| Customization: | Available |
|---|---|
| Standard: | ANSI, DIN, GB, JIS, GOST, BSW, ISO |
| Type: | Forged/ Hot Press |
|
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Primary Standard: ASTM A350 (Forged Carbon Steel Components for Low-Temperature Service)
Complementary Standards:
ASME B16.9: Butt-Weld Fitting Dimensions
NACE MR0175/ISO 15156: H2S Environment Compliance
EN 10222-3: European Equivalent for LF2/LF3
| Parameter | Tolerance (ASME B16.9) |
|---|---|
| OD Tolerance | ±1.5% of Nominal OD |
| Wall Thickness | ±12.5% (Min. WT ≥87.5% Nominal) |
| Center-to-End (90° Elbow) | ±1.5 mm (≤24") / ±3 mm (>24") |
Subzero Toughness: LF2/LF3 achieve ≥27J Charpy Impact at -46°C (mandatory for cryogenic LNG/ammonia systems).
Sour Service Ready: Complies with NACE MR0175 for H2S-rich oil/gas pipelines.
Weldability: Controlled carbon content (C ≤0.30%) ensures compatibility with SMAW/GTAW processes.
Chemical Composition (LF2 Example):
| Element | ASTM A350 LF2 Requirement |
|---|---|
| C | ≤0.30% |
| Mn | 0.60-1.35% |
| P | ≤0.035% |
| S | ≤0.040% |
Mechanical Tests:
Tensile Strength: ≥485 MPa
Yield Strength: ≥250 MPa
Impact Toughness: ≥27J at -46°C (LF2/LF3).
Oil & Gas: Subsea pipelines, sour gas processing plants.
Cryogenic Systems: LNG storage tanks, liquid nitrogen transport.
Power Plants: Low-temperature cooling water circuits.
Corrosion Protection: VCI-coated packaging for humid/coastal shipments.
Documentation: EN 10204-3.1/3.2 Certificates + NDE Reports (UT/RT).
Grade Comparison:
| Grade | Min. Test Temp | Key Difference |
|---|---|---|
| LF1 | -46°C | Standard impact testing |
| LF2 | -59°C | Enhanced low-temp toughness |
| LF3 | -59°C | Higher purity (lower P/S) |
Heat Treatment:
LF2/LF3: Normalized at 900-925°C + tempered for optimal grain structure.
The pressure-temperature rating is the maximum allowable working pressure (bar unit) of the material and grade used at the rated temperature (Celsius).
Whether flange joints are used at high or low temperatures, leakage due to external forces and moments generated by the connected piping or equipment should be considered. To prevent leakage, pipe flanges and flanged fittings should avoid the application of severe external loads and sharp thermal gradients.
Application at temperatures in the creep range will result in decreasing bolt loads as relaxation of flanges, bolts, and gaskets takes place. Flanged joints subjected to thermal gradients may likewise be subject to decreasing bolt loads. Decreased bolt loads diminish the capacity of the flanged joint to sustain loads effectively without leakage. At temperatures above 200°C (400°F) for Class 150 and above 400°C (750°F) for other class designations, flanged joints may develop leakage problems unless care is taken to avoid imposing severe external loads, severe thermal gradients, or both.
Some materials, especially some carbon steel materials, exhibit a significant decrease in ductility when used at low temperatures, and thus cannot withstand impact load, sudden stress changes, and high stress concentrations. Some regulations require an impact test even when the temperature is above -29 °C (−20°F).
No pressure test is required on the flange.
Flanged fitting should be tested for shell pressure.
Shell Pressure Test for Flanged Fittings
The shell pressure test for flanged fittings shall be at a pressure no less than 1.5 times the 38°C (100°F) pressure rating rounded off to the next higher 1 bar (25 psi) increment.
|
Flanged Fittings Size |
Duration, Sec |
|---|---|
|
NPS ≤ 2 |
60 |
|
2 1/2 ≤ NPS ≤ 8 |
120 |
|
NPS ≥ 10 |
180 |
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