How to Choose the Right Pump for High-Viscosity Fluids: A Complete Guide

Have you ever dealt with thick fluids like molasses, sludge, or heavy crude—you know the struggle is real. They are far from being ordinary liquids. They are sticky, slow, abrasive, and they require much more than just a simple pump. Pumps clog. Flow slows. Maintenance costs skyrocket. And if you’re not using the right pump, the entire system can grind to a halt.

High-viscosity fluids aren’t just harder to move—they demand precision-engineered solutions that most pumps simply can’t handle. Choosing the wrong pump could mean unplanned downtime, excessive energy bills, or worse—permanent equipment damage.

That’s when s come into play. For over 50 years, we have been helping various industries in the efficient movement of the toughest fluids with tremendous precision and reliability. Let’s take you through what you need to pump thick fluids-sans the stress, clogs, and expensive blunders.

What Does “Viscosity” Really Mean?

In moving liquids, the internal resistance to flow is called VISCOSITY.

Viscosity plays an important role when selecting Roto progressing cavity pumps.  It is vital to the proper selection, and all efforts must be made to obtain accurate viscosity data during the sizing process.  Viscosities of most liquids vary with changes in temperature. Pressure change, however, normally has no effect on viscosity of a fluid. In addition, viscosity of moving fluids can change depending upon the extent to which the liquid is agitated or sheared.

Meaning: Internal resistance to fluid motion. Flows in a fluid are temperature- and shear rate-dependent but not pressure-wise.

Types of Fluids:

• Newtonian Fluids: Maintain constant viscosity, although agitated (e.g., water, mineral oil).
• Thixotropic Fluids: Exhibit decreased viscosity under shear (e.g., molasses, glue, paint).
• Dilatant Fluids: Increase in viscosity when sheared (e.g., candy compounds, clay slurries).

Examples of High-Viscosity Fluids:

• Bitumen     • Molasses     • Adhesives     • Sludge  & slurry     • Tomato paste & syrups

Viscosity Impact On Pump Selection

• The more viscous a fluid is, slower the pump will have to run Thus giving more time for liquid to fill the cavity.
• Even at reduced speeds, the pump may not develop 100% volumetric efficiency and this must be accounted for in the selection process.
• Most fluids shear thin to a level well below their static viscosity. Hence pump speed and pump size should be selected as per the shear properties.
•   Greater the viscosity, Greater will be the frictional power.
•   For a range of viscosity, flow should be selected at the lowest viscosity and   power should be checked at the highest viscosity
•  Viscosity is sensitive to change in temperature. 
• Viscosity at pumping temperature should always be considered during the pump selection
•   Pumps are applied based on shear viscosity in a flow condition.  Roto can provide shear rate testing free of charge.

What Kind of Pump Works Best?

Not all pumps are designed to meet the requirements of high viscous challenges. Many conventional models fail to cope with sticky, slow-moving, or abrasive fluids. Hence, the Progressive Cavity Pumps (PCP) are considered to be the best solution.

Why Roto PCPs are a better choice?

ROTO PCPs are specifically engineered to handle high-viscosity, abrasive, and shear-sensitive fluids. Our PCP unique rotor-stator mechanism delivers a smooth, non-pulsating flow, making them ideal for challenging applications like molasses, sludge, and heavy crude. Unlike conventional pumps, PCPs maintain consistent performance with minimal wear, even under tough conditions.

Key Benefits:

✅ Smooth, Uniform Flow

Transfer without pulsations is ensured-steady transfer with ideal for delicate or shear-sensitive materials.

✅ Handling Solids and Sludge

PCPs are self-priming and can transport semi-solids like food pastes, mining slurries, or wastewater sludges. 

✅ Long Life

Less internal velocity results in reduced wear, which stands for longer life and fewer breaks. 

 From Chaos to Consistency – Read the Real Success Story Here

: https://www.rotopumps.com/wp-content/uploads/2020/12/Beetroot-Sugar-Flyer.pdf 

One of the leading sugar manufacturers in India was plagued by the problem of transferring molasses, a highly viscous and sticky by-product. The conventional pumps would clog, causing extended downtimes, expensive repairs, and exorbitant energy costs. 

How To Pick The Right Pump?

Finalizing the selection of the pump needs further consideration.

• How viscous is the liquid? (Does it resemble ketchup or is it rather like concrete?)
• Does it contain solids or abrasives? For slurries and sludge, one needs to choose rugged internals.
• Is the fluid shear-sensitive? Some materials are required to be treated gingerly in order to keep their properties.
• What are flow rate and pressure requirements?
• Will the fluid need heating? High-viscosity fluids may require a heat assist to pump them effectively. 

At Roto, we not only sell pumps, but we also provide tailored pumping solutions, backed by a wealth of data, testing, and support from experienced professionals. 

Industries We Serve

Roto Pumps are broadly employed in a variety of industries which include:

• 🛢️ Oil & Gas (Heavy crude, drilling mud)
• 🍯 Food & Beverage (Fruit pastes, syrup, sauces)
• 💧 Wastewater Management (Sludge cake, dosing applications)
• 🧪 Paints & Chemicals (Resins, glues, latex)
• 📄 Pulp & Paper (Starch, kitchen coatings, medium consistency pulp)
• 🍬 Sugar Mills (Molasses, magma, melt and flocculant)

Things Under Consideration Till Now

Pumping high viscosity fluids is certainly not a job for just any pump; as a matter of fact, it’s not a one-size-fits-all job-it requires smart design and technical insights and mechanical engineering of pumps for withstanding the rigors of operation.

The advantages you get with Roto Progressive Cavity Pumps are 

• Non-clogging efficient operation 
• Minimal maintenance requirements, 
• Long service life 
• High-energy sustainability

Still not sure what configurations actually suit your application? Our team will help you in making the right choice.

👉 Let’s talk: contact@rotopumps.com

Explore more at: www.rotopumps.com