5 Ways to Solve Hydraulic System Faults
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5 Ways to Solve Hydraulic System Faults

Views: 1256     Author: Site Editor     Publish Time: 2024-01-16      Origin: Site

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When a hydraulic system fails, it is relatively difficult to find the cause of the failure, and it is generally easy to eliminate it when found. There are various ways to diagnose hydraulic system faults, a few of which are listed below.


How to use hydraulic system diagrams to find faults?


A hydraulic system diagram is a diagram that shows the working principle of hydraulic equipment, some simple, some complex. It indicates that the system of the executive components can assume the work, can achieve the action cycle, the control mode and each component of the articulation with each other. Generally equipped with solenoid action cycle table and work cycle diagram, but also lists the travel switch and other sending components. 


Familiar with the hydraulic system diagram, is engaged in hydraulic design, use, adjustment and maintenance of engineering and technical personnel of the basic skills, is the basis for the exclusion of hydraulic failure, is also to find the cause of hydraulic failure of one of the most basic, the most commonly used method. In the practical work of maintenance, to continuously improve the ability to familiarize with the hydraulic system diagram, in order to better apply the hydraulic system diagram to find hydraulic faults. 

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Hydraulic system diagrams are often complex and the first step in the common method is to learn to separate out the local circuits associated with the fault from the whole hydraulic system so that the problem becomes simple, more focused and more accurate in finding the exact part of the fault. 


The second step is "cause enumeration", the possible causes and parts of the fault are as follows. 

1. Damaged piston seal. 

2. Safety relief valve, adjusted pressure is too low or the spool is stuck in the open position. 

3. Suction valve, too much internal leakage. 

4. Main relief valve, the adjustment pressure is too low or the pressure cannot be adjusted upwards. 

5. Pump, the output flow is reduced, the internal damage of the pump. 

6. Suction pipe, due to broken or poor sealing into the air, so that the pump can not suck oil. 

7. The oil tank, the amount of oil is not enough. 

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The third step is "step-by-step investigation". 

1. If the oil tank is not enough oil, it is easy to observe with the naked eye, and the above reasons can be excluded according to the situation 7. 

2. If the pump internal damage or suction pipe into the air, then by the pump oil supply of other parts (such as rotary motor) should also be unable to act. If not, reasons 5 and 6 above can be ruled out. 

3. put the manual reversing valve in the hydraulic cylinder up position, adjust the main relief valve, if the pressure does not go up, the rotary hydraulic motor is also difficult to turn and can not walk. If yes, the cause of failure in 4; if not, exclude cause 4. 

4. safety valve and suction valve have problems, only affect the hydraulic cylinder, if other parts are really not affected, then consider dismantling and repairing the safety valve and suction valve. 

5. If the piston seal of the hydraulic cylinder is damaged, not only is the pressure insufficient, even if lifted, it will slowly and naturally fall. That is, the natural sinkage is large. If you check the amount of natural settlement, it is not difficult to make a judgment whether the lifting force is related to the damage of the piston seal of the bucket rod cylinder. The workload of dismantling and repairing the bucket rod cylinder is slightly greater and must be carefully confirmed. 

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In the use of the above methods to find the cause of failure, must be carefully analyzed, correct judgment, scientific decision-making, as little as possible to avoid repeated disassembly, to prevent disassembly and reassembly of hydraulic components may cause adverse effects on the accuracy of the analysis process in the disassembly of faulty components before gradually narrowing the object of suspicion is very important, which is beneficial to reduce the labor intensity of workers, reduce unnecessary disassembly. 


The use of hydraulic system diagrams to find hydraulic failure is one of the common methods, usually also used to "grasp the two heads" (grasp the pump and the implementation of components), "even the middle" (connected to the middle of the control element, that is, a variety of control valves) method, this method can be rationalized, on the This method is very helpful for the correct analysis of the causes of faults. 

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How to find faults using sensory diagnosis?


Sensory diagnosis is a method of examining, identifying and judging the location, phenomenon and nature of faults in the operation of the equipment directly through the sensory organs of the person, and then the brain makes a judgement and deals with it. This is in line with the traditional diagnosis of disease in China, "looking, smelling, asking and treating", and is also through the direct sensation of the eyes, ears, nose and hands of the maintenance personnel, coupled with the investigation and comprehensive analysis of the operation of the equipment, to achieve the purpose of making accurate judgements on the condition of the equipment and the fault situation. 


The practical effectiveness of sensory diagnosis depends entirely on the technical quality and experience of the individual inspector. The application of this diagnostic technique requires not only continuous accumulation of practical experience, but also attention to learning from the experience of others in order to be effective. The methods of sensory diagnosis are as follows. 


Diagnosis by questioning - asking with the mouth


Ask the operator whether the fault is sudden, gradual, or after repair. Usually the operator can be asked about the following. 

1. What are the abnormalities of the hydraulic equipment, the parts of the fault and how the fault occurred, etc. 

2. What is the change in the quality of the product processed before and after the failure. 

3. What is the maintenance and repair situation. 

4. whether there are any irregularities in the use of the equipment, the replacement of the fluid, etc. 

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Visual diagnosis - seeing with the eyes


1. Observe the working oil in the tank for bubbles and discolouration (white cloudy, black, etc. ), the noise, vibration and crawling of hydraulic equipment are often related to the large number of bubbles in the oil. 

2. Observe the sealing parts, pipe joints, hydraulic components of the installation of the joint surface and other places of oil leakage, combined with the observation of the pressure gauge pointer in the work process of vibration, pressure and pressure can not be adjusted up and so on, can identify seal damage, loose pipeline and high and low pressure cavity crosstalk and other abnormal phenomena. 

