WHAT IS ASME STAMPING AND ITS TYPES

Meena Rezkallah, P.Eng.
Jun 6
3 min read

🔩 What is ASME Stamping?

ASME stamping refers to the process of certifying and marking pressure equipment (like boilers, pressure vessels, and piping systems) in compliance with the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC). The stamp is a symbol of quality, safety, and compliance with strict design, fabrication, inspection, and testing standards.

🛠️ Purpose of ASME Stamping

ASME stamps:

Demonstrate compliance with ASME BPVC rules.
Ensure safety of pressure-retaining items under high temperature/pressure.
Allow international trade by meeting widely recognized standards.
Provide traceability and legal assurance of fabrication quality.

✅ What Does ASME Stamping Involve?

Design Review: Equipment is designed according to the ASME code section.
Fabrication by a Certified Shop: Only manufacturers with an ASME Certificate of Authorization can stamp equipment.
Inspection by an Authorized Inspector (AI): AI from an Authorized Inspection Agency (AIA) verifies compliance during fabrication.
Quality Control: A documented Quality Control System (QCS) is implemented and audited.
Stamping: Once approved, a code symbol stamp (e.g., “U”, “S”, “R”) is affixed along with a nameplate.

📦 Examples of ASME Stamps

Stamp	Applies To
U	Pressure vessels (Sec VIII)
S	Power boilers (Sec I)
PP	Boiler external piping
R	Repair/alteration of vessels
UV	Safety relief valves

🌍 Where Is It Required?

Industrial sectors: Oil & Gas, Power Generation, Chemical, Nuclear, Pharmaceuticals
Legal compliance: In countries like the USA, Canada, GCC, India, and others
Client specifications: Major EPCs and end-users (e.g., Shell, ADNOC, Aramco) mandate it

📌 Summary

ASME stamping is a globally recognized certification that proves a pressure-retaining item was manufactured in accordance with the highest standards of safety, quality, and code compliance under the ASME BPVC.

How to Select the ASME Stamping Types

ASME Stamp	Code Section	Equipment Type	Typical Application	Key Notes / Criteria
S	Section I	Power Boilers	Utility/power plant boilers, HRSGs, main boilers	Required for high-pressure steam boilers (>15 psig); includes superheaters, economizers, and integral piping
A	Section I	Boiler Assembly	Boiler fabrication companies	For assembly only; final assembly by another organization
PP	Section I / B31.1	Boiler External Piping	Boiler outlet piping, power plant steam lines	Stamped separately; applies to piping after boiler proper
H	Section IV	Heating Boilers	Hot water or low-pressure steam boilers	For boilers under 15 psig (steam) or 160 psi (water); HVAC systems
HLW	Section IV	Potable Water Heaters	Commercial/residential hot water generators	For water heaters >200,000 BTU/hr or >120 gallons; must meet potable water reqs
U	Section VIII Div. 1	Pressure Vessels	Columns, drums, reactors	Most common stamp; for pressure vessels up to 3,000 psi
UM	Section VIII Div. 1	Miniature Pressure Vessels	Small tanks, instrument air receivers	For vessels meeting miniature criteria: ≤6" ID, ≤1.5 ft³, ≤600 psi
U2	Section VIII Div. 2	Pressure Vessels (Alt. Rules)	High stress design, FEA	Advanced analysis for fatigue, corrosion, thinner walls
U3	Section VIII Div. 3	High Pressure Vessels	Hydrogen vessels, separators	For vessels >10,000 psi; hydrogen or explosive services
T	Section XII	Transport Tanks	Road/rail transport	For vessels used in transportation (mobile units)
RP	Section X	Reinforced Plastic Vessels	FRP vessels for corrosive chemicals	Used in chemical, water, wastewater, and underground tanks
UV	Section VIII	Pressure Relief Valves	Valves on pressure vessels, boilers	Required if valve is to be ASME certified and used on U/S/H-stamped equipment
UD	Section VIII	Rupture Disks	Disks relieving pressure	For rupture disks used on ASME-stamped equipment
N	Section III	Nuclear Components	Reactors, pressurizers	Mandatory for nuclear island components; regulated by NRC
NPT	Section III	Nuclear Parts	Forgings, valves, pipe fittings	Parts for N components; must be traceable with QA/QC
NA	Section III	Nuclear Assemblies	Subsystems	Applies to fabricators assembling N, NPT components into subsystems
NS	Section III	Nuclear Supports	Pipe/equipment supports	For pipe hangers, supports in nuclear facilities
NV	Section III	Nuclear Pressure Relief Valves	Valves in nuclear plants	Valves relieving pressure in Classes 1, 2, or 3 systems
R	NBIC	Repairs/Alterations	Field repairs of ASME-stamped items	Requires repair by R-certified entity and AI involvement
VR	NBIC	Pressure Relief Valve Repair	Valve repair/refurbishment	Required if scope involves valve repair with National Board