# ASME B16.34 vs. API 600: A Comparative Guide to Two Common Valve Standards

Navigating the world of industrial valve standards can be complex, but understanding the key differences between major specifications is crucial for engineers, procurement specialists, and maintenance teams. Two of the most referenced standards for pressure-containing valve components are **ASME B16.34** and **API 600**. While they often intersect, their scopes and applications differ significantly. This guide provides a clear comparison to help you make informed decisions for your projects.

## **Detailed Functional Comparison: Scope and Application**

**ASME B16.34** is a foundational standard titled “Valves – Flanged, Threaded, and Welding End.” Published by the American Society of Mechanical Engineers, it establishes requirements for the design, fabrication, pressure-temperature ratings, and testing of valves made from materials like carbon, alloy, and stainless steel. Its primary focus is on the pressure-containing boundaries of the valve body, bonnet, and cover.

**API 600** is a standard from the American Petroleum Institute specifically for “Bolted Bonnet Steel Gate Valves for Refinery and Pipeline Service.” As the title implies, it is more prescriptive and product-specific. API 600 builds upon the pressure-temperature ratings of ASME B16.34 but adds extensive requirements for valve design features, materials, dimensions, and testing that are critical for the demanding conditions of the oil, gas, and petrochemical industries.

### **Key Design and Material Differences**

**Pressure-Temperature Ratings:** Both standards reference common pressure classes (e.g., Class 150, 300, 600). ASME B16.34 provides the base methodology for determining these ratings. API 600 valves must conform to these B16.34 ratings but often mandate more conservative material selections and design margins for refinery service.

**Valve Construction:** API 600 is highly detailed regarding gate valve-specific features. It mandates requirements for:
* A bolted bonnet with a pressure seal or gasket.
* Minimum stem diameters for robustness.
* Specific seat and sealing designs.
* Material grades for components, often requiring trim materials suitable for erosive or corrosive services.

ASME B16.34, being broader, does not dictate these specific construction details but sets the performance baseline for the pressure envelope.

### **Testing and Inspection Requirements**

**ASME B16.34** outlines mandatory shell and seat pressure tests that all conforming valves must pass.

**API 600** incorporates all testing requirements from ASME B16.34 and frequently adds more stringent or supplementary inspections. This can include more rigorous non-destructive examination (NDE) of critical parts, extended duration tests, and specific requirements for fugitive emission testing in modern editions.

## **Frequently Asked Questions (FAQ)**

**Q: Can a valve be compliant with both ASME B16.34 and API 600?**
A: Yes, absolutely. In fact, a valve marked “API 600” is inherently compliant with the pressure-temperature requirements of ASME B16.34. API 600 is essentially a “bolt-on” specification that adds refinery-specific requirements to the core B16.34 standard.

**Q: Which standard should I specify for my project?**
A: The choice depends on the application:
* **Specify ASME B16.34** for general industrial service, power generation, or commercial building systems where the primary concern is pressure integrity.
* **Specify API 600** for severe service in oil refineries, chemical plants, pipelines, and other hydrocarbon processing applications where reliability, safety, and specific design features are paramount. It is the industry benchmark for critical gate valves.

**Q: Are there other related standards I should know about?**
A: Yes. API 602 covers compact steel gate valves, and API 603 is for corrosion-resistant bolted bonnet gate valves. Both are more specialized