Tubewell Steel & Engg. Co. is a leading manufacturer and stockist specializing in Alloy Steel Pipes, Tubes, Fittings and Flanges for critical industrial applications.
ASTM A691 electric-fusion-welded chrome-moly pipes in large diameters and heavy walls for high-pressure, high-temperature service.
Tubewell Steel & Engg. Co. supplies alloy steel welded pipes to ASTM A691 / ASME SA691 – electric-fusion-welded with filler metal from ASTM A387 chrome-moly plate. A691 pipes extend chrome-moly piping beyond the practical limits of seamless production, delivering large diameters and heavy walls for steam headers, transfer lines and refinery service.
Large-diameter chrome-moly piping, fusion welded from pressure-vessel plate
ASTM A691 covers carbon and alloy steel pipe that is electric-fusion-welded with added filler metal, made from pressure-vessel-quality plate, for high-pressure service at high temperatures. For chrome-moly service the plate is ASTM A387 – Grade 12 for 1CR, Grade 11 for 1-1/4CR, Grade 22 for 2-1/4CR, Grade 5 for 5CR, Grade 9 for 9CR and Grade 91 for the 91 designation. The plate is press- or roll-formed and the longitudinal seam is joined by submerged-arc welding (LSAW), giving pipe whose chemistry matches the equivalent A335 seamless grade.
A691 pipe is ordered by grade and class. The first digit of the class defines the heat treatment (1 – none, 2 – stress relieved, 3 – normalized, 4 – normalized & tempered, 5 – quenched & tempered) and the second digit defines the radiography and pressure-test requirements; Class 22, 32 and 42 are the most widely specified. Grade 91 must be supplied normalized and tempered. Every pipe is supplied with EN 10204 3.1 / 3.2 certificates, weld radiography films or reports, IBR documentation on request and third-party inspection by BV, TÜV, SGS, Lloyd's or EIL.
Standard supply range for alloy steel welded pipes
| Parameter | Details |
|---|---|
| Standard | ASTM A691, ASME SA691 |
| Grades | 1CR, 1-1/4CR, 2-1/4CR, 5CR, 9CR, 91 |
| Plate Material | ASTM A387 Gr 12, 11, 22, 5, 9, 91 – Class 1 or Class 2 |
| Classes | 10–13, 20–23, 30–33, 40–43, 50–53 (CL 22, 32, 42 most common) |
| Type | EFW, LSAW (Longitudinal Submerged Arc Welded), ERW on request |
| Size (NB) | 6" NB to 48" NB (larger on request) |
| Outer Diameter | 168.3 mm to 1219 mm |
| Wall Thickness | SCH 10, 20, 30, STD, 40, XS, 60, 80 and custom up to 50 mm |
| Length | Single Random, Double Random, Cut Length (up to 12 m) |
| Ends | Plain End, Bevelled End (ASME B16.25) |
| Heat Treatment | As-welded, Stress Relieved, Normalized, Normalized & Tempered, Q&T (as per class) |
| Dimension Standard | ASME B36.10M |
| Testing | Radiography of weld, Hydrostatic, Transverse Weld Tension, Guided Bend, PMI |
| Certificates | EN 10204 3.1 / 3.2, IBR Form III-A, RT Reports, TPI Reports |
| Class | Heat Treatment | Radiography | Pressure Test |
|---|---|---|---|
| CL 12 | None (as-welded) | Yes | Yes |
| CL 22 | Stress Relieved | Yes | Yes |
| CL 32 | Normalized | Yes | Yes |
| CL 42 | Normalized & Tempered | Yes | Yes |
| CL 52 | Quenched & Tempered | Yes | Yes |
A691 grades with plate specification and international equivalents
| A691 Grade | Plate (ASTM A387) | Plate UNS | EN | W.Nr. | Seamless Equivalent | Nominal Composition |
|---|---|---|---|---|---|---|
| 1CR | Grade 12 | K11757 | 13CrMo4-5 | 1.7335 | A335 P12 | 1Cr-0.5Mo |
| 1-1/4CR | Grade 11 | K11789 | 13CrMo4-5 | 1.7335 | A335 P11 | 1.25Cr-0.5Mo-Si |
| 2-1/4CR | Grade 22 | K21590 | 10CrMo9-10 | 1.7380 | A335 P22 | 2.25Cr-1Mo |
| 5CR | Grade 5 | S50200 | X12CrMo5 | 1.7362 | A335 P5 | 5Cr-0.5Mo |
| 9CR | Grade 9 | S50400 | X11CrMo9-1 | 1.7386 | A335 P9 | 9Cr-1Mo |
| 91 | Grade 91 | K90901 | X10CrMoVNb9-1 | 1.4903 | A335 P91 | 9Cr-1Mo-V-Nb |
Weight %, heat analysis of ASTM A387 plate used for A691 pipe
| A691 Grade | C | Mn | P | S | Si | Cr | Mo | Others |
|---|---|---|---|---|---|---|---|---|
