Reading and understanding drawings

We will look at various drawings, which are both useful and necessary during works with insulation;

• Isometric drawings
• P&ID drawings
• GA drawings
• Layout drawings
• Legends and information on these

We will now learn to be able to orient yourself with the use of GA drawings, be able to read and understand isometric and layout drawings as well as P&ID diagrams including the legends. We should also be able to identify the insulation system/structure on a defined line using the ISO drawings and the information about insulation found on the P&ID diagram and legends.

Reading drawings

Reading and understanding isometric drawings, P&ID diagrams and layout drawings is essential for understanding systems and classifications on these.

The Legend is an explanation of symbols and expressions used, as well as tools for decoding line number information.

The Legend will also contain explanations for insulation classes that differ from the standard setup in specifications.

P&ID shall always be the governing diagram/document and overrides isometric drawings if there is a conflict of information. P&ID is usually "owned" by the process discipline.

An isometric drawing shows a three-dimensional object in two dimensions (2D drawing that resembles to be a 3D drawing). Isometric drawings are "owned" by the piping discipline.

The term "isometric" means "which is measured on the same scale", and is a drawing in perspective, but with the same scale everywhere. An isometric drawing is a drawing of 3 axis (x, y, z).

N (direction) and E (elevation) – axis shows location of pipe and equipment in the module.

Layout may vary based on drawing manufacturer and customer requirements. The following shows what technical information the material list/component list can contain. Each component has a number so that you can see where the different lists are in your drawing.

Piping and Instrumentation diagram (P & ID) can also vary from different drawing producers and customer requirements.

• P&ID is an abbreviation for the English phrase "Piping and Instrumentation Diagram".
• A P&ID diagram is in process industry a diagram showing the interconnection of pipe lines, installed equipment and instrumentation used to control the process. Created, "owned" and maintained by Process Engineers/Discipline.
• P&ID diagram plays an important role in maintenance and modifications to process equipment and instrumentation
• A P&ID is not drawn to scale, that is, the pieces of equipment on the diagram are not the correct size relative to each other. Therefore, pumps and valves on a P&ID can often look very large compared to tanks and other equipment.
• How the different parts are positioned relative to each other does not appear in a P&ID. For example, equipment that appears to be far apart on the diagram may in reality be located in close proximity.
• Important information that can be found on a P&ID can be:
  • Line number and pipe dimensions on pipelines
  • Insulation classes on pipelines
  • Specification changes on pipelines/insulation on areas
  • Requirement for Passive Fire protection (usually under notes)
  • Overview of start-up and relief pipelines
  • Flow and fall direction
  • Connection between different systems
  • Physical interface between class separations (insulation classes, material classes, and so on)
  • Identification of mechanical equipment like pumps, heat exchangers, PIG-locks and so on

General Arrangement drawings

• General event drawings (GA) presents the overall composition of a module/building.
• GA drawing of a module shows a general overview of geometry and arrangement of pipelines, valves and equipment like tanks and
• GA drawings are often drawn for individual The drawing shows the dimensions and geometry of the equipment using 2D or 3D perspective, from above, from the side, and from the front.