4th Class Edition Plant Diagrams and Drawings PDF

Unit A-10 • Fundamental Industrial Communication Skills Objective 1 Explain the layout of plant diagrams. Plant Diagram Layout There are many different diagrams available for plant operators: • Process Flow Diagram (PFD) • Pipe & Instrument Diagram (P&ID) • General Arrangement (GA) Diagram • Block...

Unit A-10 • Fundamental Industrial Communication Skills Objective 1 Explain the layout of plant diagrams. Plant Diagram Layout There are many different diagrams available for plant operators: • Process Flow Diagram (PFD) • Pipe & Instrument Diagram (P&ID) • General Arrangement (GA) Diagram • Block Diagram • Electrical Single Line Diagrams and Schematics • Equipment Diagrams Each of these diagrams has a specific purpose, with custom features, and symbols in its use. Before discussing the individual types, it is useful to identify the features that are common to all standard plant diagrams. Standard Plant diagrams can be divided into five major areas or parts. 1. Title Block 2. Grid System 3. Revision Block 4. Notes and Legends 5. Engineering Diagram (graphic portion) The information contained in the diagrams themselves will be covered in subsequent objectives. This objective will cover the non-diagram portions of a print. The first four parts listed above provide important information about the actual diagram. The ability to understand the information contained in these areas is as important as being able to read the diagram itself. Failure to understand these areas can result in improper use or the misinterpretation of the diagram. Title Block The title block of a diagram, usually located on the bottom or lower right hand corner, contains all the information necessary to identify the diagram, and to verify its validity. Information most often included in the title block includes: a) The diagram title, diagram number, site location, and diagram owner. b) Signed and dated approval of the plan developers. c) A reference list of other diagrams that are related to the system or component. It can also list all the other diagrams that are cross-referenced, depending on the plant’s conventions. d) Diagrams can be classified as either with or without scale. i. Diagrams without a scale usually show only functional information about the component or system. ii. Scale diagrams permit large objects to be depicted in a size small enough to fit on paper. Scale diagrams also permit the enlarged depiction of small parts, so details are easier to observe. 2-4 4th Class Edition 3 • Part A Plant Diagrams and Drawings • Chapter 2 Grid System Because standard diagrams tend to be large and complex, finding a specific point or piece of equipment on a diagram can be quite difficult. To help locate a specific point on a referenced print, most diagrams, especially Piping and Instrument Diagrams (P&ID) and electrical schematic diagrams, have a grid system. The grid can consist of letters, numbers, or both that run horizontally and vertically around the diagram’s edge. Revision Block As changes to a component or system are made, the diagrams depicting the component or system must be redrafted and reissued. When a diagram is first issued, it is called revision zero, and the revision block is empty. With each revision made to the diagram, an entry is placed in the revision block. This entry, often placed beside a triangle or within a cloud shape, provides the revision number; a title or summary of the revision; and the date of the revision. There are two common methods of indicating where a revision has changed a formal diagram. The first is the cloud method, where each change is enclosed by a hand-drawn cloud shape. The second method involves placing a circle (or triangle, or other shape) with the revision number next to each affected portion of the diagram. The cloud method indicates changes from the most recent revision only. The second method indicates all revisions to the diagram because all of the previous revision triangles or circles remain on the diagram. Figure 1 provides several examples of revision annotations. Figure 1 – Example Revision Annotations (a) Revision Block (b) Changes 4th Class Edition 3 • Part A 2-5 Unit A-10 • Fundamental Industrial Communication Skills Notes and Legend Diagrams are comprised of symbols and lines that represent components or systems. Although a majority of the symbols and lines are standardized among all diagram types, a few unique symbols and conventions must be explained for each diagram. The notes and legends section of a diagram lists and explains any special symbols and conventions used on the diagram, as illustrated in Figure 2. Figure 2 – Example Notes and Legend Section 2-6 4th Class Edition 3 • Part A Plant Diagrams and Drawings • Chapter 2 Objective 2 Explain the use of process flow diagrams (PFDs). Process Flow Diagram (PFD) The process flow diagram (PFD) is a simplified schematic of a plant, or portion of a plant. It uses graphic symbols to show the major equipment items, and the major process flow between the equipment. The components of the PFDs are not drawn to scale, only the inter-relationships between the equipment in the process are shown, but not in exact orientation. PFDs provide valuable information for plant operating and engineering staff. They help with general understanding of the process flows and control strategy. PFDs are good resources for the purpose of training new personnel. Layout of the PFD A separate PFD may be prepared for each plant process. If a single sheet is too crowded, more sheets may be used. For simple processes, more than one process may be shown on a sheet. Process lines should have the flow rate, direction of flow, and other required data, such as pressures and temperatures. Main process flows should go from the left to the right of the sheet. Line sizes are not shown on a PFD. With PFDs, simplicity in presentation is important. Typical details shown on PFDs include: a) Major process equipment with process line orientation, including proper name and numbering. b) Main piping, including major bypass and recirculation lines, and direction of flow. c) System ratings and operating values including flows and rates, pressure, and temperature values (often at the major vessels or control points). d) General configuration and process orientation of equipment. e) Major instrumentation, such as major control valve locations (excluding isolating and shut-off valves), and basic instrumentation orientation. f ) Make up of fluids in the process. 4th Class Edition 3 • Part A 2-7