Varnish: The Silent Killer of the Lubrication & Hydraulic System

A secret threat hides in this complex world of machinery, capable of causing damage to lubricating and hydraulic systems with a precision that resists discovery until it's too late. This deadly opponent is known as varnish, a seemingly harmless term with severe repercussions. Varnish is a jelly-like substance that attaches to oil and surfaces in machinery, gradually reducing the system's functioning and reliability. Let us go into the world of varnish to learn about its mechanics and what harm it can do.

Understanding Varnish Formation: The Culprits

Varnish doesn't just appear out of nowhere; it's the result of a complex interplay of factors within machinery. Three primary pathways contribute to varnish formation: oxidation, micro-dieseling, and carbonization.

1. Oxidation: The battle against oxidation begins as soon as machinery operates at elevated temperatures. Harmful catalysts, such as water and wear metals, intensify the oxidative process. This leads to the formation of unstable byproducts that are insoluble in oil. Gradually, these byproducts separate from the oil, leading to an increase in oil temperature and rapid oxidation rates. Acid breakdown occurs, and solid substances begin to form. Varnish then finds its resting place on the nearest machine surfaces.

2. Micro-Dieseling: This process involves the compression of air bubbles that transit from low to high-pressure zones within fluid circuits. The compression of these bubbles generates heat, oxidizing the oil and resulting in carbon byproducts. These byproducts contribute to the gradual formation of varnish.

3. Carbonization: Changes in fluid pressure cause air bubbles to pass through high-pressure zones. As they undergo compression, the temperature within these bubbles rises. This elevated temperature is sufficient to initiate the oxidation of oil and the subsequent carbonization process, leading to the formation of carbon byproducts and, ultimately, varnish.

The Chilling Effects of Varnish: A Multifaceted Threat

The consequences of varnish formation can be devastating for lubrication and hydraulic systems:

Sticky Seizure: Moving parts within machinery, such as servo valves, can succumb to sticking or seizing due to varnish deposits, impeding their functionality.

Restricted Flow: Varnish can plug or restrict small oil flow orifices in filters and valves, leading to reduced efficiency and potential malfunctions.

Thermal Inefficiency: The effectiveness of heat exchangers can be compromised, leading to decreased performance and potential hydraulic malfunctions.

Premature Failure: Bearings may fail prematurely or experience increased temperatures due to the presence of varnish, leading to costly repairs and downtime.

Catalytic Impact: Turbine and hydraulic oils can undergo catalytic deterioration due to varnish, accelerating oil breakdown and system degradation.

Dirt Accumulation: Specific locations can accumulate dirt with a shiny appearance, signifying the insidious presence of varnish deposits.

Detection and Prevention: The Ongoing Battle

Detecting and preventing varnish requires a multi-faceted approach:

Testing Methods: Techniques such as Membrane Patch Colorimetry, Particle Count, Ultracentrifuge, Acid Number, Karl Fischer Method, RULER, and IR Spectroscopy (FTIR) can unveil varnish potential in oil.

Filtration Strategies: Employing stage-wise mechanical filtration technology, low vacuum dehydration technology for moisture removal, and water particle coalescence and separation systems can mitigate varnish formation.

Filter Selection: Opt for filters like cellulose-based offline filters and conventional inline pressure filters (glass fiber) to combat varnish effectively.

Varnish Removal: A Delicate Operation

If varnish has already infiltrated the oil, removal processes can be challenging, yet they are vital for system longevity. Effective varnish removal techniques exist, although they work slowly. These methods can successfully eradicate varnish, albeit with potential implications for filter longevity.

In conclusion, varnish is a hidden adversary that poses a substantial threat to lubrication and hydraulic systems. Its formation is intricate and gradual, often escaping immediate notice until its damaging effects become apparent. Understanding its pathways, consequences, detection methods, and prevention strategies is paramount for maintaining the health and efficiency of machinery. As machinery continues to evolve, the battle against varnish remains ongoing, demanding constant vigilance and adaptation to ensure smooth operations and extended equipment life.