Lube and Hydraulic Oil Dehydration Systems: How to Choose the Right Oil Purifier

By PowerFlow Fluid Systems | May 31, 2023

What areLube and Hydraulic Oil Dehydration Systems

Lube and hydraulic oil dehydration systems are a key component for addressing water contamination in oil reservoirs and related circuits. Lubrication and hydraulic fluids for industrial machinery are commonly contaminated with water. AMPTIAC Quarterly reports that 75% of hydraulic system failures are caused by fluid contamination. Water is second only to particulate matter as a source of significant contamination of machine oils. Rotating equipment is especially vulnerable. For example, as the water content in turbine lube oil gradually increases, the machine develops multiple failure points. These include bearings, bushings, seals, shafts and more.

While other forms of contamination must be mitigated, water contamination presents unique challenges. Free and emulsified water are easily identifiable. Free water accumulates and stratifies, while emulsions typically appear as cloudiness or rag layers. Dissolved water is invisible but just as toxic as the other forms. According to NORIA, “Depending on the oil type and temperature, a bearing can lose 75% of its life due to water contamination before the oil becomes cloudy.” Reducing water content well below the saturation level is desirable. This prevents the release of free water in oil coolers while curbing additive depletion and degradation of critical oil properties, such as viscosity, lubricity, and film strength. Lube and Hydraulic Oil Dehydration Systems address these issues using thermodynamic processes to remove water and other contaminants from the oil. Other terms commonly used for these machines are Oil Purification Systems, Oil Purifiers, and Vacuum Dehydration Oil Purifiers.

PowerFlow XLP5 Oil Purifier

Figure 1 – XLP Series Oil Purifier (Visit our XLP Series product page and request a quote. https://www.pwrfs.com/product/lube-hydraulic-oil-purifiers/ )

As discussed here, their primary function is to remove ALL forms of water from the oil. Most also remove free and dissolved gases, as well as particulate contamination. Therefore, oil dehydration does not fully define these machines. As a system, they integrated processes that remove free and dissolved water and gases, oil/water emulsions, and particulate. As such, the terms Oil Purifier or Oil Purification System are more appropriate.

When to Install Oil Dehydration Systems

Though often advertised to the contrary, most oil/water separation technologies are not intended to remove dissolved water or any gases. This is where systems that use vacuum dehydration are distinguished from those employing coalescing filters, water-absorbing media, corrugated plates, and centrifuges. A Lube and Hydraulic Oil Dehydration System is recommended when managing water content in lube or hydraulic fluid systems becomes a challenge.

Sources Of Water Contamination in Lube and Hydraulic Oil

There are several ways water enters lube and hydraulic fluid systems. These include:

Direct absorption from humid air in the headspace of the oil reservoir
Rapid condensation in the headspace of the oil reservoir
Rain and washdown water ingression through leaky hatches and seals
Leakage from steam seals
Leakage from oil coolers and heat exchangers

Preventative measures for mitigating these ingression mechanisms should be in place. However, water will likely find its way into these systems. This is when an Oil Dehydration System is convenient and often the most reasonable solution.

How Vacuum Dehydration of Oil Works

Before exploring the benefits of using Lube and Hydraulic Oil Dehydration Systems, it is essential to understand how they work. By our definition, Oil Purifiers use vacuum dehydration technology to enhance water removal performance. In some systems, the oil may also be heated to optimize dehydration. However, under vacuum, the required thermal input is reduced. Vacuum and heat make the process of liberating water more efficient. However, the process must be optimized. Less heat prevents thermal oxidative stress of the oil, additive depletion and foaming. Vacuum dehydration at moderate heat and vacuum is the most efficient way to remove water while preventing premature oil degradation.

Vacuum Mass Transfer vs Flash Distillation

Two commonly used vacuum dehydration processes are “vacuum mass transfer” and “flash distillation.” Vacuum mass transfer uses moderate vacuum levels (ࣘ≤22inHg) and heat (≤120 deg. F) to accelerate moisture evaporation with minimal risks of oil degradation. Flash distillation uses a deep vacuum (25-28 inHg) and high heat (150+ deg. F) to boil or flash water from the oil, a process that carries a higher risk of oil degradation. We only discuss vacuum mass transfer here.

Inside an Oil Purifier’s dehydration process, preheated oil is distributed as a thin film over a dispersion media, such as packing rings. The purpose of the packing is to create a thin oil film with as much surface area as possible. This increased surface area significantly improves the process’s efficiency. As seen in Figure 2, there are three critical features needed to achieve this:

A vacuum chamber/tower where oil flows from top to bottom while dry air flows from bottom to top.
A means of distributing the oil evenly over the inside cross-section of the chamber/tower by creating an oil spray in the form of an umbrella.
A flow configuration where the oil passes from top to bottom through/over the dispersion media, such as packing rings, expanding the surface area and creating a thin, cascading film.

