The Pump Room
Blog style practical advice and industry insights to help keep your systems running smoothly.
Pumping viscous liquids - The basics
Pumping thick, sticky or heavy liquids can be a challenge. Viscous liquids behave differently than thin, water-like liquids and require the right pump type, setup and system design to keep things flowing smoothly.
Here are the key things to consider when pumping viscous liquids:
1. What is a viscous liquid?
The term Viscosity is used to refer to thick or resistant to flow a certain liquid or product is.
Some examples of viscous liquids include:
- Oils and greases
- Paints and coatings
- Syrups
- Resins
- Adhesives
The thicker the liquid is, the harder the pump will need to work in order to move it.
2. Use the right kind of pump
Some pumps handle viscous liquids better than others. Here are some common types you will find:
- Gear pumps: Great for thick, lubricating liquids
- Peristaltic: Great for thick, shear-sensitive, abrasive liquids
- Progressive cavity pumps: Handle high viscosity well and are great for pastes and sludges
- Air-operated diaphragm pumps (AODD pumps): these are great for when viscosity can change and offer gentle handling.
Depending on the viscosity and the product itself, there may often be more than one kind of pump that can handle it.
Generally these types of pumps all fall under the family of what we call “positive-displacement pumps”.
3. Viscosity can vary!
Ever arrive at the factory on a cold morning and all of a sudden the pumps don’t work?
A lot of viscous liquids can change their viscosity, settle, harden or clog your system depending on the environment.
- Secondary systems such as heating and jacketing are often used to try and manage the liquids viscosity or help make it easier to pump.
- Using solvents or thinners for example can also help adjust the viscosity.
4. Viscous liquids have an effect on flow and system head
It’s critical to size/choose your pump with the actual viscosity and system resistance in mind.
- Viscous liquids encounter a lot of friction loss in the piping system and in turn generate a higher system head.
- Pumps moving these kind of liquids often need to run slower than standard motor speeds like you would encounter in water pumps for example.
- Pump speeds can be manipuated by using gearboxes, pulleys/belts or electronic equipment like Variable Frequency Drives
- Some pump designs allow you to adjust internal components to allow for better Viscosity handling and efficiency.