Gasket Design Criteria Table Of Contents

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Gasket Design CriteriaTable of ContentsPageWorldwide Customer Service Network2Introduction3Section I - Gasket SelectionSoft Cut Gaskets .Thermiculite .PTFE Products - Sigma .PTFE Products - Fluoroseal .Flexitallic Flexicarb .Compressed Non-asbestos Fiber Gaskets .Sheet Materials Chemical Compatibility Selector Guide .Sheet Materials Chemical Compatibility Chart .Insulating Sets .Metal Jacketed Gaskets .Spiral Wound Gaskets.Sizing Parameters for Spiral Wound Gaskets .Flexpro Gaskets .MRG Gaskets .Ring Type Joints .Specialized Ring Type Joints .Lens Rings .Weld Gaskets .4679111213141517182128303132343536Section II - Joint Integrity CalculationsASME Boiler & Pressure Vessel Code Calculations .PVRC Method .373842Section III - Gasket InstallationBolt Torque Sequence .Troubleshooting .Metallic Gasket Materials .Useful Material Data .Bolting Data .Useful Technical Data .Torque Required To Produce Bolt Stress .Ordering Flexitallic Gaskets for Special Flange Designs .Metric Unit Conversions .Terms .4446474951525456575960T H EA N S W E RI SA L W A YS 1

Worldwide Customer Service NetworkOwned ManufacturingPlantsLicenseesACL Specialised Gaskets Pty. Ltd.Brisbane, AustraliaTel: 61 73 268 0666Flexitallic Ltd.Cleckheaton,Yorkshire, UKTeI: 44 1274 851273Flexitallic Ltd.Rochdale, Lancashire, UKTeI: 44 1274 851273AGS Group Inc.Edmonton, Alberta, CanadaTel: 1 780 466 5050Flexitallic L.P.Houston,Texas, USATel: 1 281 604 2400Arne Bo PedersenStavanger, NorwayTel: 47 5185 9000Flexitallic CanadaOntario, CanadaTel: 1 519 332 8300Automotive Components N.Z.Auckland, New ZealandTel: 64 98284119Joint VenturesDragon Industrial ServicesPembroke, UKTel: 441646 622200Equiter S.A. de C.V.Guadalajara, MexicoTel: 52 3 612 8483Eriks BV.Rotterdam, NetherlandsTel: 31 72 514 1514Flexitallic de Venezuela S.A.Caracas,VenezuelaTeI: 58 2 41 783550FMI Sima S.R.L.Brescia, ItalyTel: 39 030 7386 033Goldcrest Engineering & Service Co.(GESCO)Pataya, Chonburi, ThailandTel: 1 66 38 716 716Branch Offices & WarehousesFlexitallic Ltd.Aberdeen, Scotland, UKTel: 44 1224 725241Henry Gallacher Ltd.Stockton, Teesside UKTel: 44 1642 750111Flexitallic GmbHBurscheid, GermanyTel: 49 2174 8950Industrial Gasket & SupplyTorrance, California,USATel: 1 310 530 1771Flexitallic L.P.Cherry Hill, New Jersey, USATel: 1 856 321 9301Lake Charles RubberLake Charles, Louisiana, USATel: 1 337 433 1002Flexitallic L.P.Chicago, Illinois, USATel: 1 630 268 0418Saudi Gasket FactoryJeddah, Saudi ArabiaTel: 996 2 665 2966Flexitallic Ltd.Singapore 048581Tel: 65 6 321 91122T H EA N S W E RI SA L W A YS

