Detail Drawing

Communication for Engineers

Anthony Johnson B.Sc., M.I.Mech.E, C.Eng, FHEA , Andrew Gibson B.Sc., CIM, MIEx , in Sustainability in Engineering Design, 2014

5.5.4 Two-dimensional modeling

Two-D modeling is a modern term given to the production of two-dimensional drawings. Historically, 2-D drawings represented every component, every subassembly, and the general assembly. A 2-D detail drawing has to be as technically accurate as the component it represents. The technique of drafting has grown, by necessity, to be a very precise method of describing the shape and size of components. It is subject to precise standards such as British Standards BS8888 or the American Society of Mechanical Engineers (ASME) Y14.2, Y14.3, and Y14.5.

5.5.4.1 Detail drawings

Detail drawings, sometimes called manufacturing drawings, usually show a single component and give all the information necessary for the manufacture of that component. The items these drawings should specify are:

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The form or shape of the component

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Full dimensions, tolerances, and surface finish

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Specific material designation, heat treatment, and the like

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Machining instructions and processes

5.5.4.2 Assembly and subassembly drawings

Assembly and subassembly drawings are essentially the same thing. However, an assembly drawing is of a discrete product, such as a pneumatic bollard. A subassembly is an assembly of parts, such as those in an internal combustion engine, which are destined to be part of a much larger assembly, such as a passenger vehicle.

An assembly drawing shows an assembly of parts and specifies how the whole component is assembled. The drawing should show the finished product with all the parts assembled in their correct relative positions. This is done by producing the drawing in such a way as to show how adjacent parts fit together. Sometimes an assembly procedure is stated. Certainly assembly instructions such as "Grease shaft before applying seals" should be stated on the drawing, as should other similar instructions. It is beneficial to add overall size dimensions and perhaps specify the position of parts relative to some datum.

5.5.4.3 General assembly drawings

A complicated product such as a passenger vehicle is made up of several subassemblies, such as engine, the vehicle body, seats, suspension, and the like. The general assembly drawing is an assembly of all the subassemblies, showing their location within the overall product.

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Deliverables

Richard Beale , Paul Bowers , in The Planning Guide to Piping Design (Second Edition), 2018

4.2.15.1.4 Vendor drawings

Vendor drawings are the detail drawings provided to the engineering company for approval by an external supplier of purchased equipment. They are used by the external supplier for the fabrication of this equipment. These take the form of such items as pumps, vessels, tanks, exchangers, specialty items, and instruments. They can also be complete skidded units such as compressors. Generally speaking, the external supplier will ship these items to the field or to a module fabrication shop to be installed by others. The installer requires copies of the vendor drawings in order to cost and plan the execution of the installation.

Vendor drawings are issued as a listed attachment to the EWP. A cover sheet and a drawing index are not required.

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Nuts, bolts, screws, and washers

Colin H. Simmons , ... Neil Phelps , in Manual of Engineering Drawing (Fifth Edition), 2020

Drawing nuts and bolts

It is often necessary to draw nuts and bolts, and a quick and easy method is required to produce a satisfactory result.

Nuts and bolts are not normally drawn on detail drawings unless they are of a special type. They are shown on assembly drawings and, provided they are standard stock sizes, are called up in parts lists and schedules. A description of the head, the thread and the length are generally sufficient. Templates are available for drawing nuts and bolts and can be recommended for their time saving advantages.

It is conventional drawing practice to show, as first choice, nuts and bolts in the across corners position if a single view only is illustrated since this is instantly recognizable.

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Workholding devices

Peter Scallan , in Process Planning, 2003

7.7.4 Design and construction

Once having formulated the final solution, it must be documented in the form of tool drawings. These will be detail drawings for all the component parts of the jig/fixture and an assembly or arrangement drawing depending on the complexity of the tool. In producing the tool drawings, a number of practices and methods are followed. The first of these is that the component is drawn first, usually in red ink, and the jig/fixture is then designed round this to suit the component and the sequence of operations. Another common practice is to employ third angle projection for tooling drawings. As stated in Chapter 2, this is the system of orthographic projection commonly used in the North American continent as opposed to first angle projection, which is more commonly used in the United Kingdom and Europe. Finally, in cases where dimensional information is included, all numbers are written horizontally to allow them to be read without turning the drawing.

