Piping instrument diagrams design phases

This phase is where the basic design work, such as process flow design, is performed. Piping and instrumentation diagrams (P IDs) and equipment... 

In the detailed design stage, everything must be specified. Each phase of the preliminary design must now be done in much more detail. The flow sheets develop into piping and instrument diagrams. The duty requirements for a piece of equipment become a specification sheet. The layout drawings may be replaced by a scale model, and a construction bid or detailed cost estimate is obtained to verify the previous cost estimate. 

The design-freeze phase is that interlude between the completion of the piping and instrumentation diagrams and the determination of operating procedures. For new facilities, a full hazard and risk assessment should be performed here. At this point, alterations in process design still can be made relatively inexpensively since equipment has not yet been ordered. Ozog (1985) details the steps needed in the procedure. 

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