Hydraulic Filter Elements

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Find your filter…easy.

Sona Filtration offers high-quality replacements for many of today’s major brands of hydraulic filter elements.  Our filters are engineered from state-of-the-art components and filtration media and offer an economical solution.  SONA makes it easy to eliminate downtime by offering thousands of filters for fast shipment from inventory. 

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Why good filtration is required


There is a consensus that 70% to 90% of equipment wear and failure is attributed to contamination. In other words, solid particles, such as dirt, are the chief culprits because of their ability to directly attack metal surfaces. Selection of a high-quality filter is a cost-effective way of reducing this contamination. All hydraulic fluids contain dirt to some degree. Dirt in hydraulic fluid is the downfall of even the best designed hydraulic systems. As a result, contamination particles can bring huge and expensive machinery to a stop.

Dirt vs Hydraulic Fluid

Contamination causes trouble in a hydraulic system because it interferes with the fluid which has four functions:
1. To act as a medium for energy transmission
2. To lubricate internal moving parts of hydraulic components
3. To act as a heat transfer medium
4. To seal clearances between close-fitting moving parts

Dirt interferes with the transmission of energy by plugging small orifices in hydraulic components like pressure valves and flow control valves. In this condition, pressure has a difficult time passing to the other side of the spool. The valve’s action is not only unpredictable but unsafe.
Because of viscosity, friction, and changing direction, hydraulic fluid generates heat during system operation. When the fluid returns to the reservoir, it gives the heat up to the reservoir walls. Dirt particles interfere with liquid cooling by forming a sludge which makes heat transfer to reservoir walls difficult.

Clean hydraulic systems run cooler than dirty systems. Probably the greatest problem with dirt in a hydraulic system is that it interferes with lubrication.

Dirt can be divided into three sizes with respect to a particular component’s clearances; that is, dirt which is smaller than a clearance, dirt which is the same size, and dirt which is larger than a clearance.

Extremely fine dirt, which is smaller than a component’s clearances, can collect in clearances especially if there are excessive amounts and the valve is not operated frequently. This blocks or obstructs lubricative flow through the passage. An accumulation of extremely fine dirt particles in a hydraulic system is known as silting.

Dirt which is about the same size as a clearance rubs against moving parts breaking down a fluid’s lubricative film. Large dirt can also interfere with lubrication by collecting at the entrance and blocking fluid flow between moving parts.

A lack of lubrication causes excessive wear, slow response, erratic operation, solenoid burn out, and early component failure.

Dirt is Pollution

Dirt in a hydraulic system is pollution. It is very similar to bottles, cans, paper and old tires floating in your favorite river or stream. The difference is that hydraulic system pollution is measured using a very small scale. The micrometer scale is used to measure dirt in hydraulic systems.

Sources of Contamination

When engineering a complex hydraulic system, designers must consider the ways in which contaminants reach the fluid, as well as the quantity and size of the particles. Those factors influence the size, micron rating, and location of filters.

Built-In or from Maintenance

During manufacturing or maintenance, large quantities of particles and solid debris are introduced. Even the most thorough flushing doesn’t eliminate all foreign matter, some of which dislodges once the system is put into operation. Also, there is no guarantee that all of the right procedures will be followed, so, as equipment can sustain significant wear in the first few days after start-up, high-quality filtration is essential at this stage.

Tank Leakage

Loose inspection plates and other unsealed joints in a tank allow a great deal of dirt into the fluid, particularly when surrounding air is polluted.

Air through Breather

Most hydraulic systems draw in and expel air as the oil level in the reservoir changes. Often, this is the main source of dirt ingestion, especially when filter breathers either are not installed or maintained.

Dirty Oil

New oil is seldom as clean as required for a modern hydraulic system, even when it is described as “clean” by the supplier. When stored improperly or not well filtered before filling the reservoir, it likely will be many times as contaminated as the system can tolerate.

Pump Wear

Pumps, especially when worn, are a key source of metal wear particles. Hard wear metals are of great concern for several reasons:
1. Potential for damage to valves, cylinders, and motors immediately downstream.
2. Ability to generate large numbers of additional particles within the system.
3. Action as a catalyst in the fluid oxidation process.

Piping Slag

Older pipes can flake off quantities of larger particles, such as scale, rust and welding slag.

Dirt On Cylinder Rods

When sliding back and forth, cylinder rods can draw in large quantities of smaller particles, depending on the concentration of airborne dirt and quality of the rod seals. This is a particular problem in systems with numerous large cylinders.