FLEXITALLIC GASKET DESIGN CRITERIAIntroductionFLEXITALLIC, the world’s leading manufacturer and supplier of static seals and the originator of the Spiral Wound Gasket, iscommitted to sealing solutions for today’s industry. With greater emphasis than ever before placed on joint tightness, more attention is focused toward variables associated with the integrity of the bolted gasketed joint. Flexitallic Gasket Design Criteria manual offers the engineer and end user assistance in meeting the goal of providing fundamentally sound static sealing practice.Developed and collated by Flexitallic’s worldwide team of engineers, this publication is the “engineer’s handbook” of static sealstechnology.Flexitallic has identified three factors which must be considered to achieve a leaktight joint Gasket Selection Gasket Design Gasket InstallationThe GasketA gasket is a compressible material, or a combination of materials, which when clampedbetween two stationary members prevents the passage of the media across those members.The gasket material selected must be capable of sealing mating surfaces, resistant tothe medium being sealed, and able to withstand the application temperatures and pressures.Overcoming Flange ImperfectionsScoringsDistortiontroughHow Does It Work?A seal is effected by the action of force upon the gasket surface. This force which compresses the gasket, causes it to flow into the flange macro and micro imperfections. Thecombination of contact stress, generated by the applied force between the gasket and theflange, and the densification of the gasket material, prevents the escape of the confined fluidfrom the llelFlange ImperfectionsOn seating, the gasket must be capable of overcoming the macro and micro imperfections.Macro defects are imperfections such as flange distortions, non-parallelism, scoring,troughs, while superficial imperfections such as minor scratches and minor scores are considered micro imperfections.BoltLoadHydrostaticEnd ForceForces On The GasketIn order to ensure the maintenance of the seal throughout the life expectancy of the assembly, sufficient stress must remain on the gasket surface to prevent leakage. The residual boltload on the gasket should at all times be greater than the hydrostatic end force acting againstit.The hydrostatic end force is the force produced by the internal pressure which actsto separate the flanges.Blow OutForceGasketConsiderations For Gasket SelectionsMany factors should be considered when selecting a gasket to ensure its suitability for theintended application. Gasket properties as well as flange configuration and applicationdetails are part of the selection process.T H EA N S W E RI SA L W A YSInternal Pressure is exertedagainst both the flange and thegasket. 3

SECTION IGasket SelectionGaskets can be classified into three categories: soft cut, semi-metallic and metallic types.The physical properties and performance of a gasket will vary extensively, depending on the type of gasket selected and thematerials from which it is manufactured.Physical properties are important factors when considering gasket design and the primary selection of a gasket type is based onthe following: Temperature of the media to be contained Pressure of the media to be contained Corrosive nature of the application Criticality of the applicationSoft CutSheet materials are used in low to medium pressure services. With careful selection thesegaskets are not only suitable for general service but also for extreme chemical services andtemperatures.Types: Non-asbestos Fiber Sheets, PTFE, Biaxially Orientated Reinforced PTFE, Graphite,Thermiculite, Insulating Gaskets.Semi-metallicThese are composite gaskets consisting of both metallic and non-metallic materials. Themetal provides the strength and the resilience of the gasket and the non-metallic componentprovides the conformable sealing material. These gaskets are suitable for low and high pressure and temperature applications. A wide range of materials is available.Types: Spiral Wound Gaskets, Flexpro Gaskets (covered serrated metal core), MetalJacketed Gaskets, MRG’s (metal reinforced gaskets).MetallicThese gaskets can be fabricated in a variety of shapes and sizes recommended for use in highpressure/temperature applications. Except for weld ring gaskets, high loads are required toseat metallic gaskets, as they rely on the deformation or coining of the material into theflange surfaces.Types: Ring Type Joints, Lens Rings, Weld Rings, Solid Metal Gaskets.4T H EA N S W E RI SA L W A YS

Gasket SelectionService Class 300YesNoCritical ServiceRTJ type flange or Class 600YesFlange intendedfor RTJ typeYesUseRTJNoUseSWG,Flexpro, orWeld RingNoYesNoCritical ServiceYesUseSWG,Flexpro, orWeld RingNoUse LS,SWG,Flexpro,MRG, orWeld RingUse Soft CutUseSWG,Flexpro,MRG,Weld Ring,Thermiculite 815,or ST/RGS3Select sealing material and metal type (when appropriate) on basis of service, temperature, and nature of medium.Soft cut gaskets should always be of the minimum thickness consistent with the state of the flanges to be sealed, andcompatible with the medium.T H EA N S W E RI SA L W A YS 5

