NSF gasket materials are used in commercial food service equipment, water treatment or distribution systems, and other applications that can affect human health and safety. Rubber compounds that are registered with NSF International (formerly the National Sanitary Foundation) must pass rigorous tests to ensure that potentially harmful substances won’t migrate from the gasket material when in contact with food or drinking water.
NSF standards aren’t regulatory requirements, but failing to use NSF gasket materials can put larger product designs at risk. Conversely, using NSF certified compounds can increase the likelihood of regulatory acceptance. In some jurisdictions, public authorities such as health departments require food service equipment and drinking water systems to meet a specific NSF standard. Buyers also expect to see an NSF mark on products such as commercial ovens or water filtration systems.
NSF Gasket Materials: Certified vs. Compliant
NSF marks or labels aren’t component-label designations, but product designers still need to understand the differences between NSF certified and NSF compliant materials.
- NSF certified gasket materials are registered with NSF International and have been tested and evaluated by NSF International to a specific standard.
- NSF compliant gasket materials meet relevant NSF requirements, but are not registered with NSF International. Typically, these materials are tested by the supplier or an independent laboratory.
Both types of materials cost more than commodity rubber, so it’s important to select the right compound for your application. You don’t want to over-engineer the gasket, but you don’t want to use a material that can’t meet your requirements either.
If your application requires NSF gaskets, then there are two major standards you need to know about. Both were developed in junction with the American National Standards Institute (ANSI), a U.S. standards organization.
- NSF/ANSI 51 applies to commercial food service equipment.
- NSF/ANSI 61 covers water treatment or distribution products.
These aren’t the only NSF/ANSI standards that can apply to gaskets, but they’re commonly used.
NSF 51 Gasket Materials
NSF 51 applies to materials and coatings that come into contact with foodstuffs. In addition to rubber gaskets, this standard covers components such as tubes and valves. Applications for NSF 51 gasket materials include broilers, beverage dispensers, cutting boards, and stock pots. This NSF standard is for commercial food equipment, but some household appliances (such as coffee makers) may also contain components made of NSF 51 materials.
Rubber compounds that meet NSF/ANSI 51 requirements can be approved for contact with all food types, or for contact with specific types of food substances. Test reports for NSF gasket materials also indicate the material color and the maximum use temperature. The latter specification can be especially important for gasket designers who need to meet high-temperature requirements for bakeries or dairies.
Silicone gaskets are often used in food contact applications because these synthetic elastomers are chemically inert, won’t outgas, and won’t leach into food. Additional NSF 51 gasket materials include food-safe EPDM. If an NSF 51 registered material isn’t certified for all food types, then the test report may call-out approved substances such as:
- Aqueous acidic
- Aqueous non-acidic
- Bakery products with free fats and oils on the surface
- Bakery products without free fats and oils on the surface
- Dairy, oil in water emulsions
- Dairy, water in water emulsions
NSF 61 Gasket Materials
NSF 61 applies to a wide range of water system components. In addition to rubber gaskets, this standard covers adhesives, lubricants, pipes, filters, and fittings. Applications for NSF 61 gasket materials include faucets, drinking fountains, and water treatment systems. In both the U.S. and Canada, products that are certificated to NSF/ANSI Standard 61 meet regulatory requirements for public health and safety. In California, Title 22 drinking water standards also apply at the component (gasket) level.
NSF/ANSI 61 compounds are subjected to a battery of tests. The simplest is a cold water test at pH levels 5, 8, and 10, which are the most common pH levels for waters in North America. Chemical testing is more challenging, but for good reason. Often, sodium hypochlorite (bleach) is used to disinfect drinking water systems. Rubber gaskets that are made of standard Viton® can withstand bleach, but they’re cured with lead that can migrate into drinking water. To achieve NSF 61 certification then, lead-free Viton® GF is used. NSF 61 EPDM rubber gaskets are also used in drinking water systems.
Do you have questions about NSF gasket materials? Elasto Proxy works with a trusted network of material suppliers and can convert sheets and extrusions to create custom gaskets. With our water jet cutting equipment, we can eliminate tooling charges and make fine, fast cuts that maximize material usage. We can also store your finished goods and ship them according to your sales forecasts or on-demand.
For more information, contact us.