In valve specifications, API, ASME, and ISO often appear side by side.
Many suppliers list all three proudly—yet few explain what each one actually controls.

This confusion leads to:

• Rejected bids
• EPC technical clarifications
• Valves that are “compliant” but still unacceptable

This article breaks down what these standards really mean, what they do not, and how EPCs use them in real projects.

API — Performance Under Real Service Conditions

API standards focus on how a valve performs, especially in harsh industries like oil & gas, petrochemical, and power generation.

What API controls

• Pressure containment
• Seat tightness
• Cycle life
• Fire safety
• Fugitive emissions
• Inspection & testing procedures

Common API valve standards include:

• API 600 – Steel gate valves
• API 602 – Forged valves
• API 608 – Ball valves
• API 609 – Butterfly valves
• API 598 – Inspection & testing
• API 607 / API 6FA – Fire testing

What API does not control

• Factory management quality
• Production consistency
• Documentation systems

📌 What EPCs think when they see API:

“This valve has proven performance criteria and defined failure limits.”

ASME — Design Rules & System Compatibility

ASME standards define how valves fit into piping systems.

ASME does not test how well a valve seals—it defines design boundaries.

What ASME controls

• Pressure class ratings (150 / 300 / 600 / 900…)
• Pressure–temperature curves
• Body wall thickness
• Flange dimensions
• Material stress limits

Key ASME standards:

• ASME B16.34 – Valve design rules
• ASME B16.5 / B16.47 – Flange dimensions
• ASME B31.1 / B31.3 – Piping codes

What ASME does not control

• Seat leakage rate
• Fire-safe behavior
• Valve cycling durability

📌 What EPCs think when they see ASME:

“This valve will fit the piping and survive system pressure and temperature.”

ISO — Manufacturing & Quality Systems

ISO standards govern how valves are manufactured, not how they perform in service.

The most common requirement is ISO 9001.

What ISO controls

• Quality management systems
• Process consistency
• Traceability
• Document control
• Corrective actions

Typical ISO standards:

• ISO 9001 – Quality management
• ISO 14001 – Environmental management
• ISO 45001 – Occupational safety

What ISO does not control

• Pressure rating
• Fire testing
• Seat tightness
• Valve design limits

📌 What EPCs think when they see ISO 9001:

“This supplier can manufacture consistently and be audited.”

How EPCs Actually Combine API, ASME, and ISO

EPC questions → which standard answers them

• Will the valve seal properly under pressure?
  → API (seat tightness, shell test, leakage criteria)
• Will the valve survive a fire event?
  → API (API 607 / API 6FA fire testing)
• Does the valve match Class 150 / 300 / 600 piping?
  → ASME (pressure class & flange dimensions)
• Is the pressure rating valid at high temperature (e.g. 400°C)?
  → ASME (pressure–temperature curves, material stress limits)
• Is the supplier capable of consistent, auditable production?
  → ISO (ISO 9001 quality management system)

A typical EPC specification might read:

API 600 gate valve, ASME B16.34 Class 300, ISO 9001 certified manufacturer

Each line answers a different risk.

Common Misunderstandings That Cause Bid Rejection

❌ “ISO certified valve”
→ ISO certifies the factory, not the valve.

❌ “ASME valve”
→ ASME defines design limits, not sealing performance.

❌ “API quality valve”
→ API defines performance requirements, not manufacturing discipline.

❌ Listing all standards without clarity
→ EPCs may ask for clarification—or reject the bid.

The One Rule to Remember

• API = How the valve behaves
• ASME = Where the valve fits
• ISO = How the valve is made

No single standard is sufficient on its own.

Final Thoughts for Suppliers & EPC-Facing Manufacturers

Understanding standards isn’t about adding more logos to your catalog.
It’s about matching the right standard to the right risk.

Suppliers who clearly explain which standard solves which problem:

• Reduce EPC questions
• Improve technical acceptance
• Win trust faster

‍

‍

‍