ASTM A182 F53 Blind Flange | RF & RTJ ASME B16.5
ASTM A182 F53 Blind Flanges are forged super duplex stainless steel flanges used to close piping ends, valve connections and equipment nozzles in corrosive and high-pressure piping systems.
F53 corresponds to UNS S32750, commonly known as 2507 Super Duplex Stainless Steel. The material combines high mechanical strength with strong resistance to chloride pitting, crevice corrosion and stress-corrosion cracking.
F53 blind flanges are available with Raised Face (RF) and Ring Type Joint (RTJ) facings to ASME B16.5 for offshore, seawater, desalination, chemical-processing and oil & gas applications.
ASTM A182 F53 Blind Flange Overview
| Item | Specification |
|---|---|
| Material | ASTM A182 F53 |
| UNS | S32750 |
| Common Name | 2507 Super Duplex |
| EN Material No. | 1.4410 |
| Product | Blind Flange |
| Standard | ASME B16.5 |
| Facing | RF, RTJ, FF where applicable |
| Size | NPS 1/2–24, subject to Class |
| Pressure Class | 150–2500, subject to applicable size |
| Typical Service | Offshore, Seawater, Chemical, Oil & Gas |
| Sour Service | Available when specified |
What Is ASTM A182 F53?
ASTM A182 F53 is the forging grade corresponding to UNS S32750 super duplex stainless steel.
It should not be confused with Duplex 2205 grades such as UNS S31803 or S32205.
S32750 contains approximately 25% chromium together with nickel, molybdenum and nitrogen. This alloy balance provides a combination of:
- High yield and tensile strength
- Strong resistance to chloride pitting
- Good resistance to crevice corrosion
- Improved resistance to chloride stress-corrosion cracking
- Good toughness
- Good performance in many seawater and process environments
Material suitability should still be evaluated against actual temperature, chloride concentration, crevice conditions and project requirements.
ASTM A182 F53 Chemical Composition
Typical F53 / UNS S32750 composition includes:
| Element | Requirement |
|---|---|
| Carbon, C | 0.030% max |
| Chromium, Cr | 24.0–26.0% |
| Nickel, Ni | 6.0–8.0% |
| Molybdenum, Mo | 3.0–5.0% |
| Nitrogen, N | 0.24–0.32% |
| Manganese, Mn | 1.20% max |
| Silicon, Si | 0.80% max |
| Phosphorus, P | 0.035% max |
| Sulfur, S | 0.020% max |
| Copper, Cu | 0.50% max |
The actual heat chemistry is reported on the Material Test Certificate.
Mechanical Properties
Mechanical requirements for ASTM A182 F53 depend on the maximum section thickness at heat treatment.
| Maximum Section Thickness | Tensile Strength Min. | Yield Strength Min. | Elongation Min. |
|---|---|---|---|
| Up to 50 mm / 2 in | 800 MPa | 550 MPa | 15% |
| Over 50 mm / 2 in | 730 MPa | 515 MPa | 15% |
Maximum hardness is controlled by the applicable ASTM A182 requirements.
This thickness-dependent distinction is particularly relevant to large or high-pressure blind flanges because their forged sections can be substantially thicker than standard Weld Neck flange sections.
ASTM A182 F53 RF Blind Flange
F53 Raised Face Blind Flanges are used to close piping connections using conventional gasketed RF flange joints.
Typical applications include:
- Seawater piping
- Offshore process systems
- Desalination plants
- Chemical-processing systems
- Valve isolation
- Pressure vessel nozzles
- Future piping tie-in points
Typical order:
ASTM A182 F53 Blind Flange, NPS 8″, Class 600, RF, ASME B16.5
A standard blind flange has no pipe bore, so pipe schedule is normally not required.
ASTM A182 F53 RTJ Blind Flange
F53 RTJ Blind Flanges use a machined Ring Type Joint groove and metallic ring gasket for high-integrity flange connections.
RTJ configurations are commonly specified for:
- High-pressure oil and gas systems
- Offshore platforms
- High-pressure manifolds
- Process piping
- Critical isolation points
Typical pressure classes include Class 600, 900, 1500 and 2500 where permitted by the applicable ASME B16.5 size range.
