Machine Design

Valve stems sealant surge

Edited by Lawrence Kren & Victoria Reitz

A 735HPA dispense valve applies sealant to an automobile valve cover. A snuffback action at the stroke end prevents drooling.

Carefully metering the right amount of sealant and silicones in assembly processes is key to endproduct looks and function. But the high pressures needed to push these viscous materials from bulk containers, through several feet of tubing, and out a narrow dispensing orifice, make it difficult to get consistent results.

Surging is a common problem. It happens when pressurized material suddenly expels at the start of a dispensing cycle. The result is a wider bead at the beginning of a line than at the end. Fixing the problem can be time consuming because many dispensing devices require multiple adjustments to reduce surging to an acceptable level.

But a new air-operated 735HPA dispense valve from EFD Inc., East Providence, R.I., stops surging with one simple adjustment. Simply remove the air input hose from the valve top, insert an Allen wrench, and adjust the internal stroke limit stop to increase or decrease spool travel. This lets users fine-tune both the amount of opening surge and closing snuffback for neat, uniform beads.

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