Some seals and gaskets
1. o-ring
2. fiber washer
3. paper gaskets
4. cylinder head gasket

A gasket is a mechanical seal that fills the space between two objects, generally to prevent leakage between the two objects while under compression. Gaskets save money by allowing less precise mating surfaces on machine parts which can use a gasket to fill irregularities. Gaskets are commonly produced by cutting from sheet materials, such as gasket paper, rubber, silicone, metal, cork, felt, Neoprene, fiberglass, or a plastic polymer (such as polychlorotrifluoroethylene). Gaskets for specific applications may contain asbestos. It is usually desirable that the gasket be made from a material that is to some degree compressible such that it tightly fills the space it is designed for, including any slight irregularities. In mathematics, an Apollonian gasket or Apollonian net is a fractal generated from three circles, any two of which are tangent to one another. ... The Sierpinski triangle, also called the Sierpinski gasket, is a fractal, named after Waclaw Sierpinski. ... A gasket holding the main-royal on a modern square-rigged training ship. ... Image File history File links Download high-resolution version (510x700, 72 KB)Gaskets: o ring fiber washer paper gaskets cylinder head gasket Scan, upload MH 11:06, 2005 Jun 19 (UTC) I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high-resolution version (510x700, 72 KB)Gaskets: o ring fiber washer paper gaskets cylinder head gasket Scan, upload MH 11:06, 2005 Jun 19 (UTC) I, the creator of this work, hereby release it into the public domain. ... Typical O-ring and application An O-ring is a loop of elastomer with a round (o-shaped) cross-section used as a mechanical seal. ... Assorted washers: flat, split, star and insulated A washer is a thin disk with a hole, usually in the middle. ... The cylinder head from a GMC van. ... Different kinds of gaskets, #4 indicating a V4 head gasket. ... Compression seal example A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage (e. ... Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. ... For other uses, see Paper (disambiguation). ... This does not cite any references or sources. ... Not to be confused with the element silicon. ... This article is about metallic materials. ... For other uses, see Cork. ... A selection of 4 different felt cloths. ... Neoprene is the DuPont Chemical trade name for a family of synthetic rubbers based on polychloroprene. ... Bundle of fiberglass Fiberglass (also called fibreglass and glass fibre) is material made from extremely fine fibers of glass. ... For other uses, see Plastic (disambiguation). ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... Polychlorotrifluoroethylene is a polymer with the following mer structure: ... For other uses, see Asbestos (disambiguation). ...

Properties

One of the more desirable properties of an effective gasket in industrial applications for compressed fiber gasket material is the ability to withstand high compressive loads. Most industrial gasket applications involve bolts exerting compression well into the 14 MPa (2000 psi) range or higher. Generally speaking, there are several truisms that allow for best gasket performance. One of the more tried and tested is: "The more compressive load exerted on the gasket, the longer it will last". There are several ways to measure a gasket material's ability to withstand compressive loading. The "hot compression test" is probably the most accepted of these. Most manufacturers of gasket materials will provide or publish these results. Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. ... This article is about screws and bolts. ... MPA is a TLA (three-letter acronym) that may mean: Macedonian Press Agency Marine Protected Area Maritime Patrol Aircraft Maryland and Pennsylvania Railroad (AAR reporting mark MPA) Master of Public Administration Master of Public Affairs Max Planck Institute for Astrophysics Metropolitan Police Authority Mid-atlantic Pagan Alliance Motion Picture Association... A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in²) is a non-SI unit of pressure based on avoirdupois units. ... A truism is a claim that is so obvious or self-evident as to be hardly worth mentioning, except as a reminder or as a rhetorical or literary device. ...

Gasket Design

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Gaskets come in many different designs based on industrial usage, budget, chemical contact and physical parameters. The main types of gaskets are Sheet, Solid Material, Spiral Wound, Double Jacketed and "Kammprofile". Image File history File links Wikitext. ...

Sheet Gaskets

Sheet Gaskets are by the far the cheapest option for gaskets. The premise is simple in that a sheet of material (in older situations the material would be compressed asbestos, but now generally a fibrous material such as graphite is used) has the gasket shape "punched out" of it. This leads to a very crude, fast and cheap gasket. These gaskets can fill many chemical requirements based on the inertness of the material used and fit many budgetary restraints. Common practice prevents these gaskets from being used in many industrial processes based on temperature and pressure concerns.

