Gasket - Wikipedia, the free encyclopedia
`
`Page 1 of 7
`
`Gasket
`
`From Wikipedia, the free encyclopedia
`
`A gasket is a mechanical seal which fills the space between
`two or more mating surfaces, generally to prevent leakage
`from or into the joined objects while under compression.
`
`Gaskets allow "less-than-perfect" mating surfaces on machine
`parts where they can fill irregularities. Gaskets are commonly
`produced by cutting from sheet materials.
`
`Gaskets for specific applications, such as high pressure steam
`systems, may contain asbestos. However, due to health
`hazards associated with asbestos exposure, non-asbestos
`gasket materials are used when practical.
`
`It is usually desirable that the gasket be made from a material
`that is to some degree yielding such that it is able to deform
`and tightly fills the space it is designed for, including any
`slight irregularities. A few gaskets require an application of
`sealant directly to the gasket surface to function properly.
`
`Some (piping) gaskets are made entirely of metal and rely on a
`seating surface to accomplish the seal; the metal's own spring
`characteristics are utilized (up to but not passing (cid:305)y, the
`material's yield strength). This is typical of some "ring
`joints" (RJ) or some other metal gasket systems such as those
`made by Grayloc (an Oceaneering International company).
`These joints are known as R-con and E-con compressive type
`joints.[1]
`
`Contents
`
`(cid:1389) 1 Properties
`(cid:1389) 1.1 Gasket design
`(cid:1389) 1.2 Sheet gaskets
`(cid:1389) 1.3 Solid material gaskets
`(cid:1389) 1.4 Spiral-wound gaskets
`(cid:1389) 1.5 Constant seating stress gaskets
`(cid:1389) 1.6 Double-jacketed gaskets
`(cid:1389) 1.7 Kammprofile gaskets
`(cid:1389) 1.8 Flange gasket
`
`Some seals and gaskets
`1. o-ring
`2. fiber washer
`3. paper gaskets
`4. cylinder head gasket
`
`Polytetrafluoroethylene (PTFE) gasket
`
`http://en.wikipedia.org/wiki/Gasket
`
`8/26/2014
`
`LMK Technologies, LLC Ex. 2003
`BLD Services, LLC v. LMK Technologies, LLC
`IPR2015-00723
`
`

`

`Gasket - Wikipedia, the free encyclopedia
`
`Page 2 of 7
`
`(cid:1389) 2 Improvements
`(cid:1389) 3 Reasons for failure
`(cid:1389) 3.1 Uneven distributed pressing force
`(cid:1389) 3.2 Stress relaxation and torque loss
`(cid:1389) 3.3 Surface not smooth
`(cid:1389) 3.4 Temperature
`(cid:1389) 4 See also
`(cid:1389) 5 Sources
`(cid:1389) 6 External links
`
`Properties
`
`Gaskets are normally made from a flat material, a sheet such
`as paper, rubber, silicone, metal, cork, felt, neoprene, nitrile
`rubber, fiberglass, polytetrafluoroethylene (otherwise known
`as PTFE or Teflon) or a plastic polymer (such as
`polychlorotrifluoroethylene).
`
`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".
`
`Compressed fiber gasket
`
`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 tests. Most manufacturers of gasket materials will
`provide or publish the results of these tests.
`
`Gasket design
`
`Gaskets come in many different designs based on industrial usage, budget, chemical contact and physical
`parameters:
`
`Sheet gaskets
`
`The premise is simple in that a sheet of material has the gasket shape "punched out" of it. This leads to a
`very crude, fast and cheap gasket. In previous times the material was compressed asbestos, but in modern
`times a fibrous material such as high temp graphite (http://macrosealinc.com/high-temperature-graphite-
`
`http://en.wikipedia.org/wiki/Gasket
`
`8/26/2014
`
`

