As you specify a pump, you make important choices about the materials of construction (metal vs. plastic) as well as the elastomers you choose. Elastomers, including diaphragms, valve balls, valve seats, and valve seat o-rings, play a big role in the overall goal of increasing the lifespan of the pump while protecting the people who use it.
The last thing anyone operating an AODD pump wants is to have a diaphragm failure that causes the fluid being pumped to be vaporized into the air, potentially harming whoever’s in the area. If this happens when you’re pumping water, it may be a minor problem in the short term. But if you’re pumping a harsh chemical, you could have a major OSHA incident on your hands.
To prevent the above scenario from playing out at your plant, it’s important to choose elastomer materials carefully to ensure safety, improve pump functionality and increase longevity.
Chemical compatibility is the most important factor to consider when evaluating AODD pump elastomer properties. Among many other resources, Versamatic offers a comprehensive Chem Guide to help users determine which materials are a good fit for the type of fluid being pumped.
Other things to keep in mind include the material’s abrasion resistance, whether it’s a rubber or a thermoplastic, temperature limitations, flexibility, and purchase price.
After ensuring chemical compatibility, your choice comes down to tradeoffs between the other categories. Because every pumping system is unique, there may be some trial and error involved. We always recommend consulting with your distributor or manufacturer first to see what they recommend based on your system and the material being pumped. If you run one type of diaphragm and don’t have much success with it, you can take what you learn from the issues you’re seeing and adjust your selection.
The Materials Selection Guide below covers the key categories AODD pump operators must take into account when specifying diaphragms.
| Diaphragm Material |
Chemical Resistance |
Abrasion Resistance |
Temp. Limitations |
Temp. Max. Operating |
Temp. Min. Operating |
Flex Life | Purchase Price |
|---|---|---|---|---|---|---|---|
| EPDM | B+ | B+ | B+ | 280˚F/138˚C | -40˚F/-40˚C | B | $$ |
| FKM | A | C | A+ | 350˚F/177˚C | -40˚F/-40˚C | D | $$$ |
| Hytrel® | B+ | A+ | B | 220˚F/104˚C | -20˚F/-29˚C | A | $$ |
| Neoprene | D | B | C | 200˚F/93˚C | -10˚F/-23˚C | A | $ |
| Nitrile | C+ | B | C | 190˚F/88˚C | -10˚F/-23˚C | A- | $ |
| PTFE | A+ | F | A+ | 220˚F/104˚C | -35˚F/-37˚C | C- | $$$ |
| Santoprene® | A | A+ | A+ | 275˚F/135˚C | -40˚F/-40˚C | A+ | $ |
A+ = Best; F = Not recommended
$ = Least expensive; $$$ = Most expensive
Santoprene® is a registered trade name of Exxon Mobil Corp. Hytrel® is a registered trade name of E.I. DuPont.
Consult the elastomer material profiles listed here for a closer look at your choices for diaphragms, valve balls, valve seats, valve seat o-rings.
Elastomer type: diaphragms, valve balls, valve seats, valve seat o-rings
Profile: A rubber with very good water and chemical resistance. Has poor resistance to oils and solvents, but is fair in ketones and alcohols.
Elastomer type: diaphragms, valve balls, valve seats, valve seat o-rings
Profile: A rubber that shows good resistance to a wide range of oils and solvents; especially all aliphatic, aromatic, and halogenated hydrocarbons, acids, animal, and vegetable oils. Hot water or hot aqueous solutions (over 70°F) will attack FKM.
Elastomer type: diaphragms, valve balls, valve seats
Profile: A thermoplastic that offers good resistance to acids, bases, amines, and glycols at room temperatures only. Good abrasive resistance qualities.
Elastomer type: diaphragms, valve balls, valve seats, valve seat o-rings
Profile: An all-purpose rubber that has resistance to vegetable oils. Generally not affected by moderate chemicals, fats, greases, many oils, and solvents. Generally attacked by strong oxidizing acids, ketones, esters, nitro hydrocarbons, and chlorinated aromatic hydrocarbons.
Elastomer type: diaphragms, valve balls, valve seats, valve seat o-rings
Profile: General purpose, oil-resistant rubber. Shows good solvent, oil, water, and hydraulic fluid resistance. Should not be used with highly polar solvents like acetone and MEK, ozone, chlorinated hydrocarbons, and nitro hydrocarbons.
Elastomer type: diaphragms, valve balls, valve seats, valve seat o-rings
Profile: Chemically inert, virtually impervious. Very few chemicals are known to chemically react with PTFE; molten alkali metals, turbulent liquid, gaseous fluorine, and a few fluorochemicals such as chlorine trifluoride or oxygen difluoride, which readily liberate free fluorine at elevated temperatures.
Elastomer type: diaphragms, valve balls, valve seats, valve seat o-rings
Profile: Injection-molded thermoplastic elastomer with no fabric layer. Long mechanical flex life. Excellent abrasion resistance.
Use the information above to help guide you in your elastomer material decisions. As always, if you have further questions about AODD pump material selection or performance, reach out to a local distributor, or contact Versamatic today.
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