Off-Line Hydraulic Filters & Oil Filtration | Hidroman
Off-Line Hydraulic Filters & Oil Filtration | Hidroman
Off-Line Hydraulic Filters and Hydraulic Oil Filtration Systems
Continuous Kidney-Loop Filtration for Hydraulic Systems
Hydraulic oil cleanliness is essential to the reliable operation of pumps, valves, hydraulic motors, cylinders, and other precision components. Solid particles and other contaminants can contribute to component wear, reduced performance, and unplanned equipment downtime.
Off-line hydraulic filters, also known as bypass or kidney-loop filtration systems, clean hydraulic oil through a separate filtration circuit rather than directly through the machine’s main hydraulic circuit. Depending on the system design, this arrangement can provide continuous or periodic oil filtration without relying on the main circuit’s operating flow.
Hidroman provides hydraulic filtration solutions for industrial applications, including the Seide RK90 off-line filter, NSFA Typ D side-stream filtration systems, and HK FAPC oil service equipment.
What Is an Off-Line Hydraulic Filter?
An off-line hydraulic filter is an auxiliary filtration system connected to a hydraulic reservoir or oil circuit. A dedicated pump circulates the oil through a filter element and returns the filtered oil to the reservoir.
Because the filtration loop operates separately from the main hydraulic circuit, it can help improve overall reservoir cleanliness while the machine is operating, provided the installation and operating conditions allow it.
Off-line filtration can complement existing suction, pressure, and return-line filters. It should be selected as part of a complete contamination-control strategy rather than treated as a universal replacement for the machine’s primary filters.
Why Use Off-Line Hydraulic Filtration?
1. Improve Hydraulic Oil Cleanliness
An appropriately selected filter element captures solid particles within its specified filtration performance range. This helps maintain the oil cleanliness required by the hydraulic system.
2. Help Protect Hydraulic Components
Contamination can contribute to wear and malfunction in hydraulic pumps, servo valves, proportional valves, control valves, motors, and other precision components. Effective filtration helps reduce contamination-related damage.
3. Support Preventive Maintenance
Controlling oil contamination can help reduce the risk of contamination-related failures and support more predictable maintenance planning. Actual results depend on the system design, contamination level, filter performance, and maintenance practices.
4. Retrofit Existing Equipment
Off-line filtration systems can often be added to existing machinery without redesigning the main hydraulic circuit, subject to suitable reservoir connections, electrical supply, installation space, and fluid compatibility.
5. Support Oil Condition Monitoring
Depending on the selected configuration, filtration equipment may be combined with particle monitoring, filter condition indicators, or oil condition sensors. These options can help maintenance teams monitor cleanliness and filtration performance.
Hidroman Off-Line Filtration Products
1. Seide RK90 Off-Line Filter
The Seide RK90 is an off-line filtration unit designed to clean hydraulic oil through an auxiliary circuit. It can be used to supplement the existing filtration arrangement and help improve oil cleanliness.
Technical information listed on the current Hidroman webpage:
Pump flow rate: 12 L/min
Motor power: 1.1 kW, 1,450 rpm
Number of filters: 1
Filter capacity: 400 L/min
Dirt-holding capacity: 90 g
Weight: 12 kg
Electrical supply: 380–400 V
Replacement filter element: SDM5060-05, 5 micron
Technical verification required: Some values listed on the current product page differ from those in the available RK90 brochure. Confirm the latest manufacturer documentation before using these figures for equipment selection, purchasing, or quotation purposes.
2. NSFA Typ D Side-Stream Filtration Systems
NSFA Typ D filtration systems are designed for side-stream filtration in hydraulic and lubrication applications. Their separate filtration circuit can operate independently of pressure and flow changes in the main system.
The Hidroman page lists the following fluid types:
Mineral oils
Synthetic oils
Turbine oils
Vegetable oils
Models and specifications listed on the Hidroman webpage:
| Model | Electrical supply | Motor power | Nominal flow rate | Listed system volume |
|---|---|---|---|---|
| NSFA Typ D 10/400V 055 | 400 V | 0.55 kW | 10 L/min | Up to 400 L |
| NSFA Typ D 60/400V 1.5 | 400 V | 1.5 kW | 60 L/min | Up to 2,000 L |
| NSFA Typ D 20/230V 1.5 | 230 V | 1.5 kW | 20 L/min | Up to 600 L |
| NSFA Typ D 20/400V 1.5 | 400 V | 1.5 kW | 20 L/min | Up to 600 L |
| NSFA Typ D 40/230V 1.5 | 230 V | 1.5 kW | 40 L/min | Up to 1,200 L |
| NSFA Typ D 40/400V 1.5 | 400 V | 1.5 kW | 40 L/min | Up to 1,200 L |
| NSFA Typ D 40/24V 035 | 24 V | 0.35 kW | 40 L/min | Up to 1,200 L |
Model designations and technical values should be confirmed against the latest manufacturer documentation before ordering. Other flow rates and motor configurations may be available upon request.
Listed accessory: FI ND E MA — low-pressure filter unit for MA.
