What are the Causes of Malfunctions in the Hydraulic System?
What are the Causes of Malfunctions in the Hydraulic System?
What are the Causes of Malfunctions in the Hydraulic System?
Below are the causes and failure rates in hydraulic systems.
Insufficient Hydraulic Oil Usage 15%
Use of Aged Hydraulic Oil 20%
Solids in Hydraulic Oil 20%
Fluid Parts in Hydraulic Oil 5%
Use of Inappropriate Hydraulic Oil 20%
80% of malfunctions are due to oil.
We can detect 80% of the faults by measuring the condition of the oil.
In order to shorten the downtime, it is of great importance to measure the oil condition.
Operating Costs Can Be Reduced by Measuring Oil Condition:
Getting rid of unplanned stops
Better planning of service measures
Spare parts supply and stock optimization
Longer machine life
Increased safety for machine and operator
Pollution Types in Hydraulic System
Solid and liquid contaminants entering the system through moving parts
Wearing system parts
condensation
Parts entering the system during assembly, repair and maintenance
Adding Dirty Oil
Leaks and bad seals
bad air filter
Leaks from the coolant
Classification of Solids Pollution
human hair 75 micron
street dust 40 micron
White blood cells 20 micron
Talc powder 10 micron
bacteria 3 micron
The human eye cannot see below 40 microns. Human hair is 75 microns.
NAS
4National Aerospace Standards
4 Standards created by The Aerospace Industries Association of America for all kinds of materials used in the aviation industry and aircraft
How to Take a Hydraulic Oil Sample?
Sampling
Sampling Methods
Dynamic Sampling
Must be turbulent-turbulent flow
Static Sampling
Sampling from the hydraulic tank
Sample containers must comply with ISO 3722.
Dynamic Sampling
The system must have been running for at least 2-3 hours
Sampling equipment should be carefully cleaned with suitable cleaning tools before sampling.
The laboratory should have cleaned sample containers.
Sampling equipment must be flushed with at least 2 liters of oil taken from the system to be sampled.
It is very important to measure the oil condition.
Sampling
Static Sampling / Sampling from Hydraulic Tank
The system must have been running for at least 2-3 hours. The temperature of the hydraulic fluid must be constant. The tank should be turbulent.
The tank cover is generally suitable for this process. The tank cover area is cleaned and the filter is removed.
The sample bottle is filled with a vacuum pump and a clean suction element.
It should be taken from the middle of the oil level in the tank.
It is recommended to discard the first sample and use the following samples.
Sampling
Advantages
Samples can be measured later
The sample can be analyzed in the laboratory
Samples can be taken from several parallel points
Disadvantages
Sample processing has a strong influence on the measurement result
Qualified personnel are needed
Sample bottles and media must be very clean
Not recommended for very clean liquids
Pollution Measurement Methods
Gravimetric / Weight Analysis Method
-0.8µm to 1.2µm in size is passed through a membrane filter.
-Captured particles are weighed and analyzed in mg/l.
-Used at high pollution levels.
-It's the Old Method. Analysis is difficult.
Microscopic Analysis
-The fluid is passed through a 0.8µm to 1.2µm filter
-The image formed by the pollutants on the filter is analyzed microscopically.
-It's the old way. Results may vary based on expert opinion. Sample preparation is critical.
-Advantage: The type of pollutants can be seen
by eye
- Expert personnel determine the pollution class by comparison method.
Automatic / By software
- The software compares the image with the templates and determines the pollution class.
Pollution Measurement Methods
Electronic Analysis with Laser Assistance
If there are no particles in the measuring cell, all light will pass through the photo diode.
If a particle enters the measuring cell, a shadow is created on the photodiode.
The size of the particle can be determined by the light intensity detected in the photodiode.
The flow will be calculated based on the velocity of the particles.
Pollution Measurement Methods
Electronic Analysis with Laser Assistance
standard method
LED or laser light source
Advantages:
common method
Recognized standard
Standardized measurement procedure
Disadvantages:
Affected by bubbles and droplets
Limited at maximum viscosity
sensors
Heat
Pressure
Viscosity
Moisture
Conductivity
Insulation (On Electrical Charge Storage)
Metal part sensors
Data storage devices
monitors
Software that analyzes data
Relative humidity (rH) sensor
Water, oil soluble.
