ASME B1.20.2M-2006 pdf download.Pipe Threads, 60 deg, General Purpose
1 SCOPE This Standard specifies the designations, dimensions, and tolerances and establishes a verification system for 60 deg included angle pipe threads. It is applicable for general purpose pipe and fitting connections. Where pressure-tight joints are required, it is intended that taper pipe threads conforming to this Standard be made up wrench-tight with a sealant. To prevent galling on certain piping materials such as stainless steel, the seal- ant should contain a lubricant. Internal parallel (straight) pipe threads, series NPSC, are used with external taper pipe threads, series NPT. Internal taper pipe threads, series NPT, are used with external taper pipe threads, series NPT. 2 REFERENCE AND SYMBOLS 2.1 Reference Standard The following publication is referenced in this Stan- dard. The latest edition shall apply. ASME B1.20.1, Pipe Threads, General Purpose (Inch) Publisher: The American Society of Mechanical Engineers (ASME), Three Park Avenue, New York, NY 10016-5900; Order Department: 22 Law Drive, P.O. Box 2300, Fairfield, NJ 07007-2300 2.2 Symbols The following symbols are used (see Fig. 1): D p outside diameter of pipe E 0 p basic pitch diameter at small end of external thread (or end of pipe) E 1 p basic pitch diameter at plane of hand-tight engagement length (L 1 ), external thread, large end of internal thread E 2 p basic pitch diameter at plane of effective thread length (L 2 ), external thread E 3 p basic pitch diameter at plane of wrench-tight engagement E 5 p basic pitch diameter at L 5 K 0 p basic minor diameter at small end of external thread (or end of pipe) L 1 p length of hand-tight engagement between internal and external threads L 2 p length of effective thread, external thread L 3 p length of thread beyond L 1 allowing wrench-tight engagement, internal thread; also wrench makeup
3 TAPER PIPE THREAD FORM 3.1 Thread Profile The form of thread profile specified in this Standard shall be known as the Standard Taper Pipe Thread Form. The relations as specified herein for form of thread and general notation are shown in Fig. 2. 3.2 Angle of Thread The angle between the sides of the thread is 60 deg when measured in an axial plane. The line bisecting this angle is perpendicular to the axis. 3.3 Truncation and Thread Height The height, H, of the sharp V thread is H p 0,866025P where P p pitch of thread The basic maximum height of the truncated thread, h, (see Fig. 2) is based on factors entering into the manufac- ture of cutting tools and the making of tight joints. Maximum h p 0,800000P The crest and root of pipe threads are truncated a minimum of 0,033000P. The maximum depth of trunca- tion for the crest and root of these pipe threads will be found in Table 1. The crest and roots of external and internal threads may be truncated either parallel to the pitch line or parallel to the axis. The illustration in Fig. 2, giving a sectional view of this standard thread form, represents the truncated thread form by a straight line. However, when closely examined, thecrests and roots ofcommerciallymanufac- tured pipe threads appear slightly rounded. When crests and roots of threading tools or chasers lie within the limits shown in Table 1, the pipe threads of products produced by such means are acceptable on the basis of in-process control.
4 SPECIFICATIONS FOR GENERAL PURPOSE TAPER PIPE THREADS, NPT 4.1 Taper Pipe Threads, NPT NPT threads made in accordance with these specifica- tions consist of an external taper and an internal taper thread, to form the normal type of joint having general application on pipe and fittings. See Fig. 3. NPT taper pipe threads are intended to be made up wrench-tight and with a sealant whenever a pressure-tight joint is required. Sealing is affected by out-of-roundness, which is pos- sible between the wrench-tight mated parts in final assembly. This will vary depending on the method for producing the thread in conjunction with the elasticity and/or ductility of the mating parts and the resultant conformance at final assembly. 4.1.1 Thread Designation. NPT taper pipe thread designation shall consist of the following sequence: nominal pipe size; dash; number ofthreads per 25,4 mm; and “NPT.” If the thread is left-handed, add “-LH.” Right-handed threads require no special designation. EXAMPLE: 1 ⁄ 4 -18 NPT 1 ⁄ 4 -18 NPT-LH NOTE: Each letter in the symbol, NPT, has a definite significance as follows: N p National (American) standard, P p Pipe, T p Taper. 4.1.2 Thread Dimensions. Basic dimensions are specified in Table 2. See para. 3.1 for profile. 4.1.3 Taper of Thread. The taper of the thread is 1 in 16 measured on the diameter and along the axis. 4.1.4 Engagement Between External and Internal Taper Threads. The normal length of engagement between external and internal taper threads when screwed together hand-tight is shown in Columns 6 and 7 of Table 2. This length is controlled by the construction and use of the gauges. It is recognized that in special applications, such as flanges for high-pressure work, longer thread engagement is used, in which case the pitch diameter (dimension E 1 in Table 2) is maintained and the pitch diameter, E 0 , at the end of the pipe is proportionately smaller.