Oil Flushing Types: Applications and Properties

Oil flushing is a fundamental process for maintaining the cleanliness and efficiency of industrial systems, including hydraulic systems, turbines, and pipelines. Over time, contaminants such as dirt, sludge, and varnish can accumulate in these systems, affecting their performance and lifespan. Oil flushing techniques are employed to remove these impurities, ensuring smooth operation and preventing system failure. At INVEXOIL, we produce Oil Flushing Units and Cleaning & Flushing a Hydraulic System Service, each tailored to address different oil flushing needs.

This article will explain different Oil Flushing Types, principles, and their applications and give you a better insight into which technique will suit your system requirements.

The importance of Oil Flushing

The importance of oil flushing cannot be overstated. It helps:

Ensure system cleanliness: By removing contaminants and preventing clogging in critical components.

Extend equipment lifespan: Reducing wear and tear caused by contaminants.

Improve operational efficiency: Keeping systems running smoothly and preventing costly repairs or downtime.

With various techniques to choose from, selecting the right Oil Flushing Type is vital for achieving optimal system performance.

Oil Flushing Types and Their Applications

This is the list of 14 popular oil flushing systems in the industry (2024):

A. High-Velocity Oil Flushing

1. Standard High-Velocity Flushing

2. Puls-Induced Wave Flushing

B. Chemical Flushing

3. Solvent-Based Flushing

4. Mild Chemical Flushing

5. Hot Oil Flushing

B. Continuous Oil Flushing

6. Live System Flushing

7. Inline Filtration

8. Rinse/Purge Flushing

9. Particle Count Flushing

10. Umbilical & Control Line Flushing

11. Hydrodynamic Flushing

12. Air Blow Flushing

13. Filter Flushing

14. Montoring-based Flshing

 

A. General Oil Flushing Techniques

The flushing techniques of oil are generally categorized based on the system type and the extent of contamination. These methods include:

High-Velocity Oil Flushing (HVOF)

High-Velocity Oil Flushing is based on the principle of generating turbulent flow of oil at high velocities to dislodge contaminants and clean the interior surfaces of the system. It is ideal for systems that demand high cleanliness, like turbines, hydraulic circuits, and compressors. This technique is divided into two subcategories:

1. Standard High-Velocity Flushing: Primarily focoused on achieving high flow rates to push debris through the system.

2. Puls-Induced Wave Flushing: Enhances the cleaning process by introducing pressure pulses that create waves, reaching hard-to-access areas for more effective cleaning.

Chemical Flushing

Chemical Flushing: This method uses the action of chemical agents to dissolve and degrade contaminants, such as varnish and sludge. It is effective for systems that have a very high level of contamination. The two major subcategories of this are:

3. Solvent-Based Flushing: Uses aggressive chemicals to clean systems with heavy deposits and varnish.

4. Mild Chemical Flushing: A less aggressive approach for systems that have components which cannot bear harsh chemicals.

5. Hot Oil Flushing

The use of heated oil in Hot Oil Flushing reduces the viscosity of the contaminants, making it rather easy to flush out hardened sludge and debris. This method is very ideal for systems with temperature-resistant deposits or heavy grease buildups, such as compressors and hydraulic systems.

Continuous Oil Flushing

Continuous Oil Flushing refers to the system remaining live while oil is circulated and filtered to maintain cleanliness without downtime. This method is applied for offshore platforms and emergency shutdown systems. It contains two main subcategories:

6. Live System Flushing: Oil flushing is done with the system in operation to minimize downtime.

7. Inline Filtration: Filters are continuously used to remove contaminants during normal system operation.

8. Rinse/Purge Flushing

This involves draining the system and filling it with neutral or new oil to flush out the residual contamination. This technique is done during gear lubricant changes or when changing over to a different type of oil.

 

B. Specialized Techniques

Certain oil flushing methods are designed to suit very special applications or adverse conditions. These include:

9. Particle Count Flushing

Partcile Count Flushing process continuously monitors the oil cleanliness with particle counters and flushes the system until it reaches a certain level of cleanliness. It is mainly used in high-precision applications such as aerospace and hydraulic systems, where contamination could result in the failure of the system.

