How to Choose the Right Dispense Valve

Phil Black - PII Editor 25/02/2010

321 2 minutes read

Listen to this article

Choosing a dispense valve for a specific fluid or application can be confusing. Here are some things to consider before making a final decision.

Design. Fewer parts typically mean less maintenance. Are wetted parts and moving parts kept separate? Does the design incorporate seals lasting millions of cycles, or O-rings that will eventually wear and leak?

Size and Weight.

Smaller designs provide greater flexibility, whether the valve is stationary or mounted on a movable fixture. On movable fixtures, lighter valves can reduce wear and tear, and often make a machine less expensive to build by requiring a less robust design.

Maintenance.

How complex is maintenance? Are spare parts readily available? Can the valve be cleaned in place, or need to be removed and disassembled? When rebuilding is required, can it be performed in-house, or must the valve be returned to the manufacturer?

Several basic valve types are available to handle most fluids and applications:

Diaphragm – General-purpose valves ideal for dispensing controlled amounts of most low- to medium-viscosity fluids.

Piston – General-purpose valves for a wide variety of medium to high-viscosity fluids. A valve with a snuffback at the end of the dispensing cycle will prevent dripping between shots.

Spool – Good for dispensing thick materials like greases and silicones at high pressures. An adjustable stroke control is useful for keeping shots and beads consistent by regulating opening surge and closing snuffback.

Needle – For low-viscosity fluids like solvents, inks and uv-cure adhesives. A design that seats the needle in the dispense tip adapter will minimize dead fluid volume between shots.

Spray – Low Volume Low Pressure (LVLP) designs can apply a uniform coating without overspray to keep production areas cleaner and reduce fluid use.

Special-purpose valves are also available for specific applications. Examples include auger valves for solder paste and particle-filled fluids, spinner valves and radial spray valves to coat cylinder interiors, and piezoelectric jet valves for applications where a dispense tip cannot be used.

Regardless of the valve type chosen, a dedicated valve controller will provide several important benefits. These include allowing valves to run at maximum speed, providing precise control of shot size, simplifying setup, and permitting adjustments to be made without stopping the production line.

Finally, always look beyond a valve’s purchase price to determine true cost of ownership. In many cases, even a few minutes of unexpected downtime will wipe out any “savings” from choosing a lesser quality valve with a lower initial price.