Butterfly Valve End Connection Types ExplainedTfw Valve

In valve selection, choosing the wrong end connection type can lead to system leakage, installation challenges, higher maintenance costs, or even unexpected shutdowns. The performance of a butterfly valve depends not only on the disc and seat but also on the type of end connection and the industrial standards it follows. These factors ultimately determine its suitability, reliability, and compatibility with the pipeline system.

This article serves as your reliable guide to understanding the differences among butterfly valve connection types and their corresponding standards. It also provides a practical selection framework to help you make the optimal choice for your project.

Before diving into the details, the table below offers a quick overview of the most common butterfly valve end connection types—allowing you to grasp the key distinctions at a glance.

Connection Type	Key Characteristics	Advantages	Disadvantages	Typical Applications
Wafer	The valve body is sandwiched between two pipe flanges and fastened with long through-bolts.	Compact design, lightweight, and the most cost-effective option.	Cannot be used as an end-of-line valve; requires full pipeline disassembly for maintenance.	Water treatment, general low-pressure service, and cost-sensitive projects.
Lug	The valve body features threaded inserts (lugs) that allow independent bolting to each flange end.	Can serve as an end-of-line valve, allows one-side disassembly for maintenance, highly flexible.	Slightly heavier and more expensive than wafer type.	Fire protection systems, HVAC, and pipelines requiring isolation of equipment such as pumps or instruments.
Flanged	The valve body includes integral flanges bolted directly to the pipe flanges.	Provides the best sealing performance, high pressure rating, and easy disassembly for maintenance.	Heavier, more expensive, and requires more installation space.	Petrochemical plants, power generation, high-pressure water supply, and critical service points requiring frequent maintenance.
Butt Weld	The valve ends are directly welded to the pipeline.	Permanent leak-free joint, highest mechanical strength, and minimal flow resistance.	Non-removable once installed; requires skilled welders and precise welding procedures.	High-temperature and high-pressure services, hazardous media (e.g., hydrocarbons), and high-purity pipelines.
Socket Weld	The pipe is inserted into the valve’s socket end and then welded around the joint.	Easy to align and simpler to install than butt weld type.	Risk of stress cracking in the weld area under cyclic loads.	Small-diameter (typically DN50 and below) high-pressure pipelines.

Overview of Butterfly Valve End Connection Types

Wafer Butterfly Valve

Structural features. A wafer valve has no integral flanges. During installation, it is positioned between two pipe flanges and clamped in place with long through-bolts. Sealing is achieved as the body gasket/liner is compressed against the mating flange faces.
Connection standards. Although the body itself is flangeless, its outside diameter, sealing land, and bolt pass-through locations must match the pipeline flange standard. Common references include ASME B16.5 (Class series) and EN 1092-1 (PN series). Be sure to specify the governing flange standard when ordering; otherwise the valve may not fit the line.
Advantages. By omitting integral flanges, wafer valves offer the most economical, compact, and lightweight solution—ideal for tight layouts and cost-sensitive projects.
Limitations. The key constraint is that a wafer valve cannot be used at the end of a line and does not accept a blind plate. For service or replacement, both upstream and downstream flange joints must be loosened, which increases maintenance effort.
Typical applications. Widely used for water, air, and other non-critical, low-pressure services at ambient temperature. A common choice in water treatment and building services.

Lug Butterfly Valve

Structural features.A lug-type butterfly valve has threaded inserts (lugs) arranged around its body. These lugs allow bolts to be inserted from one side only—directly securing the valve to the corresponding pipe flange without the need for long through-bolts.
Connection standards.Just like the wafer type, the lug dimensions and bolt circle diameter must conform to a specific flange standard, such as ASME B16.5 or EN 1092-1. Compliance with these standards ensures proper alignment and secure fastening to the pipeline flanges.
Advantages.This design allows the valve to be used as an end-of-line valve, for example at the termination of a fire-protection branch line. A major benefit is in-line serviceability: by closing the valve, downstream piping or equipment can be removed for maintenance without disturbing the upstream system.
Typical applications.Lug-type butterfly valves are a standard choice in fire-sprinkler systems and are also widely used in HVAC installations or sections of pipelines that need isolation for pumps, heat exchangers, or instruments—offering excellent flexibility and convenience during maintenance.

