An erection drawing normally includes i overall and principal dimensions in sufficient detail to establish space requirements for installation, operation, and servicing including clearances for opening of doors, removal of plug-in units and travel or rotation of any moving parts including the centres of rotation, angles of elevation and depression , ii interface mounting and mating information e.
The purpose of process flow diagram PFD is generally i to show the plant design basis indicating feedstock, product and main streams flow rates and operating conditions, ii to identify the scope of the process, iii to show graphically the arrangement of major equipment, process lines and main control loops, and iv to show utilities which are used continuously in the process. A PFD normally comprise of but not limited to i all the process lines, utilities and operating conditions essential for material balance and heat and material balance, ii utility flow lines and their types which are used continuously within the battery limits, iii equipment diagrams to be arranged according to process flow, designation, and equipment number, iv simplified control instrumentation pertaining to control valves and the likes to be involved in process flows, v major process analyzers, vi operating conditions around major equipment, vii heat duty for all heat transfer equipment, viii changing process conditions along individual process flow lines, such as flow rates, operating pressure and temperature etc.
Internals of equipment are shown in PFD only if required for a clear understanding of the working of the equipment. It is the primary schematic drawing used for laying out a process control installation. It is a diagram which shows the interconnection of process equipment and the instrumentation used to control the process. Normally a standard set of symbols is used to prepare drawings of processes. During the design stage, the diagram also provides the basis for the development of system control scheme.
It is also vital in enabling development of control and shutdown schemes, safety and regulatory requirements, start-up sequences, and operational understanding. It forms the basis for the live mimic diagrams displayed on graphical user interfaces of industrial control systems such as SCADA and distributed control systems.
Control drawing is that drawing which is used for the control of certain activities. There are usually six categories of control drawing Fig 1 as given below. The first category of control drawing is the procurement control drawing. It provides criteria for performance, acceptance, and identification of supplier items by disclosing the engineering design characteristics required normally for control of interfaces and to ensure repeatability of performance.
It is prepared to specify criteria for i purchased items, ii alterations to purchased items, iii selection from purchased items, iv development and qualification of new items, and v item identification.
It includes i performance requirements to ensure that performance characteristics critical to the intended application are met, ii envelope dimensions to ensure physical interchangeability in using assemblies, iii interface characteristics to ensure functional interchangeability in using assemblies, iv qualification requirements necessary to verify that performance requirements and functional interchangeability, v identification requirements including marking, instructions, lot serialization, etc.
The second category of control drawing is the vendor Item drawing. It provides an engineering description and acceptance criteria for purchased items. It provides sufficient engineering definition for acceptance of interchangeable items within specified limits. It is used to provide engineering requirements for a purchased item. It is not the intent of a vendor item drawing to portray a complete design disclosure.
This drawing discloses sufficient information to ensure identification and re-procurement of interchangeable items. The drawing includes i configuration, ii dimensions of item envelope and their limits, iii mounting and mating dimensions and their limits, iv interface characteristics and their limits, v acceptance criteria, vi performance, maintainability, reliability, environmental, and other functional characteristics, vii schematic, interconnection, or other appropriate diagram to define item function or provide inter-connection information.
The third category of control drawing is the source control drawing. It provides engineering description and acceptance criteria for purchased items which need design activity imposed qualification testing and exclusively provide performance, installation, and interchangeability characteristics specifically required for the critical applications. It establishes item identification for the controlled items.
It is used to provide a means of establishing engineering requirements for the selection, qualification testing, and acquisition of an item, and documentation to assure interchangeability of specified items.
It includes i configuration, ii dimensions of item envelope and their limits, iii mounting and mating dimensions and their limits, iv interface characteristics and their limits, v acceptance criteria, vi qualification test requirements, viii performance, maintainability, reliability, environmental, and other functional characteristics, ix schematic, interconnection, or other appropriate diagram to define item function or provide interconnection information, and x identification requirements including marking instructions.
