API 600 vs API 602 - QRC Valves

API 600 and API 602 are key valve specifications used in industrial applications, particularly in the oil and gas sector. This article explores the differences between these standards, including their design scope, pressure ratings, materials, and typical applications. API 600 covers larger bolted bonnet gate valves vs API 602, which applies to compact forged steel valves. We’ll also discuss selection factors and compliance requirements.

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Overview of API 600

API 600, developed by the American Petroleum Institute (API), specifies the requirements for bolted bonnet steel gate valves. These valves are primarily used for blocking services where reliable shutoff and minimal pressure drop are necessary. Also, it covers cast steel valves that are in larger-diameter pipeline services. 

API 600 valves are common in high-pressure, high-temperature services such as refineries, petrochemical plants, and steam distribution systems. For these applications, durability and compliance with rigorous standards are paramount.

Key characteristics of API 600 valves include:

• Size Range: Typically 2 inches and larger
  
• End Connections: Generally flanged, although butt weld ends are also possible.
  
• Construction: Cast body with a bolted bonnet
  
• Design: OS&Y (Outside Screw and Yoke) configuration, thus allowing easy indication of valve position

Overview of API 602

API 602 is the governing specification for compact forged steel gate, globe, and check valves. These valves are common in applications with space limitations or where high integrity is necessary in smaller diameter piping systems. Forged construction offers superior grain structure, enhancing mechanical strength, as well as resistance to pressure-induced stresses.

API 602 valves are a mainstay in power plants, chemical injection skids, process skids, and other compact or high-pressure applications.

Key characteristics of API 602 valves include:

• Size Range: Typically 2 inches and below, although some designs can extend slightly beyond
• End Connections: Socket weld, threaded, or flanged
• Construction: Forged body for enhanced toughness and reliability
• Design Options: Gate, globe, and check configurations

Key Differences Between API 600 vs API 602

Here are the most distinct differences between the two standards.

Application Size and Pressure Considerations

Larger pipelines and critical process systems favor API 600 valves due to their robust cast construction and full port designs. In contrast, smaller high-pressure systems benefit from the compactness and toughness of API 602 valves. The choice between cast and forged construction impacts overall valve performance, weight, and durability under cyclic or thermal stresses.

Material Properties of API 600 vs API 602

API 600 and API 602 valves use similar materials (e.g., WCB, WC9, CF8M), but forged bodies in API 602 valves offer superior strength and fine-grained structures compared to cast equivalents, making them ideal for high-pressure, high-cycling environments.

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Pressure Ratings and Materials of API 600 vs API 602

Selecting the right valve involves understanding both the pressure class it must withstand and the materials suitable for the service conditions. API 600 and API 602 valves cover a wide range of pressure ratings and material options to meet different operational demands.

Pressure Classes

• API 600 valves are generally designed for larger pipelines and are manufactured to handle ANSI pressure classes ranging from Class 150 up to Class , depending on system requirements. These cast steel gate valves are optimized for medium- to high-pressure services in critical applications.
• API 602 valves, although smaller in size (typically 2″ and below), can also be rated for high pressures, commonly available in Classes 150, 300, 600, 800, , and even . Their forged body construction provides superior mechanical strength and integrity, especially in cyclic or high-pressure conditions.

Materials of Construction

API 600 valves are often cast from materials like WCB (carbon steel), WC9 (chromium-molybdenum alloy steel), and CF8M (stainless steel). API 602 valves typically use forged equivalents such as A105 (carbon steel), F22 (low alloy steel), and F316 (stainless steel).

Both standards allow various material grades, including:

• Carbon Steels (WCB, A105)
• Low-Alloy Steels (WC9, C5, C12)
• Austenitic Stainless Steels (CF8M, CF3M)
• Specialty Alloys (Monel, Inconel, Duplex)

Typical Applications of API 600 vs API 602

API 600 Applications:

• Refineries and petrochemical plants
• Large-bore steam and utility piping systems
• Oil and gas production and transportation pipelines
• General industrial service in chemical plants
  

API 602 Applications:

• Power generation skid packages
• Chemical injection systems
• High-pressure compact process lines
• Boiler feedwater piping and utility stations

Selection Considerations

Selecting between an API 600 and API 602 valve involves evaluating operational needs and system constraints. In each case, adherence to the valve standard enhances system reliability, safety, and efficiency.

Generally, valve selection should prioritize long-term performance, compliance with relevant standards, and suitability for the specific operating environment.

• Space Constraints: API 602 valves offer clear advantages in tight spaces or modular designs.
• Maintenance Access: Larger API 600 valves provide easier access for maintenance due to their removable bonnets and accessible internals.
• Pressure and Temperature Ratings: Both valve standards cover a wide temperature and pressure range. Verify that the selected valve can safely accommodate expected operating pressures and thermal cycles.
• Connection Type: Choose socket weld or threaded ends (API 602) for high-pressure small piping, or flanged ends (API 600) for easy installation and removal in larger lines.
• Cost and Lead Time: Compact forged valves may offer cost benefits at smaller sizes, while cast valves dominate larger diameters despite longer manufacturing lead times.
• System Codes and Compliance: Ensure valves meet project specifications, such as ASME B31.3 or B31.1 piping codes.

Compliance and Quality Assurance

Compliance with API 600 or API 602 is critical to ensure valves meet defined mechanical and performance criteria, especially under demanding service conditions. Proper documentation and inspection ensure operational safety and simplify future audits or maintenance interventions.

Key compliance aspects include:

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• Third-Party Testing: Independent verification of design pressure, seat tightness, and materials
• Material Traceability: Full traceability from raw materials to final product
• Documentation: Manufacturer’s data reports (MTRs), certification of compliance, and quality control records
• Certified Suppliers: Always source valves from API-certified manufacturers or authorized master distributors like QRC Valves to ensure product authenticity, quality, and warranty support

Choosing Between API 600 vs API 602 at QRC Valves