Understanding Different Types of Valve Connections and Fittings

Blog posted by Russ Bailey on Jan 29th 2024

Hey there, fellow valve enthusiasts! We know valves play a crucial role in regulating the flow of liquids and gasses in a broad range of applications. Something you might not know much about are valve connection types. Valve connection types are important, as selecting the best valve connection for your application may improve both valve and system performance.

If you're not clued-up on valve connection types, fear not, ValveMan is here to help! Read on for an overview of flange, threaded, welded, compression and other types of valve connections.

What are Valve Connections?

Put simply, valve connections refer to the type of connection between valves and piping or equipment. Knowing about valve connection types is useful because:

It leads to better system design and operation. The most efficient and suitable connections and fittings for a given application are selected.
It allows for effective maintenance and troubleshooting — knowing about valve connections assists in identifying parts that may cause leaks, loss of pressurization or failures.
It is cost-effective. Selecting the right valve connections can control capital costs and costs associated with energy loss, maintenance, leaks or premature wear and tear.

Next, let's look at some common valve connection types.

Types of Valve Connections

Understanding the different types of valve connections is crucial for effective piping setups and optimal installation, operation and maintenance. Here are a few common valve connection types:

Flange connections are used in piping systems because they are easy to install and remove, which makes maintenance efficient. A flange connection includes a pair of flanges, a gasket or ring, bolts and nuts — assembled to ensure a secure and fluid tight seal. Flanges have holes which allow valves to bolt to pipes or other equipment. Gaskets or rings are placed between flange faces and ensure a leak free seal.

Flanged Ball Valve

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Threaded connections (also referred to as screwed connections) use male and female threads to connect valves to pipework and other equipment. Male threads are external to a valve or fitting, and female threads are internal. This connection is suitable for small-diameter valves and where conditions require frequent disassembly and reassembly.

Threaded ball valve

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In welded connections, pipes, valves and fittings are welded together. This creates a permanent, leak-proof connection. A welded connection is suited to high pressure and high temperature applications.

Socket weld ball valve

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These are the most popular valve connection types, but there are also some less common ones that we will mention:

Compression fittings use a nut and ferrule (or ring) to seal the connection between valves and pipes. When the nut is tightened, the ferrule compresses around the pipe. These are typically used in high-pressure applications that need to be easily disconnected and reconnected.

Compression fitting ball valve

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A union is a fitting that allows threaded pipework to be dismantled and reassembled. They may be standalone pipe fittings or integrated in other components, such as valves.

Union connection check valve

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Specialized applications may use other connections. These connections are often unique and suited to particular applications.

Let's look at valve connection types in more detail.

Flanged Connections

A flange is a (typically) circular disc with bolt holes spaced around the circumference. A pair of flanges, a gasket or ring, bolts, nuts and washers are assembled to create a flange connection between two components. Flanges can connect pipes, valves, pumps, and other equipment, creating a secure and fluid tight seal. Key characteristics of flanges include their durability, strength, and the ability to withstand substantial pressure, temperature, and chemical reactions.

There are many standards which cover flanges, common standards include:

Worker torquing flange bolts and nuts, licensed under CC BY 3.0

Types of Flanges

Some common flange types include:

Cast Flanges: These flanges are integral with the equipment body. Equipment such as pumps and larger valves use cast flanges.
Slip-On Flanges: These are slid onto a pipe or valve and welded to the ends via fillet welds.
Weld Neck Flanges: These have a long tapered hub which is welded via butt welds. Weld neck flanges are often used for high-pressure or critical applications.

Advantages of Flange Connections

Flanged connections provide a tight and secure seal.
Connections are reusable, and relatively easy to assemble and disassemble.
Use in large pipe and severe operating conditions such as high pressure, high temperature, shock and vibrations.

Disadvantages of Flange Connections

Flanged connections are bulky.
Connections may be expensive, particularly for specialty flanges.
Flanged connections require skilled labor for correct installation.
Vulnerable to corrosion or failure due to incorrect material selection.

Common Applications of Flange Connections

Flanged connections are widely used in valves and pipeline systems that transport natural gas, vapors, petroleum products, water or high-temperature fluids. They are also installed in fire protection systems and in large, high-pressure air conditioning systems.

Threaded Connections

As the name suggests, threaded connections are between valves, pipes or other equipment screwed together. Components with male and female threaded ends are manually screwed together to create a secure, tight seal. These connections are popular for their straightforward design and ease of installation, enabling users to screw or unscrew components by hand or with the use of basic tools.

Types of Threads

Many thread designs are used to form threaded connections between valves, pipes and fittings — these include:

National Pipe Thread (NPT): Commonly used in North America. These are tapered threads providing a secure seal, together with the use of sealant such as pipe tape or dope.
British Standard Pipe (BSP): Widely used globally. BSP threads can be either tapered or straight threads.
Metric: These threads follow international standards (ISO) and are identified by their diameter and thread spacing.

There are many thread standards available governing different thread designs, common standards in industry include:

Advantages of Threaded Connections

Simple to install, assemble and disassemble.
Cost-effective connection option.
Many pipe materials can be threaded.

Disadvantages of Threaded Connections

Not suitable for large bore valves and pipes.
Prone to leaks over time.
Limited pressure and temperature handling capability.
Might require thread sealant for an effective seal.