Dry air is continuously drawn upward through the packing over the thin oil film. Water and air/gas molecules transfer from the oil to the upward-moving air. The air/water vapor exits the chamber at the top and may be routed to a condenser to manage water collection. Finally, it is expelled through the vacuum pump. Dehydrated/deaerated oil exits the bottom of the chamber and is typically routed through a particulate filter to achieve the desired cleanliness level. This system could run as a batch or continuous process, but the latter is more efficient.

Vacuum Dehydration Process for Oil Purifier

Figure 2 – Diagram depicting a simplified view of oil dehydration in a vacuum chamber

Lube and Hydraulic Oil Dehydration Systems

– The Benefits

Before investing in a system, it is essential to consider the long-term benefits.

Benefit #1: Improved safety

Safety is always number one. Especially with rotating equipment, mechanical failure and control issues can result in serious accidents. The average cost of a recordable injury is tens of thousands of dollars. A lost-time injury costs even more. Purity of lube and hydraulic fluids can be an important factor for avoiding dangerous equipment failures, such as broken shafts and hydraulic overspeed. Prevention of a single injury will always justify the cost of an Oil Purifier.

Benefit #2: Less frequent oil changes

It is easy to see how stretching the useful life of lube and hydraulic fluids is economically beneficial. Factors that have a significant impact on the return on this investment are:

Reducing the money spent on replacement fluid
Lowering labor costs and freeing up time for other maintenance and repair projects
Shrinking disposal fees

Accordingly, extending the oil’s lifespan by several thousand hours makes a strong case for investing in an Oil Purification System. Our infographic examines the relationship between oil health diagnostics, various contaminants and Oil Purifiers.

Benefit #3: Less unscheduled machine downtime

Often, machinery endures significant wear and tear or massive and sudden breakdowns that can cause immense losses to a business. According to Forbes magazine, “next to a safety or environmental mishap, unplanned/unscheduled downtime represents one of the costliest events at any industrial or manufacturing plant.” Every event is different, but costs can run into millions of dollars. When downtime results from contaminated lube or hydraulic fluid, it is almost inevitable that the costs will dwarf the investment in an Oil Purifier. Machinery Lubrication published the following top reasons that unscheduled downtime is unwelcome:

Production losses and schedule delays (business interruption)
Lost revenue and profit (unhappy management/ownership)
Promised delivery dates are missed (unhappy customers)
The blame game and damaged relationships between operations and maintenance (morale issues)
Hurried (botched) repairs cause future problems (cycle of despair)
The lack of available replacement parts and skilled trades prolongs the downtime interval
Repairs are at a “cost premium” due to rushed parts purchases, use of overtime labor and collateral damage
Chaotic reactive tasks replace scheduled “proactive” tasks (leads to future problems)
Increased work pressure and job stress (job satisfaction issues)
Safety risks from rushed work, unskilled work, inferior parts, cutting corners, job stress, etc.

Alone, any of these demonstrates the value and ROI of a Lube and Hydraulic Oil Dehydration System.

Benefit #4: Better machine performance

A company’s productivity depends on how well its equipment performs. When lube and hydraulic fluids are correctly maintained, it improves machine reliability. This results in better performance, higher availability and productivity. It also promotes a safer work environment and a smaller environmental footprint. On the other hand, contaminated lube and hydraulic fluids lead to derated capacity, sluggish operation, hydraulic control issues and other performance issues. Plant Services’ surveys indicate that one of the energy industry’s most important metrics is “return on capital employed,” which correlates with rotating equipment performance. This suggests that if rotating equipment is underperforming due to contaminated lube or hydraulic fluid, investment in an Oil Purifier may significantly and favorably impact key business metrics.

These and other benefits, unique to each plant, offer ample, quantifiable justification for capital investment in an Lube and Hydraulic Oil Dehydration System. If capital is tight, rental units are available to protect machines through a budget cycle. There are many sizes and features to consider, making it easy to find a system that suits any needs or budget.

How To Choose Lube and Hydraulic Oil Dehydration Systems

With many options available in the market, it is essential to understand how to evaluate them effectively. The most important characteristics will determine whether this investment meets your expectations. Doing some homework and making an educated decision is vital. The crucial machine attributes are operational complexity, reliability, and oil processing performance. The best Oil Purification Systems have these seven characteristics:

Effectively remove all forms of water, gases, and particulate from oil without degradation or additive depletion
Require minimal operator attendance to start, stop and run the unit
Offer adequate, simple and convenient monitoring and control
Require minimal scheduled or routine maintenance
Operate at full capacity over the entire range of application conditions, including oil temperatures, pressures and viscosities, piping configurations, and environmental conditions (including sound levels)
Produce minimal environmental footprint
Operate with minimal energy and utility requirements

The best way to evaluate these essential qualities is to compare systems with a full-scale, onsite trial. Nothing beats a test drive. In this scenario, ensure that a knowledgeable factory or distributor representative is on site during the trial to answer questions, train and assist the test personnel. It would also be beneficial to have the operations and maintenance staff participate and provide input in the evaluation.