Flanged Butterfly Valve

Structural features.A flanged butterfly valve has fully integrated flanges on both ends of the valve body. These flanges are bolted to the mating pipe flanges with gaskets in between, forming a strong, reliable, and leak-tight connection.
Connection standards.This is the most standardized yet complex connection type, divided into several major systems:

ASME System (U.S. Standard): Complies with ASME B16.5, where pressure ratings are expressed as Class (e.g., Class 150, Class 300).
European System: Follows EN 1092-1, where pressure ratings are expressed as PN (e.g., PN10, PN16).
Other Standards: Such as the Japanese JIS B2220 standard, which uses K to denote pressure ratings (e.g., 10K, 16K).

Important note: Flanges from different standards (for example, Class 150 vs. PN16) are not dimensionally interchangeable—their outer diameters, bolt hole numbers, and sizes may differ. Always ensure that the valve flange standard matches the pipeline flange standard before installation.
Advantages.Flanged butterfly valves offer superior sealing performance, higher pressure ratings, and easy installation or removal. The standard bolted design allows convenient inspection, replacement, or system modification.
Typical applications.They are widely used in demanding industrial sectors such as chemical plants, power stations, offshore platforms, and high-pressure water supply systems. Whenever frequent maintenance or high pressure integrity is required, the flanged type remains one of the most reliable and service-friendly choices.

Butt Weld (BW) Type Butterfly Valve

Structural features.In a butt-weld butterfly valve, the valve ends are directly welded to the pipeline, creating a seamless and permanent connection between the valve body and the pipe.
Connection standards.The end bevel geometry strictly follows ASME B16.25, which specifies groove shapes, angles, and land dimensions to ensure proper alignment and full-penetration welds with pipes manufactured per ASME B36.10.
Advantages.Provides a permanent, leak-free joint with the highest mechanical strength and minimal flow resistance—ideal for applications where zero leakage and structural integrity are paramount.
Typical applications.Commonly used in high-temperature, high-pressure, or hazardous service conditions, as well as high-purity pipelines where welded joints eliminate potential leak paths and contamination risks.

Socket Weld (SW) Type Butterfly Valve

Structural features.In this design, the pipe is inserted into a socket at the valve end and then fillet-welded around the outer edge, forming a secure connection that maintains alignment during installation.
Connection standards.Socket dimensions typically comply with ASME B16.11 or equivalent standards, ensuring compatibility with standard pipe sizes and wall thicknesses.
Advantages.Offers easy alignment and simpler installation compared with butt-weld valves, while still providing a robust, pressure-tight joint.
Limitations.The small crevice at the weld root can become a potential site for crevice corrosion or stress cracking, especially under cyclic loading or corrosive service.
Typical applications.Widely used for small-diameter (generally DN50 and below) high-pressure pipelines, where ease of installation and secure sealing are both required.

How to Choose the Right Butterfly Valve End Connection

Now that you understand the different connection types, let’s turn information into action. The following key questions will help you decide which connection type best suits your system:

1. What are your system’s pressure and temperature conditions?

Low pressure / ambient temperature (e.g., general water systems): Wafer or Lug types are the most economical and practical choices.

Medium to high pressure / high temperature (e.g., steam lines, high-pressure industrial processes): Flanged or Butt Weld types are essential for safety and durability.

2. Will the valve require future maintenance or disassembly?

Frequent inspection or maintenance needed: Choose Flanged for its ease of removal and reinstallation.

Occasional in-line isolation or partial system maintenance: Lug type offers the flexibility to isolate one side while keeping the other in service.

Permanent installation, prioritizing absolute reliability: Butt Weld is the ultimate leak-free option.

3. What are your budget and space limitations?

Limited budget or compact installation space: Wafer provides the best cost-performance ratio and minimal footprint.

Ample budget and space available: Flanged offers long-term convenience, reliability, and ease of maintenance.

4. What is your industry and medium?

Water treatment and building services (HVAC): Wafer or Lug types are the preferred standards.

Petrochemical, power generation, or marine systems: Flanged and Butt Weld are the mainstream options.

High-purity or hazardous media requiring zero leakage: Butt Weld remains the only viable choice.

Conclusion

Understanding butterfly valve end connection types helps prevent installation errors, leakage, and costly downtime.

Whether your system requires a Wafer, Lug, Flanged, or Welded connection, choosing the right type enhances safety, simplifies maintenance, and extends the valve’s service life.

Explore TFW Valve’s complete range of butterfly valve solutions to find the ideal configuration for your industrial or water infrastructure applications—engineered for reliability, performance, and long-term value.

If you have any further questions, please contact us.