The role of oil filtration in maintenance

the key role of oil filtration in the industry

As a building block of machinery and equipment, oil has many tasks to perform. In addition to lubricating moving components, the oil carries away heat and contaminants generated by friction, protects against corrosion, and protects the system from the harmful effects of water and air.

One of the main tasks, as part of maintenance, is to keep the oil clean at the required level, since about 70-90% of all failures and malfunctions, in lubrication and hydraulic systems, are caused by contamination of lubricants.

Regular monitoring of oil cleanliness, through laboratory testing, is an essential part of machine diagnostics, providing reliable information about the type of contaminants in the oil.

impurities in industrial oil – origin

Contaminants can enter the oil system from outside, precipitate inside due to oil aging/decomposition, or arise from friction.

The most common contaminants that can enter the oil system from the outside include:

• ambient dust – silica
• pollutants from the production process – coal dust, cement, ash, etc.
• post-assembly contaminants, introduced during repair or maintenance work without proper cleanliness during their execution

In the case of contaminants generated inside oil systems, these can be:

• metallic particles formed during the operation of the device
• corrosion particles
• particles of paint coating, for example, protecting the oil tank

the size of contaminants in oil and their effect on lubricated surfaces

Knowing the origin of the contaminants and their type, it is important to mention particle sizes. Contaminants in the oil can be divided into visible and invisible to the unaided eye. Metallic particles, visible to the “naked eye,” can be seen, for example, on drain plugs equipped with magnets. Their appearance, indicates significant wear or serious damage to machine components, indicating that the device in question is already on the critical path. Regular oil testing allows early detection of small wear particles (abrasion) invisible to the naked eye and enables preventive measures to be taken to protect the machine from failure.

Contaminants, found in the oil, affect the wear of the mating surfaces and the oil film. The mechanism of surface wear is shown below.

measuring the amount of impurities in the oil

The amount of contamination is not the only factor affecting the rate of wear. The second, equally important, is the amount of impurities per unit volume. To determine their amount per unit volume of oil, measurement methods have been introduced, which are divided into microscopic (membrane) and automatic (blockade, laser).

The advantage of the microscopic method is the ability not only to count particles, but also to determine the type of particles and, most importantly, their origin. The downside of this method is that it is relatively labor-intensive.

The advantage of the blocking method is that it can determine the purity classes of oils that, due to their very dark color (e.g., motor oils, oils with molybdenum disulfide), cannot be tested by other methods.

The advantage of the laser method is the relatively fast measurement (some variations of this method also make it possible to identify the type of process by which contaminants are generated).

oil purity class

After counting the particles in each size range, these numbers are assigned to the corresponding purity classes, usually according to standards:

• NAS 1638
• ISO-DIS 4407 (for microscopic method) – ranges of counted particles: >5 µm and > 15 µm
• ISO-DIS 4406 (for automatic methods) – ranges of counted particles: >4 µm, >6 µm and > 14 µm

A specific oil cleanliness class, required for proper operation, can be assigned to each device. Nowadays, manufacturers usually explicitly state this parameter in the technical and operating documentation of machines. In the absence of such records, you can contact a company specializing in lubrication service to determine the optimal cleanliness class for the specific operating conditions of this equipment.

Maintaining the purity class required by the manufacturer should, under normal operating conditions, ensure the proper functioning of the device, but it often happens that the actual conditions under which the device operates (load, temperature, environmental pollution, etc.) make it necessary to change the output parameters of the lubricant to meet actual needs.

correlation of failure frequency with oil cleanliness level

Based on a 3-year study conducted on 117 different hydraulic devices (injection molding machines, hydraulic tools, conveyors, mobile equipment, including excavators, shipping hydraulics), an index of the relative level of service life was developed, shown in Tab. 2.

The process of removing contaminants is carried out using filter units, equipped with appropriate system filters, which are designed to maintain the required oil cleanliness class. Bypass units are also used to remove contaminants and improve the oil cleanliness class in the tank during movement, especially of small systems.

Oil bypass filtration can be used continuously or periodically, for example, when the cleanliness grade of the oil used in the machine is found to have deteriorated.

Bypass filtration is carried out using filter units, the capacity of which is selected on the basis of such parameters as the capacity of the oil system, the viscosity of the oil used in the device, the operating temperature of the oil in the device, the dimension of the connection stubs.

Oil filtration – what does it consist of?

Filtration, is the process of separating solid contaminants, by mechanically retaining one solid in the porous baffles of the filter.

what oils and liquids can be filtered?

Hydraulic oil, gear oil, heating oil, lubricating oil as well as flame-retardant fluids, coolants, machining fluids and fluids from chilled water systems (glycols) can be filtered.

types of oil filters?

Division of filters due to placement in the oil system:

• full-flow (system)
• bypass
• series and bypass

Division of filters according to the principle of operation:

• surface filters – mesh
• volumetric: nonwoven, cellulose, porous sinter, porous plastics
• magnetic, centrifugal, ion exchange filters

Taking care of oil cleanliness ensures a longer service life and protects machines from the undesirable effects of contaminants in systems. The use of the presented oil filtration systems reduces the risk of failure, lowers operating costs, as well as protects the environment by reducing waste.

Taking care of oil cleanliness ensures a longer service life and protects machines from the undesirable effects of contaminants in systems. The use of the presented oil filtration systems reduces the risk of failure, lowers operating costs, as well as protects the environment by reducing waste.

summary

As intensive research, backed by industrial practice, indicates, improving oil cleanliness beyond the value required by the manufacturer in the DTR document reduces wear on machine components. This increases equipment reliability, availability, and lengthens the time between repairs.

From this relationship, the following conclusions can be drawn: the lower the amount of contaminants in the oil, the more the equipment’s failure-free period is extended, and maintenance costs are reduced.

Oil filtration services offered by Ecol, are carried out using specialized equipment, with the highest safety standards for people and the environment.

Our company’s 30 years of experience in the care of oil systems, acquired knowledge of filtration methods, supported by state-of-the-art diagnostics, guarantee the safety and reliability of the machinery fleet.