What is the maximum viscosity fluid I can apply with a Uni-Roller^®?

Maximum fluid viscosity in a Uni-Roller® system depends on several variables. There is no single maximum viscosity that applies to all applications.

Dispenser tube hole size
Uni-Roller® systems use multiple dispenser tube configurations. The most common are 5-hole standard tubes and 20-hole low-volume (LV) tubes.
• 5-hole tubes have larger orifices and perform better with higher-viscosity fluids.
• 20-hole LV tubes have smaller orifices and are more sensitive to viscosity, making them better suited for lower-viscosity fluids.

Fluid pressure
Higher-viscosity fluids require higher supply pressure, typically in the range of 70–100 psi. As viscosity increases, pressure drop along the length of the dispenser tube also increases, from the push-connect inlet to the far end of the tube. If viscosity is too high or supply pressure is too low, uneven fluid distribution along the dispenser tube may occur.

Roller cover type
Increasing fluid viscosity results in longer roller cover saturation times, which can affect priming time and the maximum achievable production line speed.
• Polyester felt (PF) roller covers are more porous and generally handle higher-viscosity fluids better.
• Polyurethane foam (P) roller covers are less porous and may struggle with thicker fluids.

Application-specific considerations
Maximum allowable viscosity is highly dependent on the specific application and should be evaluated on a case-by-case basis. Applications that dispense small amounts of viscous fluid over long periods may perform well, while applications requiring higher volumes over short periods may not.

General guideline
In most applications, fluids with viscosities below approximately 400 cSt work well with 5-hole dispenser tubes and polyester felt roller covers.

For applications above this range, contact Unist for an application review and recommendation.