FRIESS electrostatic oil cleaners provide deep purification for non-conductive oils such as hydraulic and lubricating oil. They remove fine particles, sludge, resin and oxidation products and are suitable for injection-moulding machines, hydraulic power units, steelmaking equipment, hydropower stations and industrial hydraulic systems.
Electrostatic deep-cleaning technology
Designed for industrial oils with water content below 500 ppm, the DSD uses electrostatic deep cleaning to remove fine particles, sludge and oxidation products, helping extend oil and equipment life.
Designed for industrial oils with water content below 500 ppm, the DSD uses electrostatic deep cleaning to remove fine particles, sludge and oxidation products, helping extend oil and equipment life.
Hydraulic Oil Purification for Hydropower Stations
Governors, gate actuators and auxiliary hydraulic systems in hydropower stations operate continuously for long periods. Fine particles, sludge and oxidation products in the oil impair valve response and accelerate wear on pumps and seals.
FRIESS electrostatic oil cleaners are available in different sizes to match tank volume and contamination load. Continuous offline purification does not interrupt normal equipment operation.
Typical applications: Governor systems, gate actuators, lubrication systems and large hydraulic power units
Hydraulic Oil Purification for Injection-Moulding Machines
Injection-moulding machines operate at high temperatures with continuous circulation and frequent directional changes. Hydraulic oil can develop oxidation products, sludge and extremely fine wear particles that impair the stability of proportional valves, servo valves and hydraulic pumps.
FRIESS electrostatic oil cleaners capture fine particles and soft contaminants that conventional filter elements often cannot retain, helping to extend the service life of both the oil and precision hydraulic components.
Typical applications: Injection-moulding machines, die-casting machines and other high-precision industrial hydraulic equipment
Contaminant particles catalyse oil oxidation and promote varnish, deposits and sludge, causing valves to stick and respond slowly.
High-speed oil flow carries particles into valve edges and nozzles, gradually cutting grooves that reduce control accuracy and increase internal leakage.
Particles entering lubrication clearances break down the oil film, damage pumps, valves and moving surfaces, and generate additional wear particles.
Fine particles in hydraulic systems cause wear and erosion and also accelerate oil oxidation. Continuously removing particles, sludge, varnish and deposits helps reduce failures and extend the service life of the oil and precision components.
Typical lubricating-film thickness
Long-term oil-service example
Potential reduction in failures
Particles of every size, from coarse to extremely fine, accelerate wear on pumps, valves, pistons and seals, ultimately increasing maintenance and downtime costs.
Continuously removing extremely fine particles, sludge and soft contaminants slows oil ageing and extends the life of both the oil and precision components.
As long as the oil remains chemically within specification, maintaining cleanliness reduces complete oil changes, waste-oil disposal and the associated labour.
Key distinction: Built-in filters mainly control hard particles above a certain size; deep purification also removes ultrafine particles and soft deposits that accelerate oxidation.
Pump flow decreases
Internal valve leakage increases
Control accuracy gradually declines
The lubricating film between moving components can be only 1–4 µm thick. When contaminant particles enter the clearance, they disrupt the film, damage surfaces and create new wear particles, forming a cycle of contamination, wear and further contamination.
Valve metering edges
Nozzles and throttle points
High-velocity flow-direction changes
As hydraulic oil flows through the system at high velocity and pressure, particles strike valve edges, nozzles and other components with considerable energy, eroding surfaces and generating new contaminants. Continuous impact leaves grooves and wear marks.
Above 60 °C
For every approximately 10 °C increase
The oxidation rate roughly doubles
Deposits and varnish are typical products of oil ageing. Particles and contaminants catalyse oxidation; the more contaminated the oil, the faster it normally ages.
Oxidation products reduce lubricating performance and thicken the oil, increasing flow resistance and energy consumption. Deposits can also form adhesive layers in clearances and on surfaces, causing valves to stick, respond slowly and lose control accuracy.
Hydraulic-component manufacturers specify the oil-cleanliness level required for safe operation. Precision components such as proportional and servo valves are particularly sensitive to particle contamination.
