Hydraulic excavator cooling components maintenance and inspection
When using a fully hydraulic used excavator, it is important to pay attention to the inspection and maintenance of the engine radiator, hydraulic oil cooler, and heat-related parts. Otherwise, the engine’s heat dissipation efficiency will be reduced, and the oil and water temperatures will increase, causing power to drop and wear to increase. In severe cases, it may lead to accidents of early engine damage, so the inspection and maintenance of these parts cannot be ignored.
The heat dissipation of the hydraulic excavator engine adopts suction air cooling, which allows the air passing through the radiator core to be well distributed. To ensure the original heat dissipation effect of the hydraulic excavator engine during use, it is necessary to ensure the integrity of the heat dissipation-related parts. The following aspects affect the heat dissipation effect:
1. Prevent hot air from reflux during use
The filler around the radiator is commonly known as “sponge”. But it cannot be replaced by any “sponge”. The requirements for it on the hydraulic excavator are that it must have good corrosion resistance and temperature resistance, and poor air permeability, because its main function is to prevent hot air from reflux. That is, to prevent the cold air sucked from the front of the radiator from rising in temperature and then entering the rear of the radiator (engine compartment) and not flowing back to the front of the radiator. If some high-temperature gas flows back to the radiator, the cooling effect of the system will inevitably be reduced, causing the oil and water temperatures to rise, making the engine unable to work normally and causing early damage. Therefore, during the use of the hydraulic excavator, you must not neglect the inspection and repair of the “sponge” around the radiator, and replace the damaged parts in time.
2. Ensure that the hot air is discharged smoothly
① The partitions of the engine compartment behind the radiator cannot be disassembled and discarded at will, otherwise the hot air will form vortices during the circulation process, affecting the discharge of the hot air. ② The exhaust holes of the engine compartment must be kept unobstructed, especially the exhaust holes of the engine and the lower guard plate of the oil pump must not be blocked or placed with objects, otherwise the discharge of the hot air will be blocked. The reduced air intake will increase the cabin temperature and also increase the intake temperature. The electrical components will age and be damaged early due to excessive temperature.
3. Ensure the air circulation area of the heat dissipation part
The ventilation area of the radiator core is very easy to be blocked due to air flow and various reasons during the use of the hydraulic excavator. If there is a protective net, the blockage should be cleared in time. If there is no protective net, it should be cleaned and cleaned in time according to the changes in the environment and the pollution of the outside of the radiator under the construction conditions. Otherwise, the air flow channel will be blocked and the ventilation area will be reduced, which will inevitably reduce the heat dissipation efficiency. It is more important to prevent the pollution inside the radiator. During use, the antifreeze and cleaning must be replaced regularly according to the random technical documents. Do not add contaminated water to replace the antifreeze. If the internal liquid flow channel is blocked, it is difficult to check and clean. The only way is to replace the radiator.
4. Ensure the air intake of the heat dissipation part
In addition to preventing hot air backflow and ventilation area, the most important factors affecting the air intake are the air duct and fan. There are three main types of air ducts: Venturi type, ring type, and box type. There are strict requirements for the installation position of the fan and the air duct, and there are also requirements for the distance between the fan and the engine. Because the air duct is usually used to improve the fan efficiency, so that the air is more evenly distributed on the radiator core, and prevent the hot air backflow in the engine compartment. According to the recommended installation requirements of Cummins engine: ① The distance between the fan and the radiator core is 50.8~101.6mm. ② The maximum linear speed of the fan blade tip is limited to 4000~5200 meters/minute. ③The gap between the fan blade tip and the air guide hole is 1.5% of the fan diameter. The smaller the gap, the higher the efficiency. When the gap is greater than 2.5%, the air supply of the fan will drop sharply. Therefore, the size and geometry of the air guide and fan cannot be changed during maintenance and repair, nor can the installation position of the radiator and fan be changed, otherwise the original heat dissipation effect and reliability cannot be guaranteed. In particular, most of the fans are made of non-metallic materials, which will deform when exposed to high temperatures. If there is deformation, the air supply of the fan will be reduced.
