How Much Is A David Yurman Ring – Metal O-rings are the metallic variations of commonly used elastomeric O-rings. They are typically utilised in static sealing applications that are incompatible with the physical and chemical features of elastomeric O-rings. These O-rings have high tolerance to radiation in addition to high vacuum, and are generally employed for flanged applications. Ideally, metal O-rings are put in both open and closed grooves and axial pressure is applied between two parallel surfaces. What’s more, grooves that hold the O-rings are made to be vertical to the direction of the fluid stream. When placed between compressed and surfaces to a predetermined elevation, deforms and generates contact between the jointing and sealing faces. Inherently, O-rings’ metallic elasticity displays a affordable deflection and generates maximum sealing contacts through operation to make sure the sealing action. Besides elastic deflection of the metal, structural assembles of the O-rings also play a significant part in creating the sealing force. Although most metals can be used for manufacturing metal O-rings, the choice of metals must be such that the linear growth co-efficient of the O-ring metal fluctuates slightly from the linear growth co-efficient of the metal(s) of jointing surfaces. Metal O-rings are vulnerable to rust unlike elastomeric O-rings, and as such, are coated with a suitable material to prevent rusting. This material is thicker compared to the base metal and serves another purpose of preventing the impact of surface abnormalities. The coating materials that are typically used are soft metals, such as silver, and non-metals such as PTFE.
Metal O-rings are primarily classified according to their basic structural attribute, they are categorized as follows:
- Solid Metallic O-Rings
- Hollow Metal O-Rings
Solid Metallic O-Rings
Solid metal rings are wires of round profile connected like a ring. These types of O-rings need special grooves for their efficient functionality. This requirement of special grooves restricts the use of strong metal O-rings to certain applications, such as engine cylinder heads. Solid metal rings are generally manufactured in copper and appropriate for application in nuclear reactors, for assessing radiation flows. These O-rings can manage pressures of around 4MPa and temperatures hitting 500°C and are suitable for moderate pressure and medium sized vacuum applications.
Hollow Metal O-Rings
Hollow metal O-rings are structurally more sophisticated in comparison with solid metal O-rings and formed by curved tubes bent into the shape of a ring. Hollow metal O-rings generally function like their elastomeric counterparts, i.e. when pressed between jointing surfaces, so they exhibit spring-back effect causing a bigger sealing surface between the seal and the jointing surfaces. These O-rings are sub-classified based on the qualities of the hollow segment of the ring.
- Plain Hollow O-Rings
- Self Energized Hollow O-Rings
- Pressure Filled Hollow O-Rings
These are hollow metal O-rings with nitrogen at atmospheric pressure or vacuum inside them. Plain hollow O-rings are employed in low stress or low vacuum applications. Though plain hollow O-rings display similarity in temperature and pressure handling capabilities with solid metal O-rings, they offer considerably better spring-back and sealing capacities. Normally, plain hollow metal O-rings are manufactured in Inconel 750 and garnished with silver.
Self-energized hollow O-rings have holes or vents in their surfaces to utilize the system pressure or atmospheric pressure for sealing activity. Based on the orientation of these grooves, the O-rings are further classified into internally vented O-rings and externally vented O-rings. Internally vented O-rings made of mild steel and garnished with PTFE can withstand pressures of around 3500 kg/sq cm and temperatures of 600°C. Externally vented O-rings are employed in applications where the outside pressure is higher than the pressure inside the seal.
Pressure filled hollow O-rings are altered plain hollow bands using pressurized inert gasses in them. These O-rings can be utilised in tongue and groove flanges and can handle temperatures from cryogenic temperatures up to 850°C. Pressure filled O-rings are employed in vacuum cleaning applications.
- Metal O-rings can’t be used in highly dynamic sealing applications
- These O-rings are rendered useless when they are used once because they can’t retain their shape after only use
- Broad tolerances of the groove can’t be accommodated by the metal O-rings, especially in bigger sizes
- Careful fitting ought to be done in order to prevent their deformation until their seal is tightened.