10. Umbilical and Control Line Flushing

This technique is used for cleaning small-diameter, long-distance lines, often seen in subsea systems or offshore control lines. Low-viscosity oil and precise flushing techniques are employed to ensure thorough cleaning.

11. Hydrodynamic flushing

Hydrodynamic Flushing combines water with oil to achieve pre-commissioning or heavy-duty cleaning in large pipelines or industrial systems. This technique is effective for cleaning out substantial deposits that require both oil and water to loosen and flush away.

12. Air Blow Fkushing

Air Blow Flushing uses compressed air to blow the loose debris from the system before the oil flushing. This can be a pre-flush to remove solid contaminants that would otherwise clog the oil system.

 

c. Verification and Support Methods

To make the flushing of oil more effective, there are some methods employed for verification as well as support:

13. Filter Flushing

In Filter Flushing, high-efficiency filters are integrated into the oil flushing process to capture contaminants while they are being removed. This method is particularly effective during routine maintenance or live system flushing.

14. Montoring-based Flshing

Monitoring-Based Flushing utilizes state-of-the-art sensors, such as particle counters, temperature, and flow sensors, in continuously monitoring and validating the flushing process. This ensures that the desired cleanliness standards of the system are achieved, especially for systems with strict performance requirements.

 

Table: Overview of oil flushing types, comparing their properties and operational requirements for various industrial applications.

Oil Flushing Types	Chemical Properties	Physical Properties	Cost of the Flush System	Duration to Repeat Flushing	Time Consuming	Temperature	Pressure
High-Velocity Oil Flushing	Moderate reactivity, uses standard oil	High turbulence and flow velocity	Medium to High	1-3 years	1-2 hours	Ambient to 80°C	High (up to 2000 psi)
Chemical Flushing	High reactivity, solvent or mild chemicals	Variable based on agent type	High	2-5 years	4-8 hours	40°C to 60°C	Low to Moderate (500-1000 psi)
Hot Oil Flushing	Low reactivity, heated oil	High heat capacity, reduced viscosity	Medium to High	1-3 years	2-6 hours	60°C to 100°C	High (1000-1500 psi)
Continuous Oil Flushing	Minimal, uses regular oil	Continuous circulation, minimal interruption	Low	Ongoing	Continuous operation	20°C to 50°C	Low to Moderate (200-600 psi)
Rinse/Purge Flushing	Neutral, uses clean/new oil	Minimal turbulence	Low	1-2 years	1-3 hours	Ambient to 50°C	Low (100-300 psi)
Particle Count Flushing	Minimal, oil-based	Precision monitoring, low turbulence	High	2-5 years	4-6 hours	40°C to 60°C	Moderate (500-1500 psi)
Umbilical & Control Line Flushing	Low reactivity, low-viscosity oil	High accuracy for small lines	Medium to High	2-5 years	4-6 hours	20°C to 40°C	Low to Moderate (200-600 psi)
Hydrodynamic Flushing	Minimal chemical presence	Combines water and oil, high flow rates	High	5+ years	8-12 hours	60°C to 90°C	High (1000-2000 psi)
Air Blow Flushing	None, uses compressed air	High velocity, low viscosity	Low	1-2 years	1-2 hours	Ambient	Low (100-300 psi)

 

Conclusion

Oil flushing is very helpful in maintaining industrial systems in clean conditions, with good efficiency and longer working life. Choose the suitable type of Oil Flushing to keep your system optimum and avoid breakdowns that lead to huge losses. Whatever the condition, be it severe contamination, high-precision systems, or live operational conditions, INVEXOIL has a solution ready for you. Learn more about Invex’s Oil Flushing Systems and Cleaning & Flushing a Hydraulic System Services.

 

References

https://ifmservices.com/wp-content/uploads/2024/05/HVOF-WhitePaper.pdf

https://www.articleted.com/article/194876/29149/4-Effective-Methods-of-Industrial-Oil-Flushing-to-Maintain-Piping-Systems

https://www.sciencedirect.com/science/article/pii/S0048969724037690

https://www.researchgate.net/publication/273945596_Survey_of_lubrication_oil_condition_monitoring_diagnostics_prognostics_techniques_and_systems