PFI ES-16-2013 ACCESS HOLES BOSSES AND PLUGS FOR RADIOGRAPHIC INSPECTION OF PIPE WELDS.pdf

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1、PFI Standard ES-16 |Denotes Revision (Revised December 2013) ACCESS HOLES, BOSSES AND PLUGS FOR RADIOGRAPHIC INSPECTION OF PIPE WELDS 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

2、 anyone is entirely voluntary. Copyright by PIPE FABRICATION 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 http:/www.pfi-ins

3、titute.orgPFI Standard ES-16 |Denotes Revision (Revised December 2013) ACCESS HOLES, BOSSES AND PLUGS FOR RADIOGRAPHIC INSPECTION OF PIPE WELDS METRIC CONVERSIONS The conversion of quantities between systems of units involves a determination of the number of significant digits to be retained. All co

4、nversions depend upon the intended precision of the original quantity and are rounded to the appropriate accuracy. Pipe sizes together with applicable wall thickness are not shown with metric equivalents. The SI (metric) values where included with the customary U.S. values in this Standard are the r

5、ounded equivalents of the U.S. values and are for reference only. Metric units were derived utilizing the following conversion factor: Conversion Factor _ _ inches to 25.4 millimeter Foreword Previous versions of this standard provided a simple method for plugging the hole required for inserting a g

6、amma source into a pipe to allow panoramic radiographic exposures. The original radiographic plug designs, (Figures 1 through 7), have been used extensively, providing many years of reliable service, and these designs have not changed. Experience has demonstrated that their time to failure is compar

7、able to the piping systems they were installed in when the systems have not experienced long term creep damage. Creep is plastic deformation under load that is dependent on stress, time, temperature, and material. PFI had been alerted to occurrences of plug seal weld failures where the piping system

8、 had experienced significant creep damage. PFI reviewed the reported failures and initiated a research project sponsored by ASME and PFI and published as STP-PT-050. The initial study used finite element creep simulation to examine a plug geometry compliant with Figures 2 through 5 of this standard

9、and then compared the results with a bored out, or thimble-shaped plug used by some high temperature component manufacturers, using a similar simulation, The results indicate there are no substantial benefits, and possibly a detrimental impact, to using the bored out plugs. However, the studys resul

10、ts also indicated that after prolonged service, for both types of plugs, the stresses initially carried by the plugs threads are increasingly carried by the circumferential plug seal welds. In addition to thread corrosion, creep stretches the hole in which the plug is located, possibly increasing st

11、ress on the circumferential plug seal weld. This research was consistent with reported failures of radiographic access port plugs due to creep. A subsequent study was initiated to evaluate the use of an integrally reinforced boss compliant with Figures 8 through 11. The analysis considered grade P91

12、 pipe at temperatures of 900 F and 1150 F using a grade F22 boss in an effort to avoid PWHT of the plug seal weld after radiographic examination. The boss geometry was designed so that the surface that the plug seal weld attaches to meets the B31.1 thickness exemption for PWHT. The analysis confirme

13、d that this geometry will yield a life expectancy comparable to the pipe itself. The analysis also revealed a decrease in service life at 1150 F due to the dissimilar material interface. For this reason, it is recommended that the use of grade F22 boss on a P91 header be limited to 1100 F. No other

14、dissimilar material combinations were considered in this analysis. PFI Standard ES-16 |Denotes Revision (Revised December 2013) 1. Scope This standard covers recommendations for access holes, bosses and plugs for the radiographic inspection of pipe butt welds where the radiographic source is located

15、 on the inside of the pipe. Radiographic access ports should not be used unless necessary. Since routine double-wall radiography is capable of making high-quality radiographs on pipe that is 5/8” inch thick or less and NPS 16” inch and smaller, radiographic access ports are unnecessary and should no

16、t be specified. When digital radiography will be used, greater thickness and larger sizes of pipe may be radiographed without resorting to access ports. Figures 1 through 7 are recommended for applications where temperatures are below the creep range. For RT bosses used in piping systems that may op

17、erate within the creep range, alternative bosses, as provided in Sections 6, 7 A complete list of PFI members and available membership CHARTER MEMBERS CONTRACTOR MEMBERS ASSOCIATE MEMBERS AFFILIATE MEMBERS HONORARY MEMBERS Associate and Affiliate member contributors Walter Sperko Sperko Engineering

18、Services, Inc. Greensboro, NC Thomas Warrelmann Victaulic Company of America Easton, PA Sheryl Michalak Welding 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. Henc

19、e, such needs are continually considered and reviewed by the Engineering Committee of the Pipe Fabrication Institute 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.