Redesigned Pinch Valves Eliminate Leaks


A leading manufacturer of agricultural spraying equipment was having trouble with field failures when the rubber tubes with pinch valves that feed the spray nozzles began failing during the peak spraying season. The flanged tubes open to allow spraying and the pinch valve is closed to stop the spray. Between the high pressure, aggressive chemicals, and pinch cycles, the existing tube was failing during critical planting and fertilizing time, causing chemicals to leak and uncontrollably spray all over. The situation made the spraying operation inefficient and it was wasting expensive chemicals and potentially contaminating fertile farmland with high concentrations of liquid compounds.

Complicating the matter, the company’s current supplier for the tubes could not determine what made some parts fail and others not. Each lot was tested and there were passing and failing pieces in every batch with no consistency. Worse yet, “bad” parts looked the same as “good” parts, so ferreting out bad parts was impossible. Good parts were experiencing 250,000 cycles to failure, bad parts only 10,000.

Pinch valve

Robinson Rubber redesigned a pinch valve for an agricultural spraying application. The flanged tubes open to allow chemical spraying and close to stop the spray. Defective units were cracking during herbicide and fertilizer spraying.

The manufacturer contacted Robinson Rubber to work on various rubber formulations to deliver longer life to the pinch valve. Their prototypes operated for 3,000,000 cycles before failure.

While there were no product failures, pinch valves that sat on a distributor’s shelf for more than a couple months went from shiny jet black to chalky gray. Even though none of these parts failed, there was a perceived quality issue.

Robinson Rubber chemists changed a small percentage of one of the product ingredients to prevent the color change. However, this slight change affected product life cycle – parts went from 3,000,000 cycles to only 10,000. They were shiny black, but significantly weaker. It’s the mastery of these slight formulation nuances that can make the difference between a great part and a poor one. Soon the gray pinch valves became known in the farming community as the ones that don’t fail, versus the shiny black ones that did.

Robinson Rubber

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