🧿 The main maintenance methods of ductile iron pipes

- Replacement during water outage: This requires comprehensive consideration of the costs of water outage, installation, piping, and transportation. This method is suitable for scenarios where water outage is possible.

- Specialized pipe clamps (pipe repair clamps): These allow for repairs under water and pressure, are simple to install, and the cost is proportional to the price of the corresponding half-joint, as well as the installation and transportation costs.

- Welding: This method carries a high risk and is not recommended as the primary method for the following reasons.

🧿Core Reasons Welding Is Not Recommended

2. Material Properties and Welding Metallurgy Issues

- High carbon content results in an extremely high carbon equivalent in the weld metal, which can easily form a hard and brittle structure (martensite or white cast iron) in the heat-affected zone.

- Graphite nodules may dissolve or distort in the heat-affected zone, weakening material properties and creating a tendency for hot and cold cracking, leading to uneven composition.

Thermal Stress and Deformation Issues

- Localized heating and cooling during welding generate significant residual stresses. Cast iron has poor ductility, making it difficult to release stress and prone to cracking.

- Uncontrolled bending or twisting of the pipeline may occur.

In summary, welding should only be used as a last resort in exceptional circumstances and requires experienced welders who strictly adhere to specific process specifications. Welding repair plans for critical pressure pipelines must also be rigorously evaluated and approved.