The fourth category of control drawing is the design control drawing. It discloses the basic technical information and performance requirements necessary for a contractor to complete the detailed design required to develop and produce an item. The drawing in itself does not provide complete design for which a detailed design drawing is needed. It includes those details which are necessary to develop the detail design of the item such as i configuration, mounting, mating, and other necessary dimensions, ii performance, installation, reliability, and interchangeability requirements, iii test requirements, iv schematic, connection, or other appropriate diagram if electrical, electronic or other circuitry is involved , v the mating connections, their location, and a connection diagram, and vi reference to other documentation.
The fifth category of control drawing is the interface control drawing. It depicts physical and functional interfaces of related or co-functioning items. It does not establish item identification. This drawing controls one or more of the interfaces such as mechanical, electrical, interconnections, configuration, installation, operational sequence requirements, and system switching etc.
The drawing includes i configuration and interface dimensional data applicable to the envelope, mounting, and interconnection of the related items, ii complete interface engineering requirements mechanical, electrical, electronic, hydraulic, and pneumatic etc.
The sixth category of control drawing is the identification cross reference drawing. It is an administrative type drawing which assigns unique identifiers which are compatible with automated data processing systems, item identification specifications, and provides a cross reference to the original incompatible identifier. It does not specify any engineering or design requirements beyond those already contained in the drawings, and specification etc.
Fig 1 Categories of control drawing. The mechanical schematic diagram depicts mechanical and other functional operation, structural loading, fluid circuitry, or other functions using appropriate standard symbols and connecting lines.
It is a design information drawing. It is made when operating principles cannot be readily determined from a study of the assembly drawing. It illustrates design information for i hydraulic or pneumatic systems, ii complex mechanical systems complex arrangement of gears, clutches, linkages, and cams, etc. A mechanical schematic diagram symbolically depicts elements of the unit, assembly, or system involved and displays the relation of each element by interconnecting lines.
The elements are usually arranged functionally or they are actually arranged as in their assembly or installed position. Loading diagrams for hoists and slings, flow diagrams for hydraulic or pneumatic control valves, and simple unit flow diagrams, etc.
Hydraulic or pneumatic system diagrams, complicated rigging diagrams, and complex mechanical function diagrams etc.
Civil drawing is used for specifying the shape and position of the civil foundation. It typically includes the information such as i setting out dimensions for the concrete structure on site, ii plans, sections and elevations showing layout, dimensions and levels of all concrete members, iii location of all holes, chases, pockets, fixings and other items affecting the concreting work, iv notes on specifications, finishes and all cross-references affecting the construction.
The drawing provides the detailer with the layout and sectional information required to specify the length, shape and number of each type of reinforcing bar. Reinforcement drawing is part of civil drawing. It fully describes and locates all reinforcements in relation to the finished surface of the concrete and to any holes or fixings.
A structural drawing is a type of technical drawing which depicts the design and working drawings for building as well as technological structures. It includes a plan or set of plans for the building or other structures. Structural drawings are primarily concerned with the load-carrying members of a structure.
They outline the size and types of materials to be used, as well as the general demands for connections. They do not address architectural details like surface finishes, partition walls, or mechanical systems. The structural drawings guide in detailing, fabricating, and installing parts of the structure. Structural drawings are of three types namely i design drawings, ii detail fabricating drawings, and iii erection drawings.
Structural detail fabrication drawing includes all the details needed for the fabrication of the structures. What drawings packages do people use for technical drawings? How do math and science interrelate? How do engineers use drawings? Are personal drawings a business expense?
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Still have questions? Find more answers. Previously Viewed. This eliminates the addition of measurement or machining inaccuracies that would come from "chain" or "series" dimensioning. Notice how the dimensions originate on the datum surfaces. We chose one datum surface in figure 27, and another in figure As long as we are consistent, it makes no difference. We are just showing the top view. In figure 29 we have shown a hole that we have chosen to dimension on the left side of the object.