Soft Cut GasketsCompressed Asbestos Fiber(CAF) gaskets served industry’s needs for many years.With the shift to nonasbestos gaskets, gasketmanufacturers have developed a myriad of replacement products. Some of theinitial materials developedproved inferior to theirasbestos based predecessorsin regard to temperature,chemical resistance, creepresistance and sealing characteristics.More recently Flexitallic has developed nonasbestos gasket sheet products approaching, and insome instances surpassing the capabilities of asbestos sheet gaskets. Some of these products havebeen fiber reinforced grades, manufactured by the traditional calendering or sheeter process. Otherproduct ranges are fiber-free and some of these materials have exceptionally good properties whichexceed the capabilities of CAF.Flexitallic Thermiculite is a high temperature gasket material based upon the mineral vermiculite. The product is reinforced with a metal core and is designed for use at temperatures whichexceed the capability of graphite based sheets. The temperature capability of CAF is also exceededby Thermiculite.The Flexitallic Sigma range of biaxially orientated PTFE products has superb chemical resistance, far exceeding that of CAF. These materials can be used at temperatures from cryogenic to260 C (500 F). Being intrinsically clean they are especially suitable for use in the food, pharmaceutical and electronics industries.Flexicarb is the name given to Flexitallic’s range of graphite based products. The rangeincludes graphite foil as well as graphite laminates which contain reinforcing metal cores to overcomethe fragility of the non-reinforced foil. Graphite products have excellent stress retention propertiesand are resistant to most chemical media with the exception of strong oxidizing agents. ReinforcedFlexicarb sheets are the standard sealing product for many arduous applications in the petrochemicaland refining industries.The Flexitallic SF and AF product ranges are rubber bound, fiber reinforced sheets made bythe traditional calendering or sheeter process. A wide range of fiber types are used, often in combination, ranging from cellulose, rockwool and glass to aramid and carbon.Soft cut gasket sheets are typically used in Class 150 or Class 300 flanges; some of the metalreinforced products can also be used in higher classes. The temperture capability of the fiber/rubberproducts is highly thickness dependent, with thin gaskets having a wider service envelope than thicker ones.6T H EA N S W E RI SA L W A YS

Thermiculite Exclusive to Flexitallic, Thermiculite sheet sealing materials are comprised of both chemicallyand thermally exfoliated vermiculite reinforced with a metallic core. Vermiculite, a naturallyoccurring mineral with a plate-like structure, demonstrates a much broader range of chemicalresistance than graphite but, more importantly, superior high temperature sealing characteristics.Graphite’s stress-loss due to oxidation effects has led to many examples of gasket failure. Independent testing indicated a temperature limit of 340 C (650 F) for continuous service over 5 years. Thermiculite however is thermally stable and maintains its integrity even atextreme temperatures, ensuring against thermal oxidation (see graph on page 8). Independenttesting at TTRL (Tightness, Testing, and Research Laboratory), Montreal illustratesThermiculite’s excellent sealing properties.Thermiculite’s high temperature capabilities make it an ideal choice for use in turbochargers and superchargers, diesel engine exhaust manifolds and oxidizing services in thenitrogen fertilizer manufacturing process, steam service, and many more. In addition, userswith off-shore and seawater cooling applications will value Thermiculite’s resistance to galvanic corrosion.Thermiculite gaskets can be cut and installed using traditional methods: the moderntechniques of water jet and laser cutting are also applicable to Thermiculite.Thermiculite benefits from a high technical specification which makes it suitable for useeven in demanding service conditions. A superb level of tightness is achieved even at 500 C(930 F) and the product maintains its overall effectiveness up to at least 870 C (1600 F).Thermiculite is not affected by oxidation.Product RangeThermiculite 815 - Reinforced with a tanged 316 stainless steel core. Thermiculite 815 contains a low percentage of nitrile rubber binder. This rubber is cured using a sulfur-free curingsystem.Thermiculite 816 - Differs from Thermiculite 815 only in the type of rubber binder used. Aspecial grade of SBR is incorporated into Thermiculite 816 making it suitable for use in thehigh temperature processes of photographic film manufacture where “film fogging” can occurwith other polymer types.T H EA N S W E RI SA L W A YS 7

