Duck Band Wedding Rings – Metal O-rings will be the metallic variants of typically used elastomeric O-rings. They are typically utilised in stationary sealing applications that are incompatible with all the chemical and physical features of elastomeric O-rings. All these O-rings have high tolerance to radiation in addition to high vacuum, and are generally employed for flanged programs. Ideally, metal O-rings are placed 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 designed to be perpendicular 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 exhibits a reasonable deflection and generates maximum sealing contacts during surgery to make sure the sealing action. In addition to elastic deflection of the metal, structural builds of the O-rings also play a significant role in creating 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 varies slightly from the linear expansion 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 substance to avoid rusting. This material is softer than the base metal and serves an additional purpose of negating the effect 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 primarily classified based on their fundamental structural characteristic, they are classified as follows:
Strong Metal O-Rings
Strong metallic rings are wires of circular profile attached like a ring. These types of O-rings need special grooves for their efficient performance. This requirement of special grooves restricts the usage of solid metallic O-rings to certain programs, such as engine cylinder heads. Strong metallic rings are generally made in aluminum and suitable for use in atomic reactors, for checking radiation leaks. These O-rings can handle pressures of around 4MPa and temperatures hitting 500°C and are acceptable for moderate strain and medium sized vacuum applications.
Hollow Metal O-Rings
Hollow metallic O-rings are structurally more sophisticated in contrast with solid metallic O-rings and formed by curved tubes bent into the form of a ring. All these O-rings are sub-classified dependent on the qualities of the hollow sector of the ring.
- Plain Hollow O-Rings
- Self Energized Hollow O-Rings
- Stress Filled Hollow O-Rings
Plain Hollow O-Rings:
These are hollow metallic 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 show similarity in temperature and pressure handling capabilities with solid metallic O-rings, they offer substantially better spring-back and sealing capabilities. Generally, plain hollow metallic O-rings are produced from Inconel 750 and plated with silver.
Self-energized hollow O-rings have vents or holes in their surfaces to utilize the system pressure or atmospheric pressure to sealing activity. Based on the orientation of such grooves, the O-rings are further classified 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 around 3500 kg/sq cm and temperatures of 600°C. Externally vented O-rings are employed in applications where the external pressure is higher than the pressure inside the seal.
Stress filled hollow O-rings are modified plain hollow rings using pressurized inert gasses inside them. These O-rings may be utilised in tongue and groove flanges and can handle temperatures from cryogenic temperatures up to 850°C. Stress filled O-rings are employed in vacuum cleaning applications.
- Metal O-rings can’t be utilized in highly dynamic sealing applications
- All these O-rings are rendered useless when they’re used once since they can’t keep their shape after single use
- Broad tolerances of the groove can’t be accommodated by the metallic O-rings, particularly in bigger sizes
- Careful fitting should be done in order to avoid their deformation before their seal is tightened.