Mineral and synthetic oils have a water saturation point. Oil above this point cannot accept any more water.
The saturation point of hydraulic oils is 0.03% (300 ppm).
The water holding capacity of the oil depends on the oil type, the age of the oil and the additives used.
Free water can cause corrosion and corrosion of system components. Therefore, the moisture content of the oil should always be below the saturation point.
Closed water molecules cloud the environment. With the increasing heating of the system, the solubility in water increases, the oil becomes cleaner.
Air Detection:
Laser optical sensors cannot see the difference between a particle and an air bubble. So the weather can be detected by errors and strange data,
eg. vacuum bubbles are approximately 6 µm. If this data is high, there may be air bubbles.
Gentle pressure drops towards atmospheric pressure reduce the amount of air present in the liquid.
Heat:
Increased temperature may indicate component wear or component failure.
The calculation of the remaining useful life (RUL) is partly dependent on the fluid temperature.
Raising the temperature by 10 °C shortens the life of the fluid by 50%.
A hot hydraulic system normally has a low humidity because the water molecules are evacuated through the aeration.
The ideal temperature in a system can be determined by water ingress, aging, viscosity, leakage, safety, etc., depending on the situation. It should be determined in relation to
Mixture:
The conductivity sensor can detect mixtures because the electrochemical properties differ from one base oil to another.
The insulation sensor can detect high additive fluid from low additive fluid.
Laboratory Type Measuring Devices
It can be applied in various industrial applications. It can be used for all applications where the degree of pollution must be determined precisely. It can be used in the pharmaceutical and chemical industry as well as in particle counter, hydraulic section, filter technique. The portable OPCount can be used on-site and measured online and offline.
Mobile Measuring Devices
Connection to Pressure Line Measurement with Sample Data Saving Fast measurement Easy to carry Printable Data storage digitally
Online Measuring Devices
}The sensor will be directly connected to the system
}System pressure or internal pump generates required flow
Advantages
}No sample processing or preprocessing required
}No tampering with contaminated bottles or misuse
}Can handle very clean oils
}The results are statistically significant
disadvantages
}Limited viscosity range
Solid Parts in Hydraulic System
They clog tight spaces
They erode surfaces = pollution kills pollution
It enters between the moving parts and the surface and destroys the component, destroys the oil film.
The most critical parts are the pump and proportional valves.
Water in the Hydraulic System
Corrosion
Non-water liquid destroys the film, Causes rust.
Deterioration in Fluid Properties
Drop in Temperature Resistance
As the amount of water mixed with the oil increases, the boiling point of the liquid decreases. The water in the hydraulic oil starts to boil as the oil temperature increases and water vapor is released. Cavitation and performance degradation due to water in the oil cause problems especially in critical hydraulic systems such as brakes.
Air in the Hydraulic System
Cavitation, micro diesel effect
Excessive Foaming
Shortened filter lifetimes
Increase in oil temperature and burning smell of oil
OFF-LINE FILTRATION
Extending the service life of the machine and reducing operating costs with preventive oil service
Filtering while filling
Oil filtration during machine service
Improvement of working machines with bypass filtration system to improve oil cleanliness class
deterioration of oil
Oil condition monitoring
Water Trap Filter
It absorbs free water with the help of special filter elements. They consist of layer material that converts free water into gel and binds it to the filter element.
Depending on the operating condition, the water absorption is 1300 ml per filter element.
The combination of water-absorbing filter layers with ultra-fine filter material also allows use in hydraulic and lubrication systems with high requirements for oil cleanliness.
These are often used to remove small amounts of water.
Hydraulic Oil-Water Separation Device
vacuum water separation
This procedure separates water from oil by vacuum evaporation followed by condensation (Dewatering Unit COPS).
The procedure is suitable for the rapid and efficient removal of larger quantities of free and bound water from hydraulic and lubricating oils.
Centrifugation
Water and oil can be separated by centrifugation.
This procedure can also be used to remove free water, but in larger quantities.
Other
Large amounts of water can be removed by changing the oil and flushing the system.