Liquid filters

What Are Fluid Filters?

Fluid filters are used to remove dirt particles, water, abrasion debris, and other contaminants from process fluids. Depending on the application, different filter media, filter finenesses, and designs are used.

Fluid filters are used, among other places, in hydraulic systems, lubricating oil circuits, cooling systems, the food industry, and general mechanical engineering.

How does a fluid filter work?

The contaminated fluid is routed through the inlet port to the filter element, where it is cleaned and then returned to the machine via the clean fluid outlet. During filtration, contaminants are reliably separated depending on the filter fineness and the specific filter media.

What is the purpose of a fluid filter in a system?

A fluid filter protects systems and machines from contaminants. It removes particles and foreign substances, minimizes wear, and reduces the risk of failure. Filtration improves fluid purity, increases operational reliability, and extends the service life of the system. Fluid filters are essential for the efficiency and reliability of industrial systems.

A fluid filter protects systems, machines, and individual components from contaminants. By separating out particles and foreign substances, wear protection and operational safety are improved.

What types of fluid filters are available?

ELSÄSSER Filtertechnik GmbH offers high-quality fluid filters—such as oil filters, fuel filters, and hydraulic filters—for high-performance engines, equipment, and machines across a wide range of applications. Our product range is rounded out by accessories tailored to each application, such as filter heads for in-line installation, as well as visual or electrical maintenance indicators and switches. Please refer to the following overview to determine which fluid filters are best suited to your requirements.

Oil Change Filters

Oil change filters (spin-on = screw-on elements) ensure that the lubricating oil remains free of contaminants, such as soot or cracking byproducts, thereby preventing damage. Fluid typically flows through them from the outside to the inside. The filtered lubricating oil exits through the central bore. Depending on the requirements, these spin-on filters are equipped with, for example, bypass valves, check valves, etc.

Oil filter elements

Oil filter elements are used, among other things, in main- and bypass-stream filtration. In gasoline and diesel engines, these oil filter elements are typically installed in oil filter modules that are permanently integrated into the engine. Metal-free elements round out the product portfolio. These metal-free elements can be disposed of in an environmentally friendly manner.

Fuel change filters

Fuel change filters are similar to oil change filters. However, they are primarily used in fuel filtration. Fuel filters are designed to filter out contaminants and water from the fuel. This separated water collects in the water collection chamber in the filter sump or, depending on the design, can also be drained via a water drain plug. Through its function, the fuel filter makes an important contribution to the operational safety of every engine.

Fuel Filter Elements

These filter elements are primarily used in fuel fine filtration. They are typically installed in their own housings, which are integrated into the engine.

In-line Filters

In-line filters for fine filtration are used, among other applications, in hydraulic systems within lubricating oil circuits in general mechanical engineering. They consist of a filter head with a connection nipple for attaching oil change filters. Optionally, these in-line filters can be equipped with maintenance indicators or maintenance switches to signal when filter maintenance is required. In addition, in-line filters with fuel change filters are also available.

Slot filters

Slot filters are particularly suitable for filtering heavily contaminated fluids such as lubricating oil, paints, polyol, isocyanate, and cooling lubricants. A split filter can be cleaned during operation by turning a handle. In this process, the contaminants are scraped off by a stationary scraper and sink into the sludge collection chamber at the bottom of the filter. From there, the contaminants can be discharged via a ball valve. Of course, versions with optional gear motors are also available.

Centrifuges

Centrifuges are capable of separating the finest soot particles from the bypass stream. They are used, among other things, as an alternative to bypass filters. The centrifuges are driven solely by oil pressure, without any external power source. They are driven to speeds of up to 10,000 rpm via free-jet nozzles. Due to the high centrifugal forces, centrifuges achieve a very high separation efficiency. After passing through the separator, the purified oil flows back into the oil sump without pressure.

Finding the Right Fluid Filter

The selection of the right fluid filter depends on several factors. In addition to the specific fluid, flow rate, operating pressure, viscosity, filter fineness, and service life play an important role. Only a properly sized filter ensures reliable filtration and high operational safety of the system.

What parameters are required for designing a fluid filter?

The following parameters are required for designing fluid filters:

• Flow rate
• Operating pressure
• Operating temperature / ambient temperature
• Type of contaminant to be removed
• Amount of contaminant
• Viscosity
• Required service life

How does flow velocity affect filter efficiency?

The flow velocity significantly influences filter performance. If the flow rates are too high, the load on the filter medium increases and the available contact time between the fluid and the filter decreases. Only a needs-based design of flow rate and filter area improves filtration and supports a long service life of the filter element.

What is a normal differential pressure for fluid filters?

The permissible differential pressure depends on the design, filter medium, and application. As the filter becomes increasingly clogged, the pressure drop across the filter element increases. An elevated differential pressure indicates that a filter change or cleaning is necessary. For this reason, many in-line filters are equipped with maintenance indicators or maintenance switches.

Where are fluid filters used?

Fluid filters are used in hydraulic systems, in lubricating oil circuits in general mechanical engineering, and for engine and transmission oil filtration. Other applications for fluid filters include process water in the food industry, as well as in refrigeration systems and on ships. Fluid filters can be found in a wide variety of industries.

Which fluids can be filtered?

Virtually all fluids can be filtered. This depends on the viscosity. These include, among others, hydraulic oil, lubricating oil, fuels, coolants, process water, paints, and other process fluids. For optimal design, the respective operating parameters must be taken into account.

Maintenance and Operation of Liquid Filters

Regular maintenance of liquid filters contributes significantly to process reliability and the service life of machines and systems. Maintenance intervals for filter cleaning and filter replacement should be tailored to the specific application and the corresponding level of contamination.

How do you clean an industrial liquid filter?

Cleaning an industrial liquid filter depends on the specific filter design. While many filter elements are replaced, certain slot filters are mechanically cleaned during operation. In this process, accumulated contaminants are removed and discharged through the sludge collection chamber.

What maintenance intervals apply to liquid filters?

There are no fixed maintenance intervals for liquid filters. They depend on factors such as flow rate, degree of contamination, operating conditions, and service life requirements, and are specified by the machine or vehicle manufacturer. Maintenance indicators and maintenance switches help determine the optimal time for maintenance work.

What are the maintenance costs for different filter types?

Maintenance costs are influenced by the filter design, the filter medium, operating conditions, and the required maintenance intervals. Cleanable systems, such as slotted filters, may incur different maintenance costs than filter types with filter elements that must be replaced regularly.

What are common problems with fluid filters?

Problems with liquid filters often arise from unsuitable operating conditions, incorrect filter design, or inadequate maintenance. Contaminants, changes in pressure conditions, or high particle loads can impair the performance of liquid filtration. To ensure the long-term reliability of filter systems, it is important to inspect the filters regularly and adapt them to the specific operating conditions.

Can bacteria colonize saturated filters?

Bacteria can colonize saturated filters in certain applications. Especially in media containing water or process water, microorganisms can settle on contaminated or long-used filter media. Therefore, regular maintenance, filter replacement, and adherence to the recommended operating conditions are important.

How can I tell if my engine oil already contains water?

Possible signs of water in engine oil include a milky discoloration, corrosion, and/or changes in lubricity.

Where can I buy fluid filters?

At ELSÄSSER Filtertechnik, you’ll find a wide selection of fluid filters, line filters, and compatible fluid filter accessories for a wide variety of applications. Using the filter part number, you can quickly identify the right filter or a suitable alternative.

Do you still have questions?

Our team of experts offers detailed advice to help you select the right air filter.

Contact us by phone at 07032 / 96 04-0 or via our contact form.