Piping and Instrumentation You are introduced to the topic of Piping and Process Instrumentation drawing. You will make then use of the drawing techniques developed during the module. Learning outcomes After completion of this unit, you will be able to: • Describe the different types of pipes and their uses. • Define methods of pipe connections and their applications. • Identify the different types of pipe fittings and valves. • Draw/Interpret dimensioned single-line drawings with fittings and valves. • Interpret isometric plans. • Calculate linear dimensions and straight length of pipe in angular runs. Recommended reading • Students can read up on more detail for enrichment in the following resources (Access Engineering Unisa online library): Piping Handbook, sections below describe the necessary chapters to be read. Practice questions • Work through the given diagrams and examples. The lecturer will issue questions for you to practise during the module. Refer to Study Unit 15 for additional practise questions. Introduction Plant process and thermo-fluid engineering systems are described using a variety of standardised layout plans (e.g. Process Flow Diagram (PFD), System Flow Diagram (SFD), Process and Instrumentation Diagram (PID or P&ID), Single or Double Pipe Layout Diagrams, equipment layout or plot plans). The minimum information for these diagrams can vary across industries, companies and geographical location, however, their fundamental objectives and intended communication remain unchanged. A pipe is a tube made of metal, plastic, concrete or fibreglass. Pipes are used to convey liquids, gases, slurries or fine particles. A piping system is generally considered to include interconnection of pipes, pipefittings, flanges and process equipment such as heat exchangers, vessels, pumps, compressors, fans/blowers, valves etc, and so on. Piping is used in a wide range of applications, and some are listed here: • • • • Plumbing Civil piping Process/industrial piping Transportation piping A PFD from a commercial steam turbine vendor such as Turbomeca France may have some variation in symbol representation of a turbine-condenser or flanged pipefitting compared to another firm such as General Electric Steam Power Global. The development of such diagrams is similar to the design process, continuously revised, improved and creation of various revisions. Version control and document management are necessary requirements. These diagrams are required at each of three levels in the project evolution cycle briefly described below. These three stages are globally recognised in Project Management Best Practice programs and cover industrial or commercial small to mega-build projects (Excluding the Shut-down/Turn-around Projects): Stage 1: Project inception, assignment of responsibilities, preliminary design, cost estimate, permits and licenses, project scheduling, stakeholder engagement, financial/insurance/underwriting/contract agreements, feasibility and desktop studies, identification of required code and standards. Stage 2: Detailed design, procurement, project costing, continued stakeholder engagement, detailed multi-disciplinary system/component simulation, manufacturing drawings, prototyping, and laboratory testing. Stage 3: Project execution, project and site management, site delivery and construction, construction management, plant start-up, commercial operation of systems, and hand-over to the client, including maintenance/reliability/spares documentation and project close-out/project debrief, snag list, and as-built documentation. Some important piping parameters are: • • • • • • Flow rates and system pressures Temperatures Pipe and vessel wall thickness Heat transfer rates Pipe stress and flexibility analysis and pipe support design Pipe lengths Consider each parameter and try to establish why they are important. Do some background reading on the basic physics associated with each listed parameter. Types of Piping and Selection Considerations Students can read up on more detail for enrichment in the following resources (Access Engineering Unisa online library): Piping Handbook, Section A3 Piping material. A brief description is given below. Typical pipe materials are (investigate some of the potential use cases for each material type): • Cast iron • Steel • Copper/Copper Alloy • Plastic • Concrete Main consideration for pipe selection includes temperature, pressure and corrosion. Other factors include safety, cost, compliance with project specifications and codes/standards. Temperature The temperature factor is determined by the type of fluid in the pipe, or the quantity of external heat exposed to or applied upon a pipe. Example, suppose a copper pipeline is installed with its outer surfaces in the sun of average temperature 30 ⁰C at