A351 CF8 Metal-Seated Floating Ball Valve is a premium fluid control solution that integrates superior corrosion resistance with high-strength abrasion protection. Its body is cast from ASTM A351 CF8 (Cast 304 Stainless Steel), containing 18% Chromium and 8% Nickel, providing excellent chemical stability against oxidizing acids and various chemical media. Departing from traditional PTFE soft seals, this valve utilizes a Metal-to-Metal sealing architecture.
The ball and seat surfaces are hardened using High-Velocity Oxygen Fuel (HVOF) spraying of Tungsten Carbide (WC) or Stellite alloys, achieving a surface hardness exceeding HRC 60. By combining the floating ball's pressure-induced displacement with a Belleville spring-compensated seat design, this valve effectively overcomes sealing failure in high-temperature environments (200°C to 450°C).
It is specifically engineered to shear through fibers, small solid particles, and crystallizing corrosive slurries, making it a vital isolation component for the chemical fiber, paper-pulp, and pharmaceutical refining industries.
Drawning of A351 CF8 Metal-Seated Floating Ball Valve
Technical Specifications
| Item | Specification |
| Design Standard | API 6D / ASME B16.34 / API 608 |
| Pressure Rating | Class 150 / 300 / 600; PN16 - PN100 |
| Size Range | 1/2" - 8" (DN15 - DN200) |
| Working Temperature | -29°C to 450°C (Customizable for higher temps) |
| Leakage Class | ANSI/FCI 70-2 Class V (Standard) / Class VI (Optional) |
| Hardening Process | HVOF Spraying / Laser Cladding |
| Surface Hardness | HRC 58 - 62 |
| Connection Type | Flanged (RF, RTJ), Butt-Weld (BW) |
Main Material List
| No. | Part Name | Material (ASTM Standard) |
| 1 | Body | ASTM A351 CF8 (Cast 304 SS) |
| 2 | Ball | A182 F304 + Tungsten Carbide (WC) Coating |
| 3 | Seat | A182 F304 + Tungsten Carbide (WC) Coating |
| 4 | Disc Spring | Inconel X-750 (High-temp & Fatigue resistant) |
| 5 | Stem | ASTM A182 F304 / 17-4PH |
| 6 | Packing | High-grade Flexible Graphite |
| 7 | Bonnet Gasket | SS304 + Flexible Graphite Spiral Wound |
| 8 | Thrust Washer | Nitrided Stainless Steel / Reinforced Graphite |
Main Connection and Outline Dimensions (Class 150/300)
Note: Due to the complex structure, the height (H) of metal-seated valves is typically slightly greater than that of soft-seated versions.
| Size (Inch) | DN (mm) | L (150# - mm) | L (300# - mm) | D (Flange OD-mm) | H (Height-mm) | W (Handle/Gear-mm) |
| 1/2" | 15 | 108 | 140 | 89 / 95 | 90 | 150 |
| 1" | 25 | 127 | 165 | 108 / 125 | 115 | 180 |
| 2" | 50 | 178 | 216 | 152 / 165 | 160 | 350 |
| 3" | 80 | 203 | 283 | 190 / 210 | 205 | 500 |
| 4" | 100 | 229 | 305 | 229 / 255 | 250 | 600 |
| 6" | 150 | 394 | 403 | 279 / 320 | 340 | Gear Operated |
| 8" | 200 | 457 | 502 | 343 / 380 | 430 | Gear Operated |
A351 CF8 Metal-Seated Floating Ball Valve Features
Dual Resistance: The 304 SS substrate provides chemical protection, while the Tungsten Carbide layer resists mechanical erosion and particle scratching.
Thermal Compensation Design: Inconel X-750 Belleville springs located behind the seats absorb thermal expansion at high temperatures. This prevents the ball and seats from seizing (jamming) while maintaining stable operating torque.
Sealing Options: Available in unidirectional forced sealing or bidirectional flexible sealing structures based on process requirements.
Intrinsic Fire Safety & Anti-Static: The all-metal construction (excluding packing) inherently meets API 607 fire-safety standards and provides excellent electrical continuity to prevent static buildup.
Low Maintenance Cost: The extreme durability of the metal sealing pair significantly reduces replacement frequency and unscheduled production downtime.
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FAQ
What is ASTM A351 CF8 equivalent to?
ASTM A351 CF8 is the casting equivalent to AISI 304 Stainless Steel.
Here is how it breaks down across different metal forms:
Wrought (Plate/Sheet): AISI 304
Forged: ASTM A182 F304
Cast: ASTM A351 CF8
European/DIN Standard: 1.4308
What is the meaning of CF8 valve?
In the valve industry, CF8 is a standard material code for cast 304 stainless steel:
C: Cast (manufactured using a casting process).
F: Iron-Chromium-Nickel alloy (indicates it is a stainless steel).
8: Defines the specific chemical and mechanical properties (roughly equivalent to 18% Chromium and 8% Nickel).
What is the material specification of ASTM A351?
ASTM A351 is a standard material specification for castings made of austenitic (stainless) steel for pressure-containing parts.
Key points include:
Focus: It covers high-temperature and corrosive service.
Common Grades: Includes grades like CF8 (304), CF8M (316), CF3 (304L), and CF3M (316L).
Application: It is the primary standard used for manufacturing stainless steel valve bodies, pumps, and fittings used in the chemical, oil, gas, and power industries.
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