3. HK FAPC Oil Service Unit
The HK FAPC oil service unit is designed for oil filling, filtration, and oil cleanliness monitoring in suitable hydraulic and lubrication applications.
Specifications listed on the Hidroman webpage:
Electrical supply: 230 V / 50 Hz
Motor power: 0.45 kW
Model: HK FAPC 016
Nominal flow rate: 16 L/min
Dirt-holding capacity: 280 g
Filter type: listed as 3E-Nß(c)=200; confirm the exact manufacturer designation
Maximum suction lift: 1.5 m
Maximum operating pressure listed: 4 bar
Suction hose length: listed as 1.8 / 2.0 m
The webpage also describes fine filtration, a filter condition indicator, cleanliness-class monitoring, data recording, and computer data transfer. Confirm that the required monitoring and data functions are included in the exact configuration being quoted.
For suitable applications requiring the removal of small amounts of water from hydraulic oil, an optional EXAPOR® Aqua water-absorbing filter element may be considered. Fluid compatibility and operating conditions should be checked before selection.
Listed accessories and replacement parts:
HK FAPC 1760 — equipment carrier
HK FAPC F — filter unit for HK FAPC 016
How to Select the Right Off-Line Filter
Choosing the correct off-line filtration system requires more than matching the nominal flow rate. The following application parameters should be evaluated together:
Fluid type: Confirm compatibility with mineral oil, synthetic oil, biodegradable hydraulic fluid, or the intended lubricant.
Reservoir volume: Oil volume and the desired cleanliness improvement influence the required filtration flow rate and operating time.
Oil viscosity and temperature: Check the operating limits of the pump, filter housing, and filter element.
Target cleanliness level: Consider the required ISO 4406 cleanliness code and the sensitivity of the system’s components.
Particle and water contamination: Particle removal and water removal are different filtration requirements. A suitable water-absorbing or water-separation technology may be needed.
Electrical and installation requirements: Verify supply voltage, motor power, connections, available space, and environmental conditions.
Monitoring requirements: Consider particle counters, filter condition indicators, and oil condition sensors where appropriate.
The required filtration rate and operating time depend on the initial contamination level, the desired cleanliness target, and the performance of the selected equipment. A single filter rating or operating schedule is not suitable for every application.
Off-Line Filtration vs. In-Line Filtration
In-line filters are installed directly in the main hydraulic circuit, where they protect components at specific points in the system. Off-line filters clean oil through a separate auxiliary loop, typically connected to the reservoir.
The two methods perform complementary functions. An off-line filter can help maintain reservoir cleanliness while in-line filters continue providing the protection required by the machine’s hydraulic design.
Applications for Off-Line Hydraulic Filtration
Depending on the selected filter and fluid compatibility, off-line filtration may be considered for:
Industrial hydraulic power units
Hydraulic presses and production machinery
Steel processing equipment
Mining and heavy-duty equipment
Hydraulic and lubrication systems
Industrial machinery requiring controlled oil cleanliness
Existing machines requiring an additional filtration stage
Final suitability depends on the fluid, viscosity, operating temperature, flow requirements, contamination type, and the specifications of the selected filtration unit.
Frequently Asked Questions
What is an off-line hydraulic filter?
An off-line hydraulic filter is an auxiliary filtration system that circulates oil through a separate filter loop instead of relying on the machine’s main hydraulic circuit.
What is kidney-loop filtration?
Kidney-loop filtration is another term for off-line or bypass filtration. Oil is drawn from a reservoir, passed through a dedicated filtration system, and returned to the reservoir.
Can an off-line filter operate while the machine is running?
In many applications, yes. Because the filtration loop is independent of the main circuit, oil cleaning can continue while the machine operates, provided the installation and operating conditions permit it.
Can an off-line filter replace the main hydraulic filter?
Not automatically. Off-line filtration is generally used to complement the primary filtration system. The machine’s original filtration requirements must still be met.
Can off-line filtration remove water from hydraulic oil?
Standard particulate filter elements primarily target solid contamination. Water removal requires a suitable water-separation or water-absorbing technology selected for the fluid and contamination conditions.
How do I select the correct filter rating?
The required filtration rating depends on the target ISO 4406 cleanliness level, component sensitivity, fluid viscosity, and filter performance characteristics.
Can an off-line filter be installed on existing equipment?
In many cases, yes. The installation must be evaluated for reservoir access, connections, electrical supply, available space, and fluid compatibility.
How can I request an off-line filtration solution from Hidroman?
Provide the fluid type, reservoir volume, current contamination condition, required flow rate, electrical supply, and target cleanliness level. Hidroman can use these application details to help evaluate a suitable filtration configuration.
Improve Hydraulic Oil Cleanliness with Hidroman
Clean hydraulic oil is an important part of reliable equipment operation and preventive maintenance. A properly selected off-line filtration system can help control contamination, protect hydraulic components, and support a more effective maintenance strategy.
Contact Hidroman to discuss off-line hydraulic filters, side-stream filtration systems, and oil service equipment for your application.