Requirements vary by component, so the recommended cleanliness class is both a system-acceptance criterion and an important basis for selecting purification equipment.
Meeting the specified oil cleanliness is essential for technical reliability and may also affect the equipment warranty. Some manufacturers may reject warranty claims if the hydraulic oil does not meet their cleanliness requirements.
Select oil-purification equipment capable of continuously maintaining the target cleanliness class and verify performance through regular oil analysis.
More information: hydraulic-oil analysis and cleanliness-class assessment.
Follow the maintenance intervals and requirements specified by the manufacturer
Have trained personnel perform and document maintenance
Check oil condition regularly through oil analysis
Replace hydraulic oil only when its chemical condition is out of specification
Prevent water ingress and dewater the oil when necessary
Keep seals and hoses intact and replace damaged parts promptly
Keep the working environment clean to reduce contaminant ingress
Do not allow the oil level to fall below the specified minimum
Store hydraulic oil in clean, sealed and suitable containers
Use clean equipment and filter new oil during filling and top-up
Inspect the filtration system and oil cleanliness regularly
Filtration methods can be classified by installation position or by filter medium and operating principle. Each performs a different task, and industrial hydraulic systems normally use a combination.
Prevents larger particles from entering the hydraulic pump; resistance must remain low to avoid insufficient suction or cavitation.
Filters the oil before it reaches sensitive components; the housing and element must withstand system pressure.
Filters return oil before it enters the tank, preventing operating contaminants from being carried back into the reservoir.
Uses a thick, porous medium to capture particles; soft contaminants can rapidly cause blockage.
Retains solid contaminants with a fine screen; filtration accuracy is mainly determined by mesh size.
Purifies continuously at a stable low flow, independent of main-system flow fluctuations, and can be serviced without stopping production.
Electrostatic Purification Principle
A high-voltage electrostatic field is created between two electrodes. It acts on charged contaminant particles in the oil, deflecting them toward the collector media. Because EFR uses a different operating principle, it can remove ultrafine particles that conventional filter media struggle to retain.
Limitations of Conventional Filter Media
Ultrafine particles can pass through conventional media, while soft contaminants such as sludge, resin and varnish can rapidly block the filter element.
How EFR Is Different
EFR continuously removes oxidation-promoting ultrafine particles and existing soft deposits, slowing oil ageing and helping restore oil performance.
01Capture Ultrafine Particles
Removes particles finer than conventional depth filters can reliably retain.
02Remove Soft Contaminants
Continuously removes sludge, resin, varnish and other oxidation deposits.
03Continuous Offline Operation
Easy to connect, monitor and maintain without interrupting the main hydraulic system.
04Low Consumable Use and Long Service Intervals
High-capacity collector media reduce consumable use and extend maintenance intervals.
The large electrostatic purification chamber provides high contaminant capacity and opens easily. Maintenance personnel can replace the collector media quickly and directly assess captured contamination by comparing the media before and after use.
Hydraulic oil consumes energy and generates carbon emissions throughout raw-material extraction, production, transport and waste-oil disposal. Reducing oil changes lowers purchasing, transport and disposal burdens at the same time.
OPTION 01
Suitable for clearly defined applications requiring a permanently installed purification system.
OPTION 02
Verify performance in your own system first; when purchasing, up to two months of rental fees can be credited against the equipment price.
OPTION 03
Suitable for projects that prefer staged investment and lower initial capital expenditure.
During a trial, we can assist with connection, operation and performance assessment. Detailed conditions are agreed for each project.
FRIESS products are made in Germany and have operated reliably in numerous industrial applications for many years. We combine oil type, system volume and contamination load to provide durable, dependable and easy-to-maintain purification solutions.
When selecting hydraulic-oil purification equipment, assess purification performance, system compatibility and life-cycle cost—not only the initial purchase price.
01
Review the existing suction, pressure and return-line filtration and determine whether offline deep purification is required.
02
Select the equipment size according to tank volume, system flow and contamination load.
03
Use the cleanliness requirement of the most sensitive component as the purification target.
04
Consider both hard particles and soft contaminants such as sludge, resin and varnish.
05
Evaluate offline connections, installation space, consumables, maintenance intervals and whether shutdown is permitted.
