PRD Test Lab

The National Board’s goal is to maintain the integrity of the National Board marks and symbols (NB, VR, and T/O) and the ASME Certification mark with V ,UV, UD, HV, and NV designators. By doing so, we make it possible for National Board members to rely on the presence of these marks in their efforts to protect the general public.


National Board Activities

  • Pressure Relief Device Certification
    The NB mark must be used by pressure relief device manufacturers and assemblers to identify pressure relief devices that have been certified by the National Board in accordance with NB-501, National Board Certification of Pressure Relief Devices.
  • VR Repair Program
    The National Board offers the Certificate of Authorization and VR Stamp for the repair of pressure relief valves. Requirements are included in the current mandatory edition of the National Board Inspection Code (NBIC), Part 4, and NB-514, Accreditation of VR Repair Organizations.
  • T/O Testing Program
    The National Board offers the Certificate of Authorization for use of the T/O mark which indicates accreditation as a pressure relief valve Testing Organization. The program includes provisions for minor adjustments to restore valve performance. Requirements are based upon the current mandatory edition of the National Board Inspection Code (NBIC), Part 2, Part 4, and NB-528, Accreditation of T/O Test Only Organizations.
  • Investigation Testing
    The National Board supports members who request tests be conducted on pressure relief devices involved in boiler and pressure vessel accidents. This service is provided at no cost to the National Board member. Please contact Pressure Relief or Executive staff for more information.
  • Testing Laboratory
    As the world's only independent ASME certified flow laboratory, located north of Columbus, the National Board Testing Laboratory remains the leader in promoting accurate performance measurement of pressure relieving devices and the development of technical standards. Please click on the above Testing Laboratory link for additional information including test device size, pressure, and capacity limitations.


ASME Supporting Activities

  • ASME Designee – Shop Reviews
    The National Board is the ASME designee to conduct shop reviews of organizations for the ASME Certification mark with V, HVUV, and UD designators.
  • ASME Designee – Valve Selection and Test Witnessing
    Representatives from the National Board are assigned to visit company sites to select production sample valves for testing at National Board- and ASME- accepted labs.
  • ASME Designee – Laboratory Acceptance


Committee Participation

The National Board supports the following technical committees:

  • ASME Subcommittee on Safety Valve Requirements
  • ASME Subgroup on Pressure Relief Valves (Section III, Nuclear)
  • NBIC Subgroup Pressure Relief Devices
  • ISO/TC 185, international committee concerned with overpressure protection
  • U.S. Technical Advisory Group on ISO/TC 185


For more information regarding the National Board Pressure Relief Department,
please Contact Us.