What micron filter is best for hydraulic systems?

There's no one "best" micron rating for each hydraulic system. The ideal filter will depend on the pressure of your machine, sensitiveness of its components, and the desired ISO cleaning code. For most industrial hydraulic systems, the 10-micron (b10 greater than 200) filter provides a secure balance between flow and contamination control performance. High-pressure systems that use proportional valves and servo valves typically require between 3 and 5 microns. Low-pressure mobile devices can usually operate safely on 20 to 25 microns. Microns. The objective is always to ensure that filtration is compatible with the most sensitive part of your system and not pick an individual number.

Why does the micron rating alone not provide the complete picture?

Many people think of micron ratings as a straightforward measurement to search for the performance of filtration; however, it is actually about two numbers that work together: the micron rating and the ratio of beta. A filter that is rated at 10 microns but with an unsatisfactory beta ratio could allow large amounts of contamination to be filtered through, but an item with a higher beta ratio of similar microns will catch particles more frequently.

Beta ratio (b) is a measure of the efficiency of filtration at a certain size of particle. A B10 = 75 filter catches 98.7 percent of particles when they are 10 microns. A 200-b10 filter can capture 99.5 percent of particles with similar sizes. For systems that have tight tolerances such as servo valves, piston pumps, proportional valves The difference in size matters greatly, since a slight increase in the number of particles at the size of the critical one can increase wear significantly.

Filtering the component's sensitivity to match

Every hydraulic system has a "weakest "link"—the component most vulnerable to contamination-induced wear. Filtration must be designed to ensure the safety of that component rather than the system's average.

The proportional valve and the servo (3-5 Microns)

These components have very tight clearances, often just 5 microns. Any particle that is even a fraction of the clearance gap may cause sticking, erosion, or hysteresis problems. Systems with proportional or servo valves usually require filtration within the 3 to 5 micron range in absolute and are often coupled with a goal ISO clean code 16/14/11, or cleaner.

Motors and Piston pumps (5-10 microns)

Radial and axial piston pumps feature close-tolerance moving parts that are prone to contamination of silt size. A 5-10 micron filter is advised, using beta ratios as high as greater than 200 being recommended for applications that require a high degree of precision.

Vane pumps (10-15 microns)

Vane pumps are moderately prone to contamination, specifically near the vane's tip and the cam ring interface. A 10 to 15 micron rating is generally enough for these pumps.

Mobile equipment and pumps for gears (15-25 microns)

Gear pumps have greater inner clearances, and they are also more resistant to the effects of contamination. Excavators, mobile hydraulic machines, loaders, and agricultural machines typically employ 15 to 25 microns of filtration while balancing the need for protection against the need for a longer-life filter in field conditions that are dusty.

Understanding ISO cleanliness codes

Microns are just one aspect of the equation. It is important to know that the ISO 4406 cleanliness code tells you the amount of particles within your fluid in three sizes generally greater than 4 microns. It can also be greater than 6 microns and >14 microns in three numbers, such as 18/16/13.

Lower numbers indicate cleaner fluid. A single drop in value on an ISO scale is roughly 50% of the particles' count for that size. So even the smallest improvements in cleanliness code can lead to significant reductions in contamination.

The codes for target cleanliness differ based on the component:

• Servo valves: 16/14/11, or cleaner
• Proportional valves 17/15/12
• Piston pumps/motors: 18/16/13
• Vane pumps: 19/17/14
• Gear pumps 20/18/15

The choice of a micron rating must always be based on the ISO target of the component that is most sensitive rather than in a direction that is based on a general industry standard.

Absolutely against. Micron nominal ratings

This difference causes more confusion than every other topic of filtration.

The nominal rating is an approximate non-standard measure that indicates that the filter is able to capture a certain percent of particles with this size; however, the precise efficiency differs by manufacturer and testing method. For example, a "10-micron nominal" filter from one brand could perform differently than a filter from another company's nominal rating.

Absolute rating, on the other hand, is compared to ISO 16889 (the multi-pass test) and provides a precise beta ratio for a particular micron size. Absolute ratings are much more reliable for applications that require precision since they are based on standard tests that are repeatable.

If you are requesting filters for systems that are sensitive, make sure to request that you know the micron count as well as the beta ratio instead of using only nominal figures.

Which place should filtration be located within the circuit?

The micron rating decision also depends on the position of the filter within the hydraulic circuit

• Suction filters are usually smaller (74-149 millimeters) to shield the pump from debris of large size without limiting flow or creating cavitation.
• Pressure line filters provide the main defense of downstream components and are typically in the area where the critical micron rating between 3 and 10 microns -- is utilized.
• Return line filters filter out contaminants that are generated within the system, usually rated 10 to 25 microns, prior to the time that fluid is allowed to return to the reservoir.
• Off-line (kidney-loop) filtering systems operate continuously and independently of the main circuit, typically using extremely fine elements (1-5 millimeters) to gradually improve overall cleanliness of the fluid while avoiding pressure drops to the primary circuit.

A well-designed system does not rely on just one filter location. Combining return and pressure line filtration, often augmented by off-line filtration, provides greater consistency in the control of contamination than a single filter on its own.

Common errors when choosing micron ratings

Over-filtering, without taking care of pressure drop. Filters that are extremely fine cause resistance to flow, which could cause differential pressure to rise, which can cause heat and decrease the lifespan of filters in the event that the pump or housing isn't designed to support it.

Insufficient filtering can prolong service intervals. The choice of a more coarse filter to decrease maintenance frequency usually puts the cost elsewhere; the wear of components is increased as well as more frequent valve or pump replacement as well as unplanned downtime, which can cost more than routine filter changes.

Ignoring beta ratio. Two filters that have the same micron count may have drastically different performance when their beta ratios are different.

The failure to account for submicron and varnish contamination. Fine particulate isn't the sole danger—oxidation of varnish and its precursors may cause deterioration to valve performance even if ISO cleanliness standards are acceptable.

For all industrial hydraulic systems, which do not include proportional valves or servos A 10-micron absolute (b10 > 200) filter is a good broad-based starting base. High-precision components in systems should be able to move up to 3-5 microns, and mobile systems that are rugged typically operate within 15-25 microns. The most reliable method is to pinpoint the component that is most sensitive to your system and determine its ISO cleanliness code, and then choose filtration options—such as beta ratio and placement—to ensure that you reach that level.

Which micron filter is ideal for an industrial hydraulics system?

A 10-micron absolute filter that has an alpha ratio of b10 > 200 is a good system that uses piston pumps or vane pumps that do not have servo-valves.

Is a smaller micron count always superior?

Not necessarily. Over-filtering can raise the pressure drop and shorten filter life without offering proportional benefits if the system's parts don't need that degree of cleanliness.

What is the difference between absolute and nominal micron ratings?

Nominal ratings are merely estimates and can vary based on the manufacturer; however, absolute ratings are measured according to ISO 16889 standards and specify the exact beta ratio for a specific particle size.

What do ISO cleanliness codes refer to micron ratings?

The micron rating is the measurement of what size particles are removed by a filter. In addition, ISO cleanliness codes determine the quantity of particles left in the fluid. Both combine to create a system of contamination control.

Do suction and pressure and return filters have various microns?

Yes. Suction filters tend to be larger to protect the pump Pressure filters are rated with the highest rating to safeguard downstream components, while return filters have moderate levels to catch any contamination before it enters the reservoir.