Clear, fast maintenance procedures help reduce labour and downtime costs. The FRIESS EFR display indicates operating time and maintenance intervals for timely contamination checks. Collector media and electrodes are readily accessible, and the hydraulic system can remain in operation during servicing. High contaminant capacity allows a typical inspection interval of about 2,000 operating hours; the actual interval depends on the contamination load.
The optimum filtration solution depends on the specific system. Most hydraulic systems combine several filtration methods to achieve the target cleanliness. Follow the oil and equipment manufacturers’ requirements when selecting equipment and setting maintenance intervals.
Conventional filters can control hard particles above a certain size but often cannot remove the ultrafine particles that accelerate oil ageing or soft contaminants such as varnish and resin. This is the principal application advantage of FRIESS EFR electrostatic oil purification.
When viscosity, acid number, additive condition and other chemical parameters remain within specification, continued use after purification is usually more economical and reduces resource consumption and waste-oil disposal.
A substantial share of hydraulic-system damage is related to oil contamination. Keeping the oil continuously clean reduces component wear and failures, lowering spare-parts replacement, top-up oil and maintenance labour costs.
Continuous oil purification with FRIESS EFR, combined with proper maintenance, can significantly reduce the total operating cost of a hydraulic system.
As long as the hydraulic oil remains chemically within specification, continuous contaminant removal allows extended use with only leakage losses topped up. This postpones complete oil changes and new-oil purchases.
Clean oil also reduces damage to valves, pumps and other components and lowers the risk of unplanned downtime. Oil changes, repairs and downtime often represent a major share of hydraulic-system operating cost; reducing these expenses improves both equipment availability and overall economy.
Varnish, resin and other oxidation products are typical signs of oil ageing caused by reactions between the oil and oxygen in the air. Particles and contaminants catalyse oxidation, so heavier contamination accelerates oil ageing.
Oil temperature also has a strong influence on oxidation. Below 60 °C the reaction is relatively slow; above 60 °C, every increase of about 10 °C roughly doubles the oxidation rate. Prolonged excessive oil temperature should therefore be avoided.
Conventional depth filters retain particles in the pores of the filter media. Ultrafine particles can pass through under pressure, while sticky varnish and resin deposits can rapidly block the element. EFR captures these contaminants with an electrostatic field rather than tiny pores, enabling continuous offline removal of ultrafine particles and soft oxidation deposits.
FRIESS EFR is not directly limited by conventional filter-media pore size. The electrostatic field acts on charged particles of different sizes, removing ultrafine particles that conventional filters struggle to retain. It also captures soft oxidation deposits such as sludge, resin and varnish.
Although offline purification uses a relatively low flow rate, the unit can operate continuously and ultimately achieve a very high oil-cleanliness level—often cleaner than untreated new oil.
The payback period of FRIESS EFR depends on:
For systems with a large oil volume and high oil-change cost, avoiding one complete oil change may allow the equipment to pay for itself within two to three months. Many projects achieve payback in about one year, depending on savings in oil purchasing, waste-oil disposal, spare parts and downtime.
When contamination reaches a certain level, the oil must either be replaced or purified. Complete oil changes are expensive in large systems; as long as viscosity, acid number, additive condition and other chemical parameters remain within specification, continued use after purification is usually more economical and reduces resource consumption and waste-oil disposal.
If the oil has undergone irreversible chemical degradation or contamination is too severe for economical recovery, replace it in accordance with the oil and equipment manufacturers’ requirements.
The time required to reach the target cleanliness depends on system oil volume, initial contamination, contaminant type and existing filtration. Dirtier systems and oils require a longer initial purification period; after the target is reached, the treatment load and time needed to maintain cleanliness decrease substantially.
Because every system operates under different conditions, no universal time can be given without data. We can provide a more accurate estimate based on oil analysis, tank volume and operating conditions.
Beyond cost savings, using FRIESS oil skimmers、electrostatic oil cleaners、magnetic filters、coolant purification systems、oil-water separators、vacuum oil purifiersoffers many other advantages.
We will be pleased to explain which solution best fits your application.