The detail and assembly/arrangement drawings are used to manufacture the jig/fixture. Various construction methods and materials are used. For example, jigs and fixtures may consist of cast components, fabricated parts from plate and/or machined parts. Many of these parts may be bought in as standard parts from suppliers, the use of which is explained further in Section 7.11. The size and shape of the workholder and the workpiece will be the primary factors in deciding the construction method. The time in which the jig/fixture must be designed and manufactured will also influence the construction method employed.

Once constructed, the jig/fixture must be evaluated to make sure it performs the function for which it is designed. There are three stages to this evaluation. The first is to check the manufactured jig/fixture against the drawings to make sure it complies with these. Once satisfied that this is the case, the second stage is producing a test run of parts. The test parts will then be carefully inspected to ensure that they also comply with drawing specifications. The third and final stage of this evaluation is to ensure that the tool can be operated safely and easily.

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Pipe Supports

Alireza Bahadori PhD, CEng, MIChemE, CPEng, MIEAust, RPEQ , in Oil and Gas Pipelines and Piping Systems, 2017

6.9.1 Rod Hangers

Rod hangers, either rigid or spring type, are adjustable vertical assemblies consisting of structural attachment, hanger rod (with or without intermediate components), and pipe attachment.

Spring assemblies should be shipped to the job site with the springs compressed in the installed position as indicated on the pipe support detail drawing and/or requisition. They should have caution tags attached that warn that the spring locks must be removed before the line is put in service. Additionally, the spring supports should have the marks "C" or "H" on the casing load indication scale:

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Mark "C" indicates the cold position of the spring when the line is at ambient temperature but filled with its actual service fluid. For tank lines filled with the actual service fluid, it indicates the position when the tank is empty and has zero settlement.

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Mark "H" indicates the operation positions of the spring. For tank lines, it indicates the position when the tank is filled and has settled.

Spring supports should be installed with the spring locks in place. These spring locking plates or pins should not be removed before hydrostatic testing and insulation of the piping system is completed.

Normally, all construction aids such as spring locks, temporary supports, welding tracks, etc., should be removed prior to commissioning. However, when the spring force on the empty line will cause possible damage to connected vulnerable equipment, the spring locks should remain in position until the line is filled with the actual service fluid.

The relevant support and support drawing should bear the warning "Lock Against Empty Conditions" and the locks should be attached with the spring support during operation.

Hanger rods for lines subject to expansion/contraction of more than 75   mm should be set out of plumb, equal to half of the calculated travel of the pipe at the point of support, in the opposite direction to the travel as indicated on the support detail drawing, the piping arrangement drawing, and/or the isometric drawing.

Guides may be sliding, rolling, or others.

Saddles or pipe shoes should be attached to piping to prevent damage to insulation.

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The Tools of the Design Process and Management of Design

Anthony Johnson B.Sc., M.I.Mech.E, C.Eng, FHEA , Andrew Gibson B.Sc., CIM, MIEx , in Sustainability in Engineering Design, 2014

4.2.7.5 Detail design

The detail design phase defines the complete specification of the geometry, materials, and tolerances of all the parts through the provision of detail drawings, assembly drawings, and general assembly drawings. It also includes the specification of all the bought-out parts complete with preferred suppliers and component designations. The result of this phase is the complete and precise physical description of all the parts in the product. These drawings can then be issued to the manufacturing function for precise manufacture and assembly.

The detail drawings require an index in order to be understood and coordinated. Along with the detail drawings, therefore, there should be a general parts list, which will act as a "map" and precisely instruct the manufacturing function to group components into assemblies and, further, assemblies into the full product. Figure 4.5 shows a portion of a typical parts list, which lists all the parts along with raw material sizes and specifications. It should be noted that this particular parts list shows elements of three subassemblies.

Figure 4.5. A Typical Parts List Showing Elements of Three Subassemblies.

The detail design phase takes the concept design and applies it to the material components and, in effect, plans the manufacture and assembly of the product. During this process, the designers consider the selection of materials, manufacturing techniques, machine tools, and processes such as forging, injection molding, and casting. Further processes such as chromium plating and painting are added to the specification.

