Plant Diagrams and Drawings PDF

Plant Diagrams and Drawings • Chapter 2 Objective 3 Explain the use of piping and instrumentation diagrams (P&IDs). Piping and Instrumentation Diagram (P&ID) The P&ID includes more and different detail than the PFD. The P&ID expands upon the basic information from the PFD to show details of: • Eac...

Plant Diagrams and Drawings • Chapter 2 Objective 3 Explain the use of piping and instrumentation diagrams (P&IDs). Piping and Instrumentation Diagram (P&ID) The P&ID includes more and different detail than the PFD. The P&ID expands upon the basic information from the PFD to show details of: • Each major piece of equipment • General piping orientation • Basic control and instrumentation devices, and their orientation The P&ID is not drawn to scale, although sizing is often included. The P&ID will not show the exact orientation of equipment, except for order of occurrence. These diagrams only present information on how a system functions, not the actual physical locations. Because P&IDs provide the most concise format for how a system should function, they are used extensively in the operation, repair, and modification of the plant. P&ID Details The typical detail shown on a P&ID includes: a) Flow lines (including process piping) complete with line identification, and specifications which include: • Size • Insulation requirements • Valve sizes and types (including drains, vents, and fittings), and connections (threaded, flanged, or welded) b) Equipment details: • Vessel size • Insulation requirements • Power • External mechanical details • Controls • Instrumentation • Utilities • All connections c) Instrumentation identified for: • Monitoring • Indicating • Transmitting • Recording • Controlling devices for pressure, temperature, level, and flow rates • Safety • Relief • Shutdown • End devices 4th Class Edition 3 • Part A 2-9 Unit A-10 • Fundamental Industrial Communication Skills Purpose of the P&ID The P&ID is used for the following purposes: a) During the design and pre-construction phases, the engineering contractor will use the P&ID to develop detailed lists of parts equipment, instrumentation, and electrical devices from which cost estimates and bid proposals can be generated. The P&IDs graphically show the results of the mechanical design engineer’s work. They include all that is incorporated in the completed construction project. The P&ID and the PFD are usually sufficient to define the scope of a project. b) During construction, P&IDs provide the field construction and inspection personnel with a reference to ensure that all equipment, instrumentation, piping, valves, and insulation, are properly located and interrelated. c) After construction, P&IDs are an invaluable operational and training reference for plant operating and engineering staff. They assist in understanding the details of the process, its instrumentation control system, the relationship between process, utility, and electrical systems. They provide an index to detailed piping, isometric diagrams, and equipment or instrument data sheets. Figure 4 shows the main elements of a typical P&ID diagram. Figure 4 – Typical P&ID Without Title Block 2-10 4th Class Edition 3 • Part A Plant Diagrams and Drawings • Chapter 2 This diagram may look similar in makeup to the PFD shown in Figure 3, but it has much more detail. Although still not to scale, it supplies the type of information required to order or maintain component inventories. You may note some of the following features: • Valve sizing • References to other diagrams • Piping identifiers Common P&ID Symbols P&IDs come in sets for a particular plant or section of a larger plant. The set of diagrams includes a legend showing all the symbols. The previous chapter indicated standard diagram symbols. Figure 5 shows a sample of a list of standard symbols. Figure 5 – P&ID Symbols