First, the importance of construction machinery maintenance
Construction machinery maintenance is the abbreviation of construction machinery maintenance and repair. Maintenance is a technical activity aimed at continuously expanding or improving the performance of construction machinery; Repair is a technical activity to restore or improve the performance of construction machinery. The function of maintenance can be summarized as "increasing profits, saving raw materials, optimizing the return on investment, prolonging the service life of equipment, reducing production costs and avoiding accidents and technical disasters". Maintenance provides an important preliminary guarantee for the orderly and efficient work of construction machinery. It can be said that with the continuous emergence of high-tech products, advanced maintenance can ensure the trouble-free operation of equipment and keep the equipment in good condition.
In essence, maintenance is an investment in the future. Maintenance is not only troubleshooting, but also a long-term and continuous investment to ensure the survival and development of enterprises and obtain economic benefits of enterprises. Doing this work well is of great significance to ensure the normal production of enterprises, increase output, improve product quality, improve labor productivity, reduce costs and improve other technical and economic indicators. At present, there are still many problems in the maintenance of construction machinery, so we should conscientiously sum up the experience and lessons and thoroughly study the measures to do well in the maintenance of construction machinery. The future maintenance will be green maintenance, advanced maintenance and reconstruction engineering maintenance. Maintenance is not only a means to restore the original performance of construction machinery, but also a means to improve the performance of construction machinery, thus improving the engineering quality. Maintenance is also an investment, as important as fixed assets. Without maintenance investment, it is difficult to guarantee the return of fixed assets and expand fixed assets. Maintenance is no longer an auxiliary means and emergency measures, but an integral part of productivity and an important task related to economic development.
Second, the types and consequences of failures in the use of construction machinery
(1) There are six common faults of construction machinery:
1. Failure: such as fracture, cracking, pitting, ablation, deformation, strain, cracking, indentation, etc.
2. Degradation failures: such as aging, deterioration, peeling, abnormal wear, etc.
3. Looseness failure: such as loosening and falling off.
4. Misalignment faults: such as too high or too low pressure, stroke disorder, too large or too small clearance, interference, etc.
5. Blockage and leakage faults: such as blockage, water leakage, air leakage and oil leakage.
6. Failure modes of performance degradation or functional failure: such as functional failure, performance degradation, overheating, etc.
(2) There are four types of fault consequences:
1. Hidden fault consequences: Hidden faults have no direct impact, but may lead to serious and often disastrous multiple fault consequences.
2. Safety and environmental consequences: if the fault will cause casualties, it will have safety consequences; If an enterprise violates industrial, local, national or international environmental standards due to failure, failure will have environmental consequences.
3. Availability consequences: If the failure affects production (output, product quality, after-sales service or operating expenses other than direct maintenance expenses), it is considered to have availability consequences.
4. Non-use consequences: what falls into this category is obvious functional failure, which neither affects safety nor production, and only involves direct maintenance costs.
Third, the failure cause analysis and its steps
The purpose of fault analysis is not only to identify the nature of the fault and find the cause of the fault, but also to clarify the fault mechanism and put forward effective improvement measures to prevent the fault from happening again. Through fault analysis, the real cause of the fault is found, and measures are taken from the aspects of design, material selection, processing and manufacturing, assembly adjustment, use and maintenance to improve the reliability of mechanical products. For example, in the process of centrifugal pump operation, due to the machinery itself, process operation or high temperature, high pressure, material corrosion and other conditions, it often causes various failures such as head reduction, insufficient flow, abnormal sound, vibration and so on. Through the concrete analysis of the fault situation, find out the reasons and take measures, so as to make the equipment run normally, and at the same time, it can also guide the design, processing, assembly, use and maintenance, and improve the reliability of mechanical products.
When analyzing faults, we usually start with the fault phenomena and find out the reasons and fault mechanisms through the fault phenomena. Due to the limitation of field conditions, the observed or measured faults may be systematic, such as the centrifugal pump not sucking liquid; It may also be that a component, such as the packing of a centrifugal pump, is overheated; It may also belong to the surface damage of a part, such as a shaft or sleeve. Therefore, for different levels of product structure, their failure modes have a causal relationship with each other. For example, the failure of "bearing burning" is the reason why its superior centrifugal pump can't operate normally, and it is also the result of its subordinate "bearing overheating" failure mode.
Fault cause analysis is a comprehensive subject, involving system analysis, structural analysis, experimental analysis, and knowledge of fatigue, fracture, wear and corrosion. Fault analysis mainly includes the following steps:
1. Field investigation. It mainly includes the collection of background data and the use conditions such as the time, environment and sequence of faults; Shoot or photograph the fault site; Collect and sort out the main historical data of fault parts, such as design drawings, operating procedures, acceptance reports, fault records, maintenance reports, etc. Preliminary inspection, identification, protection and cleaning of faulty parts.
2. Analyze and determine the cause and mechanism of the failure. It mainly includes nondestructive testing, performance test, macroscopic and microscopic examination of fracture, etc. Necessary theoretical analysis and calculation, such as strength, fatigue and fracture mechanics analysis and calculation; The cause and mechanism of the failure are preliminarily determined.