five hours average daily sunshine during the summer months. This copper pipe is now subjected to a steady thermal energy source causing the material temperature of the pipe to increase. Adequate thermal expansion consideration must be taken into account at pipe fittings and supports. Thermal stress must also be factored into the design. Another example is the transport of cryogenic or high temperature fluids, in these scenarios the effect of fluid temperature on the pipe material must be assessed and will include aspects such as thermal expansion and thermal stress. Piping flexibility is then a requirement in the design of a piping layout. Pressure The pressure factor is a process or system state variable and depends on the design of the piping system. The pipe internal pressure will largely determine the wall thickness of the pipe. Mass flow rates will largely determine the pipe inner diameter (volumetric flow rates are suitable for incompressible flow and non-2-phase flow). Note both factors are coupled in the selection of pipe diameter and wall thickness, that is, you need to consider both pressure and relevant flow rate in the analysis. Fail or abnormal operation considers scenarios such as sudden valve shut during normal operation. A sudden pressure rise will occur within the pipe and this maximum must be accounted for in the design of the piping system. Therefore maximum pressure may occur during abnormal operation. A pipe blockage can create an obstruction and cause pressure rise and/or flow-rate reduction of fluid transport within a pipe. Safety The design of the piping system must be safe during failed scenarios as best as possible and clearly safe during normal operation. It is not possible to design for every abnormal scenario. Various failover systems must be introduced (e.g. vents, emergency shut-off valves, secondary or multiple alternate routing, and limit switches, warning alarms, process control sensing elements, and so on). A HAZAD/OP analysis or similar will identify risks and establish the required fail-safe systems necessary depending on the nature of the fluid, piping system and proximity or impact on civilian environments. Example, a nuclear piping system will feature a far greater number of fail-safe systems than a low-pressure domestic water reticulation system. Corrosion Transport of fluid within a pipe may contain trace, dissolved or contaminated elements such as mineral salts, chemical deposits, solid particles, and so on. Mineral deposits could be naturally occurring whereas chemical deposits can arise from chemical-dosing operations in a plant. Solid particles such as flue gas can be entrapped in air pipelines or if scrubbers have inadequate measures to eliminate flue gas particles. State changes (such as boiling) can cause mineral or solid deposits to build up within the pipe, fluid motion creates relative movement between the solid particles and pipe inner surface to cause wear. Depending on the chemical potential between the fluid and pipe material, chemical reactions can occur that will cause the pipe material to corrode. Galvanic corrosion can occur on both inner and outer surfaces depending on conditions to support this effect. Pipe Connection, Fittings and Valves Pipe Connection Students can read up on more detail for enrichment in the following resources (Access Engineering Unisa online library): Piping Handbook, Section A2 Piping Components: A2.6, A2.7, and A2.8. A brief description is given below. There are various pipe connection methods that may be used to join two pipes. The selection of a suitable connection will depend on the following considerations among others: • • Connection strength (line pressure, expansion stress dependent) Leak tight requirement (hazard type and environment dependent) • • • • • Line pressure (low, intermediate and high line pressure; this will impact connection integrity and leak proof requirements) Joint/connection flexibility (environment effects on joint movement such as seabed piping, thermal expansion, structural support movement relative to joint) Hazard nature of pipe fluid (pure oxygen gas, LPG, inert gas, water, flammable or toxic aspects) Pipe material (ductile iron, steel, copper, concrete, plastic) Environment factors (e.g. corrosion, ground location, thermal and seismic effects) Typical pipe connections: • • • • • • • • Weld Screwed Flanged Soldered Bell (Hub) and Spigot Mechanical joint Solvent Flaring Fittings Students can read up on more detail for enrichment in the following resources (Access Engineering Unisa online library): Piping Handbook, Section A2 Piping Components: A2.1 until A2.6. A brief description is given below. Pipe fittings allow a pipe to change direction or size, or to allow branching or connections. These are necessary when a pipe has