Chapter Objectives

This chapter will help you understand the need for documentation and become familiar with the use of symbols in process control flow diagrams.

The following are covered in this chapter:

• Alarm and trip systems and documentation

• Programmable logic controller (PLC) documentation

• Interconnection symbols and flow line abbreviations used in piping diagrams

• Instrument Society of America (ISA) list of standard symbols

• Standard instrument symbols and identification letters

• Standard functional actuator symbols

• Control loop numbering system and pipe and identification (P and ID) drawings

15.1 Introduction

Documentation covers front-end engineering and detailed engineering drawings. Of the overwhelming amount of documentation needed in a plant, the only documentation that will be introduced is limited to documentation you may encounter and need to use, such as alarm and trip Systems, PLC documentation, and pipe and identification diagrams (P and ID). Of these the P and ID is the detailed documentation covering instruments, their location, process control loops, and process flow details. Documentation standards and symbols have been set up and standardized by the ISA in conjunction with the American National Standards Institute (ANSI).

15.2 System Documentation