Troubleshooting and precautions of common faults o

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Troubleshooting and precautions for the common faults of Beiqi wheeled crane

troubleshooting and precautions for the common faults of Beiqi wheeled crane

China Construction machinery information

Guide: due to the poor service conditions of wheeled cranes, the failure rate is relatively high, and the faults must be eliminated and repaired in time, and the crane is not allowed to work with diseases. The faults of hydraulic wheel crane can be divided into three categories: mechanical fault, electrical fault and hydraulic system fault. Mechanical failure is relatively straight

due to the poor service conditions of wheeled cranes, the occurrence rate of faults is relatively high. The faults that occur must be eliminated and repaired in time, and the crane is not allowed to work with diseases

the faults of hydraulic wheel cranes fall into three categories: mechanical faults, electrical faults and hydraulic system faults. Mechanical faults are relatively intuitive and easy to find and eliminate. However, hydraulic or electrical system failures often occur in the interior of components, so it is generally not easy to accurately judge the cause and location of the failure. Therefore, in order to do a good job of troubleshooting, you must be very familiar with the hydraulic or electrical system

during the use of the crane, due to natural wear and tear of parts, processing quality problems of parts, assembly quality problems of components, improper operation and maintenance, and the influence of operating conditions or working conditions, the faults are complex. It is impossible for the random technical data to list all kinds of faults in detail. At the same time, the troubleshooting method is not to remember what to do or what not to do under what circumstances. Therefore, in order to do a good job of troubleshooting, we must systematically and carefully study the basic knowledge, be able to comprehensively understand the structural principle of the crane and various working mechanisms, and be familiar with the working principle of hydraulic and electrical systems; Be familiar with the appearance characteristics and internal structure of various components and parts, as well as their installation positions and disassembly methods on the whole machine; Master relevant knowledge of technical performance, technical requirements, maintenance and commissioning. Only with these basic skills can we correctly analyze the cause and location of the fault and eliminate it according to the fault phenomenon

don't mess around after the crane breaks down. Especially for brakes, safety devices, electrical and hydraulic systems, etc., care should be taken

I. troubleshooting methods and steps

troubleshooting should generally be carried out according to the following methods and steps: clarify the fault phenomenon, analyze the cause of the fault, determine the inspection position, disassemble and inspect, determine the fault, and repair the test. If you fool around, it will only get worse

1. Find out the fault phenomenon

the fault phenomenon is the abnormal situation in the operation of the crane. For example, the working mechanism runs fast and slow, crawls and vibrates, and there is abnormal sound, smell, smoke or fever; There are oil leakage, operation failure, performance degradation, safety device out of control, etc

when a certain fault occurs in the crane, some phenomena are obvious and intuitive, and some are not easy to detect. Therefore, it is necessary to carefully observe and clarify the fault phenomenon. For example, when the crane vibrates during operation, it is not easy to find out the cause, because an oil pipe joint leaks oil, which is very intuitive

2. Analyze the cause of the fault and determine the inspection position

analyze the cause according to the fault phenomenon. Generally, list the various causes of similar phenomena according to practical experience and comparing with relevant data. If it is preliminarily judged that it may be an electrical system fault, it is necessary to further understand the working principles and devices of various actions of the system according to the electrical system schematic diagram, check the schematic diagram with the physical object, analyze the factors causing the fault, and gradually infer and find out. When looking for faults, different methods of seeing, hearing and touching can be used to judge whether the components of each device are abnormal; It is also necessary to use testing instruments (such as multimeter, oil pressure detector, vibration measuring instrument, barometer, etc.), because although it is simple and easy to check by human sensory organs, the examiner must have a certain level of technology and rich experience. Because everyone's sensory sensitivity is different, the inspection results are often different, and can only be simply qualitative inspection, which is difficult to quantitative analysis. Therefore, it is more accurate to use the testing instrument to further determine the effect

using "comparison method" to find faults is also a feasible and effective method. The comparison method, that is, the replacement method, uses qualified parts of the same model (new parts or normal parts of the same model) to replace suspicious parts. If the fault is eliminated after replacement, the original is faulty

in addition, there are methods such as drawing fault analysis reasoning diagram and causal analysis diagram to find faults. This is scientific and reliable

3. Disassembly and inspection, determine the cause of the failure

for determining each part of the disassembly and inspection, the order of disassembly and inspection should be determined according to the possibility of causing the failure, as well as the simplicity and complexity of the disassembly and inspection. The usual practice is to dismantle the simple first and then the complex; Those with high possibility of disassembly and inspection first and those with low possibility of disassembly and inspection later

there are many types of wheeled cranes with complex structures and various fault symptoms, which can be summarized into two categories: one is due to the damage of mechanical parts, which is called damaging fault. If the brake belt breaks, it will cause brake failure. The other is caused by loose connection, gap change, pipeline blockage, impurity intrusion, etc., which is called non-destructive fault, or maintenance fault. For example, the oil suction filter of the hydraulic system of the hydraulic crane is blocked, which affects the pressure of the hydraulic system

4. Repair work

for non-destructive faults, as long as necessary cleaning, lubrication, supplement, adjustment, fastening and other work can be eliminated. If the oil suction filter is blocked, the fault can be eliminated by cleaning

for damaging faults, we should take a cautious attitude to decide which parts must be replaced and which parts should be repaired and reused. This should be combined with technical capacity and equipment conditions, and economic benefits should be considered at the same time