VALVE SYMBOLS LINE SYMBOLS GATE VALVE INSTRUMENT AIR LINE GLOBE VALVE INSTRUMENT ELECTRICAL CHECK VALVE INSTRUMENT CAPILLARY TUBING PIPE CONTROL VALVE PLUG VALVE P & I.D ABBREVIATIONS BALL VALVE CSO - CAR SEAL OPEN CSC - CAR SEAL CLOSED DF - DRAIN FUNNEL MISCELLANEOUS SYMBOLS LC - LOCK CLOSED SPECTACLE BLIND OPEN LO - LOCK OPEN NC - NORMALLY CLOSED SPECTACLE BLIND CLOSED NO - NORMALLY OPEN ORIFICE FLANGES PO - PUMP OUT SC - SAMPLE CONNECTION SP PIPING SPECIALTY ITEM SO - STEAM OUT BUTTERFLY VALVE Diagram Abbreviations represent standard terms that are used on P&ID diagrams. Some examples are NO for normally open valves, NC for normally closed valves, and SO for steam out. Specialty Symbols may be used for specific items that are not common on all P&ID diagrams. For example, spectacle blinds and specialty piping items. Instrumentation data is also contained on P&IDs and is listed with the piping symbols. Figure 6 shows a list of P&ID instrumentation symbols. It includes symbols for flow, temperature, level, and pressure instruments. There are also symbols for miscellaneous items such as transmitters and hand control valves. Symbols for board mounted and locally mounted instruments are also shown. The board mounted (control room) instruments appear as circles with horizontal lines through them. The locally or field mounted instruments have no line. 4th Class Edition 3 • Part A 2-11 Unit A-10 • Fundamental Industrial Communication Skills Note that the first letter stands for the measurement type. F for Flow P for Pressure T for Temperature L for Level The second letter is for the type of instrument. I = Indicator R = Recorder T = Transmitter C = Controller A = Alarm RC = Recording Controller LIC = Level Indicating Controller LAH = Level Alarm High LAL = Level Alarm Low LG = Level Gauge (sight glass, gauge glass) 2-12 4th Class Edition 3 • Part A Plant Diagrams and Drawings • Chapter 2 Figure 6 – P&ID Instrumentation Symbols TEMPERATURE INSTRUMENTS FLOW INSTRUMENTS FA FLOW ALARM TA TEMPERATURE ALARM FE FLOW ELEMENT TI TEMPERATURE INDICATOR FI FLOW INDICATOR TR TEMPERATURE RECORDER FR FLOW RECORDER TRC TEMPERATURE RECORDING CONTROLLER FRC FLOW RECORDING CONTROLLER TW TEMPERATURE WELL LEVEL INSTRUMENTS PRESSURE INSTRUMENTS LEVEL ALARM PC PRESSURE CONTROLLER LAH LEVEL ALARM HIGH PI PRESSURE INDICATOR LAL LEVEL ALARM LOW PR PRESSURE RECORDER LC LEVEL CONTROLLER PIC PRESSURE INDICATING CONTROLLER LG LEVEL GLASS PRC PRESSURE RECORDING CONTROLLER LEVEL INDICATOR PSV PRESSURE SAFETY VALVE LIC LEVEL INDICATING CONTROLLER PRV PRESSURE RELIEF VALVE LRC LEVEL RECORDING CONTROLLER MISCELLANEOUS SYMBOLS LA LI T TRANSMITTER FIELD MOUNTED INSTRUMENT HCV HAND CONTROL VALVE INSTRUMENT ON FIELD PANEL HH INSTRUMENT ON CONTROL ROOM PANEL LL UCP CONTROL SYSTEM (DCS) FUNCTION – DISPLAYED CONTROL SYSTEM (DCS) FUNCTION – NOT DISPLAYED HH SYSTEM SAFETY FUNCTION VENDOR PACKAGE LOGIC LL UCP UNIT CONTROL PANEL FUNCTION (VENDOR) By putting together equipment, piping, and instrumentation symbols, simple control loops can be created. These are built into more complete P&ID diagrams. Figure 7 shows an example of a simple instrument loop that senses and adjusts a tank level. This is an example of an electrical single line diagram. 4th Class Edition 3 • Part A 2-13 Unit A-10 • Fundamental Industrial Communication Skills Figure 7 – Simple Control Loop The pneumatic transmitter (LT) senses the tank level. Note the control lines. They indicate the control system is pneumatic. The output of the level transmitter is routed to a field panel mounted level recording controller (LRC). The level controller records the level, and sends a modified pneumatic signal to the diaphragm-operated level control valve. Notice that insufficient information exists to determine the relationship between the sensed tank level and valve operation. 2-14 4th Class Edition 3 • Part A