Side-by-Side Comparison of an ASME U and ASME UM Vessel

ASME (American Society of Mechanical Engineers) defines a code of standards for the operational safety of pressure vessels. The ASME pressure vessel construction rules are very extensive including fabrication methods, construction materials, design temperature, design pressure, loading, stress values, corrosion allowances, lining, thickness, and approval of every ferrell, port and valve attached to the vessel.

Apache Stainless is an ASME manufacturer with decades of expertise in U and UM certifications for all types and sizes of stainless vessels, from 1 gallon to 167,000 gallons. In the infographic is a side-by-side comparison example of an ASME U (left) and ASME UM (right) vessel and the required certification for each.

ASME U Stamp Vessel (left)

  • Any vessel meeting the requirement of ASME Section VIII can be marked with the U Symbol.
  • Most local and state laws require vessel designs 15 PSI and higher to be ASME Code Certified.
  • Qualified manufacturers receive a triennial joint review (audit) by their authorized inspection agency, and the National Board of Boiler and Pressure Vessel inspectors.
  • U vessels require an Authorized Inspector (3rd party ASME inspector) to review with approved calculations.
  • U vessels require an ASME pressure test with the Authorized Inspector residing over the test.

ASME UM Stamp Vessel (right)

  • UM vessels are smaller in volume (less than 5 cubic feet)
  • UM qualified manufacturers receive an annual ASME review by their authorized inspection agency and are also subject to the same triennial joint review (audit) as mentioned above.
  • UM vessels have size specifications, including:
  • 5 cubic feet of volume or small with pressures not exceeding 250 PSI
  • 3 cubic feet of volume or smaller with pressures not exceeding 350 PSI
  • 1.5 cubic feet of volume or smaller with pressures not exceeding 600 PSI
  • UM Vessels are inspected and tested by a manufacturer’s own certified individuals.

Note that there may be exceptions to the ASME Certification requirements, depending on your state and local municipality.

Apache manufactures tanks and vessels for compliance and regulated industries, including pharmaceutical, food and beverage, petrochemical, biofuels, chemical and life science. We hold these certifications: ASME U Certificate, ASME UM Certificate, National Board of Boiler & Pressure Inspectors R Certificate, and National Board of Boiler & Pressure Vessel Authorization to Register Certificate.

Download Side-by-Side U and UM infographic.