Pollution control in hydraulic system installation

Abstract

Hydraulic system contamination is a major cause of hydraulic failures. To ensure the safe and reliable operation of the installed hydraulic system, a series of specific measures are taken for the installation of the hydraulic system to achieve contamination control during the installation process.

Key words

Safety measures for hydraulic systems and pollution control

1 Overview

Hydraulic transmission technology has developed rapidly since its birth in the 18th century. Today, hydraulic transmission equipment is widely used in various industries, and this is particularly evident in modern large-scale production lines and construction machinery. Hydraulic transmission technology has its incomparable advantages, which is the main reason for its rapid development. Meanwhile, hydraulic transmission equipment also has its vulnerable side, among which the low anti-pollution ability is a prominent weakness. According to relevant records, 70% to 80% of hydraulic failures are caused by oil contamination. To ensure the normal and reliable operation of the hydraulic system, it is essential to keep the entire hydraulic system clean.

2. Hazards and Causes of Hydraulic System contamination

When contaminants are mixed into the hydraulic system, they will accelerate the wear, burning, and even damage of hydraulic components, or cause valve malfunction, or generate noise. Contaminants can clog the throttle holes or throttling gaps of hydraulic components, alter the working performance of the hydraulic system, cause actuation imbalance or even complete failure, and lead to misoperation and accidents. Dust particles in the hydraulic cylinder will accelerate the damage of seals, scratch the inner surface of the cylinder barrel, increase leakage, cause insufficient pushing force or unstable movement, crawling, reduced speed, and produce abnormal sounds and vibrations. It may also cause the filter screen to clog, making it difficult for the hydraulic pump to draw in oil, resulting in poor oil return and causing cavitation, vibration and noise. When the clogging is severe, the filter screen will be punctured due to excessive resistance, completely losing its filtering function and creating a vicious cycle in the hydraulic system.

There are many reasons for contamination in hydraulic systems. From the perspective of the mechanism of contamination generation, it can be divided into two types :(1) Latent contaminants during the manufacturing and installation processes, mostly solid particles such as chips, burrs, molding sand, coatings, abrasives, welding slag, rust flakes and dust, which pose a relatively significant threat to the hydraulic system. Therefore, management at this stage must be strengthened. Ensure that the installed hydraulic system can operate safely and reliably.

Pollution control in the fabrication and installation of hydraulic systems

3.1 Pollution Control in Parts Processing

The processing of parts generally requires the adoption of the "wet processing" method, that is, lubricating fluid or cleaning fluid should be added to all processing procedures to ensure the quality of surface processing.

3.2 Cleaning of components and parts

Before assembling new hydraulic components, all old hydraulic components that have been contaminated must be cleaned before use. During the cleaning process, the following points should be noted:

The disassembly, assembly and cleaning of hydraulic components should be carried out in a clean room that complies with national standards. If conditions permit, it is best to pressurize the operation room to make the indoor pressure higher than the outdoor pressure to prevent the indoor air from being contaminated by dust. If conditions restrict, the operation room should also be isolated separately. Generally, it is not allowed for the assembly room of hydraulic components to be in the same room as the mechanical processing room or the fitter's room. It is even more strictly prohibited to disassemble and assemble hydraulic components in the open air, under sheds, in storage rooms or warehouses.

When disassembling and assembling hydraulic components, operators should wear work clothes and work caps with fibers that are not easy to fall off to prevent fibers, dust, hair, dander, etc. from scattering into the hydraulic system and causing artificial contamination. Smoking and eating are strictly prohibited in the operation room.

2) The cleaning of hydraulic components should be carried out on a dedicated cleaning table. If conditions restrict, it is also necessary to ensure the cleanliness of the temporary workbench.

3) Kerosene and hydraulic oil of the same grade as the working oil of the hydraulic system are allowed to be used as the cleaning solution.

4) After cleaning, the parts must not be wiped with cotton, linen, silk or chemical fiber fabrics to prevent the fallen fibers from contaminating the parts. It is also not allowed to blow air onto the parts with a leather tiger (the leather tiger contains dust particles inside). If necessary, compressed air can be used to dry the parts.

5) After cleaning, the parts must not be placed directly on the ground, concrete floor, floor, fitter's bench or assembly workbench. Instead, they should be put into covered containers and filled with hydraulic oil.

