In industrial and structural engineering, ERW (Electric Resistance Welded) stainless steel pipes are widely used in various fields due to their cost advantages, stable quality, and good dimensional accuracy.
However, many purchasing personnel often focus only on price or standards when selecting pipes, neglecting key technical details, leading to problems later on.
This article will take a practical application approach to help you systematically understand how to correctly select ERW stainless steel pipes.
I. What is ERW Stainless Steel Pipe?
ERW stainless steel pipe is made by rolling steel strip into shape and then welding the seams together using resistance welding (without filler material). Its characteristics include:
- Stable weld quality (modern high-frequency welding technology)
- High dimensional accuracy and good roundness
- High production efficiency and lower cost than seamless pipe
II. Typical Application Scenarios
1. Industrial Applications
- Oil and gas transportation (low and medium pressure)
- Water treatment systems
- Chemical fluid transportation
- Food and pharmaceutical equipment (requiring high surface finishes)
2. Structural Applications
- Steel structural frames
- Building supports
- Bridges and pile foundations (some projects)
- Mechanical structural components
III. Five Key Factors in Selection
i. Material (Grade) Selection
| Material | Characteristics | Suitable Environment |
|---|---|---|
| 304 | General-purpose, good corrosion resistance | Indoor, general industrial use |
| 316 / 316L | Excellent resistance to chloride corrosion | Marine, chemical environments |
| 201 | Lower cost, but weaker corrosion resistance | Dry environments |
Recommendations:
- For corrosive media → Choose 316L
- For normal environments → 304 is sufficient
- For budget-sensitive environments → Use 201 with caution
ii. Dimensions (OD & WT)
- Outer Diameter (OD): Determines flow rate or structural dimensions.
- Wall Thickness (WT): Determines pressure resistance.
Common misconceptions in engineering:
- Only considering the outer diameter, neglecting the wall thickness.
- Calculations should consider pressure or load.
iii. Standards
- Common standards include:
- ASTM A312 (Stainless Steel Pipe)
- ASTM A778 (Welded Stainless Steel Pipe)
- EN 10217-7 (European Standard)
- GB/T 12771 (Chinese Standard)
Recommendation:
- For export projects: Prioritize ASTM/EN standards.
- For domestic projects: GB standards are sufficient.
IV. Weld Quality and Inspection
The core of ERW pipe lies in the weld:
Key Inspection Methods:
- Eddy Current Test (ECU)
- Ultrasonic Testing (UT)
- Hydrostatic Test
Recommendations:
- Industrial Applications → NDT report required
- Structural Applications → Basic inspection required at least
V. Surface and Post-treatment
Different applications have vastly different surface requirements:
| Surface Finish | Application |
|---|---|
| Pickled | Industrial pipelines |
| Polished | Food processing / decorative use |
| Sandblasted | Structural applications |
VI. ERW vs Seamless Stainless Steel Pipe (How to Choose?)
| Item | ERW Pipe | Seamless Pipe |
|---|---|---|
| Cost | Lower | Higher |
| Precision | High | Moderate |
| Pressure Capacity | Medium | High |
| Weld Seam | Yes | No |
Recommended Selection:
- High Pressure/High Temperature → Choose Seamless Tube
- Conventional Industrial/Structural Applications → ERW is More Economical
V. Three Common Mistakes in Procurement
- Comparing Prices Only
- Ignoring Material, Standards, and Testing → High Risk Later
- Ignoring Delivery Capacity
ERW pipes are usually made to order:
- Is there stock available?
- Is the delivery time stable?
- Lack of Clear Technical Parameters
Many inquiries only state:
- “Stainless Steel Pipe”
The correct approach should include:
- Material (e.g., 304 / 316L)
- Dimensions (OD × WT)
- Standards
- Application