R stamp companies are accredited to make pressure vessel repairs or pressure vessel alterations by the National Board of Boiler and Pressure Vessel Inspectors. These organizations undergo extensive certification processes and are monitored by at third part authorized inspector to ensure that they are following all the rules and regulations to keep your facility and employees safe. If you have a Boiler or Pressure Vessel bearing an S Stamp, H Stamp, or U stamp and have work performed by a contractor without an R stamp, you could be in violation of the law and you could void the stamp on your vessel. If you are unsure, call and ask us. We would be happy to talk about your application and help you find a solution.