How to select the right butterfly valve: Key rules and steps

Butterfly valves are widely used in various industries due to their compact structure, cost-effectiveness, and suitability for regulating or isolating flow. However, selecting the right butterfly valve for a specific application requires a systematic evaluation of operating conditions, valve types, materials, and standards. Below is a comprehensive guide to help ensure optimal butterfly valve selection based on performance, reliability, and economy.

1.Identify Service Conditions and Medium Characteristics

Understanding the working environment is the first and most critical step:

Fluid type: Gas, liquid, steam, slurry, or corrosive media.

Medium characteristics: Temperature, viscosity, abrasiveness, and chemical properties (e.g., acids, alkalis, oils, steam).

Pressure and temperature range: Determine the maximum working pressure (PN/Class) and temperature.

High-temperature media: Choose metal-seated butterfly valves.

Low-temperature service: Consider material brittleness at low temperatures.

Flow control requirement:

On-off control (fully open or closed), or

Throttling control (modulating flow).

2.Choose the Appropriate Structural Type

By Disc Design:

Concentric (centerline) butterfly valve:

Simple design, cost-effective.

Suitable for low-pressure, ambient temperature applications (e.g., water systems).

Double offset butterfly valve:

Better sealing than concentric type.

Ideal for medium-pressure, medium-temperature service.

Triple offset butterfly valve:

Metal-to-metal sealing.

Designed for high-pressure, high-temperature, and critical services (e.g., oil & gas, steam pipelines).

By Connection Type:

Wafer type:

Compact design.

Ideal for space-limited pipelines.

Flanged type:

Easy to install and remove.

Suitable for high-pressure and large-diameter pipelines.

Welded type:

Reliable under high pressure or special applications (e.g., chemical processing).

3.Select the Proper Materials

Body Material:

Cast iron (e.g., gray iron, ductile iron): For low-pressure, ambient conditions.

Carbon steel (e.g., WCB): For medium to high pressure.

Stainless steel (304/316): For corrosive fluids.

Special alloys (e.g., duplex, Hastelloy): For aggressive or high-temperature services.

Seal Material:

Rubber (EPDM, NBR): For non-corrosive media such as water and air.

PTFE (Teflon): Chemically resistant and heat-resistant; used in chemical industries.

Metal seals (stainless steel, alloy): Withstand high pressure and temperature; used in triple offset designs.

4.Nominal Diameter (DN) and Pressure Class

DN (Nominal Diameter): Must match pipe inner diameter to avoid erosion or noise due to high flow velocity.

Pressure Rating: Select according to system requirements (e.g., PN10, PN16, Class 150, Class 300).

5.Choose the Right Actuation Method

Manual (lever or gear): For small-diameter valves (DN ≤ 300) or infrequent operation.

Electric actuator: For automated or remote-controlled systems.

Pneumatic actuator: For fast switching and explosive environments (e.g., compressed air systems).

Hydraulic actuator: Ideal for large-size valves requiring high torque (e.g., hydroelectric plants).

6.Determine Required Sealing Class

Based on ISO 5208 standards:

Class VI: Allowable micro-leakage (typical for concentric butterfly valves).

Class V or zero leakage: Achievable with triple offset metal-seated valves.

Special sealing demands:

Food-grade, vacuum-tight, fire-safe valves as per application needs.

7.Consider Installation and Maintenance Requirements

Installation space:

Wafer type requires space between flanges.

Flanged type requires room for bolts and nuts.

Maintenance:

Concentric valves are easier to maintain.

Triple offset valves have longer service life but are more complex to repair.

Flow direction: Some valve types (especially double and triple offset) have flow direction restrictions.

8.Verify Industry Standards and Certifications

Standards:

GB (China), API 609 / ANSI (USA), EN (Europe), JIS (Japan)

Certifications (based on industry):

FM/UL (fire protection), NSF (potable water), ATEX (explosion-proof), API (oil & gas)

9.Evaluate Total Cost of Ownership

Choose a valve that balances initial investment, maintenance cost, and expected service life:

Triple offset valves have a higher upfront cost but offer longer durability, making them ideal for continuous high-demand operations.

10.Typical Application Examples

Water Treatment (ambient pressure/temp):

Concentric butterfly valve with EPDM seal and cast iron body.

Chemical Pipeline (corrosive media):

Flanged triple offset valve with 316 SS body and PTFE seat.

Steam System (high temp/pressure):

Triple offset metal-seated valve with electric actuator.

11.Special Notes

Avoid using butterfly valves for high-viscosity fluids (e.g., asphalt) or media with solid particles (risk of jamming).

For large-diameter valves, check stem strength and actuator torque.

In throttling conditions, account for cavitation and vibration risks.

By following these comprehensive selection steps, users can ensure that the butterfly valve chosen fits the actual service conditions while balancing performance, safety, and cost-effectiveness. Whether for general water systems or critical petrochemical applications, accurate selection is the key to long-term reliability and operational efficiency.

If you need further selection guidance or customized solutions, please feel free to contact Haihao Group for technical support. Email:sales@haihaogroup.com