Handling Fine Abrasive Fluids in Positive Displacement Pumps

What are Fine Abrasive Fluids?

Fine abrasive fluids contain particles or abrasives that erode the internal surfaces of a fluid pump through physical interaction. These abrasives can either be contaminants, such as those found in wastewater, or intentionally included particles like paint or ink pigments in printing applications, or suspended metals. We will focus here specifically on suspended abrasive particles less than 1mm in size.

Abrasive wear on a gear tip

Common Abrasive Particles and Their Impact

When we talk about abrasive fluids the rule of thumb is: the harder the solid particle, the greater concern it is for pump wear. Hard particles such as titanium dioxide (TiO2) are especially harmful, rapidly wearing down components made from softer materials. Even softer pigments can erode non-metal components such as plastic gears or rubber seals. Therefore the choice of materials becomes critical to managing wear and ensuring longevity in pump manufacturing. At Diener Precision Pumps as the first step in the design of a custom pump model for our clients our pump engineers ensure to understand well the nature of the fluid to be handled as this information is vital for selecting the right materials that balance the pump’s durability and cost.

Viscosity’s role in Abrasive Fluids

Viscosity plays a crucial role in how abrasives interact within a pump. In thicker fluids, the abrasive particles are cushioned by the liquid’s viscosity, providing protection, especially in configurations like hydrodynamic bearings. However, for gear pumps for example, which rely on precise component interactions, viscosity has a lesser effect on minimizing wear. Expert gear design and choice of materials here determine the pump’s wear resistance and durability.

Managing Operating Conditions

Abrasive wear increases exponentially with speed, making it important to carefully control the pump’s speed when handling abrasive fluids. Diener Precision Pumps recommends that in some cases, oversizing the pump and operating it at a slower speed, where possible, can mitigate wear. However, this must be balanced against the need to maintain efficiency and minimize internal leakage, which is crucial in sensitive applications like medical equipment or food and beverage handling systems.

Choosing the Right Pump Materials

The selection of the correct pump type is crucial for handling abrasive fluids. Rotary positive displacement pumps, such as external gear pumps, often have component-component contact, which can lead to rapid wear if the wrong materials are used. Hardened steels, ceramics like Alumina, and carbides such as tungsten carbide are common choices to minimize wear.

The Challenge of Seals

Fine abrasive particles can be especially damaging to sliding seals, as they get trapped between surfaces and cause premature wear on the pump’s internal walls and the soft seal materials. At Diener Precision Pumps we manufacture magnetically coupled gear pumps that eliminate the need for sliding seals, providing a durable and effective solution for pumping even abrasive liquids with small, non-magnetic particulates. Magnetic coupling extends the pump’s life for abrasive fluid handling, which is especially important in applications which require consistent safe performance over time like in laboratory analytics and medical systems.