Views: 0 Author: Site Editor Publish Time: 2023-06-10 Origin: Site
The idea behind solid materials is to use metals that can't be stamped out of sheets but are still cheap to produce.These gaskets typically have a higher level of quality control than sheet gaskets and can often withstand higher temperatures and pressures.The key disadvantage is that the solid metal must be compressed considerably to be flush with the flange head and prevent leaks.Material selection is difficult; since mainly metals are used, there is a risk of process contamination and oxidation.Another disadvantage is that the metal used has to be softer than the flange to ensure that the flange does not warp and thus prevent a seal with the future gasket. Even so, these gaskets have their place in the industry.
Spiral wound gaskets contain a mixture of metal and filler material.Typically, the metal of the gasket (usually carbon-rich steel or stainless steel) is wound outward in a circular helix (other shapes are also possible), and the filler material (usually flexible graphite) is wound in the same way, but from the opposite start sideways.This results in alternating layers of filler and metal.The filler material in these gaskets acts as the sealing element, and the metal provides structural support.These washers have proven reliable in most applications and allow for lower clamping forces than solid washers, albeit at a higher cost.
Constant seal stress washers
Constant sealing stress gaskets consist of two parts; a solid load ring made of a suitable material such as stainless steel,and two sealing elements of some compressible material mounted in two opposing channels, one in the center of the load ring sides.Sealing elements are usually made of materials suitable for the process fluid and application (expanded graphite, expanded polytetrafluoroethylene (PTFE), vermiculite, etc.).Constant seal stress washers get their name from the fact that the load ring profile takes flange rotation (deflection under bolt preload) into account.For all other conventional gaskets, when the flange fastener is tightened, the flange deflects radially under load, causing gasket compression and gasket stress to be highest at the outer edge of the gasket.Since load rings for constant seal stress gaskets take this deformation into account when creating the load ring for a given flange size, pressure class,and material, the load ring profile can be adjusted to evenly distribute the gasket load ring radially across the seal area.Furthermore, since the sealing element is fully restrained by the flange faces in the opposing passages on the carrier ring, any in-service compressive forces acting on the gasket are transmitted through the carrier ring and avoid any further compression of the sealing element, thus remaining in use" Constant” gasket seal stress.As a result, the gasket is immune to common gasket failure modes including creep relaxation, high system vibration, or system thermal cycling.The basic concepts for improving the tightness of constant seal stress gaskets are (i) if the flange sealing surfaces are capable of sealing, (ii) the sealing element is compatible with the process fluid and application, and (iii) sufficient gasket seal stress is present in the necessary installation to affect the seal,realized on, then the possibility of the gasket leaking in service is greatly reduced or completely eliminated.
Double jacketed gasket
Double jacketed gaskets are another combination of filler material and metal material.In this application the tube with the end similar to the "C" is made of metal and an extra piece is made inside the "C" to make the tube thickest at the junction.The filler is pumped between the housing and the workpiece.In use, compression gaskets have a large amount of metal at the two tips where they make contact (due to shell/piece interaction) and these two places carry the burden of the sealing process. Since only one shell and one piece are required, these gaskets can be made from almost any material that can be made into sheets, and the filler can then be inserted.
Kammprofile gaskets (sometimes spelled Campprofile) are used in many older seals because of their flexibility and reliable performance.Kammprofiles work by having a strong corrugated core and a flexible cover.This arrangement allows for very high compression and an extremely tight seal along the ridge of the gasket.Since graphite rather than metal cores typically fail, the Kammprofile can be repaired later during periods of inactivity.For most applications, the capital cost of Kammprofile is high, but this is more than offset by long life and high reliability.
Fish bone gasket
Fishbone washers are a direct replacement for Kammprofile and Spiralwound washers.They are entirely CNC machine made from similar materials, but the design of the washers eliminates the inherent disadvantages.Herringbone washers do not unfold in warehouses or factories. Rounded edges will not cause flange damage.The added "Stop Step" prevents the Fishbone Washer from being over-compressed/crushed, which is often caused by hot torque techniques at factory start-up.The gasket's bone remains malleable and accommodates thermal cycles and system pressure peaks, resulting in a durable and reliable flange seal that outperforms significantly all other gaskets of this nature.
A flange gasket is a gasket designed to be installed between two lengths of pipe that flare out to provide a greater surface area.
Flange gaskets come in a variety of sizes, classified by inside and outside diameter.There are many standards for pipe flange gaskets. Gaskets for flanges can be divided into four categories:
1. Sheet gasket
2. Corrugated metal gasket
3. Ring gasket
4. Spiral wound gasket
Sheet gaskets are simple, they are cut to standard sizes with or without bolt holes, in various thicknesses and materials to suit the piping medium and temperature pressure.Ring gaskets are also known as RTJs.They are primarily used in offshore oil and gas pipelines and are designed to work at extremely high pressures.They are solid metal rings of different cross sections, oval, circular, octagonal, etc.Sometimes they have a hole in the center for pressure.Wound gaskets are also used in high-pressure pipelines, made of stainless steel outer and inner rings, and the center is filled with a helically wound stainless steel strip, wound into a V shape with graphite and PTFE.Internal pressure acts on the V-shaped face, forcing the gasket to seal against the flange face. Most spiral wound gasket applications will use two standard gasket thicknesses: 1/8 inch and 3/16 inch. For 1/8" thick washers, compression to 0.100" thick is recommended. For 3/16", compress to 0.13" thickness.