Process and Instrumentation Diagram Development工艺仪表流程图的发展.doc

Process and Instrumentation Diagram DevelopmentIn Water and Waste Water Treatment PlantsSteven J. Marrano, P.E.Instrumentation and Controls EngineerThe process and instrumentation diagram (“PID” as it often called) represents a document that can take on many different forms depending upon the following factors:Nature of the process being depicted. The more complicated the process, or the more one process is interconnected to other portions of the PID, the more complex the PID will become.The individual or firm performing the design work. Some firms do not feel the need to develop PIDs. This approach is used to achieve economies on system design.Design philosophy. Some design philosophies include PIDs as an item issued with the instrumentation or electrical design (developed at the middle or end of the project). Other design philosophies allow the PIDs to be used as the basis for all other design disciplines. In this philosophy, the electrical, mechanical, and piping engineers on a project would start their work once the PIDs are complete.Intended audience once the design is complete.Among the several design engineers I have spoken to, these factors dominate how detailed or general the process and instrumentation diagram will become. Different industries tend to use different terminology and presentation of technical information. In the chemical or pharmaceutical sectors of process control, it is common to have mechanical (or Engineering Flow) diagrams to show major pieces of equipment and associated ratings, and separate process and instrumentation diagrams that show how the instruments connect to the process. The water and wastewater industry tends to favor a hybrid presentation of mechanical and instrumentation information on the same drawing.Process and Instrumentation DiagramsWe should begin by reviewing the PID’s purpose and what information it depicts. One set of authors Luckiewicz, E., Sandler H: Practical Process Engineering: A Working Approach to