The next best alternative is to request a copy of the O&M manual. A thorough review of this document with the previously mentioned attributes in mind can provide helpful information. For example, it will likely contain the following:

A list of operational limits
Important installation requirements
Detailed start-up, running and shutdown procedures
Component maintenance requirements
Critical safety, environmental and hazard information

Sales and marketing material often omit much of this, but it can be found in technical documentation, usually provided after ordering machines. Feel free to request additional documentation, data and drawings. Sales personnel should be able to help with this and provide valuable contextual information.

Frequently Asked Questions

Q. Do I need online or offline Oil Dehydration Systems?

For continuous dehydration of lube and hydraulic fluids in systems with large reservoirs (500+ gallons), offline systems are the norm. Given the relatively high oil flow rates in the lubrication or hydraulic circuits of this size, it would be commercially infeasible to install inline/online vacuum oil purifiers. Therefore, these systems are almost always installed on continuously recirculating kidney loop pulling from the bottom half of the reservoir and returning the dehydrated oil to the upper part of the reservoir.

The oil purification system’s flow capacity should be proportional to the size of the oil reservoir. A rule of thumb is to size a dehydrator to circulate the oil volume at least 6-8 times per day. There are many variables, and it is best to consult with an expert about your specific application. However, the following table offers some guidance for systems like our XLP Series lube and hydraulic oil dehydration systems:

Q. What vacuum level and oil processing temperature should I consider?

It is important to determine which parameters are required to achieve the rated performance level at the Oil Purifier’s fully rated flow capacity. This is often where things get interesting. More heat and a deeper vacuum increase the likelihood of thermal oxidative stress in the operating oil, additive depletion, and severe foaming issues. These parameters also dramatically increase the energy demand of the dehydration system. Consider machines that only require moderate heat and vacuum. Shoot for a maximum required oil temperature of 145 deg. For less and a vacuum level of -18 to -22 inHg. Oil purifiers using vacuum mass transfer rather than flash distillation will meet these recommendations.

Q. What filtration performance is needed for my oil?

Consider the ISO Cleanliness Level recommended for your machinery’s lube and hydraulic fluid. At a minimum, we recommend filters rated at beta 1000 (99.9%) removal efficiency at 5 microns or better.

Q. Should I consider the oil viscosity when evaluating Vacuum Oil Dehydration Systems for lube and hydraulic Fluids?

A Lube and Hydraulic Oil Dehydration System will not be reliable if the oil viscosity exceeds its limitations. Verify that the oil viscosity will always remain within the machine’s operating limits.

Q. Are there any concerns with the placement of Oil Dehydration Systems with respect to the distance and elevation of the oil reservoir?

Yes. Verify the minimum and maximum suction head pressure. If your system will be installed above, below, or at a distance from the oil reservoir, you need to understand how that will affect the machine’s ability to operate reliably.

Q. Should Lube and Hydraulic Oil Dehydration Systems have a foam sensor?

Only if they are prone to generating foam. If a Vacuum Dehydration System offers a foam management system or windows for monitoring foam, BEWARE. This means the machine may need to operate with parameters that commonly result in significant oil foaming. If foaming is not properly mitigated, the dehydrator may not operate reliably at the rated capacity. You may be required to reduce the flow rate, thereby diminishing the processing capacity you pay good money for. Read the manual to get the full picture before making a decision.

Conclusion

As you can see, a Lube and Hydraulic Oil Dehydration System can benefit any industrial plant that relies on lubricated or hydraulically operated machinery. Fluid health is critical to machine health. Industrial data suggest that the health and reliability of the machinery used by a business correlate with productivity, profit, safety, and environmental metrics. Consider the impact that could be realized by making a wise investment in a Vacuum Oil Purification System. Then, use this guide to help you navigate the process of selecting the right system for your needs.

You can start your research now and consider companies like PowerFlow Fluid Systems. We offer decades of experience designing and building the best Oil Purification Systems. Visit our XLP Series product page and request a quote. https://www.pwrfs.com/product/lube-hydraulic-oil-purifiers/

PowerFlow Fluid Systems supports industrial sustainability with innovative, environmentally responsible solutions to optimize the performance of virtually all fluid systems throughout the plant.