- 1. Overview of ASTM A691 Standard
- 2. Why ASTM A691 Excels in High-Pressure and High-Temperature Environments
- 3. Typical Grades and Their Industrial Applications
- 4. Comprehensive Quality Testing — Ensuring Reliability
- 5. LONGMA: Combining Strength, Quality, and Global Trust
- 6. How LONGMA Helps Buyers Minimize Procurement Risk
- 7. Conclusion
In industries such as refining, petrochemical, and power generation, pipelines operate under extreme temperature and pressure conditions. Choosing the right pipe material is not just a matter of performance — it’s a matter of safety, reliability, and long-term cost efficiency. Among various alloy steels, ASTM A691 alloy steel pipes stand out for their exceptional strength, heat resistance, and durability, making them the first choice for critical applications.
As a manufacturer with more than 20 years of industry experience, LONGMA provides a full range of astm a691 pipes, ensuring consistent quality, reliable testing, and global project compliance.
Overview of ASTM A691 Standard
| Item | Description |
| Full Name | ASTM A691 – Standard Specification for Carbon and Alloy Steel Pipe, Electric-Fusion-Welded for High-Pressure Service at High Temperatures |
| Manufacturing Process | Electric-Fusion Welding (EFW) from alloy plates, followed by post-weld heat treatment |
| Common Grades | ASTM A691 Grade 2.1 4Cr, ASTM A691 Gr.32, P5, P9, P22 |
| Typical Applications | Steam lines, heaters, heat exchangers, reactors, and pressure piping |
| Operating Temperature Range | 400°C – 650°C |
| Keywords | astm a691, astm a691 grade 2.1 4cr, astm a691 pipes & tubes in spain |
This standard defines the manufacturing, heat treatment, and testing requirements for alloy steel pipes intended for high-pressure, high-temperature service — ensuring product consistency and structural reliability.
Why ASTM A691 Excels in High-Pressure and High-Temperature Environments
| Performance Aspect | ASTM A106 (Carbon Steel) | ASTM A691 (Alloy Steel) | Advantage |
| Temperature Resistance | Up to 425°C | Up to 650°C or more | Excellent for high-temperature applications |
| Creep Strength | Limited | Outstanding (especially for Cr–Mo grades like A691 Grade 2.1 4Cr) | Resists deformation during long-term service |
| Oxidation & Corrosion Resistance | Moderate | Excellent due to chromium content | Ideal for corrosive refinery and steam environments |
| Pressure Tolerance | Good | Superior — designed for high-pressure systems | Suitable for thick-walled piping |
| Service Life | 10–15 years | 25–30 years | Lower maintenance and replacement cost |
The combination of chromium (Cr) and molybdenum (Mo) enhances both oxidation resistance and creep strength. This makes astm a691 pipe particularly reliable for prolonged exposure to elevated pressures and temperatures — a critical factor in refinery and power plant systems.
Typical Grades and Their Industrial Applications
| Grade | Chemical Composition (Main Elements, wt%) | Operating Temp. | Typical Applications |
| A691 Grade 2.1 4Cr (Gr.32) | Cr 2.0–2.5%, Mo 0.9–1.1% | ≤620°C | Steam pipelines, heater coils, and high-temp reactors |
| A691 P5 | Cr 4.0–6.0%, Mo 0.4–0.6% | ≤600°C | Reformers, furnace tubes, hydrogen lines |
| A691 P22 | Cr 2.25%, Mo 1.0% | ≤620°C | Power plant reheaters, boiler tubes |
| A691 P91 (advanced) | Cr 9%, Mo 1%, Nb/V added | ≤700°C | Ultra-high-temperature superheaters |
Note: The astm a691 grade 2.1 4cr gr 32 is the most commonly used grade for refinery applications due to its balance of mechanical strength, weldability, and oxidation resistance.
Comprehensive Quality Testing — Ensuring Reliability
To guarantee the safety and reliability of each astm a691 pipe, LONGMA’s internal laboratory performs full-cycle inspections in accordance with ASTM and ASME standards.
| Test Type | Purpose | ASTM / ASME Reference | Testing Method |
| Chemical Composition | Verify alloy formula accuracy | ASTM A691 §6 / ASTM A20 | Optical Emission Spectrometry (OES) |
| Tensile Test | Check yield & tensile strength | ASTM A370 | Room & high-temperature tensile tests |
| Impact (Charpy V-Notch) | Assess toughness & ductility | ASTM A370 (Appendix) | CVN tests at 0°C or –20°C |
| Nondestructive Testing (UT/RT) | Detect internal or weld defects | ASTM A691 §7.3 / ASME Section V | Ultrasonic or radiographic testing |
| PMI (Positive Material Identification) | Prevent material mix-up | ASTM E1476 | Portable spectrometer verification |
| Hydrostatic Test | Verify pipe integrity under pressure | ASTM A530 §10 | 100% hydrostatic testing before shipment |
Each inspection stage ensures that every pipe meets or exceeds the specified mechanical and metallurgical standards.
LONGMA’s in-house laboratory is equipped with OES spectrometers, UT/RT flaw detectors, and high-temperature tensile machines — providing independent MTCs (Mill Test Certificates) with full traceability.
LONGMA: Combining Strength, Quality, and Global Trust
| Key Capability | LONGMA Advantage |
| Experience | 20+ years in alloy steel pipe manufacturing |
| Quality System | ISO 9001, PED, and API certifications |
| Equipment | Automatic EFW welding line, controlled heat treatment, 100% UT/RT inspection |
| Internal Laboratory | Full chemical, mechanical, and NDT testing per ASTM A691 |
| Export Market | Proven track record with astm a691 pipes & tubes in spain, UAE, and Southeast Asia |
| Technical Support | Offers material selection, WPS/PQR assistance, and third-party inspection coordination |
Unlike ordinary suppliers, LONGMA not only provides certified products but also technical consultation, ensuring that your material selection and testing documentation comply with ASTM A691 and project requirements.
How LONGMA Helps Buyers Minimize Procurement Risk
- Material Assurance:100% PMI before shipment; all data stored digitally for traceability.
- Third-Party Verification:Fully open to SGS, BV, or TUV inspection.
- Contract Support:Provides testing reports, WPS/PQR, and heat treatment charts.
- Timely Delivery:Advanced production scheduling system for urgent refinery projects.
These measures directly address buyer pain points — such as quality uncertainty, non-compliance risk, and delivery delays — ensuring confidence in every procurement.
Conclusion
When it comes to high-pressure and high-temperature environments, ASTM A691 alloy steel pipes offer unmatched performance in strength, oxidation resistance, and long-term stability.
By combining advanced production, internal laboratory testing, and international certification, LONGMA has established itself as a trusted supplier of astm a691 pipes & tubes in spain and across the global market.
For your next refinery, power, or chemical project, choose LONGMA — where every astm a691 pipe is backed by quality, precision, and proven expertise.