5. Test work

for repaired parts or devices, local function test or overall performance test shall be carried out. Only after confirming that the performance of the whole machine has met the requirements can it be put into use. For example, if the oil pressure of the hydraulic system cannot rise, after removing the blockage of the oil filter, use the inspection oil pressure gauge to confirm that the oil pressure of the hydraulic system meets the set value. For another example, the friction belt of the brake of the lifting mechanism is sticky with oil. After replacing the new belt and adjusting the clearance, the no-load test and load test must be carried out

II. Precautions for troubleshooting

in the process of troubleshooting, disassembly, identification, repair and assembly are usually carried out. In addition to observing the general mechanical and electrical disassembly requirements and safety regulations, some specific problems should also be paid attention to, otherwise unexpected consequences will occur

1. Precautions for disassembly work

1) all working mechanisms of the whole machine should be stored. When it is necessary for the tire to leave the ground, a reliable object should be used to cushion the frame stably

2) during disassembly, shut down the engine and cut off the power supply to release the residual pressure of the hydraulic system and pneumatic system

3) when disassembling the battery, be careful not to be burned by the electric fluid in the battery

4) when disassembling heavy parts, reliable lifting and unloading machinery should be used to assist the operation, and do not rush to start, so as to avoid hurting people or damaging machine parts

5) for disassembly work with little assurance, it should be familiar with and understood in advance

6) for the parts requiring special tools to disassemble, the designated tools should be used, and it is not allowed to knock or vibrate arbitrarily

7) for devices that cannot be disassembled, they should be completely removed

8) do a good job in "marking" to avoid wrong installation, poor coordination or loss of balance

9) the removed parts shall not be placed disorderly, but shall be stored in clean containers by classification

2. Identification of important components

there are some very important components on the wheel crane. For example, the hoisting wire rope, luffing (grab) wire rope, telescopic boom wire rope and luffing (telescopic, outrigger) in China's underdeveloped regions meet the requirements of passenger car enterprises for battery quality, such as oil cylinder piston rod, brake, boom, frame, outrigger beam and axle. If these components are damaged, the consequences of the accident are unimaginable. In addition, safety devices, balance valves, hydraulic locks and other mechanical parts are also very important

combined with regular inspection, the above components should be tested and identified. Scrapping regulations shall be strictly implemented for steel wire ropes. If abnormal conditions such as deformation are found in structural parts, they should be stopped from use and handled properly

3. Repair and assembly work

for the parts determined to be repaired, they should be repaired carefully according to the structural principle and technical requirements. If it is difficult or uncertain to repair by themselves, they should be entrusted to a professional department for repair

the assembly work after repair should be carried out carefully. Usually, each part should be installed in place one by one according to the reverse process of disassembly sequence. The corresponding maintenance work should be carried out before and during assembly. For example, pay attention to the "mark" during disassembly; During the assembly of hydraulic components, all moving parts are generally coated with clean hydraulic oil, so as to ensure that there is an oil film on the friction pair and prevent dry friction at the beginning of movement; Fill the housing with oil before assembling the oil pump and oil motor

the pipe joints, oil plugging screws and other connecting screws of the hydraulic system are often disassembled and assembled, and oil leakage often occurs. In order to do a good job in assembly, polymer liquid sealant should be used for sealing. Alternatively, use sealing tape to assemble the oil leakage part of the thread. The sealing belt, i.e. PTFE raw material belt, can be used in the temperature range of -1000c to +2600c. It can resist the corrosion of various acids and bases, does not damage the threads, and has good vibration resistance. It is also convenient to remove the residual material when disassembling and repairing again. The use method of the sealing tape is that if the sealing tape is overlapped and tightly wrapped around the screw in the direction of the thread, it is considered that the experiment is invalid. There are two to three layers on the thread. Press the end tightly with your fingers and connect it with the internal thread to obtain a complete sealing effect

4. Precautions when checking and repairing electrical faults

when checking and repairing electrical faults (mainly refers to AC electric wheeled crane), in addition to strictly abiding by the electrical safety operation regulations, the following points should also be paid attention to:

1) when checking and repairing faults, the power supply must be cut off, and it is absolutely not allowed to open the electrical shield with electricity. During maintenance, the fuse of the control circuit must be removed and a warning board must be hung to prevent accidents caused by power transmission. Never allow the crane to be overhauled during operation

2) sufficient lighting must be ensured during maintenance. For the convenience of inspection and maintenance, when the portable lamp is needed, the voltage of the portable lamp should be strictly controlled within the range of safe voltage (i.e. below 36 volts), and a protective cover should be added outside the bulb. Never use one phase one ground 220 volt power supply

3) during the maintenance process, when there is a special need for live testing or maintenance, it must be confirmed that there are no other workers near the live parts and components on the frame before power transmission. During live line maintenance, there must be a specially assigned person to monitor the maintenance operators. The responsibility of the supervisor is to monitor the maintenance operators, prevent accidents against rules, and be prepared to cut off the power supply immediately in case of danger. For live maintenance, wear rubber gloves and insulated shoes. All places close to the conductive part with high quality and low price should be covered with rubber cloth or enclosed with wooden grating

4) when overhauling, the replaced parts or components must be properly handled and must not be placed randomly, let alone thrown from the crane. The overhaul is completed

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