Advanced tribological research for wear reduction and pump lifecycle extension

Varisco's mission is to design and build robust, reliable self-priming pumps and internal gear pumps suitable for the most complex and demanding applications. Commitment to innovation and continuous improvement pushes us to delve into advanced technical topics, with the aim of developing increasingly high-performance solutions.

As of 2023, Varisco has been collaborating with the Department of Industrial Engineering of the University of Padua to tackle a highly significant technical and environmental challenge: the prevention of early wear on industrial machinery and the reduction in the frequency of maintenance interventions.
These problems are often linked to friction, aggravated by the use of suboptimal materials or unsuitable operating conditions, with significant impacts also from an energy and environmental standpoint.

Tribology and Varisco internal gear pumps

Tribology, a field that studies friction, wear, and lubrication, therefore plays a central role in our project, whose objective is to identify materials and solutions capable of extending the life cycle of pumps.

Varisco positive displacement internal gear pumps are designed to handle lubricating fluids as well as complex substances – such as bitumen, resins, molasses or glues – characterised by variable rheological behaviour, often sensitive to temperature or applied stress (such as some non-Newtonian fluids, for example corn starch).

During the study we looked into some key questions

• How do these phenomena impact the normal operation of our internal gear pumps?
• Which materials improve resistance to seizure, i.e., the adhesion between metal surfaces that can lead to machine failure?
• Which materials can allow us to have better performance (in terms of durability and reliability) at a lower cost?

The project began with an analysis of the countless applications Varisco has experience with, a careful analysis of the state of the art through inter-university research, and interaction with leading tribology experts in Italy. The University of Padua boasts a well-equipped laboratory and significant experience in metallurgy, the most advanced techniques for metal coating, and an entire department dedicated to composites and polymers in general.

In parallel with the bibliographic analysis, the state of the art of company knowledge was mapped, analyzing as many mechanical parts subject to tribological stress as possible from the field or from laboratory tests under the microscope, to understand their deterioration mechanisms.

Today, many industrial sectors address tribological issues with technologies that are not yet fully developed. According to recent studies, tribological optimization in industrial processes could reduce global primary energy consumption by up to 24%: an enormous potential that Varisco has chosen to exploit.

The experimental part of the project with the university is the heart of this exercise, in fact, considering the current state it was necessary to develop a customized tool, a tribometer, capable of faithfully replicating the operating conditions of Varisco internal gear pumps. A tool that allows us to specifically study the interaction between materials and fluids, paving the way for new design solutions and a significant improvement in the lifespan and efficiency of our machines.

Tribometer Design

The tribometer was designed following the guidelines of ISO 6281 and allows:

• High rotation speeds, high radial loads and controlled operating temperature.
• Real-time monitoring torque, RPM, oil and bearing temperature.
• Accelerated and long-term tests.

Main features:

• Isolated cell for different liquids.
• Flushing and cooling system for thermal equilibrium.
• Filtering device for removing debris.
• Radial force via calibrated spring.
• Temperature control device using a feedback cooling system

Variables investigated:

• Nature of the fluid (Newtonian/non-Newtonian), viscosity (0–10⁵ cP).
• Rotation speed and radial force (up to 10⁴ N).
• Mechanical geometries and surface roughness.
• Creeping materials.

Results

The outputs allow you to obtain Stribeck diagrams to identify lubrication loads.
The results show the effects of rotational speed, radial load, fluid viscosity and geometric variations.