**1. Which is better, ERW or EFW?**
ERW (Electric Resistance Welded) and EFW (Electric Fusion Welded) pipes serve different purposes. ERW pipes are made by rolling steel coils and welding the seam using electrical resistance, ideal for low-to-medium pressure applications (e.g., water, gas). EFW pipes use filler material to fuse edges, suitable for thicker walls and high-pressure environments. ERW is more cost-effective for standard uses, while EFW is better for specialized, high-stress applications.
**2. Which is better, GI or GP pipe?**
GI (Galvanized Iron) pipes are coated with zinc to resist corrosion, making them ideal for outdoor or humid environments. "GP" (Galvanized Plain) is less commonly defined but may refer to non-galvanized or mild steel pipes. GI is generally superior for durability in corrosive conditions, while GP (if uncoated) is cheaper but prone to rust. Always clarify local standards for precise distinctions.
**3. What is the difference between ERW and seamless steel pipe?**
- **Manufacturing**: ERW pipes have a welded seam; seamless pipes are formed by extruding solid billets without seams.
- **Strength**: Seamless pipes handle higher pressure/temperature due to uniform structure.
- **Cost**: ERW is cheaper for low-pressure uses (plumbing, fencing); seamless is preferred for critical applications (oil/gas, high-pressure systems).
**4. How to identify seamless pipe?**
- **Visual Check**: No visible weld line along the length.
- **End Inspection**: Smooth, uniform edges without weld marks.
- **Markings/Certifications**: Look for "SMLS" or "seamless" labels.
- **Testing**: Ultrasonic tests detect hidden seams.
**5. Can you thread ERW pipe?**
Yes, ERW pipes can be threaded if the wall thickness is adequate. Avoid threading directly over the welded seam, as it may weaken the joint. Follow industry standards (e.g., ASTM) for proper threading practices in plumbing or structural applications.
