SA691 Grade 1CR Carbon Steel Boiler & Heat Exchanger Pipe
Overview
SA691 is a standard specification for Carbon and Alloy Steel Pipe for High-Pressure Service at High Temperatures, specifically designed for boilers, superheaters, and heat exchangers. The "1CR" designation refers to a specific grade within this specification that contains approximately 0.5% Chromium and 0.5% Molybdenum, enhancing its strength and resistance to oxidation at elevated temperatures.
These pipes are intended for use in critical high-temperature and high-pressure applications such as power plants, refinery heaters, and chemical processing facilities, where they transport steam, feedwater, or other process fluids.
Key Features & Applications
Material: Chromium-Molybdenum (Cr-Mo) alloy steel.
Key Property: Good high-temperature strength and improved oxidation resistance compared to plain carbon steel.
Primary Use: Fabrication of boiler tubes, superheater tubes, heat exchanger tubes, and pressure piping systems for high-temperature service.
Manufacturing Process: Typically produced by electric-fusion welding (e.g., SA691 is commonly an Electric Fusion Welded - EFW pipe).
SA691 1CR Chemical Composition & Mechanical Properties Table
| Property | Standard / Grade | Value / Requirement |
|---|---|---|
| Standard Designation | ASTM/ASME SA691 | - |
| Grade | 1CR (Equivalent to ASTM A335 P1) | - |
| Chemical Composition | Carbon (C) | 0.10 - 0.20 % |
| Manganese (Mn) | 0.30 - 0.80 % | |
| Phosphorus (P) max | 0.025 % | |
| Sulfur (S) max | 0.025 % | |
| Silicon (Si) | 0.10 - 0.50 % | |
| Chromium (Cr) | 0.50 - 0.80 % | |
| Molybdenum (Mo) | 0.44 - 0.65 % | |
| Mechanical Properties | Tensile Strength min | 380 MPa (55,000 psi) |
| Yield Strength min | 205 MPa (30,000 psi) | |
| Elongation min | Varies by wall thickness | |
| Heat Treatment | - | Full Annealing, Normalizing & Tempering, or Stress Relieving (as required by spec) |
Common Specifications & Dimensions
Size Range: Outside Diameter (OD) and wall thickness are manufactured according to purchase order requirements, commonly conforming to dimensional standards like ASME B36.10M.
Length: Random or cut lengths, typically double random (~40 ft / 12m) or single random (~20 ft / 6m).
Ends: Plain ends (PE) or beveled ends for welding (BE).
Important Considerations
Code Compliance: SA691 pipe is manufactured to be compliant with the ASME Boiler and Pressure Vessel Code (BPVC) Section I and Section VIII for pressure equipment.
Testing: It is subject to rigorous testing including hydrostatic or non-destructive electric tests, chemical analysis, and tension tests.
Certification: Material Test Reports (MTRs) or Certified Test Reports (CTRs) are provided to validate compliance with the specification.
Alternative Grades: For different temperature/strength needs, other SA691 grades exist (e.g., 2CR, 12CR, etc.), and SA691 1CR is often considered interchangeable with ASTM A335 P1 seamless pipe in many designs.
Disclaimer: The information provided here is for general reference only. For critical design, procurement, or fabrication, always consult the latest official ASTM/ASME SA691 specification and relevant engineering codes.
