Steel O-rings are the metallic variants of generally used elastomeric O-rings. They’re sometimes utilized in static sealing functions which can be incompatible with the bodily and chemical traits of elastomeric O-rings. These O-rings have excessive tolerance to radiation in addition to excessive vacuum, and are usually used for flanged functions. Ideally, metallic O-rings are positioned in each open and closed grooves and axial stress is utilized between two parallel surfaces. Moreover, grooves that maintain the O-rings are designed to be perpendicular to the route of the fluid move. When positioned between surfaces and compressed to a predetermined top, deforms and creates contact between the jointing and sealing faces. Inherently, O-rings’ metallic elasticity shows an affordable deflection and creates most sealing contacts throughout operation to make sure the sealing motion. Along with elastic deflection of the metallic, structural builds of the O-rings additionally play an essential function in creating the sealing pressure. Though most metals can be utilized for manufacturing metallic O-rings, the selection of metals ought to be such that the linear enlargement co-efficient of the O-ring metallic varies barely from the linear enlargement co-efficient of the metallic(s) of jointing surfaces. Steel O-rings are susceptible to rusting in contrast to elastomeric O-rings, and as such, are coated with an acceptable materials to keep away from rusting. This materials is softer than the bottom metallic and serves a further function of negating the impact of floor abnormalities. The coating supplies which can be sometimes used are comfortable metals, resembling silver, and non-metals like PTFE.
Steel O-rings are primarily categorised primarily based on their fundamental structural attribute, they’re categorised as follows:
- Stable Steel O-Rings
- Hole Steel O-Rings
Stable Steel O-Rings
Stable metallic rings are wires of round profile linked like a hoop. A lot of these O-rings require particular grooves for his or her environment friendly performance. This requirement of particular grooves restricts the usage of strong metallic O-rings to sure functions, resembling engine cylinder heads. Stable metallic rings are usually manufactured in copper and appropriate for software in nuclear reactors, for checking radiation leaks. These O-rings can deal with pressures of as much as 4MPa and temperatures reaching 500°C and are appropriate for reasonable stress and reasonable vacuum functions.
Hole Steel O-Rings
Hole metallic O-rings are structurally extra subtle as compared with strong metallic O-rings and shaped by round tubes bent to the form of a hoop. Hole metallic O-rings usually operate like their elastomeric counterparts, i.e. when pressed between jointing surfaces, they show spring-back impact inflicting a bigger sealing floor between the seal and the jointing surfaces. These O-rings are sub-classified primarily based on the traits of the hole phase of the ring.
- Plain Hole O-Rings
- Self Energized Hole O-Rings
- Strain Stuffed Hole O-Rings
Plain Hole O-Rings:
These are hole metallic O-rings with nitrogen at atmospheric stress or vacuum inside them. Plain hole O-rings are utilized in low stress or low vacuum functions. Though plain hole O-rings present similarity in temperature and stress dealing with capabilities with strong metallic O-rings, they provide considerably higher spring-back and sealing capabilities. Usually, plain hole metallic O-rings are manufactured in Inconel 750 and plated with silver.
Self Energized Hole O-Rings:
Self-energized hole O-rings have holes or vents on their surfaces to make the most of the system stress or atmospheric stress for sealing motion. Relying on the orientation of such grooves, the O-rings are additional categorised into internally vented O-rings and externally vented O-rings. Internally vented O-rings product of gentle metal and plated with PTFE can stand up to pressures of as much as 3500 kg/sq cm and temperatures of 600°C. Externally vented O-rings are utilized in functions the place the surface stress is greater than the stress contained in the seal.
Strain Stuffed Hole Rings:
Strain stuffed hole O-rings are modified plain hole rings with pressurized inert gasses inside them. These O-rings can be utilized in tongue and groove flanges and may deal with temperatures from cryogenic temperatures as much as 850°C. Strain stuffed O-rings are utilized in vacuum sealing functions.
- Steel O-rings can’t be utilized in extremely dynamic sealing functions
- These O-rings are rendered ineffective after they’re used as soon as as a result of they can not retain their form after single use
- Broad tolerances of the groove can’t be accommodated by the metallic O-rings, particularly in bigger sizes
- Cautious becoming ought to be accomplished to keep away from their deformation earlier than their seal is tightened.