Selection Requirements for Elastomeric Seals
Gallagher Fluid Seals is a Tier 1 DuPont™ Kalrez® distributor and we are proud of our longtime partnership with DuPont®, having specified thousands of perfluoroelastomer parts over the past few decades.
DuPont™ is at the forefront of perfluoroelastomer development, creating elastomers with properties that can help meet highly specific application requirements.
But how do you know which elastomer is right for your application? DuPont™ provides this helpful guide.
Selection Requirements For Elastomeric Seals
Service Conditions
- Temperature range (minimum, operating, maximum conditions). Thermal cycling and potential excursions. Define in either degrees Celsius or Fahrenheit.
- Pressure range (minimum, operating , maximum conditions). Define in either psi or Bar.
- Motion (static, dynamic). Define dynamic seal orientation in reciprocating, oscillating or rotary state. Indicate the component's duty cycle.
- Fluid to be sealed. Reference by brand name or fluid type.
Design Requirements
- Component description (O-ring, shaft seal, gasket, diaphragm, rubber to metal, extrusion, lathe cut seal, etc.).
- Desired service life.
- Assembly considerations (stretch, lubricants, storage, shelf life, mating materials, finishes or matching hardware).
- Critical dimensions and tolerances of part in question.
Inspection Requirements
- Define inspection criteria.
- Lot sampling.
- Acceptable quality levels (AQL).
- Indicate critical sealing surface.
Material Specification and Traceability
- Define material specification by ASTM D2000, SAE, AS or military material specification.
- Link proper VITON family to the specific seal manufacturer's compound number.
- Discuss how to specify sealing material with your seal supplier.
- Inquirer if -- and how -- compound changes can occur without the customer's knowledge.
- Specify if hardness buttons and "dog bone" segments are required for incoming verification.
By developing an outline form, DuPont can offer the end user a permanent worksheet reference for their elastomeric applications.
Additional Factors that Influence Fluoroelastomer Seal Performance
- Selection of appropriate elastomer type within the family (KALREZ xxx, VITON yyy, etc.).
- Integrity of the elastomer. Beware of blends with other elastomers and accept no reprocessed or "second grade" elastomers.
- Other essential compounding ingredients are important as well. Carbon black imparts broader media resistance, higher mechanical properties and longer property retention than non-black fillers. Color-coded fluoroelastomer products do not offer maximum attainable values of some properties.
- Appropriate cure and post-cure. (Imparts maximum mechanical properties, thermal stability, chemical resistance, compression set resistance and dynamic and static sealing performance.)
- Quality assurance procedures (ISO 9000 certification, properly written specifications).
Why are fluoroelastomer seals often more expensive than seals of other lower-performing elastomers?
- Starting monomers are "exotic."
- Fluoroelastomers are manufactured in relatively small volumes.
- Fluoroelastomer manufacture is a hazardous process, requiring costly process control and safety features.
Seal Material Selection Philosophy
- Accurately define end-use performance parameters.
- Focus on seal performance, not initial purchase price!
- Apply life-cycle cost analysis for seal selection.
- Correctly specify the elastomeric sealing material.
Finally, you can optimize fluoroelastomer and perfluoroelastomer seal performance by specifying DuPont products.
- DuPont™ invented VITON™, ZALAK® and KALREZ®, and only DuPont™ manufactuers VITON™ and ZALAK® fluoroelastomers and KALREZ® perfluoroelastomer parts.
- DuPont fluoroelastomer and perfluoroelastomer technologies are well-defined and performance is predictable.
