Tube Schedule 40
1. The Meaning of Tube Schedule 40
2. Tube Schedule 40 Standards and Types
ASTM A53: American Society for Testing and Materials standard, covering seamless and welded steel pipes, divided into three types:
| Type |
Full Name |
Best Applications |
Common Sizes |
|---|---|---|---|
| ERW | Electric Resistance Welded |
Low medium water, gas, and structural |
Up to 24" |
| SSAW | Spiral Submerged Arc Welded |
Large-diameter pipelines |
8" – 120"+ |
| LSAW | Longitudinal Submerged Arc Welded |
Oil, gas, high-pressure |
16" – 56" |
3. Steel Grade of Schedule 40 Tubes
The primary difference between ASTM A53 Grade A, Grade B, and the less common Grade C lies in their minimum yield strength and tensile strength, which is a direct result of their chemical composition (primarily carbon and manganese content).
| ASTM A53 Grade B |
This is by far the most common and widely used grade. Its excellent balance of strength, formability, weldability, and cost makes it the default choice for most structural and pressure applications (e.g., water lines, steam, air, oil). |
|---|---|
| ASTM A53 Grade A |
Used for lower-pressure applications or where more bending and forming is required. Its lower strength and carbon content can make it slightly easier to form. It is less common than Grade B. |
| ASTM A53 Grade C |
This grade is very rare and not commonly produced or stocked. Its higher carbon content can make it more difficult to weld and form. For applications requiring this level of strength, other specifications like ASTM A106 Grade B (for high-temperature service) are almost always preferred. |
4. Chemical Composition
The mechanical strength is achieved by controlling the amount of carbon and manganese, which are strengthening elements in steel.
| Element |
Grade A |
Grade B |
Grade C |
|---|---|---|---|
| Carbon (Max) |
0.25% |
0.30% |
0.35% for NPS 1/2-3 |
| Manganese (Max) |
0.95% |
1.20% |
1.35% for NPS 1/2-3 |
Conclusion: To achieve its higher strength, Grade B is allowed to have slightly more carbon and significantly more manganese than Grade A. Grade C has even higher allowances.
5. Mechanical Strength
This is the key factor for engineers selecting the grade. Higher strength allows for thinner walls at the same pressure rating, saving weight and cost.
| Property |
Grade A | Grade B | Grade C |
|---|---|---|---|
| Minimum Yield Strength |
205 MPa (30,000 psi) |
240 MPa (35,000 psi) |
290 MPa (42,000 psi) |
| Minimum Tensile Strength |
330 MPa (48,000 psi) |
415 MPa (60,000 psi) |
435 MPa (63,000 psi) |
Conclusion: Grade B has higher strength than Grade A, and Grade C has the highest strength.
6. Other Specifications
7. Schedule 40 Steel Tube Dimensions
| Nominal size | DN | Outside diameter |
Schedule 40 thickness |
|---|---|---|---|
| 1/2 inch | 15 | 21.3mm | 2.77mm |
| 3/4 inch | 20 | 26.7mm | 2.87mm |
| 1 inch | 25 | 33.4mm | 3.38mm |
| 1 1/4 inch | 32 | 42.2mm | 3.56mm |
| 1 1/2 inch | 40 | 48.3mm | 3.68mm |
| 2 inch | 50 | 60.3mm | 3.91mm |
| 2 1/2 inch | 65 | 73mm | 5.16mm |
| 3 inch | 80 | 88.9mm | 5.49mm |
| 3 1/2 inch | 90 | 101.6mm | 5.74mm |
| 4 inch | 100 | 114.3mm | 6.02mm |
| 5 inch | 125 | 141.3mm | 6.55mm |
| 6 inch | 150 | 168.3mm | 7.11mm |
| 8 inch | 200 | 219.1mm | 8.18mm |
| 10 inch | 250 | 273mm | 9.27mm |
