New NB-18

Welcome to the New NB-18, Pressure Relief Device Certifications

The National Board announces changes and updates to its free, online resource NB-18, Pressure Relief Device Certifications.

Here’s what has changed: 

  1. The format is no longer a single downloadable pdf document; it is now a live, searchable database with the ability to generate custom search queries based on your unique criteria. From these search results you will have the ability to generate customized reports. These reports can be printed or downloaded and saved in a variety of formats. 
  1. NB-18 is now updated each business day instead of once a week.
  1. The listings of VR and T/O holders are no longer part of NB-18, but are included in the Manufacturer & Repair Directory on our website. This listing also includes the scopes of these organizations as well as any other NB or ASME Certificates of Authorization held.
  1. The NB-18 front matter containing the Foreward/Explanation, Administrative Requirements, and the Capacity Calculation Formulae are in separate pdf documents. Links to these documents are located on the NB-18 page.
  1. The Valve/Rupture Disk Combination Capacity Factors are also in a separate pdf document accessible via a link on the NB-18 page.

About NB-18

NB-18 provides for the certification of pressure relief device designs and the accreditation of organizations that manufacture or assemble these devices. Accredited organizations are issued a certificate of authorization to apply the National Board NB symbol to devices of certified designs.

The National Board Pressure Relief device certification program was developed in the mid-1930s in an effort to enhance safety to the industry and to the general public. At that time, when jurisdictional authorities expressed concern about relieving capacities, the National Board sponsored tests at The Ohio State University to compare the stamped and actual relieving capacities. They found large differences which prompted the National Board’s membership to resolve that safety valves should be constructed to recognized standards and performance must be demonstrated by tests. At the request of the National Board, the American Society of Mechanical Engineers (ASME) appointed a special committee on safety valve requirements to cooperate with the National Board and developed construction requirements, quality standards and testing procedures.