When the left side of the block is "radiuses" as in figure 30, we break our rule that we should not duplicate dimensions. The total length is known because the radius of the curve on the left side is given. Then, for clarity, we add the overall length of 60 and we note that it is a reference REF dimension.
This means that it is not really required. Somewhere on the paper, usually the bottom, there should be placed information on what measuring system is being used e. This drawing is symmetric about the horizontal centerline.
Centerlines chain-dotted are used for symmetric objects, and also for the center of circles and holes. We can dimension directly to the centerline, as in figure In some cases this method can be clearer than just dimensioning between surfaces. Don't show me this again. This is one of over 2, courses on OCW. Explore materials for this course in the pages linked along the left. No enrollment or registration. Freely browse and use OCW materials at your own pace.
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Design Handbook: Engineering Drawing and Sketching. More Dimensioning Where to Put Dimensions Introduction One of the best ways to communicate one's ideas is through some form of picture or drawing. Figure 1 - A Machined Block. Isometric Drawing The representation of the object in figure 2 is called an isometric drawing.
Figure 2 - An Isometric Drawing. Orthographic or Multiview Drawing Imagine that you have an object suspended by transparent threads inside a glass box, as in figure 3. Figure 3 - The block suspended in a glass box. Figure 4 - The creation of an orthographic multiview drawing. Figure 5 - A multiview drawing and its explanation. Figure 6 - An object needing only two orthogonal views. Dimensioning Figure 7 - An isometric view with dimensions. Sectioning There are many times when the interior details of an object cannot be seen from the outside figure 8.
Figure 8 - An isometric drawing that does not show all details. Imagine slicing the object in the middle figure 9 : Figure 9 - "Sectioning" an object. Figure 10 - Sectioning the object in figure 8. Not every line on an engineering drawing is equal. The different options make it possible to show both visible and hidden edges of a part, centre lines, etc. The most common is a continuous line, also known as a drawing line. This represents the physical boundaries of an object.
Put simply, these lines are for drawing the objects. The line thickness varies — the outer contour uses thicker lines and inner lines are thinner. Hidden lines can show something that would not be otherwise visible on the drawings.
For example, hidden lines may show the length of an internal step in a turned part without using a section or a cutout view we explain both later. Centre lines are used to show hole and the symmetric properties of parts. Showing symmetricity can reduce the number of dimensions and make the drawing more eye-pleasing, thus easier to read.
Extension lines annotate what is being measured. The dimension line has two arrowheads between the extension lines and the measurement on top or inside, like in the image above the line. Break lines indicate that a view has been broken. If you have a part that is mm long and 10 mm wide with symmetric properties, using a break-out makes gives all the info without using as much space.
While a good way for giving information to people, CNC machines need full views in order to cut the parts. Otherwise, the manufacturing engineer has to reconstruct the whole part from the measurements.
When using a cutout view, the cutting plane lines show the trajectory of the cutout. Here you can see that the A-A cutting line brings both types of holes into the view. Each serves a certain purpose. Bear in mind that adding views should follow the same logic as dimensioning — include as little as possible and as much as necessary.
A tip for good engineering practice — only include a view if it contributes to the overall understanding of the design. Isometric drawings show parts as three-dimensional.
All the vertical lines stay vertical compared to front view and otherwise parallel lines are shown on a degree angle. The lines that are vertical and parallel are in their true length. Which means you can use a ruler and the scaling of the drawing to easily measure the length straight from a paper drawing, for example.
The same does not apply to angled lines. It is important to distinguish the isometric view from a perspective view. A perspective view is an artistic one that represents an object as it seems to the eye. Engineers stay true to the dimensions rather than optical illusions. This is the bread and butter of an engineering drawing.
An orthographic view or orthographic projection is a way of representing a 3D object in 2 dimensions. Thus, a 2D view has to convey everything necessary for part production. This kind of representation allows avoiding any kind of distortion of lengths.
The most common way to communicate all the information is by using three different views in a multiview drawing:. It may be possible that some additional views are necessary to show all the info. But again, less is more.
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