Metal C-Rings
Metal C-rings are highly elastic static seals ideal for high-demand machinery and installations, offering greater elasticity than metal O-rings and other metal seals. Their prestressed forces vary based on factors like material, heat, tolerances, and treatment. Sealing is achieved through the spring-back of the C-rings, accommodating movements within the flanged joint. The prestress/deformation is approximately 20% of the ring height.
Suitable for internal and external pressure or axial thrust, metal C-rings operate self-energizing and are available in diameters from 6.5 mm to 3000 mm, with profile sections from 0.9 mm to 6.4 mm. They come in the same materials and coatings as O-rings, with Inconel 718 as the standard material. They can be used in temperatures up to 750 degrees centigrade and can handle high-vacuum to ultrahigh pressure ranges of 5500 bar.
Advantages & Usage
- seals vacuum, gases and liquids
- pressure ranges from UHV up to 5500 bar
- service temperatures up to 750°C
- lowest leakage rates through additional coating
- Resistant to explosive decompression
- Simple force calculations (force shunt)
Metal C-Ring Types
Metal C-Ring for Internal Pressure (MCI): a resilient internally pressurized static face seal open on the inside, enabling it to bear the same pressure as its internal operational conditions. Ideal for assemblies, pressure vessels, jet engines, fuel injectors, lighter flanges, etc.
Metal C-Ring for External Pressure (MCO): a robust externally pressurized static face seal open on the outside, designed to withstand the same pressure as its external operational conditions. It comes with good springback properties to accommodate thermal cycles.
Metal C-Ring for Axial Pressure (MCA): a sturdy dynamic axial seal designed to endure the same pressure as its axial operational conditions. It’s an optimal choice for static and low-cycle dynamic axial sealing applications. It is suitable for use in various industrial settings, including hydraulic systems and high-temperature shaft sealing.
Metal C-Ring, spring energized for Internal Pressure (MCI-F): shaped like MCI, but this ring can handle higher loads, making it suitable for use with rougher mating surfaces. It excels in applications such as pressure vessel closures, manways, hand-holes, steam generators, gasoline/diesel engine fire rings, and exhaust joints. It’s the best choice for non-flat mating surfaces. While it’s primarily designed for internally pressurized joints, it can also be used for externally pressurized joints to prevent the working fluid from entering the seal cavity, albeit at a reduced working pressure rating.
Metal C-Ring, spring energized for External Pressure (MCO-F): shaped like MCO, but this ring can withstand higher loads, making it ideal for use with rougher mating surfaces. It’s primarily designed for externally pressurized joints and flanges with a rougher surface finish. Additionally, it can be used for internally pressurized joints to prevent the working fluid from entering the seal cavity, although this comes with a reduced working pressure rating.
Metal C-Ring, spring energized for External Pressure (MCO-F): shaped like MCA, but this seal is designed to handle higher loads, making it suitable for use with rougher mating surfaces. It’s primarily intended for applications that require static and low-cycle dynamic axial sealing. The addition of spring reinforcement enhances the seal’s performance and resilience, making it an ideal choice for various high-demand applications.
C-Ring Material
SS304 (Stainless Steel 304)
SS304 is a widely used stainless steel alloy known for its excellent formability and corrosion resistance. This alloy is versatile and suitable for c-rings in various commercial, industrial, and consumer applications.
However, SS304 does have its limitations. It can corrode under acidic conditions when exposed to high gas pressure over 5 bars or in the presence of salts and chlorides. It’s recommended that SS304 operates at a maximum temperature of 400 degrees Celsius.
To enhance its durability and resistance to environmental factors, a coating can be applied to SS304 seals, offering additional protection against air and salts.
Inconel X-750
Inconel X-750 is an age-hardened, nickel-based superalloy known for its high-temperature strength and corrosion resistance. It’s particularly useful in high-temperature conditions, offering high tensile and creep rupture properties. The alloy’s strength can be optimized at temperatures between 700 and 975 degrees Celsius.
Inconel 718
Inconel 718 is an age-hardenable nickel superalloy known for its exceptional high-temperature strength and good oxidation resistance. It boasts excellent cold-forming characteristics and offers a higher strength than X-750. A standout feature of Inconel 718 is its ability to undergo precipitation hardening without cracking after welding, allowing it to maintain high tensile strength while offering high formability.
This alloy suits various c-ring types up to maximum service temperature. It is especially useful in applications with large thermal and mechanical transients, such as gas turbines and aerospace components. Additionally, due to its robust properties, Inconel 718 is a preferred choice for cryogenic storage tanks, downhole shafts, and wellhead components.
Generally, stainless steel, like SS304, tends to be less expensive than nickel-based alloys like Inconel. If cost is a significant factor, SS304 might be the more economical choice.
Coating
Heat Treatment
Order Code Key
The order example MCI-532-096,80-1S1 in the example above corresponds to a metal C-ring designed for internal pressure, specifically of the MCI type.
It’s made from Inconel X-750, with a free height of 2.4 mm and a wall thickness of 0.25 mm. The ring has an outside diameter of 96.80 mm, excluding the plating thickness. This ring is conventionally cold-hardened and coated with silver, with a coating thickness ranging from 0.15 to 0.30 mm.
