The hydraulic system thoroughly break up the whole into parts.

1, the system structure and function of in-depth analysis of the hydraulic system of break up the whole into parts, and fault

Hydraulic system is complex and large, it is difficult to directly find out the specific location of the fault, and can not blindly search, and can only gradually detect the fault point. Layers of people in the hydraulic system is divided into levels and subsystems based on the division, in which the division of the right and reasonable is crucial. The subsystem division should be beneficial to the isolation of each part, so that there is a clear line between each part of the channel, and the performance of each part has no overlap, so that each part itself can be fully reflected. The hierarchical division of the system is related to the complexity of the system composition, and is also related to the structure, function, characteristics, especially the connection of the system. Complex hydraulic systems are often composed of several components, including power units and individual actuating units. Power components usually have several oil supply circuits, each loop including pumps, relief valves, unloading reversing valves and one-way valves. The execution unit is also composed of a series of executive circuits, each including a direction, speed and pressure control valve, and actuating element, each of which can be divided into components.

Example: the hydraulic system of a TTI, 800 injection molding machine, shown in Figure 9-9, can be divided in the manner shown in figure 9-10.

Hydraulic system will be divided into layers, deep layers of people to track down the fault. For example, for the system shown in Figure 9-9, the fault appeared in the whole system without pressure, then according to the principle of deep layers, break up the whole into parts to check the cause of the malfunction, successfully detected the fault point process is as follows:

1) find out where the trouble is. The system consists of three parts, in the A 58 proportional directional valve exports and dynamic model between the components of the circuit block, start the hydraulic pump and pressure regulator, pressure gauge indication system 50 is still no pressure, thus moving parts unrelated to the fault mode. At the 58 outlet of the proportional directional valve B, the oil circuit is blocked and the system pressure is normal. This shows that the power components are normal and the fault points are in the injection molding parts.

2) find out where the fault is. The injection molding unit has three circuits, blocking the loop at C, D and E as described above and identifying faults in the injection loop.

3) detect faulty components. The injection loop has 56 electrohydraulic valve, one-way throttle valve hydraulic cylinder 45, 65 and 46, the 9-9 shows that the one-way throttle valve and the hydraulic cylinder fault is difficult due to the system pressure is zero, valve failure cause symptoms most likely, by dismantling valve, reversing valve installation errors, the valve AB port is connected to the FO port on the valve plate, because the valve is Y type valve in the medium, AB interoperability, system pressure here unloading, zero pressure.

2, the fault reason analyzes fault break up the whole into parts.

In the hydraulic system, a symptom corresponds to a series of failure reasons, and through the summarization and classification of the fault causes, the different levels of the cause of the fault and the subsystems contained at each level can be divided. The cause of the fault through the causal graph or break up the whole into parts to realize the fault tree diagram.

(1) various types of reasons with causal relationship will fault causality diagram through line break up the whole into parts of the simple solution of symptoms, and each class contains the reason of specific reasons. For example, for sealing oil leakage, the failure can be divided into two categories: design, processing issues, installation and use of problems, as well as custody, transportation problems. Each problem also contains a series of small problems (Figure 9-11), once the system leaks, you can refer to figure 9-11, and in conjunction with the relevant circumstances of the scene, deep investigation of the cause of the fault.

(2) through the fault tree fault reason fault tree is a kind of break up the whole into parts will cause system as a whole to form according to the schematic diagram of gradual refinement of dendrimers, it is clearly structured, this method has been widely used in fault causality analysis on the system. The fault tree can display the complex relation of hydraulic system intuitively, and it has direct prompting function to the fault analyst.

The fault tree is composed of various symbols shown in table 9-1, and the fault tree is actually a fault tree of various logic gates. Figure 9-12 is not a hydraulic cylinder crawling fault tree.

As the fault tree diagram is the basis of fault analysis, the basic steps are as follows: to mapping system with clear definition of the selected system fault may occur (i.e., some typical symptoms involving a variety of possible reasons) as the object of study: the definition of system failure, determine its boundaries, analyses the reasons, find out the relevant events and the relationship between. As fault tree, the intermediate events and bottom events are defined, and the criterion of each event is determined, including characteristic parameters and detection methods.

The fault tree is mainly used to help guide the site work, and constantly revised and improved in the application.

After the fault tree diagram is made, the sting is used for the fault analysis to find out the cause and effect relationship of the fault, and it is most suitable for the systematic fault analysis with many influencing factors and complicated causation. At the scene, when there is a fault, according to the site and some available information, the control of fault tree, people gradually explore to detect intermediate events associated with failure and the end of the event, and the final failure mechanism, the advantage is clear, simple, to accelerate the speed of analysis and processing site fault.

When the data and data are sufficient, the quantitative analysis of the causes of the faults can be carried out according to the fault tree, that is, the probability of various fault causes is found, and then the prevention and improvement measures are taken.