1、PFI Standard ES-2 (Revised December 2013) METHOD OF DIMENSIONING PIPING ASSEMBLIES Prepared by Pipe Fabrication Institute Engineering Committee All PFI Standards are advisory only. There is no agreement to adhere to any PFI Standard and their use by anyone is entirely voluntary. Copyright by PIPE FA
2、BRICATION INSTITUTE Dedicated to Technical Advancements and Standardization in the Pipe Fabrication Industry Since 1913 USA 511 Avenue of Americas, # 601 New York, NY 10011 CANADA 655, 32ndAvenue, # 201 Lachine, QC H8T 3G6 WEB SITE www.pfi-institute.org PFI Standard ES-2 (Revised December 2013) METH
3、OD OF DIMENSIONING PIPING ASSEMBLIES METRIC CONVERSIONS The conversion of quantities between systems of units involves a determination of the number of significant digits to be retained. All conversions depend upon the intended precision of the original quantity and are rounded to the appropriate ac
4、curacy. Pipe sizes together with applicable wall thicknesses are not shown with metric equivalents. The SI (metric) values where included with the customary U.S. values in this Standard are the rounded equivalents of the U.S. values and are for reference only. Metric units were derived utilizing the
5、 following conversion factor: Conversion Factor inches to 25.4 millimeter 1. Scope 1.1 This standard covers the recommended practices for dimensioning piping assemblies in a manner that would enable the fabricator to furnish a product meeting the geometry intended by the design engineer. 2. Dimensio
6、ning 2.1 Piping is normally of a circular cross section. Thus the geometry of a piping system can be fully defined by the location of the centerline axis of the pipe. Terminal points and points of change in direction of the pipe axis are known as working points. Since two points determine a straight
7、 line, it is recommended that the pipe axes be located by means of working points. Two alternate methods of locating working points are suggested in 2.2 and 2.3. 2.2 Fig. 1A illustrates location of the working points along the axis of the pipe by providing information on the length and direction of
8、each consecutive segment of the axis. 2.3 Fig. 1B illustrates dimensioning by means of location of the working points from fixed reference planes, such as from ground elevation, column lines, etc. 2.4 While not necessary for the determination of the pipeline geometry, it is essential that the engine
9、er provide the fabricator with additional information such as: (a) radius of bend (b) type of elbow (c) gasket or other allowances (d) pipe size and wall thickness (e) type of branch connection, such as tee or nozzle (f) location of flanged or field welded joints (g) location of attachments (h) perm
10、issible tolerances (See PFI Std. ES-3) (i) material 3. Fabrication Variables 3.1 In making the piping assemblies, the fabricator takes into account the following factors; root opening, shrinkage and fitting tolerances. 3.2 In order to assure full penetration to the root of a weld, the ends to be joi
11、ned are set up with a small gap between them called root opening. This root opening may vary from 0 to 1/4“ (6.0 mm) depending on the welding technique. PFI Standard ES-2 (Revised December 2013) 3.3 Shrinkage of the weld metal occurs in cooling. This shrinkage varies with welding process, technique,
12、 piping material and pipe wall thickness. On steel the weld shrinkage usually amounts to l/16“ (2.0 mm) to 1/8“ (3.0 mm). Consequently, the fabricator must make allowances for shrinkage (See Paragraph 3.5). 3.4 All standard welding fittings and flanges are subject to tolerances on terminal dimension
13、s (end to end, face to face, or center to end, etc.). The tolerance on overall length of flanges as given in ANSI B16.5, is .06“ (1.5 mm) for sizes up to and including 10“ and .12“ (3.0 mm) for larger sizes. ANSI B16.9 gives tolerances for butt welding fittings. For 90 A complete list of PFI members
14、 and available membership CHARTER MEMBERS CONTRACTOR MEMBERS ASSOCIATE MEMBERS AFFILIATE MEMBERS HONORARY MEMBERS Associate and Affiliate member contributors Walter Sperko Sperko Engineering Services, Inc. Greensboro, NC Thomas Warrelmann Victaulic Company of America Easton, PA Sheryl Michalak Weldi
15、ng Outlets, Inc. Houston, TX PFI Standards and Technical Bulletins are published to serve proven needs of the pipe fabricating industry at the design level and in actual shop operations. Hence, such needs are continually considered and reviewed by the Engineering Committee of the Pipe Fabrication In
16、stitute to provide recommended procedures, which have been demonstrated by collective experiences to fulfill requirements in a manner for Code compliance. However, as the PFI Standards are for minimum requirements the designer or fabricator always has the option of specifying supplementary conditions in the form of requirements beyond the scope of the PFI publications.
