An ISO symbol used to represent a weld requirement consists of an arrow line, a multiple reference line, and the appropriate welding symbol or symbols, Figure 26.1. The method for representing a symbol with the use of a multiple reference line is illustrated in Figure 26.2. For symmetrical welds, a single continuous reference line is […]

International Standard Symbols for Welding

Symbol Designation INTRODUCTION TO ISO SYMBOLOGY In addition to American Welding Society (AWS) weld symbols, a set of weld symbols has been developed for international use, identified as “International Standard Symbols for Welding.” These symbols (often referred to as ISO symbols) have been approved by the International Organi­zation of Standardization and are found in the […]


Type of Test Symbol Acoustical test AET Electromagnetic ET Leak LT Magnetic particle MT Neutron radiographic NRT Penetrant PT Proof PRT Radiographic RT Ultrasonic UT Visual VT TABLE 25.1 ■ Nondestructive examination symbols. Note: Each symbol ends with the letter “T.” Nondestructive testing symbols are used to indicate the type of test or tests the […]

Inspection and Testing

OVERVIEW OF COMMON INSPECTION AND TESTING PRACTICES The primary aim of any inspection or testing program is to ensure that governing codes, standards, and specifications are followed, and that weld quality meets design standards. In addition, the weld must satisfy the operating conditions to which the weldment will be subjected. To meet these goals, the […]

Graph paper is provided at the end of this review for your use

1. Explain the significance of the following symbols: a. 0 ____________________________________ b. [_____________________________ ] c. 7. Show the variations for dual dimensioning by means of the bracket method. Use 5.750" and its millimeter equivalent (146.05) to illustrate these variations. Include dimension lines in showing the variations. 8. Fill in the missing dimensions on the following […]

Dual Dimensioning

Dual dimensioning is the use of dimensions in both the U. S. Customary (inch) and SI (metric) systems of measurement on drawings. This dimensioning technique is being used by many manufacturers during the transition period from the U. S. Customary (inch) system of measurement to the metric system. Manufacturers who market their products to international […]


The runs of pipe on a pipe layout are shown with­out any indication of pipe sizes. This is also true for fittings and valves. Dimensioning for such components is accomplished by the addition of specifications and notes to the drawings. How­ever, length, height, and location dimensions are shown on the drawing. Location dimensions are applied […]

Pipe-Welding Symbols

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 […]


FIGURE 22.6 ■ Pipe thread designation. Dimensioning data for American Standard Pipe Threads is applied in the same form to both metric and nonmetric drawings. There are two types of designations for this thread: National Pipe Taper (NPT) and National Pipe Straight (NPS). The NPT thread is a tapered thread with a taper of 0.75" […]


Screw thread designations on metric drawings are preferably shown in either ISO unified inch or ISO metric sizes. ISO is the abbreviation for International Organization for Standardization, which is concerned with establishing standards for industry worldwide. (See Unit 26 for more information.) ISO has recommended certain of the American screw thread sizes for use with […]