The ASTM A350 LF2 CL1 blind flange is a critical component in piping systems, designed for low-temperature and cryogenic applications.ASTM A350 LF2 CL1 is a low-temperature carbon steel that maintains ductility and impact resistance even at extremely low temperatures. This grade is also referred to as SA350 Gr LF2 CL1 or ASTM A350 Grade LF2 Cl1 in technical documents and drawings, representing the same material specification under ASTM A350 standards.
Using ASTM A350 LF2 CL1 Blind Flange ensures compliance with international standards such as ASME B16.5 blind flange, ASME B16.47 blind flange, and EN 1092-1 blind flange. When integrated with compatible components like ASTM A105, A/SA350 Low Temp Forged Fittings, and ASTM A350 LF2 Fittings, the system meets stringent mechanical and chemical requirements. Proper assembly with suitable gaskets (Ring Joint Gaskets (R,RX,BX), Spiral Wound Gaskets, Jacketed Gaskets) and fasteners (ASTM A193 B7 bolts, ASTM A194 2H nuts, ASTM F436 washers, ASME B18.2.1/ B18.2.2 bolts/nuts) ensures leak-free operation and long service life.
Blind Flange Introduction
A blind flange is a solid disc used to close the end of a piping system, providing a secure seal. Unlike other flanges, it has no bore and is ideal for pressure testing, pipeline isolation, or temporary closure. The ASTM A350 LF2 Blind Flange is particularly suitable for low-temperature environments, where maintaining toughness is critical.
Blind flanges can be paired with A/SA350 Low Temp Forged Fittings to create a complete piping assembly that ensures both mechanical and chemical compatibility. This flange is compatible with multiple standards including ASME B16.5, ASME B16.47, and EN 1092-1 blind flange.
| Standard | Size Range | Pressure Rating System | Typical Application with ASTM A350 LF2 |
| ASME B16.5 | NPS ½″–24″ | Class 150–2500 | Small/medium flanges in industrial piping |
| ASME B16.47 | NPS 26″–60″ | Class 75–900 | Large diameter flanges for major pipelines |
| EN 1092-1 | DN10-DN4000 | PN2.5–PN400 | European metric piping & high PN ratings |
Low-Temperature Steel Flange
Low-temperature steel flanges are engineered to maintain ductility and toughness at sub-zero temperatures, reducing the risk of brittle fracture. ASTM A350 LF2/LF3 standards define chemical composition, mechanical properties, and allowable conditions.
ASTM A350 Material
ASTM A350 LF2 & LF3 Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Cu | Ni | Cr | Mo | V | Nb |
| ASTM A350 LF2 | MIN | 0.60 | 0.15 | |||||||||
| MAX | 0.30 | 1.35 | 0.035 | 0.040 | 0.35 | 0.40 | 0.40 | 0.30 | 0.12 | 0.08 | 0.02 | |
| ASTM A350 LF3 | MIN | 0.20 | 3.30 | |||||||||
| MAX | 0.20 | 0.90 | 0.04 | 0.04 | 0.35 | 0.40 | 3.70 | 0.30 | 0.03 |
ASTM A350 LF2 & LF3 Mechanical Properties
| MATERIAL | T.S (MPA) | Y.S (MPA) | EL % | R/A % | HARDNESS |
| ASTM A350 LF2 | 485-655 | 250 min | 22 min | 30 min | 197 max |
| ASTM A350 LF3 | 485-655 | 260min | 22min | 35min | – |
ASTM A350 LF2 Class 1 vs. Class 2
The main difference between ASTM A350 LF2 Class 1 and Class 2 lies in their low-temperature toughness and intended service conditions. Class 1 has slightly lower carbon content and is designed for standard low-temperature service, providing adequate strength and ductility for general pipelines and flanges. Class 2, on the other hand, requires higher impact toughness at colder temperatures, making it suitable for high-pressure, critical, or cryogenic applications where enhanced safety and durability are needed.
Types of Gaskets for Blind Flange Assemblies
| Gasket Type | Material | Standard | Application |
| Ring Joint (R, RX, BX) | Forged steel / Inconel | ASME B16.20 | High-pressure, large-diameter ASME B16.47 flanges |
| Spiral Wound | Metal strips + filler (graphite/PTFE) | ASME B16.20 | ASME B16.5/16.47 flanges, low-temp & chemical pipelines |
| Jacketed | Graphite core + stainless steel jacket | Custom / ASME B16.20 compatible | Corrosive or insulated low-temp pipelines |
Types of Bolts and Nuts for Blind Flange Assemblies
| Component | Material | Standard | Application |
| Bolt | ASTM A193 B7 (high P) / A320 L7 (low-temp) | ASME B18.2.1 | Match flange pressure class & operating temperature |
| Nut | ASTM A194 2H (carbon steel) / 2HM (low-temp) | ASME B18.2.2 | Ensures load distribution, prevents loosening |
| Washer | ASTM F436 (hardened steel) | – | Distributes bolt load, protects flange & gasket |
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