Solid Material Gaskets

After Sheet Gaskets solid material gaskets are the most cost-effective option. The idea behind solid material is to use metals which cannot be punched out of sheets but are still cheap to produce. These gaskets generally have a much higher level of quality control than sheet gaskets and generally can withstand much higher temperatures and pressures. The key downside is that a solid metal must be greatly compressed in order to become flush with the flange head and prevent leakage. The material choice is more difficult since it is primarily metals used so process contamination and oxidiation are real time concerns, also the metal used must be softer than the flange in order to insure that the flange does not warp and prevent sealing with future gaskets. Even so these gaskets have found a place in industry although not a large one.

Spiral Wound Gaskets

Spiral wound gaskets and Double Jacketed gaskets are two of the most used gaskets in industry. Spiral wound gasket utilizes a mix of metallic material and "filler material" generally the gasket has a chosen metal, normally a carbon rich or stainless steel, wound (hence the name) outwards in a circle (although other shapes are possible this is the primary) with the filler material, generally a flexible graphite, starting at the opposite side of the circle and winding in the same direction. This leads to a growing circle of alternating layers of filler and metal. These gaskets have proven to be reliable in most applications and although more expensive than solid material they do not require as high of bolt forces to be effective. This is possible mainly because the graphite makes the primary seal with the flange and the metal only acts to keep the gasket structurally sound.

Double Jacketed Gaskets

Spiral wound gaskets and Double Jacketed gaskets are two of the most used gaskets in industry. Double Jacketed (hence forth called DJ) gaskets are another combination of filler material and metallic materials. In this application, a tube with ends that resemble a "C" is made of the metal with an additional piece made to fit inside of the "C" making the tube thickest at the meeting points. The filler is pumped between the shell and piece. When in use the compressed gasket has a larger amount of metal at the two tips were contact is made (due to the shell/piece interaction) and these two places bear the burden of sealing the process. Since all that is needed is a shell and piece, these gaskets can be made from almost any material that can be made into a sheet and a filler can than be inserted. This is an effective option for most applications.

Kammprofile Gaskets

Kammprofile gaskets are used in many older seals since they have both a flexible nature and are great sealers. Kammprofile's work by having a solid corrugated (many equally spaced bumps) core with a flexible covering layer. This arrangement allows for very high compression and an extremely tight seal along the ridges of the gasket. Since the graphite will fail generally instead of the metal core with gasket are repairable and can be done when the seal is not needed such as a shutdown of some kind. Kammprofile has a high initial cost for most applications but this can be justified both by long term savings and increased reliability.

Improvements

Many gaskets contain minor improvements to increase lifespan or acceptable operating conditions:

1. A common improvement is an inner compression ring. A compression ring allows for higher flange compression while preventing gasket failure. The effects of a compression ring are minimal and generally are just used when the standard design experiences a high rate of failure.
2. A common improvement is an outer guiding ring. A guiding ring allows for easier installation and serves as a minor compression inhibitor. In some alkylation uses these can be modified on Double Jacketed gaskets to show when the first seal has failed through an inner lining system coupled with alkylation paint.

See also

• Ozone cracking
• Polymer degradation
• Washer (mechanical)
• Vacuum flange#Vacuum Gaskets

Polymer degradation is a change in the properties - tensile strength, colour, shape, etc - of a polymer or polymer based product under the influence of one or more environmental factors such as heat, light or chemicals. ... Assorted washers: flat, split, star and insulated A washer is a thin disk with a hole, usually in the middle. ... A vacuum flange is a flange at the end of a tube used to connect vacuum containing vessels, tubing and vacuum pumps to each other. ...

Sources

1. Bickford, John H.: An Introduction to the Design and Behavior of Bolted Joints, 3rd ed., Marcel Dekker, 1995, pg. 5
2. Latte, Dr. Jorge and Rossi, Claudio: High Temperature Behavior of Compressed Fiber Gasket Materials, and an Alternative Approach to the Prediction of Gasket Life, FSA presented Paper, 1995, pg. 16