Common Applications of Threaded Connections

Screwed or threaded connections are frequently used for small bore pipework, low-pressure systems and areas where leaks are not hazardous. They are commonly found in domestic plumbing, HVAC systems, non-critical and auxiliary industrial applications.

Welded Connections

Welding is a popular joining method in industrial and residential piping applications. It involves the use of a heat source to melt and join two components, often creating a permanent bond. Key characteristics of welded joints include high strength, reliability, and lack of leaking issues.

Most metals, and even plastics like HDPE, are weldable. Some welded connections use filler material, in the form of welding rods or electrodes.

Some common weld standards include:

Butt welding a pipe, licensed under CC BY 3.0

Types of Welded Connections

Notable types of welding connections for valves and pipework include butt welds and socket welds. A butt weld connection involves aligning two components edge-to-edge before welding, creating an efficient, high-strength joint. Edges are typically cut or beveled prior to welding. A socket weld connection involves fitting a pipe into a prepared, recessed area of a valve or fitting before welding, typically using a fillet weld.

Advantages of Welded Connections

Strong and durable connections.
High pressure and temperature capability.
Allows for design flexibility.

Disadvantages of Welded Connections

Welded connections are difficult to disassemble, and often require destructive means of disassembly.
Highly skilled labor and specialist equipment is required for a proper connection.
Material distortion is possible due to the large heat input.
Socket welded connections are not as strong or robust as butt welded connections.

Common Applications of Welded Connections

Welding is widely used in piping systems as a joining method. You will commonly find butt welded connections in high-pressure and high-temperature operations. Power plants, steam lines, oil and gas applications, chemical plants and diverse manufacturing environments use butt welded piping. Socket welded connections are typically used for valves. These are more commonly found in small bore pipework. Low pressure and low risk applications such as residential plumbing, and industrial support systems make use of socket welded connections.

Compression Connections

Compression fittings operate by applying a compressive force to hold component ends together. Compression fittings usually include a compression nut and a ferrule, ring or sleeve, installed over a pipe. The nut is tightened, which then compresses the ferrule onto the pipe providing a tight seal.

Metallic and plastic compression connections are available. Several types of connectors are commonly used such as straight, reducing, and elbow type connectors.

Advantages of Compression Connections

Simple to install.
Easy to assemble and disassemble.
High pressure and temperature variants are available.
Available in different materials.

Disadvantages of Compression Connections

Prone to leakage if not tightened correctly.
Not suited to applications with excessive vibration, bending or movement.
Not readily available in larger valve or pipe sizes.

Common Applications of Compression Connections

Compression fittings are commonly used in plumbing systems for water, gas, airlines, refrigeration units and hydraulic systems. In an industrial setting, they are often used in factories for easy disassembly of valves and piping.

Other Valve and Pipe Connections

Some other connections include union connections, soldered or brazed connections, wafer or lugged type flanges, push-fit connections, clamp connections and quick release couplings.

How to Select Your Valve Connection Type

Consider the following factors when selecting the best connection type for your valve:

Existing similar valves: If you have existing valves on the same system, and they are operating without any issues, their connection end type is likely the right choice.
Standardization: Ensure adherence to industry, company and/or plant standards.
Process pressure rating: The connection type must be able to withstand the maximum pressure expected in the process pipe.
Cost: Welded connections are the cheapest type but offer limited operational flexibility while you will need expertise to install (which might present additional cost). The cost of threaded and flange connections depends on valve size, with threaded connections generally being the cheaper of the two.
Leakages: Welded connections provide are a zero leakage option. Flange connections are good for minimal leakages for larger pipe sizes and threaded connections for smaller pipe sizes.
Installation, replacement, and maintenance: Flange connections enable easy installation and maintenance of valves. Threaded connections present some challenges, while welded connections offer limited replacement and maintenance opportunity — valves typically need to be cut out.
Pipe size: Large pipe sizes above 4 inches are usually flanged or welded. Threading is common on smaller pipes, but even these may be welded or flanged for critical applications or hazardous service.
Connection standard: Check the connection standard for threaded and flange valve connections to match the pipe specification. For welding connections, check the material of the valve and pipe.

Remember that your system specifications and requirements will determine the connection that is most effective.

Final Thoughts on Valve Connections

Understanding valve connections and types of valve fittings is crucial for those working with any pipe system. Using the right valve connection is vital for effective and safe operation. Exposure to a diverse range of valves and connection types will expand your knowledge base and lead to more efficient design and problem-solving.

The world of piping and valves might be complex, but knowledge makes all the difference in ensuring smooth and safe operations. Feel free to peruse the links below for further reading and additional resources:

What to Think About When Buying a Valve

Choosing the Perfect Valve End Connection Type: NPT vs Flanged vs Socket Weld

What is the Difference Between #150, #300, and #600 Pound Flanges?

Russ Bailey

Valve industry Sales Customer relationship management Product knowledge Consultative sales approach Business growth

Russ Bailey is a seasoned professional with an impressive 35-year career in valve sales. He serves as an Outside Sales Representative for both ValveMan.com and FS Welsford, where his deep industry knowledge and exceptional salesmanship enable him to provide tailored solutions for a diverse clientele. Russ is known for his ability to build robust relationships and his unwavering dedication to customer satisfaction. With a strong commitment to excellence, Russ continues to drive business growth and contribute significantly to the success of both companies.