Chapter 7 - Flow Diagrams and Instrumentation

Abstract

This chapter provides an overview of flow diagrams and instrumentation. Flow diagrams present in a schematic drawing the flow of fluids and gases through a unit or an entire plant. With symbols representing various pieces of equipment, a flow diagram provides the piping designer with an overall view of the operation of a facility. The flow diagram found in this chapter is representative of the types used by many companies in the piping industry. The process flow diagram is the first flow diagram developed by the flow diagram department. It includes major equipment, main piping, direction of flow, operating pressure and temperature, and major instrumentation. A flow diagram is used by the piping group to develop and lay out the plot plan. When developing the plot plan, the arrangement of the equipment in the facility reflects, in part, the logical sequence of the flow depicted on the flow diagram. However, many other factors such as code requirements, client standards and preferences, worker safety, and cost also influence the positioning of equipment. Today, almost all flow diagrams are laid out with computer-aided design (CAD), using third-party piping packages such as Pro-Flow or individually developed company packages.