Ask The Engineer
Paul Coco
Senior Engineer, HSB Codes and Standards
Pressure Points Newsletter - March 2025
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Question
Regarding whether gaskets are classified as Safety Related/Code, is there an official document, statement from the NRC, or code reference that explicitly excludes gaskets from being classified as Safety Related/Code?
Answer
Gaskets are in fact outside the scope of the code in referencing ASME Code, Section III paragraphs NX*-2121(b) {where NX refers to Subsections NB, NCD, and NE}, which state:
(b) The requirements of this Article do not apply to materials used for items not associated with the pressure-retaining function of a component, such as shafts, stems, trim, spray nozzles, bearings, bushings, springs, wear plates, seals, packing, gaskets, valve seats, ceramic insulating materials, and special alloys used as seal materials in electrical penetration assemblies.
However, a common misconception is that this statement fully exempts such materials from all ASME Section III requirements. In reality, it only pertains to the specific Article in question (NX-2000). Various sections of the ASME Code address gaskets within the context of design, particularly as integral components of bolted flange joints, which are considered pressure-retaining assemblies.
For example, the qualification of flange joints, including gaskets, is detailed in NX-3600. While gaskets themselves are not classified as pressure-retaining materials under ASME Section III, their role in pressure-retaining assemblies makes them indirectly subject to design and performance criteria. Gasket seating loads and other parameters must still be calculated according to ASME Code requirements, even if the gasket material itself is not governed.
From the NRC’s perspective, while gaskets may not be classified as pressure boundary materials, they play a critical role in maintaining the integrity of pressure-retaining assemblies. If a gasket failure could compromise a safety function, it should be addressed with the same rigor as other safety-related components.
In cases requiring commercial-grade dedication, the critical characteristics of the gasket would focus on its performance parameters, ensuring it meets the loading and operational conditions outlined in the design calculations.
About the author
Paul Coco | Senior Engineer, HSB Codes and Standards | paul_coco@hsb.com
Paul joined HSB in January 2014. He is a graduate of the United States Naval Academy where he earned a Bachelor of Science in aeronautical engineering. Paul also holds a Master of Engineering Management and a Master of Science in Mechanical Engineering. He served in the U.S. Navy from 2002 through 2010. During this time, one of Paul’s many responsibilities included the role of Reactor Mechanical Division Officer and Training Officer, where he was responsible for the safe operation of a nuclear power plant onboard a Nuclear-Powered Aircraft Carrier. From 2007 through 2010, Paul joined the Mechanical Engineering department at the U.S. Naval Academy, where he taught Applied Engineering Thermodynamics for Naval Applications as a Military Professor. After Military Service, Paul then joined the U.S. Nuclear Regulatory Commission (NRC) as a reactor operations engineer, where he conducted detailed technical reviews of nuclear licenses in accordance with federal codes and standards, and performed quality assurance inspections on domestic and international nuclear vendors for nuclear safety related components. Within the HSB Codes and Standards group, Paul is responsible for providing code technical support to internal and external clients with a focus on nuclear construction to ASME Section III and the associated nuclear conformity assessment programs. He is responsible for the development, maintenance, and delivery of technical training related to nuclear construction, as well as supporting the HSB NQA Services Program. Paul is also responsible for the development of HSB’s remote inspection program and is the technical lead on emerging renewable technologies. He holds a Professional Engineer License in the state of Maryland, National Board Endorsements as an AI and ANI, and is a member of various ASME Section III committees.
