General Information
This directory contains a listing of:

• Manufacturers of boilers, pressure vessels, or other pressure-retaining items who are authorized to register these items with the National Board;
• Manufacturers of pressure relief devices who have had these items capacity-certified by the National Board;
  
• Repair organizations holding National Board Certificates of Authorization for use of either the R, VR, or NR stamps; and
• Pressure relief valve testing organizations holding National Board Certificate of Authorization for use of the T/O Certification Mark.

Please note: if a company does not meet at least one of these four criteria, it will not be listed in this directory.

Search Tips

• Be as general as possible if entering a company name. A company may spell its name differently on their certificate than how they are known to the public. We suggest typing in only the first letter or two in the company's name, or simply leave the company name field empty to ensure you receive all possible matches.
• Know the exact city for the company or plant you are trying to locate. Many times a plant may have a different physical location than the city it is commonly associated with. If you do not have this information we suggest you leave this field empty.