ASME Pressure Vessels – Fabrication Requirements



Contributed by Mike Royer – QA/QC Manager


ASME Pressure Vessels – Fabrication Requirements

Pressure vessels are used in plants and refineries and the equipment can vary in size, shape, and material type. Most of us who are familiar think of a pressure vessel as a large vessel with nozzles and flanges, some towering high in the air. Even though that is true, did you know that it is likely that you have an ASME pressure vessel in your home?

pressure vessel

The American Society of Mechanical Engineers (ASME) defines a pressure vessel as a container for the containment of pressure, both internal and external. That is a pretty broad definition. Can you think of anything in your home that contains pressure? I can give you a hint! You would have some pretty cold showers without it. That’s right, unless you have a tank less system, your water heater is considered an ASME pressure vessel.

ASME Code, Section VIII, Division 1 defines the requirements for design, welding, and for the fabrication of new pressure vessels. This code mandates that only companies who are certified by the ASME can fabricate pressure vessels and pressure vessel parts. A company who seeks certification for the fabrication of pressure vessels must undergo an ASME Joint review. This review involves a thorough audit performed by an Inspector appointed by the Texas Department of Licensing & Regulation Compliance Division. Also involved in the joint review is the Authorized Inspector or (AI), the AI is assigned to the Company by an Insurance agency. The Company seeking certification must also have a contract in place with the Insurance agency. The assigned AI will then oversee all work performed by the Company, witnesses specific activities throughout the fabrication process, and routinely audits the Company for compliance once certifications are obtained.

Along with the review, the Company is required to have in place a robust Quality program that is all outlined by a quality manual. The joint review entails a review of this manual as well as, verifying compliance to that manual. ASME Section VIII Division 1 outlines numerous specific requirements for control of materials, filler metals, inspection and testing, qualifications of personnel, traceability, documentation, etc.

After the review process have been approved, the Company can begin fabrication. A newly certified Company will receive low stress dye stamps with a letter that signifies the code of construction that the Company is qualified to perform. The ASME “U” stamp, for example, represents new vessels fabricated in accordance with ASME Section VIII Div. 1. The stamping of the “U” to a name plate signifies that a vessel has been built in accordance with the code and that the appropriate documentation has been filed with the state to register that vessel. Each vessel must have specific information affixed to the vessel so that the information can be easily identified. This includes characteristics such as minimum design pressure, design temperature, maximum allowable working pressure, manufacturer, year built, etc.

ASME Section VIII Div. 1 also contains formulas for the calculation of material thicknesses, weld sizing, and testing requirements so that calculations can be performed to determine the appropriate sizes, types of materials and welds for the desired pressures and temperatures for a vessels intended use. This particular code of construction also references various other codes such as ASME Section IX for the qualification of Welders and welding procedures, ASME Section II for materials and filler metals, and ASME Section V for nondestructive testing just to name a few. In fact, the ASME Section VIII Div. 1 code book is approximately 800 pages in length. With a code this large, and with all the other codes of construction also referenced by this code, it can be quite cumbersome to navigate and very difficult to interpret. It is largely for that reason that the ASME mandates that a qualified Authorized Inspector oversee fabrication and sign for acceptance of each pressure vessel made.

ASME NAme Plate

Once a pressure vessel is put into service any repairs or alterations must be performed to a different code of construction, the National Board Inspection Code or (NBIC). Any repairs or alterations made to a vessel that has been in service must be documented and witnessed by the AI and the proper documentation is to be submitted to the state just as done with new pressure vessels. However, one difference is that another name plate must be affixed to the original name plate and the letter “R” stamped to signify that all work was done in accordance with the applicable code. Other codes of construction apply to other components that may connect to the pressure vessel as well.

Pressure vessels require rigorous calculations and construction oversight. Despite this, vessels that are built in accordance with the code have been used safely for decades.


Mike Royer – QA/QC Manager at H+M Industrial EPC

With 20+ years of comprehensive quality assurance expertise in the industrial industry, Michael’s proficiency lies in piping, pressure vessels, modular packages, tanks, pumps, and compressors. He is familiar with AWS, ASME, API, MSS, and PFI standards and is an authority in QA/QC principles, techniques, and current technologies. He is an AWS CWI and his experience includes supervision of source inspectors, technical leadership, monitoring of inspection procedures, vendor compliance, comprehensive manual creation, and quality program management and coordination.