Ductile Iron Pipe Threading: 7 Critical Tips for Perfect and Durable Results

It is important to create secure connections between pipes. Although there are different methods, ductile iron pipe threading is one of the most popular and reliable methods. The mechanism of this type of connection is creating even threads on pipe ends and screwing pipe sections together. The process of threading ductile iron pipe fittings includes several steps, starting from measurement and marking to assembling the connection. In addition to this joining method, another popular method is called a flanged connection. In this type of connection, flanges get bolted to the pipes to create a secure and leak-tight connection. However, there are several other alternatives for ductile iron pipe threading, such as compression fittings, mechanical joints, and push-on joints; this method is still widely used for a variety of applications.

 

What Is Ductile Iron Pipe Threading?

A specific method of joining ductile iron pipe fittings together is ductile iron pipe threading. There are several different pipe jointing methods, such as flanged connections or push-on joints, yet threading ductile iron fittings is one of the most popular ones. According to Shurjoint, this method is widely used in industries such as wastewater management, water distribution networks, and industrial processes. In this method, pipes are screwed together to create a leak-tight connection.

• Ductile iron pipe threading enables easy installation and makes disassembly for repairs easier.
• It shows high compatibility with several pipe diameters or pressures.
• The threading method provides durable and strong connections.
• Ductile iron pipes have good resistance to corrosion and wear while being connected by the threading method.

How to Thread Ductile Iron Pipe?

Threading ductile iron pipe consists of a few critical steps. Each step must be taken precisely, adhering to standards and recommendations. The main procedure is creating helical grooves or threads on both ends of pipes so a secure connection is created between pipes and fittings. Workers must always have safety equipment with them while working and follow safety guidelines.

Measure and Mark

The length of the pipe used in the project must be measured and determined. Also, for a more precise operation and connection, the desirable and intended cut line must be marked. By following these few steps, a secure and standard connection will be threaded.

Cut the Pipe

To start the process, the pipes must be cut. For this, a cutoff saw or a pipe cutter can be used. The area that must be cut is the marked line on the pipes. This ensures a straight and clean cut.

Deburr and Chamfer

There must be sharp edges or burrs after the cut. These burrs must be removed from the pipe end with specialized deburring tools or a file. As the next step, the pipe must get ready for the threading process. So, a slight chamfer should be created on the outside edge of the pipe end.

Prepare the Threading Equipment

It is in this step that specialized ductile iron pipe threading tools come into use. The threading equipment must be ready and prepared for the main process. A pipe threading machine is the required tool. A proper threading die based on the pipe diameter must be prepared. The die teeth must be lubricated with an appropriate thread-cutting oil.

Thread the Pipe

The pipe in the threading machine must be positioned securely to ensure the alignment is done properly with precise control. In this step, the machine gets started, and the die advances to the pipe end. The point is that consistent pressure must be applied to the pipe end to create the threads. This process must be done in a steady manner, as it is crucial to have threads with even depths and pitches. Referring to Freshwater Systems, any change of depth or pitch in threads must be avoided.

Inspect the Threads

In this step, the threading process is complete. Thus, the threads must be inspected for potential imperfections, such as irregularities. However, if any imperfection is visually found on the threads, a thread file or a thread chaser can be used to refine the imperfect threads. This way, desirable ductile iron pipe threading is maintained.

Clean and Protect

In this step, the ductile iron threading process is mainly over. Only the cleaning and protection protocols must be done. Any metal shavings or debris on the threaded pipe end must be removed safely. Also, a protective coating, such as thread sealant or a rust inhibitor, should be applied to the pipes. This protective layer will prevent corrosion on the threaded pipes to ensure a reliable connection.

Assemble the Connection

The only remaining step is the connection assembly process. In this step, the threaded pipe gets screwed into another threaded pipe or a compatible fitting. The only point is to maintain proper alignment and engagement of the threads. The connection is tightened with a pipe wrench for a secure operation; however, over-tightening must be highly avoided, as it can cause serious damage to the threads and extra stress on the pipes.

Threading vs. Flanged Connections: What’s the Difference?

Different methods can be used to join ductile iron pipes. Ductile iron pipe threading and flanged connections are two common methods, and they offer many advantages. However, these methods also have some key differences.

Threaded Connections

• Ductile iron threading is generally used for smaller-diameter pipes. This type of connection is used for lower-pressure applications, especially where regular and routine disassembly or maintenance is required.
• Helical grooves or threads are cut on both ends of the pipes to have a threaded connection. This way, pipes can be connected to each other by being screwed together to create a leak-tight connection.
• A significant advantage of threaded connections is that they are much easier to get installed or disassembled.

Flanged Connections

• Flanged connections are normally used for larger-diameter pipes. They are mainly used in applications where a robust connection is needed.
• These connections are typically used for higher-pressure applications, as they are generally stronger.
• In flanged connections, a flange, a rimmed attachment, gets attached to both ends of the pipes. Bolts and gaskets are used for this purpose. Flanges get bolted together to create a leak-tight connection.
• The main difference between flanged connections and threaded connections is that flanged ones require more time and effort when being installed or disassembled.

 

Here is the comparison table to compare the technical differences between flanged connections and threaded connections.

 

Category	Threaded Connections	Flanged Connections
Installation	Simpler and quicker	More time-consuming
Strength	Generally weaker	Generally stronger
Pressure Rating	Suitable for lower pressures	Suitable for higher pressures
Pipe Diameter	Smaller diameter pipes	Larger-diameter pipes
Applications	Easier disassembly for maintenance	More robust connections
Cost	Generally less expensive	Generally more expensive
Maintenance	Easier to disassemble and reassemble	More complex to disassemble and reassemble
Alignment & Assembly	More forgiving	Require precise alignment and assembly
Versatility	Suitable for various pipe materials	Suitable for various pipe materials and sizes
Expansion & Contraction	Limited ability to accommodate movement	Can accommodate movement
Leakage	More susceptible to leaks with age	Less susceptible to leaks

 

What Are the Common Alternatives to Ductile Iron Pipe Threading?

There are some alternatives to ductile iron pipe threading that can offer some of the advantages this method has. Choosing the suitable option depends on some key factors, such as the material, diameter, and pressure rating. A professional engineer can give a more specialized opinion on this matter. Here are some of the most common alternatives:

• Push-on joints: In this method, a quick connection is created by pushing a pipe into a special fitting.
• Victualic couplings: This method employs a grooved coupling, which is easy to install and doesn’t require welding or threading to make the connection.
• Compression fittings: Compression nuts are used to seal a secure connection.
• Mechanical joints: The required seal for the connection is created by using fittings that are utilized with rubber gaskets.
• Flanged connections: They are considered bolted connections that use flanges for secure joins.
• Socket/butt welded connections: In this method, pipes are welded together at each pipe end.
• Grooved pipe couplings: Circumferential grooves create a flexible connection in this joining method.

Final Thoughts

A secure and leak-tight connection is crucial for ductile iron pipes and fittings. There are several methods to achieve this kind of connection. Thus, a suitable method of joining pipes together must be chosen. Ductile iron pipe threading is one of these methods. It offers several advantages in different applications. Creating this type of connection consists of several steps, yet the installation or disassembly process is quite easier than it is imagined to be. Threading ductile iron pipes has been a popular choice for a variety of applications for years.