For global buyers seeking high-quality stainless steel pipes from China, understanding supplier capabilities, standards compliance, and product specifications is essential. This guide focuses on ASTM A312 TP304 6-inch SCH 40 stainless steel pipes, widely used in industrial, chemical, and oil & gas applications.
Overview of ASTM A312 TP304 SCH 40 Pipes
ASTM A312 defines seamless and welded stainless steel pipes suitable for high-temperature, corrosive, and industrial service.
Material Grade: TP304 Stainless Steel
Nominal Pipe Size (NPS): 6-inch (168.3 mm OD)
Pipe Schedule: 40 (standard wall thickness)
Applications: Water treatment, chemical processing, food & beverage, oil & gas, HVAC systems
SCH 40 provides a balance of strength, corrosion resistance, and cost efficiency, making it a popular choice for medium-pressure pipelines.
Key Dimensions
| arameter | Metric (mm) | Imperial (inch) |
|---|---|---|
| Nominal Pipe Size (NPS) | 6" | 6" |
| Outside Diameter (OD) | 168.3 | 6.63" |
| Wall Thickness (t) | 6.35 | 0.250" |
| Inside Diameter (ID) | 155.6 | 6.13" |
| Approx. Weight per Meter | 18.3 kg/m | 12.3 lb/ft |
| Tolerance (Wall Thickness) | ±0.18 | ±0.007" |
Notes: Tolerances follow ASTM A312 / ASME B36.19M standards.
Why Source from China
Manufacturing Capacity
China has large-scale stainless steel pipe producers capable of seamless, welded, and custom lengths.
Supports high-volume industrial orders.
Global Standard Compliance
Leading suppliers provide ASTM, ASME, ISO 9001, and MTC certifications.
Ensures consistent chemical composition, mechanical properties, and dimensional accuracy.
Cost-Effective Supply
Competitive pricing due to efficient production and raw material sourcing.
Offers custom cutting, threading, and polishing services for export-ready products.
Logistics & Export Support
Experienced in shipping via sea and air, with packaging suitable for long-distance export.
Can handle bulk orders, containerized shipments, and documentation for Middle East, Europe, and North America.
Quality Control
Dimensional Verification: OD, wall thickness, and length are checked per ASTM standards
Hydrostatic Testing: Ensures leak-free and pressure compliance
Third-Party Certification: SGS, TUV, or BV inspections for MTC verification
Surface Finish: Options for pickled, passivated, or polished surfaces depending on client requirements
Applications of 6-Inch SCH 40 TP304 Pipes
Oil & Gas Pipelines: Low to medium-pressure lines
Chemical Processing: Corrosion-resistant chemical transport
Food & Beverage Industry: Hygienic and easy-to-clean pipelines
Water Treatment & Desalination: Brine and seawater handling
HVAC Systems: Chilled and hot water piping
Supplier Selection Tips
Check Certifications: ASTM A312 compliance, ISO 9001, and MTC verification
Confirm Pipe Type: Seamless or welded, depending on application
Evaluate Production Capacity: Ensure supplier can meet volume and delivery schedule
Request Sample Pipes: Test dimensional accuracy, wall thickness, and surface finish
Verify Export Experience: For projects in Middle East, Europe, or North America, check shipping and documentation capabilities
FAQ
1. What is ASTM A312 TP304 SCH 40 pipe?
It is a stainless steel pipe made of TP304 austenitic stainless steel with a Schedule 40 wall thickness, suitable for medium-pressure industrial applications.
2. What is the wall thickness of a 6-inch SCH 40 TP304 pipe?
The wall thickness is 6.35 mm (0.250 inch).
3. What is the outside diameter (OD) of a 6-inch pipe?
The OD is 168.3 mm (6.63 inch) for all 6-inch nominal pipes.
4. What is the inside diameter (ID)?
The ID is calculated as:
ID=OD−2×Wall Thickness=168.3−2×6.35=155.6 mm(6.13")ID = OD - 2 \times Wall\ Thickness = 168.3 - 2 \times 6.35 = 155.6\ mm (6.13")ID=OD−2×Wall Thickness=168.3−2×6.35=155.6 mm(6.13")
5. What is the approximate weight per meter?
Approximately 18.3 kg/m (12.3 lb/ft), based on stainless steel density ~8 g/cm³.
6. Are Chinese suppliers reliable for ASTM A312 TP304 pipes?
Yes, many suppliers provide ISO 9001, ASTM compliance, MTC verification, and third-party inspection, ensuring consistent quality and dimensions.
7. Are these pipes seamless or welded?
ASTM A312 covers both seamless and welded pipes. Seamless pipes generally offer higher strength, while welded pipes are suitable for larger diameters and cost-effective production.
8. What industries use 6-inch SCH 40 TP304 pipes?
Oil & gas pipelines
Chemical processing plants
Water treatment & desalination
Food and beverage industries
HVAC systems
9. Can SCH 40 handle high-pressure applications?
SCH 40 provides medium wall thickness, suitable for moderate pressures. For higher-pressure systems, SCH 80 or SCH 160 is recommended.
10. How is corrosion resistance ensured?
TP304 is highly resistant to corrosion in water, mild chemicals, and atmospheric environments. Passivation and pickling further enhance corrosion resistance.
11. Can these pipes be welded in the field?
Yes. TP304 is readily weldable, but proper stainless steel welding procedures and low-carbon filler rods should be used to prevent sensitization.
12. What tolerances apply to wall thickness?
Typical wall thickness tolerance for SCH 40 is ±0.18 mm (±0.007 inch) according to ASTM A312 / ASME B36.19M.
13. How do I select a reliable Chinese supplier?
Verify ASTM A312 and ISO 9001 compliance
Check production capacity for your volume
Confirm export experience and logistics capabilities
Request mill test certificates (MTC) and sample inspection
14. Is SCH 40 heavier than SCH 10S pipes?
Yes. SCH 40 has thicker walls, increasing weight per meter and pressure handling capacity.
15. Can these pipes be used in offshore oil projects?
Yes. TP304 SCH 40 pipes are resistant to seawater corrosion and suitable for medium-pressure offshore pipelines, though TP316L may be preferred for high-chloride environments.
16. What is the difference between seamless and welded SCH 40 pipes?
Seamless: Higher strength, no weld joint
Welded: Cost-effective, suitable for larger diameters, may have a slight weld factor adjustment for pressure calculations
17. Can TP304 pipes handle elevated temperatures?
Yes, TP304 can operate at moderate high temperatures, but extreme temperatures may require TP321 or TP316L for better creep resistance.
18. Are these dimensions the same in metric and imperial units?
Yes. ASTM and ASME standards define both mm and inch equivalents for global compatibility.
19. How do I calculate inside diameter for engineering design?
Use the formula:
ID=OD−2×Wall ThicknessID = OD - 2 \times Wall\ ThicknessID=OD−2×Wall Thickness
For 6-inch SCH 40 TP304: ID = 155.6 mm (6.13")
20. Where can I find a full dimension chart for all SCH 40 TP304 pipe sizes?
Manufacturers and ASTM standards provide full tables from 1/2" to 24", including OD, wall thickness, ID, weight per meter, and tolerances, which are essential for engineering, procurement, and B2B catalog preparation.
