Bridal Ring Sets Under 200 – Metal O-rings are the metallic variations of commonly used elastomeric O-rings. They are generally used in stationary sealing applications that are incompatible with the physical and chemical characteristics of elastomeric O-rings. All these O-rings have high tolerance to radiation in addition to high vacuum, and are generally used for flanged applications. Ideally, metal O-rings are put in both open and closed grooves and axial pressure is used between two parallel surfaces. Furthermore, grooves that hold the O-rings are made to be vertical to the direction of the fluid flow. When placed between surfaces and compressed to a predetermined height, deforms and creates contact between the jointing and sealing faces. Inherently, O-rings’ metallic elasticity displays a reasonable deflection and creates maximum sealing contacts during operation to make sure the sealing action. Besides elastic deflection of the alloy, structural builds of the O-rings also play a significant part in producing the sealing force. Even though most metals may be used for fabricating metal O-rings, the option of metals must be such that the linear expansion co-efficient of the O-ring metal fluctuates slightly from the linear expansion co-efficient of the alloy(s) of jointing surfaces. Metal O-rings are vulnerable to rust unlike elastomeric O-rings, and therefore, are coated with a suitable substance to avoid rusting. This material is softer than the base metal and serves an additional purpose of preventing the impact of surface abnormalities. The coat materials that are typically utilized are soft metals, such as silver, and non-metals such as PTFE.
Metal O-rings are largely categorized based on their basic structural attribute, they are categorized as follows:
- Solid Metal O-Rings
- Hollow Metal O-Rings
Solid Metal O-Rings
Solid metallic rings are cables of round profile attached like a ring. These kinds of O-rings require specific grooves for their effective functionality. This requirement of specific grooves limits the use of solid metallic O-rings to specific applications, such as engine cylinder heads. Solid metallic rings are generally manufactured in copper and suitable for application in atomic reactors, for checking radiation leaks. These O-rings can handle pressures of up to 4MPa and temperatures hitting 500°C and are suitable for moderate strain and medium sized vacuum applications.
Hollow Metal O-Rings
Hollow metallic O-rings are structurally more sophisticated in comparison with good metallic O-rings and shaped by circular tubes bent into the shape of a ring. Hollow metallic O-rings generally function like their elastomeric counterparts, i.e. when pressed between jointing surfaces, they exhibit spring-back effect inducing a bigger sealing surface between the seal and the jointing surfaces. All these O-rings are sub-classified dependent on the characteristics of the hollow sector of the ring.
- Plain Hollow O-Rings
- Self Energized Hollow O-Rings
- Pressure Filled Hollow O-Rings
Plain Hollow O-Rings:
These are hollow metallic O-rings with nitrogen at atmospheric pressure or vacuum within them. Plain hollow O-rings are used in low stress or low vacuum applications. Although plain hollow O-rings display similarity in temperature and pressure handling capabilities with good metallic O-rings, they provide considerably better spring-back and sealing capacities. Normally, plain hollow metallic O-rings are produced from Inconel 750 and plated with silver.
Self Energized Hollow O-Rings:
Self-energized hollow O-rings have holes or vents in their surfaces to use the system pressure or atmospheric pressure to sealing action. Depending upon the orientation of these grooves, the O-rings are categorized into internally vented O-rings and externally vented O-rings. Internally vented O-rings made from light steel and plated with PTFE can withstand pressures of up to 3500 kg/sq cm and temperatures of 600°C. Externally vented O-rings are used in applications where the outside pressure is greater than the pressure within the seal.
Pressure stuffed hollow O-rings are altered plain hollow rings with pressurized inert gasses in them. These O-rings may be used in tongue and groove flanges and will handle temperatures from cryogenic temperatures up to 850°C. Pressure filled O-rings are used in vacuum sealing applications.
- Metal O-rings cannot be utilized in highly dynamic sealing applications
- All these O-rings are rendered useless when they’re used once because they cannot retain their shape after single use
- Wide tolerances of the groove cannot be accommodated by the metallic O-rings, especially in bigger sizes
- Careful fitting ought to be done to avoid their deformation before their seal is tightened.