Can You Pipe Burst Ductile Iron Pipe? Challenges And Solutions
Pipe bursting is a trenchless method for replacing old pipelines, but is it effective for ductile iron pipes? Ductile iron pipes are flexible yet tough in both above-ground and underground installation, which may require pipe splitting for a replacement section. In this article, we’ll dive into pipe bursting of ductile iron pipe, innovations, and design considerations.
Due to the toughness, elongation (18%), and flexibility of ductile iron pipe, traditional methods of pipe bursting are not going to work correctly. Unlike cast iron or clay, it deforms and deflects under bursting head operation. For 4–12-inch pipes, pipe splitting is done with carbide blades; for HDPE or PE, static/hydraulic bursting systems (devices such as Grundoburst, which uses a 110-ton force) are used to cut and expand pipes.
Why Ductile Iron Pipes Cannot Be Fractured in Pipe Bursting
Ductile iron pipe is widely used due to its high strength and flexibility. However, these properties make it resistant to fracturing in traditional pipe bursting and requires another method to ease the bursting and replacement process.
Ductile Properties Resist Crushing
Via properties below, such as elongation and energy absorption, ductile iron pipe endures internal high-pressure and external heavy loads that pose some challenges for pipe bursting.
- High Tensile Strength: With a tensile strength of 60,000–100,000 psi, compared to 20,000–40,000 psi for cast iron, they resist under high stress and heavy loads.
- Elongation: Up to 18% elongation of them includes deformation and bending instead of shattering and bursting.
- Energy Absorption: Nodular graphite in ductile iron pipe neutralizes the energy impact and unlike clay or cast iron avoids brittle failure.
| Material | Tensile Strength (psi) | Elongation (%) | Fracture Behavior |
|---|---|---|---|
| Ductile Iron | 60,000–100,000 | Up to 18 | Deforms, resists shattering |
| Cast Iron | 20,000–40,000 | <1 | Brittle, shatters easily |
| Clay | 5,000–10,000 | Negligible | Brittle, shatters easily |
Why Fracturing Heads Fail
Old-fashioned pipe bursting fractures the pipe and pulls a new HDPE pipe into position by applying radial force (10–20 MPa) using a conical bursting head. (Source: Trenchlesspedia) This is ineffective for ductile iron (DI) pipe, which stalls equipment when it deforms under pressure.
Also, with thicker walls (0.5–1 inch as opposed to 0.25–0.4 inches), bell and spigot joints resist fracturing and can endure forces greater than those of standard rigs, which range from 50 to 100 tons.
The Solution: Cutting
Due to the DI pipe’s resistance, trenchless techniques such as pipe splitting are used to install HDPE after cutting 4–12-inch pipes with carbide-tipped blades (20–40 tons of force).
The Alternative Method: Pipe Splitting
As a trenchless method for ductile iron pipe replacement, pipe splitting provides a method for cutting the host pipe and making it perfect for pipes that deform under pipe bursting.
How Does the Process Go On?
It starts with slicing the pipe via a splitting head, including carbide-tipped blades, for which 20-40 tons of pulling force is required for 4- 12 inches of pipe.
Then, an expander pushes the fragmented pipes into the surrounding soil for a new pipeline, and a new HDPE or PE pipe is placed into the location and checked for right alignment
| Material | Compatibility | Technical Notes |
|---|---|---|
| Ductile Iron | Cuts 60,000 psi DI pipe without fracturing. | Uses carbide blades for 4–12-inch pipes. |
| Steel & Plastics | Handles non-brittle materials. | Effective for steel, PVC, and some PE pipes. |
Developments in Static/Hydraulic Bursting
The limitations of traditional pipe bursting can be surpassed with static/hydraulic bursting, a trenchless technique that is perfect for replacing ductile iron pipe (DIP). The Grundoburst is a remarkable piece of equipment for splitting and extending DIP for sewer and water main systems.
Grundoburst Equipment: Function and Benefits
The Grundoburst cuts DIP (4–48 inches) with static bursting heads equipped with carbide blades, and it installs HDPE or PE pipes by extending the path with hydraulic rams (up to 110 tons for 12-inch pipes). Here are some advantages of using this method:
- Flexibility: Easily manages high-strength DIP (60,000 psi) and bell and spigot joints.
- Pull Force: S. Pipe highlights that hydraulic systems create an accurate, controllable force that avoids stalls.
- Minimal Shock: Static operation protects surrounding utilities, such as gas lines, by decreasing the vibration effects.
- Safety: In the maintenance or fixing process of urban infrastructure, low-vibration design improves safety.
What to consider in ductile iron pipe replacement design?
Trenchless methods, such as pipe splitting or static/hydraulic bursting, mainly require detailed planning for sewer or water systems in ductile iron pipe replacement. Pipe size, joint type, and soil type are effective factors in this matter:
Pipe Size and Joint Type
In 4 to 12 inches diameters, pipe splitting is suggested, while static bursting is used for up to 48 inches diameters.
According to DIPRA, bell and spigot or push-on joints require carbide blades with a special design that may increase the pulling force up to 20% in trenchless replacements.
Soil Type and Upsizing
Sandy and soft soils allow 1-2 size upsizing, while clay or rocky soils are limited for upsizing and need smart sensors when replacing HDPE or PE pipes to control elongation.
Final Thought
Traditional pipe bursting doesn’t work for ductile iron pipes due to deformation performance, and pipe splitting and static/hydraulic bursting with HDPE or PE pipes are required. These trenchless methods are popularly used in sewer and water main systems, where minimized disruption and detailed alignment are the keys to a durable and safe replacement.
FAQs
1- Why is traditional pipe bursting ineffective for ductile iron pipes?
Due to the toughness, elongation (18%), and flexibility of ductile iron pipe, traditional methods of pipe bursting are not going to work properly.
2- What methods replace ductile iron pipes?
For 4–12-inch pipes, pipe splitting is done with carbide blades; for HDPE or PE, static/hydraulic bursting systems (devices such as Grundoburst, which uses a 110-ton force) are used.
3- How does pipe splitting work for ductile iron pipes?
It starts with slicing the pipe via a splitting head, including carbide-tipped blades, for which 20-40 tons of pulling force is required for 4- 12 inches of pipe.
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