They are much more reliable than jacketed gaskets double jacketed gaskets. Kammprofile gaskets are typically made of a stainless steel metal core with a flexible graphite filler material. The area a. Kammprofile gaskets are also really great for radial sheer which is seen when the flanges slip on each other really the flexible graphite filler during flange expansion and contraction due to temperature.
This gasket material is a solid metal gasket, and the metal core can be made of stainless steel or other exotic materials so that it can be put in high pressure and high-temperature flanges. These types of gaskets are the best metal gaskets for all pressure ratings of pipe flanges, especially ASME B I would argue that they are also great for heat exchangers due to their sealability tolerances with imperfections in flanges, and because they can be made for high pressure and high-temperature applications.
These spiral wound gaskets have a stainless steel inner ring, a carbon steel outer ring, and the metal core is made of stainless steel windings. The filler material is typically flexible graphite, but you can also have an elastomeric filler material such as PTFE if chemical resistance is needed. Spiral wound gaskets are more also flexible than Kammprofile gaskets so they tend to also have more compressibility and recovery, but they are harder to place in a flange at larger diameters so it is advisable to move to Kammprofile gaskets.
These types of gaskets should not be used in typical pipe flanges, and especially not in high-pressure rated pipe flanges such as pounds or greater. These gasket types can be made to have a minimum of 0. They are better than metal jacketed gaskets for heat exchangers, but should not be used in standard piping flange gaskets. Most piping flange gaskets in the oil and gas industry today are spiral wound gaskets made of stainless steel for the metal core material with either PTFE or graphite filler material.
ASME B The color coating on the outer ring which is typically carbon steel is painted on the outside of the ring so that an inspector can identify the windings material. When exposed to low temperatures, fluorocarbon elastomers can become quite hard. Fluorocarbons exhibit low gas permeability making them well suited for hard vacuum service and many formulations are self-extinguishing.
FKM materials are not generally recommended for exposure to hot water, steam, low molecular weight esters and ethers, glycol based brake fluids, or hot hydrofluoric or chlorosulfonic acids. Material advantages: » excellent chemical resistance » excellent heat resistance » good mechanical properties » good compression set resistance Material disadvantages: » poor low temperature flexibility » poor resistance to hot water and steam Temp.
At higher temperatures, polyurethane has a tendency to soften and lose both strength and fluid resistance. Material advantages: » excellent strength and abrasion resistance » good resistance to petroleum oils » good weather resistance Application Disadvantages » poor resistance to water » poor high temperature capabilities Temp. SBR is used in hydraulic brakes system seals and diaphragms, with the major of the industry usage coming from the Tire Industry.
SBR features excellent resistance to brake fluids, and good water resistance. Material advantages: » good resistance to brake fluids » good resistance to water Application Disadvantages » poor weather resistance » poor petroleum oil and solvent resistance Temp.
Ethylene-acrylic offers a high degree of oil, ozone, UV and weather resistance. Material advantages: » excellent vibration dampening » excellent heat aging characteristics » good dynamic property retention over a wide temperature range » resistance to transmission fluids, water, glycol mixtures, and alkalies Application Disadvantages » not recommended for exposure to fuel, brake fluid, aromatic hydrocarbons or phosphate esters.
Typical O-ring and application An O-ring , also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.
The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, and reliable and have simple mounting requirements.
They can seal tens of megapascals thousands of psi of pressure. O-rings can be produced by extrusion, injection molding, pressure molding or transfer molding. History The first patent for the O-ring, is dated May 12, as a Swedish patent.
Lundberg, the inventor of the O-ring, received the patent. Soon after migrating to the USA in , he patented an air brake system for streetcars trams. Despite his legal efforts, his intellectual property rights were passed from company to company until they ended up at Westinghouse. During World War II, the US government commandeered the O-ring patent as a critical war-related item and gave the right to manufacture to other organizations. Theory and design O-ring mounting for an ultra-high vacuum application.
Pressure distribution within the cross-section of the O-ring. The orange lines are hard surfaces, which apply high pressure. The fluid in the seams has lower pressure. The soft O-ring bridges the pressure over the seams. O-rings are available in various metric and inch standard sizes. Sizes are specified by the inside diameter and the cross section diameter thickness. ISO contains the most commonly used standard sizes, both inch and metric, worldwide.
Several other size specifications also exist. Successful O-ring joint design requires a rigid mechanical mounting that applies a predictable deformation to the O-ring. This introduces a calculated mechanical stress at the O-ring contacting surfaces. As long as the pressure of the fluid being contained does not exceed the contact stress of the O-ring, leaking cannot occur. Fortunately, the pressure of the contained fluid transfers through the essentially incompressible O-ring material, and the contact stress rises with increasing pressure.
