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Fluid Cleanliness

author:KETA Date:at 10:20 on October 10,2019

Keta Hydraulics recommends that customers use mineral oil-based fluid, and pay great attention to the control of fluid cleanliness. 

A large number of theoretical and experimental studies have been conducted on the statistical theory of fluid cleanliness at home 

and abroad, especially the failure theory proposed by Pall Company. Most system failures happen at the time of installation and test

run, and also the time when important parts wear out after a period of system operation. Thisstatistical formation is known as the

 "bathtub curve".


Precautions during installation:

Make sure all mounting surfaces are clean and free of contamination.

Ensure that all seals and backup rings of mounting surfaces are free of defects and properly placed.

Do not use any extra sealing material other than standard seals.

When installing the cartridge valve, make sure the cavity is clean and free of sharp edges or burs. Dip the valves in clean fluid,

insert it into the cavity and screw it in with your hand until O-ring at the top begins to get compressed.

Finally, use a calibrated torque wrench to tighten the valve with the torque shown in the catalog.

Precautions to avoid initial failure:

Before installation, hydraulic fluid should be screened and parts should be cleaned to meet standard of ISO 4406. Many OEM

equipment manufacturers have established cleanliness standards for their equipments and have proven to be effective in 

avoiding failures during installation and test run.

If possible, the newly installed system should be cleaned by bypass filter, and the actual filtration accuracy is one-third of the 

nominal requirements of the system. Filtration in the environment of the workshop can do no good, because the surrounding 

air contains a large number of impurities.
A high-pressure, bypass free, high-accuracy filter with a condition indicator should be used to minimize contamination on the 

inlet side of the valve.

O-rings should be used for sealing, not conical threads (conical pipe threads) or thread sealants. Lubricate connectors with 

clean system oil, do not apply grease.

Remove all air and moisture from the system, and parts that are difficult to prepare in advance (such as intake lines and cylinder

valve assemblies) should be arranged below the fluid.

Protect small orifice with a filter or other method to avoid the vibration that often occurs when the system gets started.Precautions 

for proper maintenance:

Each main maintenance should be treated as the new installation test run described above.

Continue to use high pressure, bypass free, high-accuracy filters with condition indicators The return oil filter cleans up contaminants

 introduced in the circuit through the piping and brake, and shall have an oil removal ratio of ß≥200, which is a typically low- cost

cleaning method with more effective filtration capability.

Regularly monitor the fluid cleanliness, and status of water and air intake. Studies have shown that up to 20% of component failures 

in hydraulic systems are due to corrosion caused by existence of water and air.

A typical 210bar (3000psi) cartridge valve design has a perimeter clearance of 4-10μm, and particle wear is mainly caused by 

particles of this size. According to Pall, 50% of component failures are due to exponential "dynamic wear" of particles in this size 


Periodically check the actuator seal, the air filter on the tank and any other inlet and outlet in the system.

Minimum fluid cleanliness requirements and recommended fluid cleanliness requirements for longer service life The performance 

and service life of the hydraulic system are closely related to the degree of contamination. For any hydraulic component, although 

many factors will affect its service life, the most effective way to extend the service life isto improve the filtration accuracy. If you 

follow the recommended fluid cleanliness requirements, it is entirely possible for Keta products to reach the product design life of 

1 million cycles, which is consistent with the results that Keta Hydraulics has verified in the laboratory.

Failure to meet minimum fluid cleanliness requirements can lead to premature failure of systems and components.


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