Gaining Key Information Will Guide Material Decisions
Correctly interpreting and deciphering the information on a chemical compatibility chart is essential to setting up an effective, and safe, sealing solution. Seals — whether they are o-rings, gaskets, or custom molded options — come in many different materials and formulations, and each will perform at different levels given the temperature and pressure constraints of the application for which they are used.
Seals used in chemical processing industry (CPI) applications face the usual constraints in terms of temperature and pressure, but also must account for chemical compatibility. When choosing a formulation for a CPI sealing application, the characteristics of the compound used must also include its ability (or inability) to handle exposure to the chemical elements expected to be encountered in executing the application.
A material may meet the temperature and pressure resistance metrics needed to perform the application. But if the material breaks down, degrades, or erodes when facing a chemical solvent likely to be seen in the application, then this is a recipe for disaster. Failure to account for chemical compatibility will set up the seal for future failure, and all the assorted costs and dangers that come when sealing failures occur.
However, by properly using chemical compatibility charts supplied by your sealing partners, organizations can identify potential trouble spots before implementing a compound or material. In addition to engineer guidance, such information can help ensure your CPI application is set up for success.
Reading a Chemical Compatibility Chart
It’s easy to be overwhelmed when facing a chemical compatibility chart. Depending on the scope offered by the provider, you could be presented with more than a dozen material or compound options, a comprehensive list of complex chemical solvents, and iconography that will vary from provider to provider.
When dealing with o-ring and other sealing solution providers, there are key categorical elements to identify and utilize on a chemical compatibility chart. Finding these columns (or rows) and understanding the information presented will help you make informed decisions and provide an excellent starting point for finding the right material for your application.
Material — This could also be labeled something similar, such as polymer, compound, or component. This identified the core material that would be used to make the o-ring. Listings for the material options, whether it’s a handful or more than a dozen, should include both the full name of the material (e.g. Perfluoroelastomer) and the abbreviated moniker designed for it (For Perfluoroelastomer, FFKM). This will cut down on mistakes in reading the data and help decision-makers more clearly identify the right option.
Chemical — Either as a separate list that allows for input options for selection of a specific chemical solvent, or incorporated as a larger chart with multiple columns, there should be designations of the specific chemical and the compatibility or resistance a given material has in relation to it. As an example, you know your application involves Benzilic Acid and you have access to or are interested in some of the other properties associated with EPDM (ethylene propylene diene monomer). Is EPDM chemically compatible for use in this circumstance? You should be able to cross-reference the polymer and chemical and find an answer.
Ratings — On a typical chemical compatibility chart, each material — when matched or referenced against a specific chemical — will be rated by the provider. These ratings are typically color-coded to show compatibility, or how well the material will perform in the presence of the chemical. The ratings are usually metered based on swell percentage, or how much volume the material will gain when working in an environment with the chemical in question. Low percentages, usually below 10 or 15%, indicate excellent compatibility and carry ‘green’ ratings indicating the material is a good choice. Less effective ratings (yellow, or ‘good’ designations) show the material has 10-25% swell volume in testing and may be suitable if the application is static in nature. Poor rated materials usually fall in the 20-40% swell volume range and may have niche uses only, and ‘Not Recommended’ materials indicate a complete incompatibility with the chemical.
Extras — These will vary greatly depending on the o-ring supplier or provider you’re working with, but could include rough estimates on the relative cost of each material option, the tear or abrasion resistance, tensile strength, or temperature resistance provided by the compound selected.
It’s important to note, however, that no matter how deep or encompassing the information presented on a chemical compatibility chart is, such charts are only tools for helping guide material selection. Most charts provide basic o-ring chemical resistance compatibility information based on isolated material testing in optimal conditions at room temperatures and pressure.
Exposing sealing materials to multiple chemicals and compounding application factors like temperature, pressure, and gland design can result in significantly different performance. Likewise, specific material compound formulations can also alter generalized performance ratings.
Putting all the information together — gleaned from the chemical compatibility chart, the knowledge of specifics of your application, and guidance from an application engineer — will give you the comprehensive scope to select the specific material and formulation needed to provide the best combination of performance and price for your application.
Learn from Marco Rubber & Plastics’ Chemical Compatibility Chart
With more than 40 years of experience, Marco Rubber & Plastics offers decades of application-specific material expertise backed by the world’s most extensive inventory and production network. Our industry-leading customer satisfaction and audit scores are built on our easy online ordering and inventory programs, adherence to quality standards, and a commitment to customer service and support.
That’s evident in our dedication to CPI applications and solutions. With our O-ring Chemical Compatibility Chart, you’ll be able to quickly identify possible material solutions or plan for future eventualities. Our chart provides compatibility information for 14 different core materials against a comprehensive chemical list covering everything from Acetaldehyde to Zirconium Nitrate, with easy-to-note notifications on potential cost and clearly identifiable ratings and recommendations. Our engineering experts are available to discuss your unique application further and provide feedback and guidance throughout the process to unveil possible better performing or more cost-effective alternatives.
Contact us today to learn more about o-ring chemical compatibility and to develop ideal sealing solutions.
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