All the hydraulic pipelines in the mining and high-grade general mining support equipment are basically composed of hoses (assembly) and related piping accessories. The hoses have more specifications and models (A and B are two types of models, from 4,10 to 筇. 1 film does not wait), a large amount of use, hose failure manifestations are also many reasons are complex. In the working face and roadway, several hundred meters long, exposed high-pressure pipelines, any failure may increase the safety hazard; failure will directly lead to the shutdown of the work surface, affect the production efficiency, increase maintenance costs; In addition, replace in harsh environments The hose will inevitably contaminate the system, increase the risk of failure in other parts of the system, and reduce the reliability and efficiency of the entire hydraulic system. This is a concern for any hydraulic system.

It is of great significance to analyze the causes of the failure of the high-pressure hose assembly during the test and its use, the impact on safety and use, and to explore the technical means for improving the quality of the domestic hose.

Hose problem form and impact

The failure modes of the hose (assembly) and joint assembly are shown in Table 1.

Accident Phenomenon Form of occurrence Harmful

U-shaped card breaks or falls off, high-pressure hose is thrown out, high-pressure medium (emulsion) sprays, sudden, dangerous, wounding

The joint is pulled out, the hose is thrown out, the high pressure medium (emulsion) sprays, sudden, dangerous, wounding

High-pressure hose blasting, debris splashing, high-pressure medium (emulsion) injection, sudden, dangerous, wounding

Drum bag, hose loses strength, high pressure hose burst precursor

Worn outer skin, exposed steel wire

Needle eye, medium sprays

Seal (aging failure of seal) failure, leakage

The arrangement of high-pressure hoses is unreasonable, resulting in deformation and affecting the flow of the liquid (emulsion); the nominal size deviation exceeds the standard and affects the efficiency of the liquid (emulsion) flow.

Table 1 Failure modes and hazards of hose (assembly) and joint assembly

As with any device, problems arise in the system. The time, manpower, and material resources required to eliminate the failure must increase production costs and reduce efficiency. In the coal mine production work face, the impact of the failure of the hose (assembly) also shows the following aspects:

(1) Directly affecting safety in production for mechanized coal miners

The main accident affecting safety production is the accidental injury of equipment operation. High-pressure hose failure is one of the safety hazards. The general working face length ranges from 150 to 300m, the high-pressure pipeline is exposed, there are many links, and the working environment is harsh. If you use it improperly, it will inevitably produce various

Damaged. Many of the failures listed in Table 1 will directly inflict damage on operators and lead to accidents. Some hoses need to maintain sealing and extra high pressure (above the system pressure) under normal conditions to ensure the support effect of the stent. Failure will reduce the effect of such support, and the effect is catastrophic.

(2) Impact on the hydraulic system Hose problems on the hydraulic system

One of the effects of the system is to reduce system efficiency. How to realize rapid shifting is a problem that has been increasingly concerned about high-yield and high-efficiency mechanized coal mining. One of the means to solve this problem is to reduce the resistance loss of each part of the hydraulic system, including increasing the diameter of the main pipeline. Unqualified hose assemblies often have dimensions and accuracy that do not meet specification requirements, especially with large internal diameter deviations, rough surfaces, reduced effective flow paths, increased drag coefficients, increased resistance losses, and influencing flow, affecting the column , Jack speed of action.

The second impact is increased system pollution and reduced system reliability. Damaged hoses must be replaced, the site conditions are poor, and it is difficult to ensure that pollutants do not enter the system during operation. According to the analysis, the replacement of damaged hydraulic components is one of the main ways of system contamination, and pollution is the key factor in the failure of the system, especially hydraulic valve components. Frequent replacement of parts will seriously affect the reliability of the system, and the system Contaminant particles can also lead to a decrease in the service life of hoses. As a result, the system is in a vicious cycle.

Hose impact on the system is indirect and hidden, but its severity is no less than the direct impact on safety, such as system reliability is reduced, resulting in failure of hydraulic components, and then affecting the efficiency of support, affecting safe production.

2. Reason analysis

Reasons for failure of mine high-pressure hose assembly and intermediate joint assembly are summarized as follows:

(1) Hydraulic (emulsion) system pressure source adopts three-plunger pump or five-plunger pump. The rated pressure is high, the flow rate is large, the pressure pulsation is large, and the pipeline components are easily fatigued and damaged. In particular, the main liquid supply pipeline is operated for a long time under the condition of high pulse pressure. The weak links of the high pressure hoses, such as the seal ring, U-shaped card, and high-pressure hose joints, are more likely to fail than the internal high-pressure hoses of the bracket. Occurrence frequency, because the latter high pressure hose only withstands high pressure when the support moves, the action time is very short, and the mechanism of failure is different.

(2) The emulsion medium is low in privateness, high in density, and relatively poor in corrosion resistance. Especially in different mining areas, the pH of water in the mining area is very different. Poor management in use, downhole emulsions often do not reach the prescribed ratio of oil to water, and the rubber is in a long period of time. In the soaking of this medium, it will inevitably deteriorate, harden, and age.

