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Selecting the Right Elastomer Seal Material for Mass Flow Controllers and Variable Area Flow Meters (Rotameters)

Elastomer seal material selection is not always a clear cut decision.  Many factors must be considered:
  • Fluid
  • Temperature
  • Pressure (Max, Min, Differential)
  • Application (static or dynamic)
  • Price
  • Customer's experience
Most major seal manufacturers offer material compatibility information and material selection guides.  Compatibility ratings are based on a manufacturer's compound/material in a specific service.  Published compatibility guides list one service at a time (glycol) at a nominal temperature (70º F). While Brooks Instrument should not be considered an expert in elastomers, we will make recommendations based on our prior application experience. The final decision is of course, always up to the customer. To aid with your next decision on elastomer seal material the following are generic elastomer property descriptions for materials found in Brooks mass flow controllers and variable area flow meters (rotameters):  Fluorocarbon, VITON® (FKM): VITON® is the trade name for DuPont Performance Elastomers Fluorocarbon or FKM material. FKM has a temperature range of -20F to +400F, and provides excellent resistance to a wide variety of chemicals, weather and compression set requirements. The relatively high level of fluorine in FKM materials allows for exceptional resistance to chemical attack, but with limited low temperature capabilities.  Brooks offers FKM elastomers manufactured to conform with FDA and USP Class VI requirements, making it ideal for use with bio-pharm applications and medical devices. Nitrile, Buna-N (NBR): Nitrile, also known as Buna-N or NBR, is a copolymer of Butadiene and Acrylonitirle. It is the most commonly used elastomer for sealing products. It has a temperature range of -40F to +250F and is exceptionally resistant to petroleum based oils and hydrocarbon fuels. Nitrile materials also exhibit excellent tensile strength and abrasion resistance properties. The material performs well with most diluted acids, silicone oils and lubricants and in water applications. It is not recommended for use with ketones, aromatic hydrocarbons and phosphate ester hydraulic fluids.  Kalrez® Perfluoroelastomer (FFKM): Kalrez® Perfluoroelastomer (FFKM) currently offers the highest operating temperature range up to 320°C (608°F), the most comprehensive chemical compatibility, and the lowest off-gassing and extractable levels of any rubber material. FFKMs deliver an extreme performance spectrum that make them ideal for use in critical applications like semiconductor chip manufacturing, jet engines and chemical processing equipment. Ethylene Propylene, EPDM, or EP (EP): EP is a copolymer of ethylene and propylene, while EPDM is a terpolymer combining ethylene, propylene and a diene monomer. EP materials offer a temperature range of -65F to +300F and offer excellent resistance to ozone, weathering, steam, water and phosphate ester type hydraulic fluids. Brooks offers EPDM elastomers manufactured to conform with FDA and USP Class VI requirements, making it ideal for use with bio-pharm applications and medical devices. For exact product temperature ranges or material availability on a specific product, please refer to our product data sheets.  Our long-tenured team of applications engineers will provide guidance, if requested, during the product selection and configuration process.

About The Author

Bill Reagan
Director of Industrial Sales, Americas

Bill is the director of industrial sales for the Americas at Brooks Instrument.

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