5. Ensure that the intake resistance and intake temperature are within the standard range (the intake resistance standard of Cummins 6BT5.9 engine is ≤15inH0o, and the engine power decreases by 1% and the heat dissipation increases by 1.5% for every 6℃ increase in intake temperature above 38℃)
The main factors that increase the intake resistance during use are: pollution of the air inlet filter, cyclone filter and air filter element. It is easy to clean and wash the cyclone filter and the imported filter in time, but it is not so easy to select the air filter element, because sometimes it cannot be purchased directly from the engine manufacturer for various reasons, and it is difficult to determine whether the purchased air filter element can meet the needs of the engine when purchased from other sellers. If the replaced paper filter element cannot meet the needs of the engine, it will directly affect the reliability of the engine and reduce the service life of the engine. This requires understanding and mastering some relevant performance and parameters of the paper filter element and the air filtration accuracy required by the engine. It should be known that the engine has very strict requirements on the filtration accuracy and intake resistance of the air. Imported diesel engines require the filtration accuracy of air to be 5um, and domestic diesel engines also require the filtration accuracy of air to be less than 20um, while the filtration accuracy of domestic filter paper is only 80um, the filtration accuracy of imported ordinary filter paper is 30um, and the filtration accuracy of imported high-efficiency filter paper is 2um. Therefore, the selected air filter element must match the power, economy and reliability of the original engine; the filter paper must have requirements such as thickness, tension resistance, original intake resistance, and filtration accuracy. The performance test of the filter element mainly includes the following four aspects: ① Flow-resistance test, to measure the pressure loss of air flow. ② Original filtration efficiency test, to calculate the dust collection efficiency of the filter element. The dust removal rate of a normal filter element should be above 99%. ③ Dust storage capacity test and cumulative efficiency test, the filter element is blocked due to excessive dust accumulation, and the intake resistance increases. The intake resistance when the engine power drops by 5% or the fuel consumption increases by 5% is a limit value. When this value is reached, the filter element must be cleaned or replaced. ④ Original intake resistance test, the pressure difference at the inlet and outlet when the rated intake volume passes through the filter element (the rated intake volume of the filter element must be greater than the intake volume required by the engine) should not exceed 3.2kPa, otherwise the filter element cannot meet the needs of the engine. The intake temperature is closely related to the position of the air inlet and the temperature of the cabin. The intake pipe and the air inlet need to be isolated from high-temperature parts or as far away as possible, and the high-temperature gas in the cabin should be prevented from entering the air inlet. At the same time, the hot air in the cabin must be discharged smoothly to minimize the temperature of the cabin. The engine is the power source of the hydraulic excavator. Whether the normal operation of the engine can be guaranteed depends not only on the design and manufacturing quality of the engine itself, but also on the maintenance inspection and scientific and reasonable maintenance of the engine during use. This scientific and reasonable maintenance is predictive preventive inspection and preventive maintenance based on the actual working conditions of the engine. During the maintenance process, the heat dissipation, air intake, exhaust and lubrication of the engine should be systematically analyzed. Through the analysis of the interaction and mutual influence factors of these four aspects, it is determined whether each part needs to be repaired or replaced to restore the original reliability and extend the service life of the engine.
The upper rotary platform located on the lower walking body of the hydraulic excavator is as important as the head and torso of the human body.
Although its structure is difficult to see from the outside, if the engine and various hydraulic devices installed in it fail or are overloaded, it will affect the overall state of the machine, reduce performance, and eventually lead to machine failure.
Therefore, the daily maintenance and inspection of the upper rotary platform of the machine should be given priority.
In order to improve the operating performance of the upper rotary platform and prevent unnecessary failure losses, what aspects should be paid attention to in the maintenance of the upper rotary platform?
Regularly check and replace the filter element
In order to prevent dust and impurities contained in the added oil from invading the main parts of the machine, protective measures are taken on the excavator. Multiple filters are installed on an excavator, and these filters play their own important roles.
(1) Air filter
The combustion of fuel in the engine requires fresh air. The air filter can remove foreign matter such as dust from the air sucked into the combustion chamber from the outside to prevent wear of the engine cylinder liner and piston ring.
(2) Oil and fuel filter
Motor oil and fuel are easily mixed with water and dust during storage and refueling. The filter can filter foreign matter and prevent wear of the internal system components of the engine. In addition, if these filter elements are seriously contaminated, it will cause the oil or fuel to flow poorly and the engine power is insufficient or poor lubrication will cause engine damage.
(3) Hydraulic oil filter
The function of hydraulic oil is to convert power into a medium, so the mixing of foreign matter such as dust is strictly prohibited. The hydraulic oil filter can prevent impurities from entering various parts of the hydraulic device.
In addition, the suction filter is installed in the hydraulic oil tank to protect the hydraulic pump in the hydraulic circuit. The oil after work will return to the hydraulic oil tank, and the return oil filter is installed in the return oil part. Therefore, the pump or other parts of the hydraulic system can be judged whether they are in an abnormal state by observing the degree of contamination of the return oil filter (such as the presence or absence of iron filings).
When the oil passes through the filter element, the impurities in it can be removed. Therefore, the contamination of the filter will become more and more serious with the accumulation of time. If the contaminated filter is not replaced in time, the oil flow will be reduced and the original performance of the machine cannot be fully utilized. In addition, if a damaged or over-contaminated filter continues to be used, impurities cannot be filtered, thereby shortening the service life of the machine.
Therefore, the filter element should be replaced regularly, and if an abnormality is found during daily maintenance and inspection, it should be replaced immediately.
To prevent machine wear, sufficient oil and grease should be added
During the operation of the hydraulic excavator, various parts of the machine will be accompanied by great friction. Grease and oil can reduce these frictions because they form an oil film that prevents the metal parts of the rotating parts from contacting each other.
Filling oil and grease is an important task, which is mainly to reduce friction and wear and enable the machine to run smoothly. However, if the oil is not filled sufficiently or deteriorated grease is added, the oil film will not be formed and the metal parts will contact each other, causing wear.
