O-ring material meets potable water standards in manufacturing

July 20, 2016

Customer relationships are key for custom solutions.

Many companies talk about having strong relationships with customers, but sometimes a manufacturing process cannot occur without that type of connection.

That was the case for a Midwestern manufacturer assembling an O-ring onto a cartridge valve using an automated, custom process. The process required an O-ring that withstood the necessary manipulation without breaking; passed an extensive life cycle test involving friction levels during hot and cold cycles; and contained only materials approved by NSF International (NSF) for devices that deliver potable water.

NSF/ANSI standards must be heeded in potable water applications. | jekccs/iStock

To complicate matters, it was only after the valve successfully passed life cycle testing and was delivered to the manufacturer that an issue became apparent. A portion of the assembly process caused enough stress on the O-rings that many broke. Those that did not break became distorted and did not roll as needed on the line, clogging the equipment.

The solution was clear — more durable O-rings must be found. However, identifying the optimal seal was not as simple as it sounds. O-rings from several suppliers failed to perform during the assembly process. More durable O-rings existed, but none conformed to potable water standards. Trelleborg quickly realized the only solution was to develop a new material from which compliant O-rings could be produced.

Limited materials, high expectations

NSF led the development of American National Standards Institute (ANSI) standards for all materials that treat or come in contact with drinking water, and in 1990, the U.S. Environmental Protection Agency (EPA) replaced its own drinking water product advisory program with NSF’s standards. Specifically, NSF 61 establishes stringent requirements for the control of equipment that comes into contact with potable water, including joining and sealing materials such as gaskets, adhesives and lubricants.

"NSF 61 limits the types of fillers and additives that can be used in gaskets like O-rings to make them more durable," explains Dan Lutz, sales manager for elastomeric products at Trelleborg Sealing Solutions. "Creating a material that has good insulation properties, is chloramine resistant, doesn’t become elongated during automated assembly, and meets those strict materials
standards was quite challenging."

Nevertheless, by combining an understanding of the degree of durability needed to prevent breakage during assembly and an in-depth knowledge of NSF 61-compliant materials, Trelleborg engineers developed a solution. Lutz and his team worked closely with the assembly team at every stage in the process, ensuring the final product would work in the manufacturing process and in the finished valve.

The result is an ethylene propylene diene monomer compound with a 70+ hardness that can withstand temperatures as low as -40˚C and as high as 125˚C. It can be formed into different seal types (O-rings, square rings and gaskets), can be surface treated for easier automated assembly, exceeds NSF 61 standards, and has excellent chloramine and chlorine resistance.

The material is being used by manufacturers of valves, faucets, ice makers, pumps, fittings and water heaters. It is an ideal material for equipment assembled automatically, and it easily can be combined with other NSF- and U.S. Food and Drug Administration-certified materials.

What could have been an issue without a solution resulted in positive results for the supplier and manufacturer. With a full understanding of the manufacturer’s process, the goal was to provide them with a solution that optimized assembly and reduced time to market.

Lutz notes that this type of shoulder-to-shoulder engineering has helped him and his team solve many difficult challenges over the years. "It’s one thing to be able to produce something to industry standards and quite another to understand a customer’s complete set of requirements, including what is — and what is not — manufacturable," he said.

Thijs Menzel is market research director and food, beverage & water segment manager at Trelleborg Sealing Solutions (tss.trelleborg.com). He has an extensive background in market research, data analysis and business development within a number of different industries. 

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