| 1CR | 0.05 – 0.17 | 0.40 – 0.65 | 0.025 max | 0.025 max | 0.15 – 0.40 | 0.80 – 1.15 | 0.45 – 0.60 | — |
| 1-1/4CR | 0.05 – 0.17 | 0.40 – 0.65 | 0.025 max | 0.025 max | 0.50 – 0.80 | 1.00 – 1.50 | 0.45 – 0.65 | — |
| 2-1/4CR | 0.05 – 0.15 | 0.30 – 0.60 | 0.025 max | 0.025 max | 0.50 max | 2.00 – 2.50 | 0.90 – 1.10 | — |
| 5CR | 0.15 max | 0.30 – 0.60 | 0.025 max | 0.025 max | 0.50 max | 4.00 – 6.00 | 0.45 – 0.65 | — |
| 9CR | 0.15 max | 0.30 – 0.60 | 0.025 max | 0.025 max | 1.00 max | 8.00 – 10.00 | 0.90 – 1.10 | — |
| 91 | 0.08 – 0.12 | 0.30 – 0.60 | 0.020 max | 0.010 max | 0.20 – 0.50 | 8.00 – 9.50 | 0.85 – 1.05 | V 0.18–0.25, Nb 0.06–0.10, N 0.030–0.070 |
Plate requirements per ASTM A387 Class 2 (Class 1 values are lower)
| A691 Grade | Plate Grade | Tensile Strength | Yield Strength (min) | Elongation in 50 mm (min) |
|---|---|---|---|---|
| 1CR | A387 Gr 12 Cl 2 | 450 – 585 MPa | 275 MPa | 22% |
| 1-1/4CR | A387 Gr 11 Cl 2 | 515 – 690 MPa | 310 MPa | 22% |
| 2-1/4CR | A387 Gr 22 Cl 2 | 515 – 690 MPa | 310 MPa | 18% |
| 5CR | A387 Gr 5 Cl 2 | 515 – 690 MPa | 310 MPa | 18% |
| 9CR | A387 Gr 9 Cl 2 | 515 – 690 MPa | 310 MPa | 18% |
| 91 | A387 Gr 91 Cl 2 | 585 – 760 MPa | 415 MPa | 18% |
Typical values by grade family (for reference)
| Property | 1CR / 1-1/4CR / 2-1/4CR | 5CR / 9CR | Grade 91 |
|---|---|---|---|
| Density | 7.75 – 7.85 g/cm³ | 7.70 – 7.75 g/cm³ | 7.77 g/cm³ |
| Melting Range | 1450 – 1510 °C | 1450 – 1500 °C | 1420 – 1500 °C |
| Modulus of Elasticity | 205 GPa | 213 GPa | 218 GPa |
| Thermal Conductivity (100°C) | 36 – 38 W/m·K | 26 – 30 W/m·K | 27 W/m·K |
| Mean Thermal Expansion (20–300°C) | 12.4 – 12.6 µm/m·°C | 11.5 µm/m·°C | 11.2 µm/m·°C |
| Specific Heat | 0.46 J/g·°C | 0.46 J/g·°C | 0.45 J/g·°C |
| Max. Service Temperature | ≈ 565 – 600 °C | ≈ 650 °C | ≈ 650 °C |
Large-diameter sizes as per ASME B36.10M – wall thickness (mm) / weight (kg/m)
| NPS | OD (mm) | SCH 10 WT | SCH 10 Wt | STD WT | STD Wt | XS WT | XS Wt |
|---|---|---|---|---|---|---|---|
| 6" | 168.3 | 3.40 | 13.83 | 7.11 | 28.26 | 10.97 | 42.56 |
| 8" | 219.1 | 3.76 | 19.97 | 8.18 | 42.55 | 12.70 | 64.64 |
| 10" | 273.1 | 4.19 | 27.78 | 9.27 | 60.29 | 12.70 | 81.53 |
| 12" | 323.9 | 4.57 | 36.00 | 9.53 | 73.88 | 12.70 | 97.46 |
| 14" | 355.6 | 6.35 | 54.69 | 9.53 | 81.33 | 12.70 | 107.39 |
| 16" | 406.4 | 6.35 | 62.64 | 9.53 | 93.27 | 12.70 | 123.30 |
| 18" | 457.0 | 6.35 | 70.57 | 9.53 | 105.16 | 12.70 | 139.15 |
| 20" | 508.0 | 6.35 | 78.55 | 9.53 | 117.15 | 12.70 | 155.12 |
| 22" | 559.0 | 6.35 | 86.54 | 9.53 | 129.13 | 12.70 | 171.09 |
| 24" | 610.0 | 6.35 | 94.53 | 9.53 | 141.12 | 12.70 | 187.06 |
| 26" | 660.0 | 7.92 | 127.36 | 9.53 | 152.87 | 12.70 | 202.72 |
| 28" | 711.0 | 7.92 | 137.32 | 9.53 | 164.85 | 12.70 | 218.69 |
| 30" | 762.0 | 7.92 | 147.28 | 9.53 | 176.84 | 12.70 | 234.67 |
| 32" | 813.0 | 7.92 | 157.24 | 9.53 | 188.82 | 12.70 | 250.64 |
| 34" | 864.0 | 7.92 | 167.20 | 9.53 | 200.82 | 12.70 | 266.61 |
| 36" | 914.0 | 7.92 | 176.96 | 9.53 | 212.57 | 12.70 | 282.27 |
| 42" | 1067.0 | — | — | 9.53 | 248.53 | 12.70 | 330.21 |
| 48" | 1219.0 | — | — | 9.53 | 284.25 | 12.70 | 377.79 |
WT = Wall Thickness in mm, Wt = Weight in kg/m (plain end). Values are nominal per ASME B36.10M; actual weights may vary within ASTM A691 tolerances. Heavier walls up to 50 mm are produced to order.
Where ASTM A691 alloy steel welded pipes are used
Large-bore main steam, hot reheat and cold reheat piping.
Large-diameter heater transfer and vacuum unit lines.
Reactor effluent and hydrogen-rich lines at high pressure.
Flue gas, reactor and fractionator overhead piping.
Synthesis gas and high-temperature process lines.
Shells, nozzles and large-bore connections for heat exchangers.
Quality you can verify on every heat
Large inventory for fast dispatch
MTC EN 10204 3.1 / 3.2
Positive material identification
Pan-India & export shipping
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