Minnesota Rubber and Plastics Converts Water Control Valve From Brass To Molded Assembly – Provides A Total Sealing Solution That Is Lighter Weight With Cost- Effective Benefits Including Material And Energy Savings

Provides A Total Sealing Solution That Is Lighter Weight With Cost- Effective Benefits Including Material And Energy Savings

Before: Water control valve for water softeners is cast from heavy brass and required multiple precision machining operations.	After: New molded assembly provides a lighter weight, total sealing solution from Minnesota Rubber and Plastics.

Minneapolis, Minnesota: Redesigning a machined brass water control valve into a molded assembly, complete with threaded inserts, is more cost effective with material and energy savings benefits. The water control valve is a key component in the operation of an updated water softener design.

Minnesota Rubber and Plastics made it happen by providing a molded valve with precise internal flow paths. Previously, the brass valve required costly secondary machining to create the complex flow paths.

The project – 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. Measuring 5 x 3-3/4 x 5 inches, the valve services both resin tanks in the water softener.

The design challenge for Minnesota Rubber and Plastics was to provide a molded 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," reported Ted Ahrenholtz, technical support manager with Minnesota Rubber and Plastics. "We knew from the start that we would be able to reduce material usage, weight and cost. Precision machined brass is expensive and heavy. Machining is slow, requires significant energy consumption and there’s a lot of residual scrap after machining."

"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 computer aided design (CAD), finite element analysis, and stereo lithograph simulation (SLS)," reported Mr. Ahrenholtz.

Minnesota Rubber and Plastics has a 50-plus year history of developing sealing solutions for complex applications. For this project, a three-part valve body configuration was arrived at with the three components hot plate welded together.

Three piece molded assembly is hot plate welded together for a water tight seal of the valve body. Many machining operations were eliminated by going to a molded valve design.

"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 mold the components," reported Mr. 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 molding on the three plastic valve body components and transfer molding on the NSF 61-compliant, chloramine resistant rubber seals and O-rings. Through the use of finite element analysis, the wall thickness was optimized, conserving plastic material while increasing overall valve strength with less weight and reduced total cost."

Advantages of the new water control valve include: a 75 percent 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.

"By partnering with our customer in a co-designing effort, we were able to design, produce and help our customer with a high performance water valve that exceeded expectations using the latest design technology and our many years of sealing experience," Ahrenholtz added. "What’s more, by eliminating the brass we eliminated the lead, so this new valve so the new valve complies with government initiatives to reduce lead."