Pressure Vessel Definition  

The Pressure Vessel Definition article provides you the definition and boundaries of pressure vessel based API code and ASME Code.

The I4I Academy ASME Training Course discusses this section and covers different types of pressure vessels.

Based on the ASME Code Section VIII, pressure vessels are containers for the containment of pressure, either internal or external.This pressure may be obtained from an external source or by the application of heat from a direct or indirect source, or any combination thereof.

Pressure Vessel Definition

The ASME Code is a construction code for pressure vessels and contains mandatory requirements, specific prohibitions and non-mandatory guidance for pressure vessel materials, design, fabrication, examination, inspection, testing, and certification.

Pressure Vessel Definition - Scope

These scopes are based ASME Code Sec VIII Div 1

  • The vessel with maximum allowable working pressure(MAWP) higher than 15 psi
  • Inside diameter to be higher than 152 mm
  • No piping or piping component
  • No rotating or reciprocating Equipment
  • Not Water Vessel up to 300psi or 210°F
  • Not within the scope of other Sections
  • Also for gas fired double shell heat exchangers < 50 psi
  • Not Steam Boilers with direct firing
  • Not for Human Occupancy (PVHO)


  • The welding end of the first circumferential joint for welded connections
  • The first threaded joint for screwed connections
  • The face of the first flange for bolted, flanged connections
  • The first sealing surface for proprietary connections or fittings
  • Non pressure parts welded directly to a pressure retaining surface
  • Pressure retaining covers
  • Pressure relief devices

What is API Code Definition from Pressure Vessel ?

pressure vessel testing

Contrary of ASME Code Sec VIII, which was developed for construction, the API STD 510 covers the in-service inspection, repair, alteration, and rerating activities for pressure vessels.

This inspection code applies to all refining and chemical process vessels that have been placed in service.

What is the API STD 510 coverage?

  • Vessels constructed in accordance with an applicable construction code
  • Vessels constructed without a construction code (non-code)—A vessel not fabricated to a recognized construction code and meeting no known recognized standard
  • Vessels constructed and approved as jurisdictionally special based upon jurisdiction acceptance of particular design, fabrication, inspection, testing, and installation
  • Non-standard vessels—A vessel fabricated to a recognized construction code but has lost its nameplate or stamping.


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