3. Analysis conclusion. When each failure analysis work reaches a certain stage or after the test work, all the information, investigation records, testimonies and test data obtained should be summarized, and a comprehensive analysis and judgment should be made according to whether there are problems in design, materials, manufacture and use, and a report with clear conclusions and pertinent suggestions should be put forward. On the one hand, improve work, accumulate information and exchange experience; On the other hand, it also provides a basis for claims and legal arbitration.
Four, troubleshooting and maintenance of construction machinery
More than 85% of construction machinery failures are caused by wear and tear. To solve the wear of parts, besides using excellent materials, selecting advanced manufacturing technology and designing reasonable mechanical structure, the most important thing is to ensure reasonable lubrication of machinery, and it also needs careful operation by operators. For construction machinery, first of all, it is necessary to reduce the wear and tear of parts as much as possible to prevent the occurrence of faults; Second, we should use maintenance methods flexibly and constantly explore and study new maintenance methods. Due to the difficulties of spare parts, materials and lifting equipment, maintenance personnel are required to give full play to their intelligence and eliminate faults as soon as possible.
1. Ensure the reasonable lubrication of machinery.
More than 50% failures of construction machinery are caused by poor lubrication. Due to the precision of construction machinery parts, good lubrication can maintain its normal working clearance and suitable working temperature, and prevent impurities such as dust from entering the machinery, thus reducing the wear speed of parts and reducing mechanical failures. Correct and reasonable lubrication is one of the effective measures to reduce mechanical failures. Therefore, we should first use lubricants reasonably, choose different types of lubricants according to different mechanical structures, and choose appropriate lubricant brands according to different environments and seasons. Can not be replaced at will, can not use fake and shoddy products; Second, always check the quantity and quality of lubricating oil. Those with insufficient quantity should be replenished, and those with poor quality should be replaced in time.
2. Operate the machine carefully and reasonably.
As a mechanical operator, check whether the coolant and engine oil are sufficient before starting, and replenish them in time before starting. After the machine is started, it should enter the low-speed preheating stage, and then start working after the coolant and engine oil reach the specified temperature. Overloading is strictly prohibited at low temperature. Operators should always check the values of various thermometers during mechanical operation, and then work after finding problems and solving them in time. When operating construction machinery, be careful not to work under the maximum load that the machinery can bear, increase or decrease the throttle evenly, ensure that the machinery is in a relatively stable load change, prevent the ups and downs of the engine and working device, reduce the wear and tear of the machinery and reduce the occurrence of faults.
3. Emergency maintenance on site
(1) Parts maintenance method
Repair damaged parts quickly by machining, welding and grinding. For example, for a pump, the mixing shaft of the hopper suddenly failed due to serious wear, and the accessories were difficult to buy at the moment. In this case, the mixing shaft can be removed, and surfacing and lathe processing can be used to quickly restore the mechanical operation and save money. The main hydraulic oil pipe of the working pump of ZL40B loader, which is discharging slag in the tunnel, suddenly burst. At that time, there were no spare parts, so the damaged tubing joint could be welded on it with different tubing to quickly restore the operation of the loader. If there is a hole in the water inlet pipe of Steyr dump truck in operation, in order not to affect the construction, branches can be cut into the shape of the hole and stuffed in the hole, which is quite effective and can quickly resume Steyr's operation.
(2) Parts replacement or replacement repair method
Replacing damaged parts with intact spare parts can be used for overhaul and on-site maintenance. At the same time, we can make full use of the surrounding materials to replace the damaged parts of construction machinery. If a PC220-6 hydraulic excavator's bucket pin piercing screw breaks during work, there are no spare parts in the warehouse and the purchase time is long, a Steyr balance shaft fixing bolt can be used to replace it, so that the excavator can resume normal work. Replacing the defective gasket with ordinary steel plate gasket, replacing the sealing gasket of low-pressure oil circuit with cigarette case and replacing the sealing asbestos rope in water pump with plastic cloth can meet the needs of emergency maintenance temporarily.
(3) Parts handling methods
Skip the faulty parts, connect the pipes or circuits, and quickly resume the operation of the construction machinery. For example, a brake cylinder cup of Steyr dump truck is damaged and leaked, resulting in poor braking. A valve was temporarily placed in the pipeline to shut off the gas in the sub-pump, which quickly restored Steyr's operation. During the winter construction of ZL40B loader, because the driver didn't drain water at night, the oil radiator was frozen and cracked, which could not be repaired in a short time. The radiator can be detached, the engine oil pipe can be directly connected with the oil circuit of the engine body, and the radiator water pipe can be short-circuited, so as to quickly resume the work of the loader.
refer to
Zhuang xitie. Predictive Maintenance of Construction Machinery [J]. Road Machinery and Construction Mechanization, 2003, (1).
[2] China Construction Industry Association Construction Machinery and Equipment Management Branch. Management, use and maintenance of construction machinery [M]. Beijing: China Building Industry Press, 1998.