How to set the order of trouble shooting?

In order to find hydraulic failure reasons efficiently, a reasonable fault detection sequence must be set up. There are two principles for scheduling fault detection sequence, one is sorting according to the possibility of fault cause, and the other two is sorting according to the disassembly and disassembly of components or components and the degree of difficulty of assembly.

1. sort by the cause of the trouble

In the process of fault analysis, the most probable fault suspect shall be examined deeply, and when the first suspected point is not found to be the real fault point, the suspected suspected fault point with relatively large possibility is examined.

Determine the cause of the failure: first, the characteristic information related to the cause of the fault is more obvious. The initial reason associated with the cause of the fault. (why) fully exist, such as element is used for a long time due to damage of components, while the element damage is the cause of the symptoms, the use of time is to determine whether it is element damage basis. The possibility of the cause of failure can also be determined according to the relevant statistical conclusions. According to the characteristic information of scheduled fault detection order, a number of possible reasons is the face of symptoms, first by them to make a preliminary study, they determine what are the characteristics of information, and then compare the various causes of fault feature information appears obvious, according to scheduled fault detection order. According to the initial causes of the breakdown of the scheduled test sequence, is used for a long time to check the components, check the high load rate of the components, first check proved to be of poor quality, easy fault components, first check the hydraulic oil pollution sensitive element. Conclusion the reason according to the probability of fault symptom statistics test sequence is scheduled, the use of statistical conclusions have been obtained, all of the same symptoms may cause the possibility of size sorting, when a failure after the first check point of the fault probability. For example, a xy-XS-400oA injection molding machine in a plant may suddenly stop working during semi-automatic operation. Problems in large and complex hydraulic equipment like this, the possible fault causes are many, but the site maintenance personnel according to the accumulated data, can quickly find the cause of the fault, the root of the problem most (about 80%) occurred in the oil source control for electro-hydraulic valve commutation, it is a small low voltage power stop the overflow valve due to oil pollution is not sealed, not out of the pressure, the valve for hydraulic reversing without reversing, the machine stops working.

2. sort and observe the degree of difficulty of hydraulic parts by disassembly, disassembly and observation

The reason of hydraulic fault may face a variety of reasons, in various fault probability is not clear (as for the first time in the failure of a not familiar with hydraulic equipment analysis) circumstances, should be in accordance with the degree of difficulty of disassembly and observation of hydraulic components of the test sequence is set, first check the relatively easy to observe or test components and environmental factors easily remove (such as oil, electrical system, cooling water etc.), then check is difficult to remove the components, especially the large volume and weight of the components; check the external factors, and then check the internal components; first check relatively simple components, structure and function to check the situation is more complex, unclear elements. For each component, check the valve first, then check the pump, and finally check the hydraulic cylinder and hydraulic motor. A case of hydraulic failure is checked according to the principle of "easy first and difficult afterwards".

A hydraulic circuit is shown in figure 9-3. The symptom of the malfunction is that the hydraulic system suddenly fails to work during the operation:

1) check the oil level of the tank to see if the oil level is above the minimum oil level.

2) a manually operated directional control valve (solenoid valve drive through a manual button at both ends of the electromagnet), if the heart valve can not move, that is the direction of valve fault; if the directional valve can change, and the action of hydraulic cylinder, that is the electrical circuit of the electromagnetic valve is out of order; if the hydraulic cylinder is not action the third step.

3) check the pressure of pumping station. Check the pressure gauge at the pump outlet to the rated value in the middle of the directional valve. If much lower, as the following: check the pressure gauge switch is opened, the pressure gauge is damaged; if the overflow valve fault; oil filter is blocked; pipeline is blocked; the pump is damaged; if the pressure is low enough for the following: check whether the serious leakage within the overflow valve to adjust the pump; whether it is right "pressure relief valve adjustment, control valve, hydraulic cylinder action should be. If the speed of movement of the hydraulic cylinder to meet the requirements of fault ruled out; if the speed can not meet the requirements, to repair the hydraulic pump; if the hydraulic cylinder in the relief valve after the adjustment is still not action, for the next inspection.

After the above work has been completed, there is still no troubleshooting, then it may be that the hydraulic cylinder is out of order. First, don't rush to remove the hydraulic cylinder, the direction valve is opened to the left or right, start the hydraulic pump after a period of time, carefully touch the wall, to see whether there is a local hot spots. If the piston seal is damaged, there will be oil leakage from the high pressure chamber to the low-pressure chamber, when the oil flow through the narrow gap, the hydraulic energy will be converted to heat, if there is no local hot spots, the next step to check. That is, the pipe joint G1 at one end of the hydraulic cylinder is disassembled and connected to a three way pipe joint, and the other ends of the three connecting pipe are respectively connected with a pressure meter and a stop valve. The direction of the valve to the left position, read pressure gauge readings, if the reading and the main gauge pressure is not close, that if the pipeline is blocked; using the same method to test another joint G2 if the pipeline blockage, then the next step. Disassemble, disassemble and test the hydraulic cylinder.

3.. Program drawing to find hydraulic failure

After a certain degree of understanding in the occurrence of the fault of hydraulic equipment, can be a combination of factors, according to the probability of each fault point size and easy first principle, the hydraulic fault finding work process of preparation. The purpose is to make sure that the site failure analysis and removal are determined in a reasonable manner and procedures, so that after the problem arises on the scene, the best way is to find out where the fault is. The work procedure chart can not only indicate the discrimination sign, but also include the various biting reasons of the symptoms. It should be prepared by experienced field technicians. With working procedures, even if the field work is not skilled people, but also can carry out a smooth analysis of the fault. An example of hydraulic failure analysis program is presented.

Fig. 9-4 is the clamping circuit of the hydraulic system of a pipe cutting machine. The fault symptom is the bidirectional movement of the hydraulic cylinder. According to the relevant factors, the working procedure diagram for finding the cause of the fault is shown in figure 9-5.