to navigate corners, obstacles or change in elevation. Changes in pipe size are often associated with a supply change in volumetric flow rate or mass flow rate (compressible flows). Branching and connections often occur in network piping and may be integrated with pipe size changes and changes in direction. The three main types of fittings are screwed, welded and flanged. Some typical pipe fittings are listed below. Typical pipe fittings: • • • • • Welded Screwed Union Coupling and half-coupling Street elbow • • • Bushing Plug Flanges Valves Students can read up on more detail for enrichment in the following resources (Access Engineering Unisa online library): Piping Handbook, Section A10.1 Selection and Application of Valves: A10.1, 10.2, 10.7 and 10.8. A brief description is given below. Valve components help to control and regulate flow within a pipe or pipe network through several functions: regulate flow rate, maintain a set pressure, and prevent backflow or pressure build-up. Valves are required to control open/close flows in a network. These functions are often accomplished through a specific valve type. Typical valve types: • • • • • • On-Off Valve (gate valve, ball valve, plug valve) Regulating valve (globe valve, angle valve, butterfly valve, needle valve, diaphragm valve) Backflow valve (check valve, swing check and lift check valves) Safety and relief valves Control valves Pressure regulating valves Typical Equipment Symbols Selected equipment symbols are described here and used in this course (Madsen). These symbols are used on process/piping and instrumentation diagrams and are contained in the Appendix. You should be familiar with these symbols as your progress through your study years. However, for this course we will consider a subset of these symbols for the purpose of an introduction to piping drawing. Additional equipment symbols from the Appendix may be added by discretion of the lecturer, keep aware on course communication for this aspect. Symbol Description Horizontal/Vertical Vessel or can represent a simple Reactor Pump Heat exchanger Concentric expander Concentric reducer Closed tank Open tank Fan Pipe Drawings The preparation of a pipe drawing involves inputs from a variety of sources and some of these are listed below. We will consider only two types in the module: basic process or system flow diagram and a basic process and instrumentation diagram. • • • • • • • Maps of the site plan Equipment layout plan Services layout plan Design and as-built documentation Operation manuals Process or system flow diagrams (PFD or SFD) Process and Instrumentation diagrams (PID) System or Process Flow Diagram This diagram gives an overview on the overall layout of a plant/process system or subsystem. The drawing does not show minor components (e.g. pressure, temperature, flow instruments and controllers), piping systems (e.g. control loops, non-primary by-pass lines, drainage lines, auxiliary loops etc.) and pipe properties (e.g. size, spec., material, ratings etc.). A process flow diagram (PFD) or system flow diagram (SFD) is an input to the development of a piping drawing which shows the pipe specification including fittings and valves. You will be required to interpret a basic process or system flow diagram and thereafter construct or interpret a pipe drawing. Some basic examples are given below. Critique these and other such drawings to develop an engineering response and judgment towards interconnected components. You are only required to identify components and understand the basic process flow. Note: no valves, flanges, fittings are shown on these PFDs. When drawing the piping diagram, we then show the valves, flanges and fittings (we need to consult various other documents as stated in the previous section to obtain the required information, however, this is not required for this course). Pump with inlet and outlet One pump, showing inlet and outlet, and flow direction. P-804 is just a name given to the pump. Two pumps, showing inlet and outlet, with a 3way valve coupling or Tee-section. P-801/2 is just a name given to the pump. Boiler Boiler showing Boiler Feed Water (BFW) in and High Pressure (HP) steam on the exit. Hot air enters at the top (note the arrow direction for line 7) and the cooler air then exits at the bottom. R-801 is just a name given to the boiler used in the PFD. Air Preheater This item heats incoming air for the boiler. Air flows from the left towards the right (note horizontal arrow direction). Steam flows through the zig-zag symbol, where we note this symbol is a heat exchanger (see symbol diagram above). H-801 is just a name given to the air preheater as used in the PFD. Single-line piping This single-line drawing is a piping drawing that shows the size and location of pipes, fittings and