Determine the technical judgment and maintenance content for the major overhaul of the paver

1. Principles for deciding on major overhauls

Due to the significant differences in the operating conditions and maintenance levels of various pavers, it is difficult to determine the reasonable time for major overhauls based solely on their service life and working hours. From our years of practice in major overhauls of pavers, we have learned that major overhauls are generally required after 4,000 to 6,000 hours of operation. The main symptoms of a paver before it must undergo a major overhaul are as follows:

(1) The engine power has significantly decreased, with symptoms such as air leakage, oil burning, and difficulty in starting occurring.

(2) A decline in hydraulic power is generally manifested as insufficient walking power or material conveying and distribution power. Specifically, it is basically normal under low-load operations, barely feasible under medium-load operations, but unable to perform heavy-load operations.

(3) The pipelines and sealing elements of the hydraulic system are aged, resulting in severe oil leakage.

(4) The circuits of the electronic control system are aged, resulting in a decline in control accuracy and a high failure rate.

(5) The paver has been in operation for about 5,000 hours, but its transfer case, transmission and reducer have never been inspected and repaired, which poses a potential fault.

2. Major overhaul contents

The major overhaul of pavers must strictly follow the relevant maintenance standards, requiring thorough disassembly and inspection. During the repair process, there should be no complacency or perfunctoriness. Taking the currently widely used 10mABG423 paver as an example, the main contents to be included during major overhauls are as follows:

(1) Engine: Undergo major overhauls in accordance with DEUTZ standards and run in as specified. If conditions permit, loading running-in and bench tests should also be carried out.

(2) Hydraulic system: It includes walking pumps and motors, auger pumps and motors, hammer pumps and motors, scraper pumps, auxiliary pumps, vibration motors, hydraulic valves of the entire machine, hydraulic cylinders, oil tanks, hydraulic pipelines and accessories, etc. Maintenance should be carried out in accordance with standards such as REXROTH. After the repair, bench tests of the hydraulic pump and hydraulic motor must also be conducted.

(3) Electrical control system: It includes the circuits of the entire machine, electrical control components, as well as the electrical control of the walking control system, leveling control system, and material level control system. With the continuous advancement of paver control technology, the technical content of the walking, leveling and material level control systems is getting higher and higher. Therefore, it should be carried out by experienced professional technicians using specialized instruments for maintenance.

(4) Transmission system: It includes the main drive box, walking reducer, auger reducer, auger chain drive box, scraper reducer and scraper chain drive box, etc.

(5) Material conveying and distribution system: Inspect or replace its vulnerable parts.

(6) Ironing plate components: Inspect or replace its vulnerable parts.

(7) Frame shaping and maintenance of the idler wheels

(8) Shaping and painting of all metal parts of the machine.

(9) Overall machine debugging

3. Choose a reliable maintenance unit

At present, most domestic construction enterprises do not have the conditions and capabilities to carry out major overhauls of pavers on their own, and generally adopt the method of entrusting repair for major overhauls. Therefore, choosing a reliable maintenance unit is the key to ensuring repair quality, reducing failure rates, extending effective operation time, enhancing productivity and meeting strict schedule requirements. Making a good choice is equivalent to saving the operating cost of the paver and improving the economic benefits of the enterprise. It is evident that the sending unit for repair should select an ideal repair enterprise from multiple aspects such as repair technology, quality, price, service, and reputation, and from the perspective of cost performance. A paver overhaul enterprise should at least meet the following conditions:

(1) Reasonable professional allocation and talent structure. The major overhaul of pavers is a systematic project that requires the mutual collaboration among engineers engaged in engine, hydraulic, electronic control and mechanical repairs. Good collaboration can enhance the maintenance quality of pavers.

(2) A stable team of maintenance technicians. The level of maintenance technicians, especially those majoring in maintenance, plays a very important role in the overall maintenance quality of pavers. Maintenance enterprises should have a stable team of maintenance technicians and frequently carry out technical exchanges and regular training to continuously improve their professional skills. Specialized technicians can be selected from among outstanding technicians who have maintained pavers for more than five years.

