How To Select Butterfly Valves under API 609 And ASME B16.34 Standards

I. Overview of API 609 and ASME B16.34 Standards

1. API 609 Standard

API 609 is a standard developed by the American Petroleum Institute (API), specifically for the design, manufacturing, and testing of butterfly valves. This standard covers various types of butterfly valves, including double flanged, wafer, and lug types. The main contents of the API 609 standard include:

• Scope of application: Applicable to butterfly valves with nominal diameter NPS 2 to 48.

• Pressure-temperature ratings: Provides detailed cold working pressure (CWP) and pressure-temperature ratings.

• Material requirements: Specifies the material selection for components such as the valve body, disc, and seat.

• Testing requirements: Including visual inspection, dimensional inspection, sealing tests, and pressure tests.

2. ASME B16.34 Standard

ASME B16.34 is a standard developed by the American Society of Mechanical Engineers (ASME), applicable to flanged, threaded, and welded end valves. This standard provides pressure-temperature ratings, material selection, design requirements, and testing methods for valves. The main contents of the ASME B16.34 standard include:

• Scope of application: Applicable to various types of valves, including butterfly valves.

• Pressure-temperature ratings: Provides detailed flange pressure classes and temperature ranges.

• Material requirements: Specifies the material selection for components such as the valve body, disc, and seat.

• Testing requirements: Including pressure tests, sealing tests, and fire resistance tests.

II. Key Factors in Selecting Butterfly Valves

1. Material Selection 

According to the API 609 and ASME B16.34 standards, the material selection for butterfly valves should consider the corrosiveness of the medium, temperature range, and pressure class. Common materials include:

• Ductile iron: Suitable for medium and low-pressure applications, with good tensile strength and corrosion resistance.

• Carbon steel (WCB): Suitable for high-temperature and high-pressure applications, with good weldability.• Stainless steel (304, 316, 316L): Suitable for corrosive media, with good corrosion resistance and high-temperature performance.

• Duplex stainless steel (2205, 2507): Suitable for highly corrosive media, with higher strength and corrosion resistance.

• Aluminum bronze: Suitable for applications requiring corrosion resistance and low friction.

2. Connection Types

The connection type of butterfly valves should be selected based on system design and installation requirements. Common connection types include:

• Double flanged: Suitable for applications requiring frequent disassembly and maintenance.

• Wafer: Suitable for compact space installations, with convenient installation and maintenance.

• Lug: Suitable for applications requiring connection to flanges, with convenient installation and maintenance.

3. Pressure-Temperature Ratings

According to the API 609 and ASME B16.34 standards, the pressure-temperature ratings of butterfly valves should meet the system's operating requirements. When selecting, pay attention to:

• Cold working pressure (CWP): Ensure the maximum working pressure of the valve at ambient temperature.

• Pressure-temperature class: Ensure that the pressure class of the valve at different temperatures meets the system requirements.

4. Sealing Performance

Sealing performance is one of the key characteristics of butterfly valves, and the appropriate sealing material and structure should be selected based on the nature of the medium and operating conditions. Common sealing materials include:

• Rubber (EPDM, NBR): Suitable for low and medium temperature ranges, with good elasticity.

• Polytetrafluoroethylene (PTFE): Suitable for high-temperature and corrosive media, with good corrosion resistance and low coefficient of friction.

• Metal seal: Suitable for high-temperature, high-pressure, and highly corrosive media, with good sealing performance and durability.

5. Operating Methods

The operating method of butterfly valves should be selected based on the degree of system automation and frequency of operation. Common operating methods include:

• Manual operation: Suitable for applications requiring manual operation.

• Pneumatic operation: Suitable for applications requiring quick opening and closing.

• Electric operation: Suitable for applications requiring remote control.