My earliest experience with a pressure vessel was as a child. We lived in a mountainous area at about 5000 feet. The boiling point of water at 5000 feet was about 200 degrees and my mother cooked almost every day with a pressure cooker so the food would get cooked in a reasonable time. The pressure cooker was a fascinating invention to me. You could add weights to the little bobber on the top to make the pressure inside five, ten or fifteen pounds. Little bursts of steam kept coming out as it regulated the pressure. And besides just cooking your meal you could can fruits and vegetables in the pressure cooker by raising the temperature high enough. Since that time I have learned that there are other uses for pressure vessels. The one I use most often is the propane tank in on my gas grill.
Outside the home there are pressure vessels that are much larger, and able to withstand much higher pressures and much higher temperatures. Most of them are used in industrial or manufacturing applications. Items like compressed air, oxygen, steam, chemicals, natural gas, and other liquids and gasses can only be stored safely under high pressures. Boilers in utility plants come immediately to mind as they operate at high pressure. But a submarine that is diving deep is equally qualified.
One directory lists over a hundred manufacturers of pressure vessels in the United States, but undoubtedly there are many more than that. Pressure vessels are used in a variety of industries that include chemical, pharmaceutical, food and beverage, oil, fuel and plastics. Although there are several standards, most pressure vessels are required to be registered as ASME pressure vessels. The ASME is the American Society of Mechanical Engineers. They and the National Board of Boiler and Pressure Vessel Inspectors (NBBI) set the standard that certification for safe manufacture and maintenance of the vessels must be made. These specifications include the design, the construction and the fabrication of the vessel. They also identify materials of construction, wall thicknesses, and their size and shape limitations. Each tank is inspected and tested before being certified. Manufacturers must obtain a “U” Stamp certification from ASME in order to fabricate pressure vessels.
Pressure vessels also receive regular inspections. And if it is ever necessary to repair a certified tank there is another set of standards for the repair and re-inspection to make sure the repair is done appropriately. In order to repair pressure vessels, fabricators need an “R” Stamp certification from ASME. Depending on their application tanks may have jackets for temperature, agitators for blending and they are made from many exotic materials so they can contain caustic or corrosive materials. At Optimation we are often involved helping our clients with pressure vessel activities. We have R Stamp certification to modify, repair, upgrade and relocate pressure vessels. And if there is a need for a new pressure vessel, we design and fabricate one under our U Stamp certification.
R and U Stamp certifications are required because of the dangerous nature of pressure vessels. The process to obtain either certification requires a rigorous audit of welding and fabrication processes and skills. It’s something we take very seriously, as our work in either repairing or fabricating a pressure vessel directly affects the safety of our clients.