Introduction
This article provides a comprehensive overview of butterfly valves.
Continue reading to learn about:
- What a butterfly valve is
- How it works
- Butterfly valve components
- Different types of butterfly valves
- Materials used in butterfly valve construction
- Advantages and disadvantages of butterfly valves
- And more...
Chapter 1: What Is a Butterfly Valve?
A butterfly valve is a quarter-turn rotary control device used to regulate fluid flow in pipeline systems. It features a rotating disc positioned directly in the flow path. This disc is controlled by an external actuator connected via a stem. When parallel to the flow, the disc completely blocks fluid passage. When perpendicular, it allows full flow. The valve opens or closes with a 90-degree disc rotation.
Teflon Seated Butterfly Valve from Butterfly Valves & Controls, Inc.Like ball and plug valves, butterfly valves operate with a quarter turn. They have simple designs and compact construction that fits between pipe flanges. These valves can be manually operated or automated for process control. While excellent for on-off applications, their flow throttling capability is somewhat limited.
Available in various models, butterfly valves are designed to handle different temperatures, pressures, and flow rates. Each type is engineered to meet specific requirements for liquid and gas pipeline systems.
Chapter 2: Butterfly Valve Components
The main components of a butterfly valve include:
- Valve Body: Constructed from durable materials, the body houses and protects internal components while connecting to the piping system. Designed for strength, it maintains integrity in demanding environments like chemical processing, water treatment, and HVAC systems.
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Disc: This component controls fluid flow through rotation. The flow rate depends on the disc's opening degree, making it essential for throttling applications.
When perpendicular to the flow, the disc blocks all fluid. A 90° rotation fully opens or closes the valve, while intermediate positions enable flow regulation. Its efficient design makes it comparable to ball valves for isolation and control processes.
- Stem: This shaft connects the disc to the operating mechanism. Sealed with O-rings, it prevents leaks and ensures reliability. Stem designs vary by valve type (concentric, double-offset, or triple-offset), with durability being crucial for high-cycle applications.
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Seat or Sealing Ring: Provides a seal between disc and body when closed, preventing leaks. Seat materials include:
Soft seats (EPDM, PTFE, NBR) for low-temperature/pressure applications with tight shutoff. metal seats (stainless steel) for high-temperature/pressure services, offering longer life with potential minimal leakage.
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Operating Mechanism: Controls valve operation through manual (lever/handwheel) or automatic (actuator) methods.
Manual operation adjusts valve position directly. Larger valves may use gear operators. Automated valves employ electric, pneumatic, or hydraulic actuators for process control and remote operation.
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Triple Offset: Features three offsets creating a conical sealing profile for bubble-tight shutoff and reduced wear. Ideal for critical applications like steam and high-pressure gas systems.
- Bushing or Bearing: Affects valve lifespan and reliability. Industrial-grade bushings resist corrosion and wear, ensuring smooth operation. Materials like PTFE or bronze enhance performance in demanding environments.
Additional Features
- End Connections: Options include wafer, lug, flanged, and butt-weld types for different installation requirements.
- Pressure/Temperature Ratings: Valves are rated for specific operating conditions (ANSI, PN, JIS classes).
- Standards Compliance: Manufacturers adhere to API 609, ISO 5752, MSS SP-67, and NSF/ANSI 61 standards for quality and safety.
When selecting butterfly valves, consider components, materials, performance requirements, connection types, and compliance standards to ensure optimal performance and longevity for your application.