(3) Complete repair equipment. Paver maintenance enterprises must have certain working conditions and be equipped with relatively complete facilities, such as workshops, lifting equipment, machining equipment, testing equipment and instruments, etc. In particular, the test equipment should include hydraulic plunger pump test benches, hydraulic plunger motor test benches, hydraulic cylinder test benches, hydraulic steering gear test benches, hydraulic cylinder test benches, hydraulic pulse test benches, gear pump test benches, engine test benches and electronic control test instruments, etc.

(4) It has sufficient spare parts reserves and reliable sources of spare parts with quality assurance. The level of spare parts reserves of maintenance enterprises, especially the inventory levels of hydraulic components and electrical control components, is not only a prerequisite for ensuring the maintenance period and quality, but also one of the important factors that ultimately determine whether the prices of spare parts are reasonable and whether on-site services are timely.

(5) Good quality reputation. Examining the maintenance quality and reputation of maintenance enterprises should be included in important decision-making steps. Facts show that a large number of maintenance techniques originate from the long-term practice of maintenance enterprises. Therefore, through the history and performance growth of a maintenance enterprise, its credibility can be comprehensively evaluated. In this regard, construction enterprises should not only conduct personal investigations but also, if possible, seek suggestions from their peers.

4. Precautions for Major Overhauls

(1) The same paver should avoid being repaired by multiple units. Some units divide the paver into several units and have different units repair it respectively. Some maintenance units, after undertaking major overhaul tasks, due to their lack of ability to carry out the repairs themselves, either hire people to do it everywhere or entrust external units to do it. In this way, the engine, hydraulic system, electronic control system and mechanical parts are repaired by different units or personnel. Eventually, no one is responsible for the performance of the entire machine. During on-site services, problems with the engine are often shifted to the hydraulic system and then to the electronic control system, with each passing the buck. In the end, it is the users of the paver who suffer. This kind of situation is not uncommon.

(2) After major overhauls, pavers should have a reasonable warranty period. Due to the significant differences in the actual workload of each paver within the same period, it is not entirely reasonable to determine the warranty period solely based on working hours or years and months. If the warranty period is set at three months after the major overhaul and factory release, it is possible that the product has not actually been put into use within three months of factory release. If the warranty period is set at 1,000 (working) hours, the warranty period may last up to two years. As the construction period in the Beijing area is generally from April to October each year, our approach is to offer users a warranty of 1,000 (working) hours or one working cycle (up to October 30 of the current year). This method is in the interests of both parties.

(3) Replacing vulnerable parts and conducting maintenance and other simple repair work cannot be equated with major overhauls. Many users have said, "Our paver was just overhauled by a certain unit last year, and the labor cost was only a few tens of thousands of yuan." When asked about the repair content, it was said: "The rammer, the ironing plate, the material conveying base plate, the sprocket, and the oil were changed, etc." This kind of repair cannot be equated with a major overhaul. It is a normal replacement of parts and maintenance, with no difficulty or risk involved. The repair unit should not charge labor fees for it as a major overhaul.

(4) During the maintenance process of the paver, it should be open to users. Users have the right to know about the major overhaul process of the paver, including disassembly and inspection, assembly, testing, commissioning processes, and the brands of the replaced parts, etc. We generally suggest that the user's unit send a captain to supervise the maintenance. On the one hand, it supervises the quality and progress of the maintenance, and when there are any problems, they can be reported to the leaders of the unit in a timely manner. On the other hand, it can be used as an opportunity to gain a deeper understanding of the structure and principle of the paver. When simple faults occur during construction, they can be resolved independently in the first instance.

(5) Arrange the maintenance time reasonably. Major overhauls are different from general equipment maintenance. It takes about 2 to 3 months from disassembly to the completion of the entire machine's debugging and leaving the factory. In northern regions, the major overhaul time of pavers is mainly concentrated in winter. Therefore, the workload of professional overhaul shops in winter is very large. Thus, users who decide to have their machines overhauled in winter should send them to the repair shop in advance to give the maintenance unit sufficient time for debugging and ensure the reliability of the paver's operation after the major overhaul.