Thermiculite Time Since Start of Test (days)9010080907080Cumulative Weight Loss (%)% Load Retention1006050403020100101001000Elapsed Time (Hours)369121518212427303336394245Each specimen heldsuccessively for 3 days ateach temperature and thechange of weight recorded70BEST EXFOLIATEDGRAPHITE TESTED60WORST EXFOLIATEDGRAPHITE TESTED50403020THERMICULITESHEET MATERIAL10100000200392Graphite @ 370 C (700 01112 1202700 750800 850 9001292 1382 1472 1562 1652Temperature CTemperature FGraphite @ 510 C (950 F)Thermiculite @ 370 C (700 F)Cumulative Iso-thermal weight loss results for the best andworst exfoliated graphite testedThermiculite @ 510 C (950 F)This graph illustrates that, unlike graphite, the load lossat operational temperatures does not increase with time.Gasket Stress, Sg (psi)10000010000aGb1000Gs1001Vermiculite’s thin, flexible, soft plates can beexfoliated like graphite. They retain thesealability and low porosity of graphite, butFlexitallic’s new Thermiculite sheet gasketswill not oxidize at high temperatures.10100100010000100000Tightness Parameter, TpGbaGsTsSs13.1 MPa1906 psi0.23.15 MPa456.12 psiN/AN/AS100S1000S10000TpminTpmax33 MPa4788 psi52.3 MPa7588 psi82.9 MPa12026 psi1858645Room Temperature Tightness (ROTT) behavior characterization(Refer to page 41 for new method for determining factors.)The above graphs are taken from the actual tests performed by TTRL.8T H EA N S W E RI SA L W A YS

PTFE Products - Sigma Flexitallic Sigma offers outstanding chemical resistance while the unique manufacturing process results in a biaxially fibrillated structure ensuring high seal integrity in the most demanding applications.Pure PTFE sheet products are highly susceptible to creep relaxation which can be reduced by the incorporation of selected fillers (Filled PTFE). The maximum reduction in creep is achieved by combining these fillers in abiaxially orientated structure such as Sigma.Flexitallic Sigma materials are inherently clean, making them suitable for use in industries where product contamination may be of concern such as food, pharmaceuticals and electronics. The components of the Flexitallic Sigmarange comply with the requirements of FDA regulations and the materials’ outstanding chemical resistance make themsuitable for sealing virtually every chemical medium across the whole pH range (1 - 14).Sigma products give unparalleled levels of sealing performance, especially when compared to conventionalmaterials used in applications involving aggressive chemical media. These comparisons are supported by data generated by recognized, independent, international bodies in the field of static sealing. Sigma products are ideally suited for applications where seal integrity is paramount, an important consideration where stringent emission controlsmay be in force.All products in the Flexitallic Sigma range are capable of sealing from cryogenic temperatures up to 260 C(500 F). For intermittent use even higher temperatures can be tolerated. Pressures from 8.5 MPa (1230 psi) down tovacuum can be accommodated. Furthermore, applications involving low gasket stresses such as glass lined, plasticand ceramic flanges, will not result in loss of sealing performance. These typically relate to the use of glass lined,plastic and ceramic flanges.The Sigma range of products has been engineered to be userfriendly: Materials can be cut easily using conventional tools andtechniques Complex geometric shapes can be accommodated,including narrow cross sections Gaskets are easy to install and remove All products are non-toxicProduct RangeSigma 500 - High compression sheet material specifically formulated for use on glass lined, plastic or ceramic flanges.Also suitable for use on flanges which are non-parallel, damaged or distorted. Sigma 500 seals under a lower boltload than the other members of the Sigma product range.Compatible with acids and alkalis at all but the highest concentrations. The high compressibility is achieved by theincorporation of holl

TeI: 58 2 41 783550 Branch Offices & Warehouses Flexitallic Ltd. Aberdeen, Scotland, UK Tel: 44 1224 725241 Flexitallic GmbH Burscheid, Germany Tel: 49 2174 8950 Flexitallic L.P. Cherry Hill, New Jersey, USA Tel: 1856 321 9301 Flexitallic L.P. Chicago, Illinois, USA Tel: 1630 268 0418 Flexitallic Ltd. Singapore 048581 Tel: 65 6 321 9112 .

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