Example:
ASTM A182 F53 Blind Flange, NPS 6″, Class 1500, RTJ, ASME B16.5
The RTJ groove must correspond to the specified mating flange and ring gasket.
ASME B16.5 F53 Blind Flanges
ASME B16.5 covers pipe flanges from NPS 1/2 through NPS 24, subject to the applicable pressure-class and size combination.
Common pressure classes include:
- Class 150
- Class 300
- Class 400
- Class 600
- Class 900
- Class 1500
- Class 2500
Class 2500 applies only to the applicable smaller size range and should not be interpreted as available through NPS 24.
For larger-diameter flanges, the applicable ASME B16.47 requirements should be reviewed separately.
Why Use F53 / S32750 for Blind Flanges?
Compared with conventional austenitic stainless steels, S32750 provides significantly higher strength and improved resistance to localized chloride corrosion.
This makes F53 particularly useful where a blind flange must combine:
- High pressure capability
- High mechanical strength
- Chloride resistance
- Offshore or marine exposure
- Reduced section thickness compared with lower-strength materials
The material is nevertheless not immune to corrosion, and severe seawater or high-temperature chloride applications should be evaluated against the complete service environment.
F53 vs F51
| Item | F53 / S32750 | F51 / S31803 |
|---|---|---|
| Stainless Family | Super Duplex | Duplex |
| Typical Chromium | ~25% | ~22% |
| Molybdenum | Higher | Lower |
| Nitrogen | Higher | Lower |
| Strength | Higher | Lower |
| Localized Corrosion Resistance | Higher | Lower |
| Typical Use | More severe chloride service | General duplex applications |
F53 and F51 are different grades and should not be treated as directly interchangeable without engineering approval.
NACE Sour-Service F53 Flanges
ASTM A182 F53 Blind Flanges can be supplied for projects requiring NACE MR0175 / ISO 15156 compliance.
Sour-service suitability depends on the applicable material condition, hardness, heat treatment and actual service environment.
The grade designation F53 / S32750 alone does not automatically establish compliance for every sour-service condition.
Surface Condition and Inspection
Typical supply and inspection options include:
- Machined flange finish
- Pickling and passivation where specified
- Controlled cleaning to avoid carbon-steel contamination
- RTJ groove dimensional inspection
- EN 10204 Type 3.1 MTC
- EN 10204 Type 3.2 when specified
- Chemical Analysis
- Mechanical Testing
- PMI
- Ferrite / phase-balance verification when specified
- PT
- UT where required
- Third-Party Inspection
- Full Heat-Number Traceability
Related F53 / Super Duplex Products
- UNS S32750 / ASTM A182 F53 / 2507 Super Duplex – material properties, standards and product forms.
- ASTM A182 F53 Weld Neck Flange – WNRF and WNRTJ configurations for welded piping connections.
- ASTM A182 F53 Blind Flange – RF and RTJ configurations for pipeline closure and isolation.
- ASTM A815 S32750 Butt-Weld Fittings – elbows, tees and reducers for super duplex piping systems.
- ASTM A790 S32750 Pipe – super duplex pipe for chloride and offshore service.
- ASTM A182 F55 Flanges – UNS S32760 super duplex forged flanges for severe service.
How to Order ASTM A182 F53 Blind Flanges
A complete RFQ should include:
- ASTM A182 F53 / UNS S32750
- Blind Flange
- Nominal pipe size
- Pressure class
- RF or RTJ
- ASME B16.5
- Quantity
- NACE requirement if applicable
- NDE / PMI requirements
- Certification requirements
Example
ASTM A182 F53 / UNS S32750 Blind Flange, NPS 8″, Class 1500, RTJ, ASME B16.5, EN 10204 3.1, PMI and NACE MR0175 / ISO 15156 as specified
ASTM A182 F53 Blind Flange Manufacturer and Supplier
We manufacture and supply ASTM A182 F53 / UNS S32750 Super Duplex Blind Flanges for offshore, seawater, desalination, chemical-processing and oil & gas piping systems.
Available products include RF and RTJ Blind Flanges to ASME B16.5, together with Weld Neck and other project-specified F53 flange configurations.
Project-specific PMI, NDE, NACE requirements, third-party inspection and EN 10204 certification can be provided when specified.
