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Learn key criteria for selecting gasket materials based on pressure, temperature, bolt load, and media factors. Understand pros and cons of various gasket materials and their applications. Discover ASTM standards for material classification.
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Gasket Fabricators AssociationTechnical Committee Presentation Estimator’s Guide to Basic Gasketing Module 2 of 5 Material Selection December 2009
Agenda • Material Selection Criteria • Pros and Cons • PSAs • ASTM F104 & D2000
Material Selection Criteria • 4 Main Criteria to consider when selecting a gasket material: • Operating Pressure • Bolt Load • Operating Temperature • Media
Operating Pressure • Pressure X Temperature Factor (Service Factor) • Multiply PRESSURE in PSI by TEMPERATURE in °F. • If value > 625,000 – a metallic gasket is required. • Each application is unique! Also consider seating stress, type of flange, etc.
Bolt Load • M + Y Values • M = Ratio between residual stress on gasket and internal pressure (Gasket Maintenance Factor). • The higher the “M” value, better against leaks. • Y = minimum gasket seating stress (initial assembly) • M + Y Values not as relevant due to newer gasketing materials. • New gasket constants initiated by Pressure Vessel Research Committee.
Operating Temperatures • Elastomers max out at ~ 600° F. • Compressed non-asbestos: 400° F continuous. • Beater-add: 250-300° F. • Flexible Graphite: 800° F. • Continuous v. Intermittent • Non-standard gasketing materials (high temp paper boards, etc.)
Media • Primarily affects the elastomer… • So different polymers for each application. • Not just for chemicals and oil/fuel products. • Abrasives, weather, ozone • Food, water, dairy, pharmaceutical • Teflon – excellent chemical resistance! • Envelope or encapsulated gaskets • Flexible Graphite – broad range of chemical resistance.
Pros Cost effective. Wide range of durometers – and sponge. Seals under lower compressive loads. Wide range of compositions. Cons Wide range of compositions. Limits on: Temperature Pressure Compression set Pros & Cons:Elastomers
Pros Cost effective Higher Pressures. Higher Temperatures. High resistance to seating stress. Cons Dust and slivers. Tool Wear. Pros & Cons:Compressed Non-Asbestos &Beater Add
Pros Excellent Chemical Resistance. Electrical Insulator. Anti-Stick Properties. Cons Cold Flow. Pros & Cons:Teflon
Pros Good with most chemicals. Good high temperature gasket – up to 5400° F in vacuum. Low creep – reduces retightening. Cons Fragile. Pros & Cons:Flexible Graphite
Gaskets with PSAs • Application environments • Adhesive chemistries • Product constructions
Surface: Environment: Application: Solvents/Chemicals Surface Texture Time Temperature Surface Contour Temperature Exposure UV Light Exposure Pressure Surface Energy Surface Contamination Factors that can influencePSA success...
Three Types of PSA Chemistries • Rubber PSA (Indoor) • Acrylic PSA (Outdoor) • Silicone PSA (Wide Temp)
Adhesive Transfer Tape or “Free Film” Double-Coated Tape Single-Coated Tape or Label stock --PSA --Liner --PSA (Exposed) --Carrier --PSA (Liner) --Liner --Carrier --PSA --Liner (optional) Common Constructions
Double-Coated Tapes Less conformable Lower temp resistance “Removable” Reinforces substrate Free Film Adhesive More conformable Higher temp resistance “Permanent” Doesn’t reinforce substrate Double-Coated vs. Unsupported Adhesive
ASTM F104 & D2000 • Classification systems specifying properties of non-metallic gasket materials. • Non-metallic gasket materials described by specific physical & mechanical characteristics. • Rubber compounds classified under ASTM D2000. • Users can specify required properties. • Suppliers can report product properties. • EXAMPLES: • ASTM F104 F725400 • ASTM D2000-99 M2HK 714 A1-10B38
Appendix • ASTM F104 – Nonmetallic Gasket Classification • ASTM D2000 • Elastomer Properties
ASTM D2000How to Read a Line Call-OutASTM D2000-99 M 2 HK 7 14 A1-10, B38, C12, EF31,EC88, F15 Z1 The most common material classification system used in O-ring specification is probably "Standard Classification System for Rubber Products in Automotive Applications" or ASTM D 2000. This system is designed to aid in the selection of practical rubber products for specific environments and provided a "line call-out" designation for the specification of elastomer seal materials. • Specification Revision • This indicates the revision year of D2000 to which the line call-out makes reference. • Measurement Units • If an M is present, metric units will be used for tensile strength, termperature, and tear strength (MPa, °C, and kN/m respectively). If no M is present, English units will be used (psi, °F, and ppi respectively). • Grade Number • Indicates the level of test requirements to which a material may be subjected. Example, Grade – basic properties; Grades 2-9 require additional testing. • Type and Class • See next page for most common polymers type and class.
ASTM D2000How to Read a Line Call-OutASTM D2000-99 M 2 HK 7 14 A1-10, B38, C12, EF31,EC88, F15 Z1 • Hardness (Durometer) • This number indicates durometer range in Shore A units (± 5 pts.). Example indicates a harness of 70±5 durometer. • Tensile Strength • Next 2 digits show minimum tensile strength – 14 in example above (metric) or 14MPa. If non-metric would be 20 (2031 psi). • Additional Requirement Suffixes • Letter & number combinations that indicate a material’s test and performance criteria per the Grade number indicated. Example above of A1-10, B38, EF31, EC88, F15 Z1. (see next slide)
More to Come! • Module 1: Understanding the Application • Module 2: Material Selection • Module 3: Cutting/Processing Techniques • Module 4: Value Adding • Module 5: Monday Morning Quarterback: Actual Results vs. Estimation
Thank You! We appreciate your time and attention. Questions?