6) Parts that have been cleaned but are not to be assembled for the time being should be stored in anti-rust oil. Special attention should be paid to rust prevention in humid areas and seasons.

3.3 Pollution Control in Hydraulic Component Assembly

The assembly of hydraulic components should adopt the "dry assembly" method. That is, after cleaning the parts, to prevent the cleaning liquid from remaining on the surface of the parts and affecting the assembly quality, the assembly should be carried out after the surface of the parts is dry.

2) When assembling hydraulic components and it is necessary to strike them, it is strictly prohibited to use iron hammers. Wooden hammers, rubber hammers, copper hammers and copper rods can be used instead.

3) When assembling, do not wear gloves and do not wipe the installation surface with fiber fabrics to prevent fiber dirt from entering the valve.

4) When hydraulic components and assemblies that have been assembled are not to be installed for the time being, all their oil ports should be blocked with plastic plugs.

3.4 Pollution Control during the Transportation of Hydraulic Components

During the transportation of hydraulic components and assemblies, it is necessary to pay attention to dust-proofing and rain-proofing. Hydraulic components transported over long distances, especially by sea, must be wrapped in rainproof paper or plastic packaging paper and placed with an appropriate amount of desiccant. Rainwater and seawater must not come into contact with the hydraulic components. Before packing and after opening the box, carefully check whether all oil ports are blocked with plugs. For oil ports that are slightly contaminated, take remedial measures in time. For severely contaminated hydraulic components, they must be disassembled and cleaned again.

3.5 Pollution Control during the final assembly of the hydraulic system

1) The hose must be acid-washed and rinsed before being connected to the actuator. Before installation, it should be blown clean with compressed air. If the hose is disassembled during the process, the hose joint should be wrapped up in time.

2) Before installing the pipe joints, they should be thoroughly cleaned with kerosene and dried with compressed air. For pipe joints that require sealing with PTFE tape, two points should be noted when wrapping the tape: First, wrap it along the thread direction; Secondly, the raw material tape should not exceed the end of the thread; otherwise, the excess part will be cut by the thread during the tightening process and enter the system.

3) Pollution control during the installation of hydraulic pipelines

Hydraulic pipelines are an important component of hydraulic systems and also a large-scale on-site construction project. Moreover, pipeline installation is a task that is prone to contamination. Therefore, the control of hydraulic pipeline contamination is an important part of the cleaning of hydraulic systems.

Before installing the pipes, all internal particle impurities must be cleaned out. It is strictly forbidden to leave stone blocks, rags or other debris inside the pipes. If there is a long interruption during the pipeline installation process, the pipe opening must be sealed well to prevent debris from entering. To prevent welding slag and iron oxide scale from entering the system, it is recommended to weld the pipes

Gas shielded welding, such as argon arc welding, is adopted.

After the pipeline installation is completed, it must undergo acid washing and system flushing. It is strictly prohibited to connect the hydraulic components into a circuit or even integrate them into the hydraulic system before the pipeline is processed, to prevent contaminants inside the pipeline from entering the actuators and control components.

Pipe pickling is divided into two types: tank pickling and circulation pickling. There are many pickling technologies and formulas. System flushing is carried out after the acid washing work is completed. It is the last cleaning measure before the hydraulic system is put into use. It is necessary to ensure that all pipelines and hydraulic components are flushed clean to meet the required cleanliness.

The system flushing should be carried out in two steps. First, connect the pipelines installed on site into a circuit. After flushing to the required cleanliness, connect the control valves, diverters and other control components to the circuit. Only when the required cleanliness is reached can the flushing be considered qualified.

3.6 Fill the hydraulic oil tank

Before filling the hydraulic oil tank with oil, the cleanliness inside it must be checked. If it is not up to standard, it should be cleaned. Before adding the oil, its cleanliness should be inspected. When filling oil, it must be filtered and it is not allowed to directly inject the oil into the hydraulic oil tank.

3.7 System Recovery

After acid washing and flushing of the system, all components and pipelines can be connected to form the working circuit as required. Special attention should be paid to the cleanliness of the pipe joints during this process. After connection, disassembly should be avoided as much as possible. If necessary, they should be wrapped with clean cloth to ensure that the pipe joints and pipe openings are not contaminated.

4 Summary

Contamination control of the hydraulic system runs through the entire processing and assembly process, requiring operators to take cleaning measures at every step to minimize contamination of the hydraulic system and ensure its safe and reliable operation.