Analysis of Fault Characteristics of Construction Machinery and Fault Diagnosis Techniques

2. Empirical diagnosis of faults in construction machinery

Diagnosis is to determine the cause and location of the fault through the fault phenomenon. Diagnosis can be divided into active diagnosis and passive diagnosis. Active diagnosis refers to the diagnosis of construction machinery before it malfunctions, that is, understanding the past and present technical conditions of construction machinery and being able to predict future changes. Passive diagnosis refers to the diagnosis of faults in construction machinery after they have occurred, which is to confirm the cause and location of the fault.

Diagnostic methods can generally be divided into two types: one is manual intuitive diagnosis, and the other is diagnosis with equipment. Both of these diagnostic methods are carried out without disassembling or removing individual small parts. To determine the technical condition of construction machinery. Identify the location and cause of the fault.

Due to the construction of construction machinery during operation. The construction site is usually far from repair shops. If a fault occurs at the construction site, the conditions for diagnosing it with equipment are often not available. Therefore, maintenance personnel need to rely on their rich experience or simple tools and instruments to check and find the fault through methods such as listening, observing, smelling, testing, touching, measuring and asking.

(1) Listen: Determine the fault based on the characteristics of the sound. When identifying faults, attention should be paid to the relationship between abnormal noise and rotational speed, temperature, load, as well as the location where the noise occurs. At the same time, abnormal noise and accompanying phenomena should also be noted. This way of judging faults has a relatively high accuracy rate. For instance, the noise of the engine connecting rod bearing, commonly known as "small bearing noise", is related to the auscultation position, rotational speed and load, accompanied by a drop in oil pressure, but has little to do with temperature changes. For example, the knocking of the engine piston cylinder is related to rotational speed, load and temperature. When the rotational speed and temperature are both low, the sound is clear. When the load is heavy, the sound is obvious. The knocking sound of the valve is independent of temperature and load. Abnormal noise indicates the changes in the technical condition of construction machinery. The louder the abnormal noise, the better. The worse the mechanical technical condition is. Aging construction machinery often makes a lot of noises and noises. It's not easy to identify the fault for the time being. This requires us to listen more often in daily life to train our hearing, constantly familiarize ourselves with the movement laws of each part of the construction machinery, the materials of the parts and the environment where they are located. Only in this way can we accurately judge the faults.

Directly observe abnormal phenomena of construction machinery. For example. Oil leakage, water leakage, the smoke color of engine exhaust, as well as loose or broken components, etc., can all be identified as faults through inspection.

(3) Smell: Determine the fault by sniffing the odor with your nose. For instance, when a wire burns out, it gives off a burnt smell. Thus, faults can be identified based on the different abnormal odors smelled.

(4) Trial: Trial means testing and has two meanings: one is to reproduce the fault through testing in order to identify the fault, and the other is to replace the suspected faulty parts (manually remove the suspected faulty parts and mainly introduce the fault of the construction machinery and replace them with good parts of the same model), and then conduct tests to check whether the fault has been eliminated. If the fault is eliminated, it indicates that the replaced component is faulty. It should be noted that when severe abnormal noises occur in some parts, failure reproduction tests should no longer be conducted (for example, when there are severe abnormal noises in the crankshaft part of the engine, failure reproduction tests should no longer be conducted), to avoid more serious mechanical accidents.

(5) Touch: Use your hand to touch the suspected faulty or malfunctioning part to identify the location of the fault. For instance, touch the brake drum with your hand to check if the temperature is too high. If it is, it will be too hot to bear. This proves that the wheel brake has a braking drag fault. For instance, by touching the vibration of the hydraulic oil pipe with one's hand and listening to the noise of the hydraulic system, it can be determined that there is air in the system, etc.

(6) Measurement: It involves using simple instruments for measurement and identifying faults based on the measured results. For instance, a multimeter can be used to measure the resistance, voltage values, etc. in a circuit to determine faults in the circuit or electrical components. For instance, use a cylinder gauge to measure the cylinder pressure to determine the fault of the cylinder.

(7) Q: By interviewing the driver, understand the usage conditions and time of the construction machinery, as well as the phenomena and medical history when the fault occurs, etc., in order to determine the fault or provide reference materials for fault diagnosis. For instance, if the engine oil pressure is too low, when diagnosing such a fault, one should first understand whether the low oil pressure is gradual or sudden. At the same time, one should also be aware of the engine's usage time, maintenance conditions, and the variation of oil pressure with temperature, etc. If the maintenance is normal but the engine has been in use for too long and is accompanied by abnormal noises, it indicates that the crankshaft connecting rod mechanism is worn out excessively, and the clearance between each part is too large, causing an increase in oil leakage and resulting in low oil pressure. If the maintenance is not good on a regular basis, it suggests that the possibility of the oil filter being clogged is very high. If the oil pressure suddenly drops, It indicates that there is a large amount of oil leakage in the engine lubrication system's oil circuit.

3. Conclusion

When diagnosing faults, it is also necessary to pay attention to the variation patterns and characteristics of the failure rate of construction machinery and its usage time during operation. In conclusion, by understanding the situation, the goal of diagnosing faults is clear, avoiding the blindness of fault diagnosis, and making fault diagnosis more accurate and prompt.