For this reason, an O-ring can easily seal high pressure as long as it does not fail mechanically. The most common failure is extrusion through the mating parts. The seal is designed to have a point contact between the O-ring and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of the O-ring body.
The flexible nature of O-ring materials accommodates imperfections in the mounting parts. But it is still important to maintain good surface finish of those mating parts, especially at low temperatures where the seal rubber reaches its glass transition temperature and becomes increasingly crystalline. Surface finish is also especially important in dynamic applications.
A surface finish that is too rough will abrade the surface of the O-ring, and a surface that is too smooth will not allow the seal to be adequately lubricated by a fluid film. In vacuum applications, the permeability of the material makes point contacts quite useless.
Instead, higher mounting forces are used and the ring fills the whole groove. Also, round back-up rings are used to save the ring from excessive deformation [6][7][8] Because the ring feels the ambient pressure and the partial pressure of gases only at the seal, their gradients will be steep near the seal and shallow in the bulk opposite to the gradient of the contact stress [9] See: Vacuum flange KF.
Also, vacuum systems that have to be immersed in liquid nitrogen use indium O-rings, because rubber becomes hard and brittle at low temperatures.
In some high-temperature applications, O-rings may need to be mounted in a tangentially compressed state, to compensate for the Gow-Joule effect. O-rings come in a variety of sizes British Standard BS which are imperial sizes or metric sizes. Metric O-rings are usually defined by the internal dimension x the cross section. Material Some small O-rings O-ring selection is based on chemical compatibility, application temperature, sealing pressure, lubrication requirements, durometer, size and cost.
Synthetic rubbers - Thermosets: Thermoplastics:. What are Gaskets? 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.
Gasket design Gaskets come in many different designs based on industrial usage, budget, chemical contact and physical parameters: Sheet gaskets When a sheet of material has the gasket shape "punched out" of it, it is a sheet gasket. Solid material gaskets. Spiral-wound gaskets Spiral-wound gaskets comprise a mix of metallic and filler material.
Double-jacketed gaskets Double-jacketed gaskets are another combination of filler material and metallic materials. Kammprofile gaskets Kammprofile gaskets are used in many older seals since they have both a flexible nature and reliable performance. 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.
The gaskets for flanges can be divided in major 4 different categories: 1. The finished product will resemble the spiral wound gasket image below, with the various components discussed here indicated with labels Pressure Class Corresponding to flange pressure classes, spiral wound gaskets are available in , , , , , and pressure classes.
Material Winding and Filler Material is identified by the color on the outer edge of the gasket. Inner Ring optional A spiral wound gasket with an inner ring is common because the inner ring helps prevent what is known as spooling. Manufacturing O-rings can be produced by extrusion, injection molding, pressure molding or transfer molding.
Typical applications Successful O-ring joint design requires a rigid mechanical mounting that applies a predictable deformation to the O-ring. Vacuum applications In vacuum applications, the permeability of the material makes point contacts quite useless. High temperature applications In some high-temperature applications, O-rings may need to be mounted in a tangentially compressed state, to compensate for the Gow-Joule effect. Sizes O-rings come in a variety of sizes British Standard BS which are imperial sizes or metric sizes.
FaLang translation system by Faboba. Related Links What is Lubricating Grease? The compression of the gasket material is dependent upon the other members of the assembly. They work together as a system and can be cost optimized as a system. Gasket compression is caused by fastener clamping force and flange design.
The flange surface area determines the flange pressure distributed across the gasket surface. The fastener size, spacing and retained fastener force produces applied flange pressure to compress and seal the gasket. The amount of load required to seal is affected by the surface finish of the joint system. Any flange surface irregularity and flexibility produce flange contact pressure variation across the gasket surface and potential leaks. The gasket must be resilient and creep resistant enough to maintain an adequate portion of the applied flange force across its entire surface to remain sealed.
There are thousands of specialized engineered gasket materials available globally from large and small material development companies. No single material has the capability to serve all applications. One thing all sealing solutions have in common: they all rely on the flexible rubber to do the sealing.
As great a material that rubber is, it does have failure modes. ASTM provides standardized accelerated aging test systems for rubber, including chemical and temperature compatibility rankings.
Engineered composites, based on rubber, are used to achieve sealing and durability performance. Rubber and fiber fillers are blended in proprietary recipes by material development companies to enhance gasket performance.
The result is a material impervious to leakage that also retains its shape under load over time. Chemical Resistance Database — Program provides compatibility of rubber used in different gasket materials to the chemical media it will be exposed to. PGC Competitive Material — Program for comparing competing material to recommend options for cost reduction or performance improvements.
ASTM F — Program used to identify gasket materials by deciphering the F callout and compare to other gasket material specifications i. Military Specifications. PGC Obsolete Materials — Program searches database for obsolete gasket materials and shows material components to select a comparable available material.
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