iso drawing, lets go through the item one by one:

• Pipe size – Given pipe size is 2″ and 1″.

• Number of joints – In the drawing there are joint 1 to 13 with 2″ pipe size and joint 14 to 16 with 1″ pipe size. There are 16 total joints in this drawing.

• Prefabricated spools – in the isometric drawing ‘SPL -02’ denotes the spool number 2. Therefore in this drawing, there are 4 prefabricated pipe spool available that is SPL-01, SPL-02, SPL-03 and SPL-04.

Pipe fittings as listed below;

• One concentric reducer 4″ into 2″.

• Four nos 90 degree elbow.

• Three nos. Weld Neck flanges.

• One 2″ flanged type gate valve.

• One 1″ welded type gate valve.

• One Un Equal Tee size 2″ x 1″ on 1″ pipe tapping

• One 1″ one side threaded nipple for two connects threaded coupling with valve.

Other things that is included in the isometric drawing is The Material grade details. This can be found in the ‘Bill of Materials’ in given isometric drawing.