APPENDIX O - SAFETY CLASS PIPING SYSTEMS
PURPOSE
This appendix provides guidance for application of Code requirements to safety class items.
SCOPE
The information in this appendix applies to all piping and components designated as safety class.
GENERAL
1) New Safety Class (SC) piping shall comply with all the requirements of ASME B31.3 Category M Fluid Service unless restricted by other fluid service requirements.
2) Modifications and repairs to Safety Class piping shall comply with all the examination and testing requirements of ASME B31.3 Category M Fluid Service unless restricted by other fluid service requirements, except as permitted in Appendix P.
3) A sensitive leak test is not required for Safety Class systems unless the fluid service meets the requirements for a Category M Fluid Service or when imposed by the requirements of the Alternative Leak Test per B31.3 paragraph 345.1c.
4) When a facility has performed component level classification of piping systems only the specific components and portion of the system classified as Safety Class are required to meet the Category M requirements.
PURPOSE
This appendix provides guidance for application of B31.3 requirements to repairs, modifications and maintenance of operating piping systems.
SCOPE
The information in this appendix applies to all piping systems for which ASME B31.3 applies.
GENERAL
Repairs and modifications to existing piping systems shall follow the requirements of the ASME B31.3 Code for materials, design, fabrication and examination. At the Design Authority's option, the three alternatives of Section A, B, or C below are acceptable to address the leak testing of repair and tie-in joints. All repair and modification joints other than the tie-in joints shall meet all the requirements of the Code. Non-welding maintenance shall follow the requirements of the ASME B31.3 Code for materials, design and fabrication. The examination and leak testing requirements for non-welding maintenance shall be as specified by the Design Authority.
Table 1 Requirement Matrix1
Modification Repair Non-Welding Maintenance
Design B31.3 B31.3 B31.3
Materials B31.3 B31.3 B31.3
Fabrication2 B31.3 B31.3 B31.3
Examination B31.3 B31.3 Design Authority3
Leak Testing B31.3 B31.35 Design Authority4
Notes:
1) This Table applies to all functional classifications (SC, SS, ML-1, ML-2, ML-3, etc.)
2) Fabrication refers to all shop or field fabrication, erection, assembly or disassembly related to new installations, modifications, repairs, or non- welding maintenance.
3) Unless restricted by other site or divisional requirements, the Design Authority is to determine the type and extent of examination. Performance of examinations shall be in accordance with site QA requirements.
4) Unless restricted by other site or divisional requirements, the Design Authority is to determine the type and extent of leak testing, if any, commensurate with the risk (likelihood and consequence) of leakage.
5) Also refer to sections A through C.
A REPAIR AND TIE-IN JOINTS THAT ARE CODE LEAK TESTED
Repair joints and tie-in joints in piping systems that are leak tested to the requirements of ASME B31.3 paragraph 345 “Testing” shall meet the following requirements.
1) Repair and tie-in joints shall be examined to the requirements of the Code.
2) When the repair joints and tie-in joints are not included in the random selection of joints to be examined, they shall be treated as a new and separate lot or lots of joints for examination purposes. Examination percentages of other joints (i.e. shop welds) included in the piping system repair or alteration may not be used to reduce the examination requirements of repair or tie-in joints.
B REPAIR JOINTS AND TIE-IN JOINTS THAT ARE IN-SERVICE LEAK TESTED
1) All repair and tie-in joints shall be examined to the requirements of paragraph 335
“Assembly and Erection”.
2) All butt-welded repair and tie-in joints shall be volumetrically examined to the requirements of ASME B31.3. All butt weld repair and tie-in joints shall be designed so they can be volumetrically examined, except as provided in 5.4.3.3. Welded branch connections used as tie-in joints shall meet the requirements of Figure 328.5.4E as being suitable for 100%
radiography. For a normal fluid service the in-process examination alternative permitted in paragraph 341.4.1(b)(1) may be specified on a weld for weld basis if approved by engineering or the inspector. The in-process method shall be supplemented by appropriate nondestructive examination.
3) Socket welded joints are allowed as repair and tie-in welds on sizes up to and including 2 inch pipe. Slip-on flanges are allowed in all pipe sizes. All socket and slip-on repair and tie- in joints shall receive a PT or MT examination of the final completed welds.
4) An in-service leak test shall be performed on repair and tie-in joints per the requirements of ASME B31.3 paragraphs 345.7.1 - 345.7.3 except as noted in C below.
C REPAIR AND TIE-IN JOINTS THAT CAN NOT BE TESTED
Repair and tie-in joints in piping systems that can be neither Code nor In-Service leak tested shall meet the following requirements.
1) Repair and tie-in joints shall be full-penetration butt welds between straight sections of piping of equal diameter and thickness, axially aligned, and of equivalent materials.
2) Repair and tie-in joints shall be volumetrically examined to the requirements of ASME B31.3.
3) When mechanical joints are required to be used for maintenance and tie-in joints and cannot be leak tested, these joints shall be examined to the requirements of paragraph 335
“Assembly and Erection”.
The processing of radioactive fluids is performed in many facilities at LANL. No section of the B31 Code of Pressure Piping addresses radioactive fluids. When starting to address what code is applicable to radioactive fluids, many engineers return to the ASME Boiler and Pressure Vessel Code, Section III, Rules for the Construction of Nuclear Power Plant Components. The scope of Section III is directly applicable to nuclear power systems and does not apply to processing facilities. To address the application of radioactive fluids more directly, an inquiry was sent to the ASME B31 Committee. Interpretation 12-20 clarifying the use of radioactive fluids in processing facilities is provided below:
Question: In accordance with ASME B31.3-1993 Edition, may the owner apply B31.3 to piping containing radioactive fluids in a chemical plant?
Reply: Yes, see the Introduction which states that, "If no section of the code for pressure piping specifically covers the installation, the owner at his discretion may select any section determined to be generally applicable... It should be noted, however, that requirements supplementing the Code Section may be necessary to provide safe piping for the intended application".
Interpretation 12-20 stresses the need for requirements supplementing the Code for radioactive fluid services.
Based on Interpretation 12-20, two issues need to be addressed to apply ASME B31.3 to a radioactive fluid service. First, when will a fluid service be considered radioactive. Second, what are reasonable supplementary requirements to apply. The following definition and requirements are provided to support the use of ASME B31.3 for radioactive fluid processing. The owner and/or the designer may specify additional requirements that are deemed necessary to provide a safe piping system design.
The following definition of a radioactive fluid applies to activities addressed by this guide:
Radioactive Fluid – A fluid with sufficient radioactivity that leakage from a piping system could cause an area to exceed the contamination limits imposed by P121, Chapter 14, Table 14-2.
The following minimum additional requirement should be applied to systems containing radioactive fluids:
1) Radioactive fluids cannot be excluded from the scope of ASME B31.3.
2) Radioactive fluids cannot be classified as Category D fluid service.
Additional requirements supplementing the B31.3 Code may be required to ensure a safe design for radioactive fluid services.