Ball Valve Connection Types
Ball valves are popular in domestic and industrial applications because of their wide range of use, low cost, and ease of maintenance. Different applications and installation environments of ball valves require different types of end connections to properly connect to process pipes or components. Though the connection types essentially do the same thing: to attach the ball valve to the pipe or component at both ends, some connection types are more advantageous for different applications. Read our ball valve article to learn how ball valves function.
The most common types of ball valve connections: flanged connection, welded connection, true union, tri-clamp, and threaded as seen in Figure 1.
Figure 1: Ball valve connection types: flanged connection (A), welded connection (B), true union (C), tri-clamp (D), and threaded connection (E).
Table of Content
- Threaded connection
- Welded connection
- Flanged connection
- Tri-Clamp connection
- True union connection
- Selection criteria
Figure 2: Ball valve with threaded connection.
Threaded connection ends are an easy way to connect small valves to pipes. They are typically used in applications that have small ball valves with a diameter less than 4" because larger diameters will be difficult to seal and are prone to leakages through the threads. They are cheap, easy to install, and easy to maintain and replace. Typically, the valve has female threaded ends that connect to a male threaded component. In some cases, the valve has male threaded ends or one male threaded end and the other a female threaded end. The threads are made by adhering strictly to thread standards, which specify the parameters of the thread. An example of a ball valve with threads can be seen in Figure 2.
Threaded connections can either be straight or tapered. Straight connections often require an O-ring that compresses to ensure a tight seal between the valve and the pipe. The tapered thread does not require an O-ring to achieve a tight seal. Both types of thread can use pipe tape or a sealant between the male and female thread, which serves as a lubricant, provides sealing, and prevents metal-to-metal contacts that cause wear.
There are three main types of international thread standards that define the parameters of the thread. Read more about thread standards in our technical article.
British Standard Pipe (BSP)
BSP is a widely accepted standard for sealing pipes and fittings in most parts of the world, with the notable exception of the United States of America. The BSP consists of both female and male threaded ends for the valve and pipe. They have a flank angle of 55 degrees with rounded roots and crests (valleys and peaks).
The BSP standard has two types of thread: the parallel (straight) threads BSPP and the taper threads BSPT. The BSPP is defined by the standards ISO 228-1:2000 and ISO 228-2:1987, while the BSPT is defined by the standards ISO 7, EN 10226-1, and BS 21.
American National Standard Pipe Thread
This is also known as the National Pipe Thread (NPT). It also has a standard for both tapered and straight thread types. The flank angle is 60 degrees with flat roots and crests. There are many types of NPT, but the two main types are the American National Standard Taper Pipe Thread (also known as NPT) and the American National Standard Straight Pipe Thread (NPS).
Metric Thread Standard (M)
Metric threads are a general-purpose screw thread standard. It is a parallel type thread known by the ‘M’ designation followed by a number indicating the threads major diameter. The major diameter and the pitch size is used to characterize the thread standard. It is a V-shaped thread with a flank angle of 60 degrees. The metric thread is defined by the standard ISO 68-1.
Figure 3: Ball valve with a butt-welded connection (A) and a socket welded connection (B)
Welded connections are used where zero leakage is important to the system. This is typically in high-temperature and high-pressure piping systems. It is also common to use welded connections with chemically dangerous fluids. Trained professionals should carry out welded connections. They are a permanent type of connection. There are two main types of welded connections for valves:
Socket welded connections
This type of welded connection has the valve diameter larger than the pipe’s diameter, such that the pipe can fit into the valve socket end. The weld is done around the rim of the valve end that is connected to the pipe. It can be seen in Figure 3 on the left (A).
In this welded connection, the valve ends and the pipe ends have the same diameter. The connection ends are placed against each other and grooved to create a space for the weld. The weld is done around the rims of the connection. Butt welding is common for smaller pipe sizes. It can be seen in Figure 3 (B).
Figure 4: A manual ball valve with flanged connection
Flanged connections are typical for valve sizes above 4 and can be seen in Figure 4. They are quite easy to install and can be easily removed for cleaning and maintenance without affecting other parts of the pipe network. They are very common in industrial applications. The flanges are solid metal plates with holes through which bolts and nuts are placed to tighten the valve to the pipe. Just like threaded connections, flanged connections follow strict standards for the parameters. The design of the plates, hole size, hole thread, and hole position are some of the parameters that are set by these standards.
The flanged connection standards are DIN 1092-1, which is used under ISO 7005 as the European standard, ANSI/ASME B16.5, which is the American National Standards Institute in conjunction with the American Society of Mechanical Engineers and SAE J518, which is the Society for Automotive Engineers. These standards have multiple types and styles of the flanges and how they are attached to the valve and pipe.
A Tri-Clamp, which is sometimes known as a Tri-Clover or a T-Clamp, is a special type of flanged connection where the flanged ends of the valve (A) and pipe are held together with a hinged clamp (B) that has a gasket in between. The tightening of the clamp squeezes the pipe and the valve end ensuring a sealed connection. There are different types of clamps such as single hinge, three-segment double hinge, and two-bolt high pressure.
Figure 5: A ball valve with tri-clamp connection (A), and a tri-clamp (B)
True union connection
Figure 6: True union connection
True union connections are typically used in PVC valves and piping and the outer diameter of the pipe matches the inner diameter of the connection. A solvent (glue) is used to prevent leakages. They allow multiple connections and disconnections of the ball valves from the pipe for maintenance or replacement. PVC components are often used in corrosive media such as seawater, acids and bases, and organic solvents.
To select the best connection type for your ball valve, several factors have to be taken into consideration. We will discuss some of these factors below:
- Other similar valves: If you have other existing valves on the same network, their connection end type is likely the right choice for the valve.
- Process pressure rating: The connection type must be able to withstand the maximum pressure expected in the process pipe. Welded connections are for very high pressure, flanged connections for pressure up to 400 bar, and threaded connections up to 140 bar.
- Cost: Welded connections are the cheapest type but offer no flexibility while you will need expertise to install. The cost of threaded and flanged connections depends on valve size.
- Zero leakages: Welded connections should be used where zero leakages are required. Flanged connections are good for minimal leakages for larger pipe sizes and threaded for smaller pipe sizes.
- Simple to install, replace, and maintain: Flanged connections make the valve easy to maintain, threaded connections are more difficult, while welded connections offer no maintenance opportunity.
- Pipe size: Large pipe sizes above 4 inches are typically flanged or welded. Smaller pipe sizes are threaded and can be welded where process fluid can be dangerous.
- Connection standard: Take care to check the connection standard for threaded and flanged connection to match the pipe. For welding connection, check the material of the valve and pipe.
To learn more about choosing the right ball valve for your operation read our technical article on the selection of ball valves.