Minnesota Rubber Produces Moulded Water Valve

Minnesota Rubber and Plastics has provided a moulded valve with precise internal flow paths for the redesign of a machined brass water control valve. Previously, the brass valve required costly secondary machining to create the complex flow paths. The project involved a dual-tank water-treatment control valve that provides a continuous supply of softened water from one tank while a second tank is being regenerated.

The control valve is critical to reliable water softener function by regulating flow rates for resin regeneration, rinsing and flushing of the water softener. The valve services both resin tanks in the water softener. The design challenge for Minnesota Rubber and Plastics was to provide a moulded water control valve equal to or better than the existing brass water control valve without sacrificing water flow rates while meeting regulatory requirements for structural performance and water purity.

Price targets, material and energy savings with just-in-time delivery were key requirements of the project. 'We met those design requirements, and more,' said Ted Ahrenholtz, technical support manager, Minnesota Rubber and Plastics. 'We began with a list of objectives developed with our customer that included meeting flow requirements, better appearing surface finish, weight and cost reduction and faster turnaround time. 'We worked together to design an assembly to replace the solid one-piece brass casting using CAD, finite element analysis and stereo lithograph simulation,' he added.

For this project, a three-part valve body configuration was developed with the three components hot-plate welded together. 'Material design for this project was extremely important not only for function and long operating life, but also to conserve material and energy needed to mould the components,' said Ahrenholtz. 'We insured that rubber and plastic materials complemented each other's tolerance capabilities and that there was a careful balance between the torque value and contact of the seals. 'We used thermoplastic injection moulding on the three plastic valve body components and transfer moulding on the NSF 61-compliant, chloramine-resistant rubber seals and O-rings.

'Through the use of finite element analysis, the wall thickness was optimised, conserving plastic material while increasing overall valve strength with less weight and reduced total cost,' he added. Advantages of the new water control valve include a 75 per cent weight reduction, non-corrosive reinforced thermoplastic body, identical inlet and outlet plumbing connections as on the brass valve, along with leak and pressure testing of each welded valve prior to shipping.


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