`

`Gasket - Wikipedia, the free encyclopedia
`
`Page 3 of 7
`
`gasket-materials/) is used. 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
`
`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; because metals are primarily used, process contamination and oxidation
`are risks. An additional downside is that the metal used must be softer than the flange — in order to ensure
`that the flange does not warp and thereby prevent sealing with future gaskets. Even so, these gaskets have
`found a niche in industry.
`
`Spiral-wound gaskets
`
`Spiral-wound gaskets comprise a mix of metallic and filler material. Generally, the gasket has a metal
`(normally carbon rich or stainless steel) wound outwards in a circular spiral (other shapes are possible)
`with the filler material (generally a flexible graphite) wound in the same manner but starting from the
`opposing side. This results in alternating layers of filler and metal. The filler material in these gaskets acts
`as the sealing element, with the metal providing structural support.
`
`These gaskets have proven to be reliable in most applications, and allow lower clamping forces than solid
`gaskets, albeit with a higher cost. [2] (http://www.bing.com/images/search?
`q=spiral+wound+gaskets&id=8C264F3FFBAA6AC593C155D7075E811633CDF20F&FORM=IQFRBA)
`
`Constant seating stress gaskets
`
`The constant seating stress gasket consists of two components; a solid carrier ring of a suitable material,
`such as stainless steel, and two sealing elements of some compressible material installed within two
`opposing channels, one channel on either side of the carrier ring. The sealing elements are typically made
`from a material (expanded graphite, expanded polytetraflouroethylene (PTFE), vermiculite, etc.) suitable
`to the process fluid and application. Constant seating stress gaskets derive their name from the fact that the
`carrier ring profile takes flange rotation (deflection under bolt preload) into consideration. With all other
`conventional gaskets, as the flange fasteners are tightened, the flange deflects radially under load, resulting
`in the greatest gasket compression, and highest gasket stress, at the outer gasket edge.
`
`Since the carrier ring used in constant seating stress gaskets take this deflection into account when creating
`the carrier ring for a given flange size, pressure class, and material, the carrier ring profile can be adjusted
`to enable the gasket seating stress to be radially uniform across the entire sealing area. Further, because the
`sealing elements are fully confined by the flange faces in opposing channels 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 elements, thus maintaining a 'constant' gasket seating stress while in-
`service. Thus, the gasket is immune to common gasket failure modes that include creep relaxation, high
`system vibration, or system thermal cycles. The fundamental concept underlying the improved sealability
`for constant seating stress gaskets are that (i) if the flange sealing surfaces are capable of attaining a seal,
`
`http://en.wikipedia.org/wiki/Gasket
`
`8/26/2014
`
`

`

`Gasket - Wikipedia, the free encyclopedia
`
`Page 4 of 7
`
`(ii) the sealing elements are compatible with the process fluid and application, and (iii) the sufficient
`gasket seating stress is achieved on installation necessary to affect a seal, then the possibility of the gasket
`leaking in-service is greatly reduced or eliminated altogether.
`
`Double-jacketed gaskets
`
`Double-jacketed 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 where 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 then 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 reliable
`performance. Kammprofiles work by having a solid corrugated 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 generally the graphite will fail instead of the metal core, Kammprofile can be repaired during later
`inactivity. Kammprofile has a high capital cost for most applications but this is countered by long life and
`increased reliability.
`
`Flange gasket
`
`A flange gasket is a type of gasket made to fit between two
`sections of pipe that are flared to provide higher surface area.
`
`Flange gaskets come in a variety of sizes and are categorized
`by their inside diameter and their outside diameter.
`
`There are many standards in gasket for flanges of pipes. The
`gaskets for flanges can be divided in major 4 different
`categories:
`
`1. Sheet gaskets
`2. Corrugated metal gaskets
`3. Ring gaskets
`4. spiral wound gaskets
`
`Copper flange gaskets used for ultrahigh
`vacuum systems
`
`Sheet gaskets are simple, they are cut to size either with bolt holes or without holes for standard sizes with
`various thickness and material suitable to media and temperature pressure of pipeline.
`
`Ring gaskets also known as RTJ. They are mostly used in offshore oil- and gas pipelines and are designed
`to work under extremely high pressure. They are solid rings of metal in different cross sections like oval,
`round, octagonal etc. Sometimes they come with hole in center for pressure .
`
`http://en.wikipedia.org/wiki/Gasket
`
`8/26/2014
`
`

