Introduction to the ASME Code


Keywords: ASME Code, Boiler & Pressure (B&PV) Vessel Code; Rules of Construction; Power Boilers; ASME Pressure Vessels; Welding Qualifications

The American Society of Mechanical Engineers (ASME) Code is a widely recognized set of standards and guidelines for the design, construction, and operation of various mechanical systems and equipment. The ASME Code remains a worldwide model for assuring equipment and vessel safety, reliability and operational efficiency. The Code is kept current by nearly 1,000 volunteer technical experts. The boiler and pressure vessel sections have long been considered essential within the electric power-generation, petrochemical, transportation and other industries.

ASME issued its first standard, “Code for the Conduct of Trials of Steam Boilers” in 1884. It subsequently evolved into “Rules for the Construction of Stationary Boilers and for Allowable Working Pressure” – the first edition of ASME’s now-legendary Boiler and Pressure Vessel Code (B&PVC) issued in 1914 and published in 1915.

Over the years, the code expanded to incorporate other mechanical systems, such as nuclear power plants, piping, elevators, and cranes, among others. This expansion reflected the growing need for comprehensive safety guidelines in an increasingly diverse range of mechanical engineering applications.

The ASME Code quickly gained recognition within the engineering community due to its rigorous technical standards and commitment to safety. State and local governments in the United States began adopting the code, making it mandatory for the construction and operation of various mechanical systems.

Technical committees composed of experienced professionals and subject matter experts continually review, update, and develop the code’s provisions to adapt to technological advancements and emerging industry needs. These committees ensure that the ASME Code remains current, reflecting the best practices and state-of-the-art knowledge in various engineering disciplines.

ASME B&PV Code is comprised of the following sections:

Section I – Power Boilers
Provides requirements for all methods of construction of power, electric, and miniature boilers; high temperature water boilers, heat recovery steam generators, and certain fired pressure vessels to be used in stationary service; and power boilers used in locomotive, portable, and traction service.

Section II – Materials
Part A covers Ferrous Material; Part B covers Nonferrous Material; Part C covers Welding Rods, electrodes, and Filler Metals; and Part D covers Material Properties in both Customary and Metric units of measure. Together, these four parts of Section II comprise a “Service Code” to other BPVC Sections, providing material specifications adequate for safety in the field of pressure equipment. These specifications contain requirements for chemical and mechanical properties, heat treatment, manufacture, heat and product analyses, and methods of testing.

Section III – Rules for Construction of Nuclear Facility Components
Provides general requirements which address the material, design, fabrication, examination, testing and overpressure protection of the items specified within each respective Subsection, assuring their structural integrity.

Section IV – Heating Boilers
Provides requirements for design, fabrication, installation and inspection of steam heating, hot water heating, hot water supply boilers, and potable water heaters intended for low pressure service that are directly fired by oil, gas, electricity, coal or other solid or liquid fuels.

Section V – Nondestructive Examination
Is another “Service Code”- containing requirements and methods for nondestructive examination which are referenced and required by other BPVC Sections. It also includes manufacturer’s examination responsibilities, duties of authorized inspectors and requirements for qualification of personnel, inspection and examination. Examination methods are intended to detect surface and internal discontinuities in materials, welds, and fabricated parts and components.

Section VI – Care and Operation of Heating Boilers
Covers operation guidelines applicable to steel and cast-iron boilers limited to the operating ranges of Section IV Heating Boilers. Section VI includes guidelines for associated controls and automatic fuel-burning equipment.

Section VII – Care of Power Boilers
Provides guidelines to assist those directly responsible for operating, maintaining, and inspecting power boilers. These boilers include stationary, portable, and traction type boilers, but not locomotive and high-temperature water boilers, nuclear power-plant boilers (see Section XI), heating boilers (see Section VI), pressure vessels, or marine boilers. Guidelines are also provided for operation of auxiliary equipment and appliances that affect the safe and reliable operation of power boilers.

Section VIII – Pressure Vessels
Division 1 provides requirements applicable to the design, fabrication, inspection, testing, and  certification of U (unfired or fired) pressure vessels operating at either internal or external pressures exceeding 15 psig. 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. Specific requirements apply to several classes of material used in pressure vessel construction, and also to fabrication methods such as welding, forging and brazing. Division 1 contains mandatory and non-mandatory appendices detailing supplementary design criteria, nondestructive examination and inspection acceptance standards.

Division 2 requirements on materials, design, and nondestructive examination are more rigorous than in Division 1; however, higher design stress intensity values are permitted. These rules may also apply to human occupancy pressure vessels typically in the diving industry. Division 2 is made up of nine parts:
1: General Requirements
2: Responsibilities & Duties
3: Material Requirements
4: Design-by-Rule Requirements
5: Design-by-Analysis Requirements
6: Fabrication Requirements
7: Inspection & Examination Requirements
8: Pressure Testing Requirements
9: Pressure Vessel Overpressure Protection

Division 3 requirements are applicable to pressure vessels operating at either internal or external pressures generally above 10,000 psi. It does not establish maximum pressure limits for either Section VIII, Divisions 1 or 2, nor minimum pressure limits for this Division.

Section IX – Welding and Brazing Qualifications
Is another “Service Code” – containing rules relating to the qualification of welding and brazing procedures as required by other BPVC Sections. It also covers rules relating to the qualification and requalification of welders, brazers, and welding and brazing operators in order that they may perform welding or brazing in component manufacture.

Section X – Fiberglass-Reinforced Plastic Pressure Vessels
Provides requirements for construction of an FRP pressure vessel in conformance with a manufacturer’s design report.  It includes production, processing, fabrication, inspection and testing methods required for the vessel.

Section XII – Transport Tanks
Provides requirements for construction and continued service of pressure vessels for the transportation of dangerous goods via highway, rail, air or water at pressures from full vacuum to 3,000 psig and volumes greater than 120 gallons.

Section XI – Rules for Inservice Inspection of Nuclear Power Plant Components
Constitutes requirements to maintain the nuclear power plant while in operation and to return the plant to service, following plant outages, and repair or replacement activities. These rules require a mandatory program of scheduled examinations, testing, and inspections to evidence adequate safety. The method of nondestructive examination to be used and flaw size characterization are also contained within this Section.


1) ASME Boiler and Pressure Vessel Code  (go.asmeorg/bpvc13)
2) ASME (2021) ASME Boiler and Pressure Vessel Code. From


ASME Code Resources


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