Cleanliness control of hydraulic components and system flushing

The significance of cleaning hydraulic systems

From a usage perspective, the primary condition for a hydraulic system to function properly is that the interior of the system must be clean. It is inevitable that the hydraulic system will be contaminated before a new device is put into operation or after a major overhaul. Although hydraulic component manufacturers pay great attention to the internal cleanliness of the components themselves, new components may still contain contaminants such as burrs, chips, burrs, dust, welding slag, and paint. Components may also be contaminated due to poor storage and handling. During the production process of the fuel tank, rust, paint chips, and dust may accumulate. Although the fuel tank is cleaned before use, many pollutants are difficult to see with the naked eye. During the installation process of hoses, pipes, and pipe joints, pollutants may be introduced into the system. Even new oil may contain some unexpected pollutants. Measures must be taken to filter out pollutants as soon as possible, otherwise malfunctions may occur shortly after the equipment is put into operation, and early failures are often serious. Some components such as pumps and motors may be fatally damaged.

The purpose of component cleaning and system flushing is to eliminate or minimize early equipment failures. The goal of flushing is to improve the cleanliness of the oil, keeping the cleanliness of the system oil within the contamination tolerance of key hydraulic components in the system, to ensure the reliability of the hydraulic system and the service life of the components.

Cleanliness of components
Component cleanliness is an indicator that reflects the residual pollutant content inside the component, which can be expressed in the following ways:

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

2. The pollutant content per unit wet volume of the component (the volume of the internal cavity in contact with the oil), mg/L；

3. The number of particles larger than 5 μ m and 15 μ m in the unit wet volume of the component is represented by the ISO4406 solid particle pollution level.

Due to the widespread use of particle counting method for assessing oil contamination, the cleanliness of components is also commonly represented by the number of particles per unit wet volume.

Evaluation method for cleanliness of hydraulic components

1. Inject a certain amount of clean test solution into the component using the shaking and rinsing method, seal the component, and vigorously shake the component using mechanical methods to flush all the pollutants inside the component into the test solution. Then, measure the degree of contamination of the test solution

2. The test bench flushing method connects the components to a pre purified test bench system, allowing the test liquid to circulate through the components, flushing all the pollutants inside the components into the test liquid, and then collecting the sample liquid from the system for pollution level measurement.

3. After thoroughly cleaning the exterior of the components using the disassembly and rinsing method, all components are disassembled and the wet area of the parts is carefully rinsed with a cleaning agent. Then, all solvents are collected and their degree of contamination is measured.

The shaking washing method is a simple and easy method for detecting the cleanliness of components, mainly suitable for static components such as pipes, pipe joints, hoses, filter housings, and oil tanks; The test 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 component assembly is combined with component cleanliness testing, it can effectively control the cleanliness of components and simplify the testing process. When the components have been cleaned and meet the specified cleanliness requirements, they can be considered as a whole and have the same level of contamination as the system. In this way, the measured system oil contamination level is the cleanliness of the components, without the need for volume conversion.