It must be emphasized here that every single component and process required to complete the product and which, therefore, adds cost to the product requires a detailed specification at this stage.

The detail design often relates to the product, but once the product has been defined precisely in terms of technical drawings, other manufacturing elements may be pursued such as specialist machine tools, jigs, and other specialist manufacturing equipment.

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Detailed Engineering and Design for Natural Gas Processing Projects

Alireza Bahadori Ph.D. , in Natural Gas Processing, 2014

15.4.5 Vessels, towers, reactors, and storage tanks

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Establish specific job Specifications for towers, pressure vessels, and storage tanks.

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Design each vessel (reactors, towers, storage tanks, etc.) and prepare detail drawings showing wall thickness, heads, shells, nozzles, supports, internals including number and locations of caps/valves, risers, baffles, weir supports, down-flow section, platform clips, insulation clips and angles, etc. in sufficient details to permit vendors to prepare shop details.

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Check Vendor's drawings for conformance with Specifications.

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Compile Vendor information on the drawings, data sheets, and Specifications.

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Finalize vessel drawings with orientation and lugs.

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Check all drawings including vendor's drawings to be virtually complete and issue for AFC.

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Perform checks for:

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Vessel foundation drawings.

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Drawings for steel work and platform supporting vessels.

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Nozzle sizes and location/orientation.

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Supply all other services required for vessel, tower, reactor, and storage tank works.

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Supply all other services as may be required to complete the above.

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Contracts and Specifications

Ken Taylor , in Plant Engineer's Handbook, 2001

(b) Technical Clauses

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Scope – general description of the works.

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Regulations – a general list of regulations, which apply to the particular type of work to be performed.

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Drawings – Details of drawings and manuals, which the contractor shall supply to other parties (e.g. building work, drawings and working drawings, and a description of details to be supplied).

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Site visits – Invitation to contractor to visit site to see for himself any possible site problems. A disclaimer against extras in the event that the contractor does not appreciate obvious site problems.

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Tests and commissioning – Details of any specific tests required, and commissioning format, and who is to witness and reports to be submitted.

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Drawing layouts and simplified methods

Colin H. Simmons , ... Neil Phelps , in Manual of Engineering Drawing (Fifth Edition), 2020

Simplified drawings

Simplified draughting conventions have been devised to reduce the time spent drawing and detailing symmetrical components and repeated parts. Fig. 9.7 shows a gasket which is symmetrical about the horizontal center line. A detail drawing indicating the line of symmetry and half of the gasket is shown in Fig. 9.8, and this is sufficiently clear for the part to be manufactured.

Fig. 9.7. Gasket plan view.

Fig. 9.8. Gasket, half detailed along line of symmetry.

If both halves are similar except for a small detail, then the half which contains the exception is shown with an explanatory note to that effect, and a typical example is illustrated in Fig. 9.9.

Fig. 9.9. When dimensioning add drawing note 'slot on one side only'.

A joint-ring is shown in Fig. 9.10, which is symmetrical about two axes of symmetry. Both axes are shown in detail, and a quarter view of the joint-ring is sufficient for the part to be made.

Fig. 9.10. Joint ring, quarter view along lines of symmetry.

The practice referred to above is not restricted to flat thin components, and Fig. 9.11 gives a typical detail of a straight lever with a central pivot in part section. Half the lever is shown, since the component is symmetrical, and a partial view is added and drawn to an enlarged scale to clarify the shape of the boss and leave an adequate space for dimensioning.

Fig. 9.11. Part of a lever detail drawing symmetrical about the horizontal axis.

Repeated information also need not be drawn in full; for example, to detail the peg-board in Fig. 9.12 all that is required is to draw one hole, quoting its size and fixing the centers of all the others.

Fig. 9.12. Simplified indication of a pattern of holes.

Similarly Fig. 9.13 shows a gauze filter. Rather than draw the gauze over the complete surface area, only a small portion is sufficient to indicate the type of pattern required.

Fig. 9.13. Partial detailing of gauze.

Knurled screws are shown in Fig. 9.14 to illustrate the accepted conventions for straight and diamond knurling.

Fig. 9.14. Detailing of straight and diamond knurling.

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