Chapter 7 - Flow Diagrams and Instrumentation

Abstract

The 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 mechanical equipment in the facility reflects, in part, the logical sequence of flow depicted on the flow diagram. However, many other factors such as code requirements, client standards and preferences, worker safety, and cost influence the positioning of equipment. Once the plot plan is finalized, the piping designer routes the pipe between the various pieces of mechanical equipment as indicated by the flow diagram using project specifications, standards, and accepted design practices. The flow diagram is usually yellowed out as each line is completed and incorporated into the design. Process engineers are responsible for developing flow diagrams. In many large engineering firms, an entire department is dedicated to the development of flow diagrams. To ensure the safe and efficient operation of a facility controlling instrumentation is an absolute necessity. Controlling instruments function by sensing conditional changes in the commodities they monitor, either in pipes or mechanical equipment.