valves. The drawing is produced to scale and is readily developed to illustrate layout and fabrication of a piping system. The single-line piping drawing is a piping layout and is an orthographic drawing developed from a varied set of documents. These usually include P&ID, site survey data, equipment location plan, electrical layout, service facilities (water reticulation, sewage, firefighting, drainage, etc.) plan and other such documents. The important aspect is to identify all the existing and planned plant/process/equipment/building components before developing the piping layout. Guidelines by relevant Codes, Standards and Government Regulations applicable to spacing and position requirements among others are important. There may be several iterations of a single-line piping drawing. In this course you will be required to develop a single-line pipe drawing given a basic P&ID diagram or a basic component layout/description which can be illustrated with a system flow diagram. Metrics in Piping and Pipe Specification The tables below illustrate common NPS (nominal pipe size in inches) or DN (diameter nominal in mm). For NPS>12”, the given dimension refers to the OD (outer diameter); whereas NPS≤12”, refers to approximately the ID (inner diameter). NPS (IN) 1/8 3/16 1/4 1/2 1 1 1/4 1 1/2 2 2 1/2 3 DN (mm) 6 7 8 15 25 32 40 50 65 80 NPS (IN) 8 10 12 16 24 28 30 42 36 40 DN (mm) 200 250 300 400 600 700 750 800 900 1000 In this course you can provide piping specification by stating the following information: • • • • • Pipe diameter Pipe length Pipe flow arrows Elevation location of all pipe direction changes in section views Pipe contents and identification number (if given) • • Size and type of valves and fittings (if given) Equipment name and numbers (if given) Example of a ½” stainless-steel pipe to transport water in a reticulation system can be stated as follows: ½” – 4’ - W – SS-100 Where: • • • • • ½” is the pipe diameter 4’ is the pipe length W refers to water, or could even be WM (water mains) SS refers to material (in this case, stainless steel) 100 refers to the system identification number unique to any project. This could also be written as SS-100. Therefore as a suggestion, use the following format for pipe-specification for this course, and depending on the information given: Pipe diameter – Pipe length – Pipe contents – Pipe material – System identification number. A simplified version showing only pipe dimensions is: ½” – 4’ Note that dimensions can also be stated in SI units. Pipe fittings and valves Pipe fittings and valves are generally considered as illustrations unique to a pipe drawing as compared to a PFD or PID. On the pipe drawing (example for a single line), all pipe fittings, valves including welds will be distinguished from each other thereby showing such detail on a pipe drawing. We will consider selected aspects for this course, and these are described in the figure(s) below based largely on the Butt weld (see the following website for socket, threaded and additional items for enrichment: http://www.wermac.org/documents/symbols_iso.html). We will use these symbols when developing or interpreting the pipe drawing. Additional pipe fittings and valve symbols from the Appendix may be added by discretion of the lecturer, keep aware on course communication for this aspect. Pipe connections1 Additional Valves1 1 http://www.wermac.org/documents/symbols_iso.html Common valves1 Flanges1 Piping elevations and sections Pipe elevations or sections are used to define vertical pipe location relative to a common datum; usually taken as Bottom of Pipe (BOP), other reference points are Top of Concrete (TOC) or Top of Steel (TOS). The elevations are defined with respect to pipe centres and the symbol is ℄ (in MS word this is “2104 Alt+x”). ℄ Elevation for each pipe is defined TO TANK EL. is defined with with respect to FDN. EL. 0m. respect to FDN. EL. 0m. ℄ EL. 6m 4”4m 4”1m 4” F2 TO TANK EL. 5m ∴This height is 1m (=6m-5m) Foundation elevation is 1m from 0m datum. Pipe Diameter in “ and length in m. ℄ Elevation defined on the left, and measured from FDN. EL. 0m datum 2” F1 ℄ EL. 1.2m BO TANK. EL. 1m 2”-4m 2” V1 FDN. EL. 0m 2” V2 Item Description Qty. 1 2” Check valve (V1) 1 2 2” Gate Valve (V2) 1 3 2” Threaded Flange (F1) 1 4 4” Threaded Flange (F2) 1 5 Elbow 90⁰ 1 6 2” pipe 4m 7 4” pipe 5m Abbreviation meanings: • • • • TO: Top of Tank BO: Bottom of Tank FDN: Foundation Elevation EL.: Elevation Additional example on single-line piping 2”- 4m 2”- 1m We consider the following PFD shown earlier, and now modified to show a 3-way tee section on the pipe-outlet segment: 2”F2 1/2”F1 2”- 1m 2”- 5m Pump 1/2”- 3m 2” V2 2” V2 1/2” V1 Item Description Qty. 1 1/2” Gate valve (V1) 1 2 1/2” Threaded Flange (F1) 1 2 2” Gate Valve (V2) 2 3 2” Threaded