(3) Due to the characteristics of the use of downhole equipment, the cleanliness of the medium is low, and more gas is entrapped in the medium. On the one hand, cavitation is easily generated. When cavitation occurs, the pressure peak may exceed 1G P a ; on the other hand, high-speed and large-flow The emulsified liquid entraps tiny impurities and impinges on the inner surface of the pipe and the joint assembly. It will plow out a groove mark and cause wire erosion. The damage of the inner rubber layer of the high pressure hose accelerates the corrosion of the steel wire of the hose preparation and reduces the compressive strength of the high pressure hose. The pressure wave has a strong impact on the high pressure hose assembly and the joint assembly, and leads to breaking (cracking) of the dangerous section of the high pressure hose assembly and the joint assembly.

(4) The production environment of coal mines has a lot of dust, high humidity, and weak alkaline water. The vibrating pipe rubs against the environment, causing the surface rubber of the high-pressure hose to wear, and the corrosion protection layer on the surface of the joint assembly to fall off, which promotes the damage process.

(5) The factories that produce high-pressure hose assemblies and intermediate joint assemblies are mostly small and medium-sized enterprises. They are restricted by the conditions of technology, equipment, and funds, and some do not even process according to the drawings. High-pressure hose assemblies and pipeline accessories are not available. To the technical requirements, product quality is uneven, low intensity, short life, serious pollution, hidden dangers for unexpected safety accidents.

(6) The layout of the design is unreasonable. Under normal conditions, the high-pressure hose is mainly subjected to internal pressure and a certain (bending) force, and the incorrect arrangement method makes the high-pressure hose subject to additional additional forces (tension, torsion) for a long time, which reduces the service life of the high-pressure hose assembly. .

(7) Over-life of failed pipe elements. Due to the inability to verify and accurately determine whether the high-pressure hoses and piping components have failed or have reached the end of their service life, there are a large number of components that exceed the lifespan (according to relevant foreign regulations, the high-pressure hoses are valid for two years after they leave the factory). These high-pressure hoses are often easy to use. In the failure, the failure rate increases.

3, the solution

The analysis shows that the causes of high-pressure hose problems are many, and these causes and consequences are mutually causal. It is difficult to distinguish between laboratory and practical use. High-pressure hose failure can be summarized as the effect of two factors: quality problems and system factors. The system factor is determined by the system structure, and its impact is difficult to improve in the short term. The quality problem has obvious human factors and can be controlled and improved. Therefore, it can be considered that the key to eliminating the failure of high pressure hoses is to strengthen the quality control of the high pressure hose assembly in all aspects of manufacturing, design, and use.

(1) The damage to the hose is caused by its own quality. The reason is very clear. The direct consequences are very clear and serious (affecting safety, causing pollution, etc.). Looking at the current status of hose production, quality issues should ultimately be attributed to the production technology management, including processing, inspection, packaging and transportation, so that the hose factory standards to meet the relevant standards, product quality can be a step up. Therefore, improving corporate management can provide instant results and significantly reduce the failure rate of rubber hoses on the work surface.

Failure rate.

(2) Strengthen basic research on hose technology and develop higher performance hose assembly products, such as improving the performance index of large diameter. In actual use, the failure frequency of the main road rubber hose is higher than that of the inner hose of the bracket, and the reasons are analyzed. The hose in the bracket only bears the load when the bracket is actuated, and the hose between the bracket frames is always in a high pressure state, and its stress condition varies. The movement of the bracket is also changing. The working conditions of the two are not the same. Increasing the performance of the main liquid supply pipeline can reduce the failure rate of the entire work surface hose, and the effect is obvious.

The basic technology of rubber hose in China, including rubber materials and joint parameters, is not the same as that of foreign countries. The result is that there is a certain gap between China's rubber hose assembly and the international advanced level. China's rubber material is relatively soft, poor wear resistance, and low life expectancy. The impact of basic technologies is long-term and requires systematic research. Strengthen the application of hose technology, improve the use of norms. Hose failure also involves all aspects of design, installation and maintenance. Through research, a uniform set of standards for the scientific use of hoses is introduced to reduce or even eliminate failures.

(3) Choose a suitable high-pressure hose assembly and strengthen the high-pressure hose factory inspection. The quality of the high-pressure hose assembly is included in production, processing, inspection, packaging and transportation, etc. It is necessary to strictly inspect the relevant indicators of the high-pressure hose. Standard requirements to ensure the normal use of high pressure hoses.

(4) Strengthen the management of high-pressure hoses in the storage process, first-in, first-out, and pay attention to the high-pressure hose to avoid damage to the outer rubber layer by dragging, corrosion, heat source, etc., to avoid the heavy material pressing and destroying the steel wire skeleton, and to avoid excessive stacking ( Not more than 3 meters), affect the underlying high-pressure hose wire skeleton.

(5) During the installation and use of the high pressure hose assembly, follow the correct installation method and assembly angle to ensure that the hose will have a normal service life and control the quality of the medium (emulsion) to avoid accidental corrosion and damage to the high pressure hose.

(6) Regularly inspect the quality of the high-pressure hose assembly in use, replace the high-pressure hose assembly that meets the service life in time, and avoid accidents and unplanned time loss.