**1. What is a spiral welded pipe?**
A spiral welded pipe (also called helical submerged arc welded, or HSAW pipe) is a type of steel pipe manufactured by rolling a steel coil into a spiral shape and welding the seam continuously along its helical (spiral) joint. This method allows for the production of large-diameter pipes with consistent wall thickness using narrower steel strips.
**2. What is the difference between ERW pipe and spiral welded pipe?**
- **ERW (Electric Resistance Welded) Pipe**: Made by forming steel sheets into a cylindrical shape and welding the straight seam using electric resistance heat. It is typically used for smaller diameters and has a straight weld line.
- **Spiral Welded Pipe**: Formed by spirally winding steel strips and welding the helical seam. It is suited for larger diameters and offers flexibility in adjusting pipe dimensions by changing the winding angle.
**3. What are the disadvantages of spiral welded pipe?**
- **Residual stress**: The spiral welding process can introduce residual stresses, requiring post-weld heat treatment for critical applications.
- **Geometric tolerances**: Less precise in maintaining roundness compared to straight-seam pipes.
- **Weld inspection**: Helical seams are harder to inspect for defects compared to straight seams.
- **Application limits**: Not ideal for high-pressure or critical services due to potential weld inconsistencies.
**4. What is the purpose of spiral pipe?**
Spiral welded pipes are commonly used for:
- Water and gas transmission pipelines.
- Structural applications (e.g., piling, scaffolding).
- Low-to-medium pressure oil and gas transportation.
- Drainage and sewage systems.
Their large diameter and cost-effectiveness make them suitable for infrastructure projects.
**5. What is the difference between seamless pipe and spiral welded pipe?**
- **Seamless Pipe**: Manufactured without welding by extruding or piercing a solid billet. It has no seams, offering superior strength and uniformity, ideal for high-pressure/temperature applications.
- **Spiral Welded Pipe**: Contains a helical weld seam, making it weaker than seamless pipe. It is cheaper and used for larger diameters where high pressure is not a priority. Seamless pipes are more expensive but have no weld-related failure risks.
