Pressure vessels, whether they are used as chemical holding tanks, chemical storage tanks, or reactors, must be manufactured to meet certain safety standards under the laws of every Canadian province and 49 of the 50 US states. Standards for boilers and pressure vessels were created in response to thousands of boiler accidents in the United States and Europe during the late 1800s and early 1900s, particularly an accident in 1905 that leveled a factory and resulted in 58 fatalities.
The standards for designing and manufacturing boilers and pressure vessels are set by the American Society of Mechanical Engineers or ASME. This code is referred to as the Boiler and Pressure Vessel Code or BPVC. The BPVC has 12 sections, identified by Roman numerals I through XII. The BPVC applies whether the pressure vessel is a vertical pressure vessel or horizontal pressure vessel.
ASME Pressure Vessel Standards
The section covering the construction of pressure vessels is ASME Code, section VIII. When a pressure vessel is constructed in compliance with section VIII, the manufacturer may stamp the pressure vessel with a certification mark. Section VIII contains three divisions.
Section VIII, division 1 defines standards for pressure vessels having an internal or external pressure greater than 100 kPa (or 15 psi). Pressure vessels manufactured according to the standards of division 1 are stamped with U, UM, or UV certification marks.
Section VIII, division 2 defines standards for pressure vessels having an internal or external pressure between 20700 kPa (or 3000 psi) and 70000 kPa (or 10000 psi). These standards also cover human occupied pressure vessels used primarily in the diving industry. Pressure vessels manufactured according to the standards of division 2 are stamped with U2 and UV certification marks.
Section VIII, division 3 defines standards for pressure vessels having an internal or external pressure greater than 70,000 kPa (or 10000 psi). Pressure vessels manufactured according to the standards of division 3 are stamped with U3 and UV3 certification marks.
What it Means to Be an ASME Pressure Vessel Manufacturer
Authorization for a manufacturer to use the ASME certification marks requires the manufacturer to have an inspection agreement with an authorized inspection agency and a quality control system to ensure compliance with all design, material, fabrication, examination, and inspection standards. For example, the geometry of the parts of a vertical pressure vessel would be defined by the ASME standards. A vertical pressure vessel manufactured by an ASME pressure vessel manufacturer must be made from an approved material (both in terms of material type and material thickness). The BPVC includes standards for carbon and low alloy steel, non-ferrous materials, high alloy steel, and cast iron. The standards vary depending on the material. For example, the standards for carbon steel, with its tensile strength of 580 MPa and a yield strength of 260 MPa, are different from the standards for cast iron, with its tensile strength of 200 MPa and a yield strength of 130 MPa. The BPVC also sets standards for fabrication, depending on whether the vertical pressure vessel is welded, brazed, or forged. The ASME standards define how the vertical pressure vessel should be examined by the manufacturer and how the vertical pressure vessel should be inspected by an authorized inspection agency.
What it Means to Be a Customer of an ASME Pressure Vessel Manufacturer
A vertical pressure vessel or horizontal pressure vessel manufactured by an ASME pressure vessel manufacturer has met industry and legal safety standards. It is sized and shaped to meet design standards, manufactured from approved materials, fabricated using approved techniques, examined by the manufacturer, and inspected by an approved inspection agency.