ABSTRACT

The P&ID or Piping and Instrumentation Diagram is the vital piece of documentation needed to do the HAZOP study that precipitates the Contingincy Analysis of a project. The P&IDs are also used to hydrotest a section of the piping with or without an equipment: you need to know the fluid category [Category D or Category M (Toxic Service)]. See piping code explained below.

INTRODUCTION

Beware of the so-called Smart P&IDs involving AI. You need Process Flow Diagrams (PFD), Equipment MAWP, Piping Class, material of construction, Insulation, and tracing shown in the P&IDs.

DISCUSSION

Controls such as ON-OFF, feedback, feedforward, cascade, ratio, split-range, etc.,must be shown on the P&IDs. Control valve fail-positions such as fail-closed, fail-open with directional arrow must be shown on the P&IDs. Control modes such as Proportional, Integral, derivative or their combinations are used tfor process control. The symbology incudes: PSV for Pressure Relief Valve, PSE for Pressure Safety Elements such as Rupture Disk, Rupture Pin, and Buckling Pin, TSE for Temperature Safety Elements such as the Fusible Plug. Instrumentation Device and Functional Symbols must conform to ISA-5.1.

Piping Code

ASME B31.3 is the piping code to follow. Pay attention to the following:

Chapter IV

Paragraph 345.3.3: Piping with expansion joints

Paragraph 345.4.3: Hydrotest with vessels as a system

Chapter VIII: Non-metallic piping

Chapter IX: High pressing piping: pressure rating > Class 2500

Appendix M: Guide to classifying fluid services: Category D fluid and Category M fluid

Appendix X: Metallic bellows expansion joint

If you need help, please contact me at 816-400-3238 or [email protected].