Flange (F2) 1 4 2” Tee Elbow 1 5 2” Elbow 90⁰ 1 6 1/2” pipe 3m 7 2” pipe 11m (add linear dim.) What will be required? • • • • Identify the symbols, fittings, and valves as indicated by the green dot. Re-draw a given single line diagram. Add pipe specification (as per suggested template). Add centre line dimensions. Pipe Isometrics You will recall an Isometric drawing is a three-dimensional representation of an object. The pipe isometric allows elevation and transverse direction changes to be readily communicated using a single drawing. The single line pipe drawing can only represent a projection of the isometric onto a view i.e., Front, Top, and Side view. The single line pipe drawing is an orthographic representation of the pipe isometric. The pipe isometric may represent fittings, valves, dimensions, additional notes and instrumentation. Two examples are shown below. Try to reproduce Figure 1 and Figure 2, show the pipe as a single line isometric, you can include only the symbolic representation of the pipe fittings and valves discussed previously. Choose your own suitable dimensions and scale. Figure 1: Example of a Pipe isometric detail drawing shown as double-line (Madsen) Figure 2: Example of a detailed Pipe isometric shown in Single-Line (Madsen) Angular Pipe Runs Angular pipe runs are calculated using the Pythagoras theorem or suitable trigonometric relationships. Such situations arise when the designer needs to use a pipe bend other than 90°, e.g., a 45°, or 60° pipe bend. Figure 3 shows an example for angular pipe run, can you demonstrate the angular pipe length is 46.7”? The vertical distance is given be difference of the centre-line elevations, you are also given the angle of the pipe bends, 45°. Figure 3: Example to calculate pipe length for an angular run (Madsen) Appendix (For enrichment only. Source Ref. (Madsen)) Common Symbols Pipe Connection/Fittings/Valves Common Valve Actuators Additional Plant and Process Equipment Piping Question 9.1 You have an incomplete diagram of a single-line pipe drawing with additional information given below: • • • • A pump draws water through a 1/2” pipe from an in-line reservoir. The inlet pipe is made of stainless steel and has a total length of 20 m. The pump discharges the water through a 2”stainless steel outlet pipe with a total length of 10 m. A tee section tap-off is located on the same elevation as the outlet pipe. This length is 5 m and is a stainless steel 2” pipe. Vertical difference between pipe inlet and outlet is negligible. Using sensible choices for component dimensions, component spacing, and line thickness, you are required to complete the given drawing using your drawing instruments or CAD: • • • Redraw the given single-line pipe drawing showing: o valves o flanges o elbow and tee connections o flow direction arrows (add this in) Show the pipe specification for the inlet, outlet and tap-off pipes. Insert the pipe specification in the balloons as shown on the drawing. Show the parts list for the pipe fittings only. (Give the Item Number, Description and Quantity) 2”F2 1/2”F1 Pump 2” V2 2” V2 1/2” V1 Figure 4: Incomplete Single-Line Drawing A. Question 9.2 You have an incomplete diagram of a single-line pipe drawing with additional information given below: A pump draws water through a 2” pipe from a reservoir located 3 m below the tank foundation. The inlet pipe is made of stainless steel and has a total length of 10 m. • • The pump discharges the water into a tank through a ½”stainless steel pipe with a total length of 10 m. This pipe terminates 1 m above Top of Tank (TO Tank). Vertical difference between pipe inlet and outlet is negligible. Using sensible choices for component dimensions, component spacing, and line thickness, you are required to complete the given drawing using your drawing instruments or CAD: • • • • Redraw the given single-line pipe drawing showing: o valves o flanges o elbow connections o tank elevations o flow direction arrows (add this in) Show pipe centre line with respect to Bottom of Tank (BO Tank). Show the pipe specification for the inlet and outlet pipes. Insert the pipe specification in the balloons as shown on the drawing. Show the parts list for the pipe fittings only. (Give the Item Number, Description and Quantity) TO TANK. EL. 5m BO TANK. EL. 0m Pump Figure 5: Incomplete Single-Line Drawing B. Question 9.3 You are given three Orthographic Views of a pipe isometric. Redraw these three views using the dimensions given and make use of line projections to understand changes in elevation and transverse directions. Then use the dimensions given to produce an isometric view. The completed isometric view is shown for illustration purposes, your orientation may differ to the view as shown. Figure 6: Orthographic drawing for a pipe isometric