Lug type Butterfly Valve

1. What is Lug Type Butterfly Valve?

A Lug type Butterfly Valve is a versatile and robust flow control solution designed for integration into demanding industrial piping systems. Distinguished by the presence of threaded metal inserts (lugs) around the perimeter of the valve body, this design allows the equipment to be bolted directly to each pipe flange using separate sets of bolts. This specific mechanical structure provides a significant advantage over wafer designs, as it enables the removal of downstream piping while the valve remains securely attached to the upstream side, a feature known as end-of-line service.

As a core component of modern fluid automation, this rotary unit combines a streamlined body with high-performance actuation. It is engineered to meet a wide array of international standards, including ANSI, DIN, JIS, and GB, ensuring seamless compatibility across global industrial infrastructures. Whether utilized in high-purity chemical processing or standard water treatment facilities, the lug-style architecture offers superior stability and ease of maintenance. The equipment can be configured with manual, pneumatic, or electric drive systems, depending on the specific automation requirements of the production facility.

2. How this Lugged Rotary Device Works?

The operational principle of this equipment centers on a high-precision rotary mechanism that manages fluid flow through a ninety-degree rotation of an internal disc. Because the body is bolted directly to the flanges, the alignment between the disc and the pipeline remains highly stable even under varying pressure conditions.

The core operational stages include:

1. Opening Phase: When the actuator—such as an AT or GT series pneumatic unit—transmits torque through the stem, the internal disc pivots from a position perpendicular to the flow to one parallel to it. This transition allows the media to pass through the body with a high flow coefficient (Cv) and minimal pressure drop.
2. Closing and Sealing Phase: Upon receiving a signal to close, the disc rotates ninety degrees back to meet the seat. In resilient-seated models, the interference between the disc edge and the elastic seat (often made of EPDM or FPM) ensures a bubble-tight seal. For high-performance applications, a double or triple eccentric geometry may be used to minimize friction during this closing action.
3. End-of-Line Functionality: A unique aspect of the lugged configuration is its ability to act as an isolation point. Because the bolts are threaded into the lugs, the valve can hold full rated pressure in one direction even when the pipe on the opposite side is disconnected for maintenance or repair.

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3. Types of Lug-style Control Units

3.1 Material Classification and Properties

To handle a diverse range of industrial media, these devices are manufactured from specialized materials:

• Plastic Series: Constructed from high-performance polymers such as UPVC, CPVC, PPH, and PVDF. The PVDF models are exceptionally durable, offering a wide operating temperature range from -40 to 140 degrees Celsius and excellent resistance to concentrated acids and alkaline media.
• Metal Series: Manufactured from robust materials like carbon steel (WCB) or stainless steel alloys (CF8, CF8M, 316L). These metal units are the standard for high-pressure systems where thermal stability and mechanical strength are paramount.
• Lined Series: Combining the pressure-bearing capacity of a metal shell with the chemical inertness of a fluorine lining (PTFE or PFA), these units are ideal for highly aggressive chemical services.

3.2 Sealing and Actuation Variants

• Resilient Seated: Features an elastic seat that provides excellent sealing for water and general chemical services.
• High-Performance Eccentric: Utilizes offset stem geometries to reduce seat wear and allow for use in steam or high-temperature gas applications.
• Automated Assemblies: These units are frequently equipped with intelligent pneumatic actuators or motorized electric actuators, allowing for precise proportional control through 4-20mA signals.

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4. Core Advantages of the Lugged System

The lugged design provides several technical benefits that enhance the safety and efficiency of industrial operations.

• Independent Bolting and Maintenance: The ability to perform end-of-line service without draining the entire system or removing the valve from the upstream pipe significantly reduces facility downtime.
• Superior Alignment: The threaded lugs ensure that the valve is perfectly centered between the flanges, reducing the risk of seal failure due to misalignment.
• Standardization: Most units are equipped with an ISO 5211 mounting pad, which facilitates the easy installation of various pneumatic or electric automation components.

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5. Industrial Applications

The stability and versatility of the Lug type Butterfly Valve make it indispensable across multiple critical sectors:

1. Chemical and Pharmaceutical: These units are essential for the safe distribution of aggressive acids and solvents. PVDF and CPVC models ensure no chemical degradation or contamination of the process media.
2. Water Treatment and Desalination: In desalination plants and sewage facilities, PPH and UPVC lugged equipment is used to manage chlorinated water and brine, where the ability to isolate sections of the piping for maintenance is a key requirement.
3. Semiconductor and Lithium Battery: In high-purity environments, pure plastic lugged units are used to handle ultrapure water and electrolytes, ensuring the absence of metal ions that could compromise product quality.
4. Metallurgy and Power: Metal high-performance models are deployed in cooling water systems and steam lines where high reliability under mechanical stress is necessary for plant safety.