SYMBOLS FOR PIPE LAYOUTS

Pipe layouts are shown through the use of single-line and double-line drawings. These drawings use special sets of symbols to identify the components of piping systems, including pipe, valves, fittings, flanges, and equipment. Figure 23.1 illustrates symbols developed and published by the American Society of Mechanical Engineers for this purpose.

In addition to these symbols, a number of companies have developed their own sets of symbols, both for single-line and double-line drawings. An example of a set of symbols developed by a company is shown in Figure 23.2. Note that the company’s symbols provide for single-line and double-line representations.

The sampling of symbols shown in Figure 23.3 is provided to show that reference to special charts for symbol interpretation will be necessary when fabricating pipe layouts that use company symbols. Such charts are usually available from the company that designs the layout and/or provides the components for the layout. The length of the stud is shown on a detailed drawing.

Special symbols have also been developed to indicate the methods to be used for connecting the compo­nents of a pipe assembly, Figure 23.3. Note that the methods shown apply primarily to single-line drawings.

Single-line drawings are generally used to show pipe layouts for nominal pipe sizes of less than 12", Figure 23.4(a) and (b). However, this practice will vary from company to company. At times, layouts using smaller pipe sizes may be shown as double-line drawings.

FIGURE 23.2 ■ Example of a set of symbols for fittings and flanges developed by a company for use on pipe drawings.

HEAVY DOTS USED TO INDICATE JOINTS ARE TO BE BUTT-WELDED

- SYMBOL FOR INDICATING END OF PIPE

-V

SYMBOL FOR THREADED JOINT

"X" IS THE SYMBOL USED TO INDICATE A BUTT-WELDED JOINT

*—=3

NOTE: DOTS GENERALLY HAVE SUPERCEDED THE "X” TO INDICATE BUTT-WELDED JOINTS.

SOLID, HEAVY LINE REPRESENTS LENGTH OF PIPE (a) CONVENTIONAL SYMBOL FOR INDICATING A THREADED JOINT.

(c) SIMPLIFIED METHOD TO INDICATE A BUTT-WELDED JOINT.

(b) CONVENTIONAL METHOD FOR INDICATING A BUTT-WELDED JOINT.

VARIATION OF SYMBOL USED TO INDICATE END OF PIPE

-В

SYMBOL FOR SOCKET WELDED JOINTS

USE OF BREAKS TO INDICATE POINTS ARE TO BE BUTT-WELDED

E=r

(e) CONVENTIONAL METHOD OF INDICATING SOCKET WELDED JOINTS.

(d) ANOTHER SIMPLIFIED METHOD USED TO INDICATE A BUTT-WELDED JOINT.

FIGURE 23.3 ■ Symbols used on single-line pipe layout drawings to indicate the method to be used to connect joints.

NO. 31

NOTE: TYPE OF FITTING FROM SPECIFIC o° MANUFACTURER'S CATALOG.

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NOTES: USE T-T4" NO. 96-F WELDING RINGS AT ALL BUTT JOINTS. ALL FITTINGS AND PIPE 4" STD. WT. ALL NUMBERS FROM T-T CATALOG NO. 311.

NO. 31

(b) CONVENTIONAL SINGLE-LINE METHOD.

-BREAKS INDICATE LOCATIONS OF WELDS

FIGURE 23.4 ■ Examples of single - line pipe layouts.

(a) CONVENTIONAL SINGLE-LINE METHOD.

NOTE: DOTS ( • ) INDICATE ALL JOINTS TO BE WELDED.

FIGURE 23.5 ■ Double-line pipe layout.

-DETAIL "A'1

Double-line drawings are used for pipe layouts that use large sizes of pipe and fittings (12" and over) and for complex pipe layouts. In the case of complex layouts, the pipe size may be less than 12". A double-line pipe layout may specify several methods of connecting the pipe and fittings, Figure 23.5.

FIGURE 23.6 ■ Preparation of pipe ends for butt - and socket-welded joints.

When pipe and fittings are to be butt welded, the ends are beveled. For joints that are socket welded, the ends are squared, Figure 23.6.

It should be noted that valves and fittings, as a rule, are shown on double-line drawings by the same symbols used for single-line drawings,

Figure 23.7. Simple fittings, such as elbows and tees, are pictorially represented, using either a con­ventional or simplified method of representation.

Double-line drawings may include use of the standard welding symbols to indicate the kinds of welds required for assembling the components of the pipe layout, Figure 23.8(a) and (b).

FIGURE 23.7 ■ Methods for showing fittings and valves on double-line drawings.

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FIGURE 23.8 ■ Double-line representation of pipe layout using conventional welding symbols.

FIGURE 23.10 ■ Methods of representing a pipe layout.

50"

50"

-X-

36"

p— 30” ( —®--------------