3. Observe the quality of the processed workpiece and analyse it, observe whether the equipment has shaking, crawling and uneven running, and find out the cause of the fault. 

4. Observe the fault area and damage, and often make a judgement on the cause of the fault. 

6

Aural diagnosis - listen with your ears

Normal equipment operation sound has a certain rhythm and maintains a continuous stability. Therefore, from the practice of accumulation, familiarity and mastery of these normal rhythm, you can accurately determine whether the hydraulic equipment is operating normally, while the rhythm of the change and the abnormal sound generated by the part can be analysed to determine the fault occurred in the part and the damage situation. Examples are as follows. 

1. High-pitched ear-piercing whistling sound is usually sucked into the air, if there is a cavitation sound, it may be the oil filter is clogged by dirt, hydraulic pump suction pipe loose, seal broken or leaky installation, or oil tank oil level is too low and hydraulic oil deterioration and degradation, dirt, defoaming performance is reduced, etc. 

2. "Hissing" sound or "clattering" sound for the oil discharge port or leakage where there is a more serious oil leakage, gas leakage phenomenon. 

3. "Ta-da" sound means that the solenoid valve of the AC solenoid valve is not good, may be the solenoid can be moved between the core and the fixed iron core of paint and other dirt block, or is too long to push the rod. 

4. coarse and heavy noise is often the hydraulic pump or hydraulic cylinder overload and generated. 

5. hydraulic pump "chatter" or "cackle" sound, often pump bearing damage and pump shaft serious wear, sucked into the air produced. 

6. sharp and short friction sound is often the two contact surfaces dry friction generated, there may also be the part of the strain. 

7. The impact sound is low and dull, often a loose screw in the hydraulic cylinder or a foreign object touching, etc. 

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Taste diagnosis - smell with your nose

Inspectors rely on the sense of smell to identify the presence of abnormal odor can determine whether the electrical components have broken insulation, short circuit and other faults, but also to determine whether there are ants, flies and other decaying things in the oil tank. 


Tactile diagnosis - touch by hand

Use sensitive finger touch to check whether vibration, shock and oil temperature rise, hydraulic cylinder crawling and other faults. Examples are as follows. 


1. Touch the pump casing or hydraulic oil with your hand, determine if there is an abnormal temperature rise in the hydraulic system according to the degree of heat or cold and determine the cause of the temperature rise and the part of the temperature rise. Skilled hand temperature measurement personnel can be accurate to 3 ~ 5 ℃ (see the table below). 

Temperature and feel
0℃ Fingers feel cold, numbness and tingling if touched for a long time
10℃ Cooler to the touch, generally tolerable
20℃ The hand feels slightly cooler, the contact time is extended, the hand feels warmer
30℃ The hand feels slightly warm and comfortable
40℃ Hand feels like touching a patient with high fever
50℃ Hand feels hotter, touching for longer time, palm sweat
60℃ Hand feels very hot, generally tolerable for about 10s
70℃ Finger can tolerate for about 3s
80℃ Fingers can only be touched momentarily, and the pain is increased, longer time may be burned

2. Feel the moving parts and tubes with your hands for vibrations. Hand feeling vibration abnormal, can be judged such as "motor pump" system and other rotary parts installed bad balance, fastening screws loose, the system has gas, etc. 

3. When the hydraulic cylinder is running slowly with the hand, the hand feels that it has a jump and a stop phenomenon, then it proves crawling. 


The sixth sense - inspiration and intention

Long-term hydraulic work of personnel, with a wealth of professional and technical knowledge and practical experience, and diligent thinking, courageous practice, good at summing up, in dealing with failures can often reach the point of perfection, the use of comfortable, often "hands to the disease". This is not an "idea", "inspiration" or a special function, but "practice makes perfect". It is a matter of "practice makes perfect" and can be achieved through the efforts of a dedicated and committed repairer. 


It should be noted that sensory diagnosis of faults has unique advantages such as simplicity and speed, but it is constrained by the technical quality and practical experience of the inspector compared to modern diagnostic techniques, otherwise it may be misdiagnosed or difficult to diagnose exactly. Therefore, the sensory diagnosis of faults should be implemented in conjunction with other diagnostic methods. 

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How do I troubleshoot a fault using the swap diagnosis method?


This method uses the replacement of newly purchased hydraulic components from the warehouse, or normal hydraulic components of the same type on other equipment, with the suspected faulty components for replacement checks. If the fault is removed, it is proven that the fault is in the hydraulic component. This swap diagnosis method is simple and easy to implement, but must be accurate and have the appropriate hydraulic components. 

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What is the instrumental diagnostic method?


Instrument diagnosis is the use of special hydraulic system fault detection equipment to diagnose faults, the instrument can be quantitative monitoring of hydraulic faults. There are many special portable hydraulic system fault detectors available at home and abroad that measure flow, pressure and temperature, and can measure the speed of pumps and motors. 


In general field testing, as the detection of flow is more difficult, coupled with the fact that hydraulic system faults are often manifested as a lack of pressure, the method of detecting system pressure is more often used in field testing. 

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What is the computer diagnosis of the hydraulic system?


With the widespread use of electro-mechanical integration in construction machinery, a single pressure test can no longer meet the needs of on-site testing, and now more and more hydraulic machinery are equipped with computers that can self-diagnose some of the faults and show them on the display, which can be used to troubleshoot according to the display. 

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