Cleanliness control and system flushing of hydraulic system

Cleanliness control and system flushing of hydraulic system

1、 Significance of hydraulic system cleaning

From the point of view of use, the first condition for the normal operation of the hydraulic system is that the interior of the system must be clean. It is inevitable that the hydraulic system will be polluted before new equipment is put into operation or after an equipment is overhauled.

Although the manufacturer of hydraulic components pays much attention to the internal cleaning of the components themselves, new components may still contain contaminants such as burrs, chips, fins, dust, welding slag and paint. Components may also be polluted due to poor storage and handling. Rust, paint chips and dust may accumulate during the fabrication of the fuel tank. Although the oil tank is cleaned before use, many pollutants are difficult to see with the naked eye.

During the installation of hoses, pipes and pipe joints, pollutants may be brought into the system. Even new fluids can contain some unexpected contaminants. Measures must be taken to filter out pollutants as soon as possible, otherwise faults may occur soon after the equipment is put into operation, and early faults are often very serious, and some components, such as pumps and motors, may be fatally damaged.

The purpose of element cleaning and system flushing is to eliminate or minimize the early failure of equipment. The goal of flushing is to improve the cleanliness of the oil, keep the cleanliness of the system oil within the pollution tolerance of the key hydraulic components in the system, so as to ensure the working reliability of the hydraulic system and the service life of the components.

2、 Cleanliness of components

The element cleanliness is an indicator reflecting the content of residual pollutants inside the element, which can be expressed in the following ways:

1. Pollutant content per unit wet area (inner wall area in contact with oil) of the element, mg/m2;

2. Pollutant content per unit wet volume (volume of inner cavity contacting with oil) of element, mg/L;

3. The unit wet volume of element is greater than 5 μ M and 15 μ M, expressed by ISO4406 solid particle pollution level.

At present, the particle counting method is widely used to evaluate the oil contamination, so the particle number per unit wet volume is also commonly used to express the component cleanliness.

3、 Assessment method for cleanliness of hydraulic components

1. Shaking Rinsing Method

Inject a certain amount of clean test fluid into the element and seal the element. Shake the element strongly by mechanical method to flush all pollutants inside the element into the test fluid, and then measure the contamination of the test fluid.

2. Test bench flushing method

Connect the element into the pre purified test bench system, circulate the test solution through the element, flush all the pollutants inside the element into the test solution, and then collect the sample solution from the system for contamination degree measurement.

3. Dismantling flushing method

After thoroughly cleaning the exterior of the element, disassemble all the elements, carefully flush the wet area of the parts with detergent, then collect all the solvents and measure their contamination.

The shaking rinsing method is a simple and easy method to detect the cleanliness of components, which is mainly applicable to static components, such as conduits, pipe joints, hoses, filter housings and oil tanks; The bench flushing method is mainly used to detect the cleanliness of dynamic components, such as hydraulic pumps, hydraulic motors, hydraulic cylinders and various hydraulic valves.

In addition, if the cleaning process after the component assembly is combined with the component cleanliness test, the component cleanliness can be effectively controlled and the test process can be simplified. When the components have been cleaned and meet the specified cleanliness requirements, the components and the system can be considered as a whole and have the same pollution level. In this way, the measured oil contamination of the system is the cleanliness of the components without volume conversion.