RAN diaphragm pumps are engineered to handle a wide range of fluid viscosities with reliability and efficiency. However, as with all positive displacement pumps, the viscosity of the fluid has a direct impact on pump performance and capacity.
As viscosity increases, the flow capacity of the pump decreases. This is especially important when dealing with thicker, more resistant fluids. Referencing industry-standard data, RAN diaphragm pumps should not exceed:
- 22,000 centipoise or 100,000 Saybolt seconds universal (SSU) on 3/8″ to 3″ pumps.
- 4,000 centipoise or 18,000 SSU on 1/4″ models.
The graph below illustrates this performance trend, showing a significant decline in pump capacity as viscosity increases. For example, fluids at 10,000 centipoise may reduce pump capacity to nearly 50% of the maximum flow rate achievable with low-viscosity fluids.
Best Practices for Pumping High-Viscosity Fluids
To ensure optimal performance and extend the life of your RAN diaphragm pump, follow these key recommendations:
- Install pumps below or near the fluid level to assist with suction.
- Increase suction line diameter—up to three times the pump’s inlet size—to reduce flow resistance.
- Use dual manifolds where applicable for smoother flow.
- Ramp up air supply gradually using a control valve to avoid pressure surges.
- Note that increasing air pressure beyond a certain point will not increase flow rate—maximum performance is pressure-limited with high-viscosity fluids.
- Consider upsizing the pump if greater capacity is needed for thicker products.
Whether you’re moving adhesives, oils, syrups, or other viscous materials, RAN diaphragm pumps are built to perform. Understanding how viscosity impacts flow and following these operational guidelines will help ensure smooth, efficient transfer of even the most challenging fluids.