Screw pumps have always been used in the transfer of high viscosity fluids. These include heavy oils, bitumen, polymers, bitumen resins as well as food grade products. Other types of pumps might fail or perform poorly at such tasks. This is due to the restraints each of the fluids impose, like excessive friction, resistance to viscosity, shear sensitivity, and high chances of forming friction in the pumping systems. For such challenges, the equipment needs to operate precisely and deliver positively, durable, and efficient output.

Understanding the Principle of Screw Pumps

The main component of a screw pump is the screw type of ‘pivots’. A screw type rotor or several of them, spinning in a casing. These rotors turn and enclose pockets of fluid in the screw threads and in the house of the pump. The fluid is taken and carried towards the screw shafts from the suction side and is discharged at the other end. This mechanism results in pulse-free flow which is continuous, smooth and independent of viscosity to a large extent. 

In centrifugal systems pumps, energy is imparted to the liquid at a high rate of rotation. However, In a screw pump, that energy is from the sealed cavities that the pump casing and the screws contain, which results in the high efficiency outcome, when pumping a viscous fluid.

Why High-Viscosity Fluids Are a Challenge

High-viscosity fluids resist movement, behaving almost like semi-solids at low shear rates. In pumping systems, this creates several issues:

High frictional losses in pipelines and pump internals.

Poor priming ability for pumps that rely on velocity or centrifugal force.

Increased wear on components if the pump is not designed for viscous media.

Temperature sensitivity , as heating may be required to lower viscosity for efficient pumping.

These challenges make screw pumps the preferred choice, as their design is inherently better suited to overcoming resistance and delivering stable performance.

Structural Variations in Screw Pumps

There are several types of screw pumps, each adapted for particular viscosity ranges and applications:

Single Screw Pumps : Also known as progressive cavity pumps, they use one rotor working against an elastomeric stator. These pumps are excellent for handling highly viscous, shear-sensitive, or solids-laden fluids.

Twin Screw Pumps : These feature two intermeshing rotors that create sealed cavities for fluid transfer. They offer smooth flow, can handle multiphase fluids (liquid with gas), and are suitable for hygienic applications in food and pharmaceutical industries.

Triple Screw Pumps : Often used in lubrication and hydraulic systems, they feature one driving screw and two idler screws. They excel in handling oils and fuels with moderate to high viscosity.

Each configuration provides specific benefits, and the choice depends on viscosity, flow rate, and system pressure requirements.

How Screw Pumps Manage High-Viscosity Fluids

1. Smooth and Non-Pulsating Flow

Viscous fluids can be sensitive to shear forces, which may degrade product quality in certain industries (e.g., food, cosmetics, polymers). Screw pumps minimize pulsation, ensuring that the fluid is delivered steadily without sudden pressure surges.

2. Positive Displacement Efficiency

Because screw pumps trap a fixed volume of liquid with each rotation, viscosity has little negative effect on their pumping ability. In fact, higher viscosities reduce back leakage, enhancing efficiency.

3. Self-Priming and Suction Capabilities

With ease, screw pumps can generate high suction lifts which is critical in pumping viscous liquids from storage tanks and from underground vessels.

4. Capability of Handling Extreme Viscosities

Screw pumps operate efficiently on fluids ranging in viscosity from a few centipoise (water) to more than 1,000,000 cP (asphalt and other dense polymers). The range indicates the ability to function under challenging conditions. 

5. Low Noise and Vibration

Screw pumps operate quieter than any other positive displacement pumps, even though more viscous fluids are being handled. Their low noise, constant flow delivery and positive-displacement mechanics pack system keeps vibration low and therefore dramatically increases the operational life for pumps and piping systems. 

Common Applications with High-Viscosity Fluids

1. Oil and Gas Industry : Screw pumps are widely used to transfer crude oil, heavy fuel oil, and bitumen. Their ability to maintain flow under high viscosity conditions makes them indispensable for upstream and downstream processes.

2.  Food and Beverage Processing : Products such as syrups, chocolate, molasses, and pastes require gentle, hygienic handling. Twin screw pumps are often employed due to their sanitary design and ability to handle both cleaning fluids and production fluids with the same pump.

3.  Chemical and Polymer Industry : High-viscosity polymers, adhesives, and resins are transferred using screw pumps, which preserve product integrity while maintaining accurate flow.

4.  Marine and Power Generation : Lubricating oils for engines and turbines are typically delivered by triple screw pumps, which provide consistent flow and high reliability.

5.  Wastewater Treatment : Sludge and slurry transfer are made easier with single screw pumps that can handle thick, abrasive materials without clogging.

Advantages of Screw Pumps for High-Viscosity Fluids

High Volumetric Efficiency even at elevated viscosities.

Wide Operating Range for flow rates and pressures.

Durability due to robust construction materials.

Flexibility in handling both clean and contaminated fluids.

Gentle Pumping Action , preserving shear-sensitive products.

Limitations to Consider

While screw pumps offer many benefits, they are not without limitations:

They require precise manufacturing tolerances, which can increase cost.

Single screw pumps with elastomer stators may face swelling or chemical compatibility issues.

Energy consumption can be higher compared to centrifugal pumps when handling low-viscosity fluids.

Comparison of Screw Pump Types

Performance Parameters of Screw Pumps

Screw pumps are virtually the most versatile and dependable devices for moving high-viscosity fluids. Their tow pack and positive-displacement mechanics systems ensures constant flow delivery. Their efficiency, and smooth flow delivery as positive-displacement pumps, is the most important feature in many sectors, from energy to food processing. Operators can select pipe configurations and construction materials designed to provide long life, low maintenance costs and optimum operating efficiency for any process. 

Screw pumps instill functional confidence in process and product integrity and stability and product integrity viscosity is the most critical challenge to address.