Viscosity is a fluid-related property that causes liquid to resist the forces ordinarily allowing it to flow freely through a pump or other mechanism. An oil viscosity chart is one way to understand how a selected material may impact how well a pump works. Here are some additional things to consider when understanding the effect of viscosity on pump performance.

Pay Attention to Oil Viscosity Chart Specifics

Becoming familiar with the information on an oil viscosity chart can help you understand how it might affect your pump. You’ll see the data represented in centipoise (cP or cps). A higher number associated with centipoise represents a liquid with more viscosity. For example, water is1 cP at 70 degrees Fahrenheit. However, SAE 60 motor oil is 1,000 to 2,000 cP.

Speaking of motor oil, it’s common for a manufacturer to publish a specific oil viscosity chart for its products. In such cases, the engine oil code has two parts — each representing oil viscosity grades according to when the substance is cold or hot. The letter W indicates the grade in cold weather. You might see motor oil labeled as 10 W-30. If so, it has a grade-10 viscosity when cold and 30 when hot.

In the context of viscosity ratings for motor oil, a lower number means the oil begins flowing faster once someone starts the engine. However, the flow rate is affected as the engine oil gets warmer with use.

People can apply these specifics to the performance of pumps other than those used for fuel, particularly when temperature is a primary consideration.

Understand That Viscosity Changes Under Different Conditions

Learning about the effect of viscosity on pump performance becomes a bit more complicated when people realize it’s not constant. Overall conditions can make viscosity more or less apparent.

There are also several types of liquids, often split into Newtonian and non-Newtonian categories. As you might guess, those in the latter group do not follow Newton’s law of viscosity.

Newtonian fluid viscosity stays the same, even if the shear rate or agitation changes. Water and mineral oils are two examples of Newtonian fluids. The viscosity of pseudoplastic fluids decreases as the shear rate increases. However, their initial viscosity may be enough to prevent them from flowing through pumps. Lotions and latex paints are some common types of pseudoplastic fluids.

Agitation increases the viscosity of dilatant fluids until they become nearly solid. The effect of viscosity on pump performance can be so severe that pump-based equipment will get bogged down and stop. That’s especially problematic for specialized vehicles like hydraulic trucks. They have several pumps that must keep functioning smoothly during use.

Thixotropic fluids — such as glues — have decreased viscosity as the shear stress increases. In contrast, rheopectic fluids show increased viscosity with added shear stress. The relationship is time-dependent for thixotropic and rheopectic fluids. Finally, Bingham plastics are similar to Newtonian fluids, except they have internal yield stress. Some oils fall into this type.

Know the Recommended Uses for Your Pump

Another way to prepare for the effect of viscosity on pump performance is to learn whether the pump you have suits your intended application. Relatedly, determine how manufacturing conditions may impact your results. People working in various roles must do the same. Those tasked with processing produce may use oil extraction machines to make fruits and vegetables release their natural oils without using chemicals. They use hot, high-pressure systems to increase the oil’s viscosity, speeding its flow rate.

Alternatively, if you have examined an oil viscosity chart and know the pump you have won’t perform well, consider investing in a high-viscosity model to avoid possible problems. A market research report predicts 5.8% growth for these pumps between 2021 to 2030.

Other recommendations are to make your discharge pipework bore size as large as possible and ensure the discharge pipe is short and straight. This will lower the resistance associated with friction losses.

You Can Minimize the Effect of Viscosity on Pump Performance

Viscosity is something you frequently must deal with, and the extent of it depends on the substance going through the pump. However, knowing how the liquid will behave and whether your equipment suits it will prevent complications.

Read more articles from Emily Newton.