`

`Gasket - Wikipedia, the free encyclopedia
`
`Page 5 of 7
`
`Spiral wound gaskets are also used in high pressure pipelines and are made with stainless steel outer and
`inner rings and a center filled with spirally wound stainless steel tape wound together with graphite and
`PTFE, formed in V shape. Internal pressure acts upon the faces of the V, forcing the gasket to seal against
`the flange faces.
`Improvements
`
`Many gaskets contain minor improvements to increase or infer acceptable operating conditions:
`
`(cid:1389) 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.
`(cid:1389) 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.
`
`Reasons for failure
`
`Uneven distributed pressing force
`
`Uneven pressing force is caused by a variety of factors, first is the human factor: asymmetric construction
`of the preload bolt, this factor can eliminate construction; theory on the flange pressed, the sealing surface
`is absolutely parallel to the practice, however, the centerline of a pipeline can not be absolutely concentric,
`and thus tighten the bolts on the flange moment, so that the flange discontinuity. Asymmetrical
`connection, the sealing surface more or less deformed, so that sealed the pressing force is reduced, the
`running load, prone to leakage. Third, the density of bolt arrangement on the pressure distribution more
`obvious impact, the closer the bolts, the more uniform the pressure.
`
`Stress relaxation and torque loss
`
`Tighten bolts on the flange, due to the vibration of the bodies, the temperature increased or decreased and
`other factors, the working process of the spiral wound gaskets stress relaxation, the bolt tension will be
`gradually decreased, resulting in loss of torque, causing a leak. In general, long bolts, the remnants of the
`torque, the smaller the diameter the more advantageous to prevent the loss of torque, with long, thin bolt is
`an effective way to prevent torque loss. Heating a certain period of time to make it stretch the bolt, and
`then to maintain a given torque, is very effective to prevent the loss of torque. There is a gasket is thinner
`and smaller the loss of torque. In addition to prevent the strong vibration of the machine and the pipe itself,
`and exclude the impact of adjacent equipment vibration, the impact of the sealing surface is not
`meaningless, not to beat the bolts tightened, can prevent the loss of torque.
`
`Surface not smooth
`
`It is important to make the sealing finish proper otherwise it will cause leakage
`
`http://en.wikipedia.org/wiki/Gasket
`
`8/26/2014
`
`

`

`Gasket - Wikipedia, the free encyclopedia
`
`Page 6 of 7
`
`Temperature
`
`Flanged leak often occurs in the cooling, because the cooling rate of cooling when the flange and bolts do
`not After cooling, the pressing force of the metal gaskets stress relaxation, combined with the cold
`contraction of the pipe, resulting in toward the bolt tensile direction force, this force will lead to leaks in,
`where the low-temperature media occasions when gasket should be noted: 1) low temperature flexible
`gasket; 2) shim thickness should be as much as possible to take a small flange gap as small as possible ; 3)
`high strength bolts, so that the strain is small.
`See also
`
`(cid:1389) O-ring
`(cid:1389) Ozone cracking
`(cid:1389) Polymer degradation
`(cid:1389) Vacuum flange
`(cid:1389) Washer (mechanical)
`
`Sources
`
`1. ^ [1] (http://www.oceaneering.com/subsea-products/grayloc/)
`
`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
`
`External links
`
`(cid:1389) Gasket Fabricators Association (http://www.gasketfab.com/)
`(cid:1389) Fluid Sealing Association, gasket division (http://www.fluidsealing.com/fsadiv.asp?DivID=5)
`(cid:1389) Gasket Selection (http://www.thomasnet.com/articles/hardware/gasket-materials)
`(cid:1389) http://europeansealing.com/en/about/esa-organisation/divisions/flange-gaskets-division
`(cid:1389) Gasket Materials Informative Resource (http://gaskets.cc)
`(cid:1389) Expanded PTFE Joint Sealant (http://www.sealsales.com/Expanded-PTFE-joint-sealant.html) User
`Guidance Informative Source
`(cid:1389) /gasket failure reasons (http://www.packagingmachiney.com/news/gasket_failure_reasons-
`1007.html)
`(cid:1389) Informative Source: Gasket Materials (http://www.gasketmaterial.net/)
`
`http://en.wikipedia.org/wiki/Gasket
`
`8/26/2014
`
`

`

`Gasket - Wikipedia, the free encyclopedia
`
`Page 7 of 7
`
`(cid:1389) Informative Source: PTFE Gaskets (http://ptfe-gaskets.net)
`
`Retrieved from "http://en.wikipedia.org/w/index.php?title=Gasket&oldid=617877818"
`Categories: Seals (mechanical) Engine technology
`
`(cid:1389) This page was last modified on 21 July 2014 at 18:06.
`(cid:1389) Text is available under the Creative Commons Attribution-ShareAlike License; additional terms
`may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a
`registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
`
`http://en.wikipedia.org/wiki/Gasket
`
`8/26/2014
`
`