If there is any one technical document that can be considered the “master” document for a capital project, it is the Piping and Instrumentation Diagram (P&ID). Ubiquitous in industrial environments, project P&IDs perform a multitude of functions, all of which are necessitated by having current and detailed process information about the facility: process definition (new or existing), OSHA required Process Hazard Analysis (PHA), tracking maintenance activities, operational planning and work processes, and much more.

In this article, we’ll explain project P&IDs and discuss how they relate to capital projects.

Project P&IDs Explained

A P&ID is a schematic drawing that depicts the configuration of equipment, piping, valving, and instruments used to control the process in a process facility. The P&ID is the blueprint for the project; it should include all major equipment, piping, and instrumentation.

Project P&IDs are the foundation for maintenance, modifications, and expansions of the process that it visually represents. For this reason, project P&IDs are kept “evergreen” and up to date, representing all existing equipment, piping, and instrumentation. For processing facilities, it provides a visual representation of:

• Important piping and instrumentation details.
• Control and shutdown schemes.
• Basic start-up and operational information.

Safety and regulatory requirements.

Project P&IDs Explained: Key Elements

Project P&IDs are the main scope documents for capital projects. The P&IDs clearly represent the work to be performed in the execution stage. A project P&ID represents the “future state” of the facility at project completion.

Project P&IDs are started at the very beginning of a project, typically in front-end loading (FEL) 2. By the time you reach the execution stage (the end of FEL 3/the beginning of detail engineering and design), the project P&ID should be complete. Things like major equipment and piping should be fully defined at this stage and shown in the P&ID.

In general, project P&IDs going into the execution phase should contain the following information:

• Major process equipment (1) - *Equipment List
• Equipment data shown in Equipment Block (2)
• Process Flow Identification (material and flow direction) (3)
• Process Piping with Specifications (4) - *Line List
• Instrumentation ID (5) - *Instrument List
• Valve and Tagged Items Identification/Specifications (6)
• Basic Automation/Controls information (e.g. interlocks, controls interface, etc.) (7)

(#) - Drawing Example Reference

 (*represents a key component of named project document)

Project P&IDs Explained: P&IDs for Existing Facilities

If a project P&ID is newly created for the project, everything on the page will be included in the project. However, if the project involves an existing P&ID, the new project components are added to the P&ID and “clouded” with a revision triangle on the cloud tied to a revision block description of the project.

Where the new project components interface with existing facility items (in particular, piping), a “tie-in” is shown on the drawing to reflect where the new piping joins the existing.

The revision block at the bottom of the drawing border will give a history of changes made to the P&ID and serves a very important document control purpose—this will be discussed more in depth at a later point.

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