The correct use and fault of the hottest construct

In recent years, in order to improve the use efficiency and operating comfort of machines, many construction machinery are equipped with air conditioners. On the one hand, air conditioners in construction machinery rely on refrigerant (the medium that absorbs and takes away heat) to circulate in the system to achieve refrigeration effect; On the other hand, it relies on the cooling water circulation from the engine to keep warm. The refrigeration part of the air conditioner is packaged in an automatic system, including: compressor, condenser, liquid storage tank, expansion valve, evaporator, fan and various electronic temperature sensors; The heating part includes: hot water valve, heat exchanger and various electronic temperature sensors. The common accessories of the two are: operation panel, blower, wind direction valve, line assembly, etc. 1. Correct use and precautions of air conditioner

1. Prevent dust from entering. Most construction machines work in harsh environments, such as excavators and bulldozers. When loading, unloading and mixing lime soil and fly ash, the amount of dust outside the machine is huge. At this time, the air inlet should be placed in the recirculation position to prevent the dust outside the machine from entering

II. In hot summer, the construction machinery is parked in the sun for a long time, and the machine is very hot. After opening the air conditioner, open a glass window, and then close the window after the hot air is discharged

III. the air conditioner should be used when the engine water temperature is normal. 3. Automatic storage: automatic storage of experimental data and experimental conditions (℃); If the engine works under heavy load for a long time and the water temperature is too high, the use of the air conditioner must be suspended until the water temperature is normal

fourth, avoid using the air conditioner for a long time during shutdown or idling, even under high temperature, so as to avoid the damage of the air conditioner due to the high temperature and pressure of the system

v. the wind speed gear of the air conditioner should be reasonably selected. In order to prevent excessive frosting of the evaporator and affect the operation effect of the system, the air supply speed and temperature control of the air conditioner should not be set to the lowest value for a long time. However, when the engine speed is lower than 1000r/min, the wind speed switch should be placed in the lowest gear to avoid insufficient power generation and cooling air of the generator

VI. when using the air conditioner, the air conditioner system must be kept clean, and the dust on the cooling fins of the condenser and evaporator must be removed frequently to maintain a good heat dissipation and ventilation effect

VII. In the season when the air conditioner is not used, it is necessary to operate the air conditioner for min every week, so as to lubricate the air conditioner system and prevent rust inside the compressor and other components. However, some users remove the compressor drive belt when not in use, thinking that this can reduce the wear of the compressor. In fact, this practice is wrong

VIII. Pay attention to the starting sequence of the engine and air conditioner, that is, start the engine first, and then start the air conditioner, so as to avoid difficulties when the engine starts with load

IX when the cooling effect of the air conditioner is poor, it must be turned off, checked and repaired in time to prevent its failure from further expansion or even deterioration

2. Common faults and troubleshooting of air conditioner system

(1) insufficient refrigeration or no refrigeration (this is the main fault of air conditioner)

insufficient refrigerant. If the refrigerant in the refrigeration system of the air conditioner is not filled for a long time, the pipeline leaks, mixes with air, etc., it can cause insufficient refrigerant in the system, and the result will be insufficient refrigeration. When the air conditioner is working, you can observe whether the refrigerant quantity in the pipeline is sufficient through the transparent window on the liquid storage tank. If you see a large bubble in the window, it indicates that the refrigerant quantity is insufficient; However, excessive refrigerant filling will also lead to insufficient refrigeration and increase pipeline leakage. At this time, the leakage of the system pipeline should be eliminated first, and then ask professionals to fill the refrigerant

the second compressor does not operate. The refrigerant cannot circulate in the pipeline and cannot be cooled (the refrigerant depends on the compressor for refrigeration). The relevant lines, relays, thermostats and electromagnetic clutches of the compressor should be repaired. The compressor is usually accompanied by abnormal knocking sound after damage; If the valve plate, bearing or sealing gasket of the compressor is damaged, it must be repaired or replaced in time

the heat dissipation of the three condensers is poor (this is the reason why the air conditioner of construction machinery is prone to failure). If the condenser (usually located in front of the engine radiator or hydraulic oil radiator) is blocked by some dust and dirt, it will cause poor heat dissipation and affect the refrigeration effect. The condenser can be repeatedly purged with high-pressure gas with a force of 30~40n; For places with serious dirt, you can brush them repeatedly with a steel wire brush, or brush them with a brush dipped in weak hydrochloric acid water with a very low concentration (pay attention to wear gloves to prevent hydrochloric acid water from contacting the skin). After the dirt is removed, you must wash them repeatedly with clean water for several times in time to prevent the residual weak hydrochloric acid from corroding them

the four refrigerant pipeline is blocked. The fault points are mostly on the liquid storage tank or expansion valve. The particle board circuit of the pipe gb/t 4897 (2) 003 should be cleaned and vacuumized again to fill the refrigerant or replaced with a new one

fifth, the air volume is too small. Most of them are caused by the blockage of the air filter, which can be installed and used after being removed and blown clean. For example, the air filter of the air conditioner of cat320b excavator is located at the lower side of the rear view window of the cab. When working in dusty places, it is more necessary to remove the dust there frequently. In addition, the blower speed of the evaporator may not be enough or not at all, which is manifested by a large amount of frost on the evaporator and insufficient air output; At this time, the blower switch and rheostat should be repaired, or the blower should be replaced

(2) noise

noise generated by compressor. When using the air conditioner, turn the vertical experiment into the horizontal experiment. Under normal circumstances, the compressor will make a "click" sound at the moment when its electromagnetic clutch is engaged or disengaged, but it is extremely quiet in operation. If there is a "boom, boom" sound during operation, it indicates that the compressor has been damaged due to the lack of refrigeration oil; At this time, in most cases, only new parts can be replaced

II tape noise. Usually, the tension of the tape driving the compressor is insufficient. When the compressor is under load, the tape slips and produces a sharp hiss. The belt can be adjusted or replaced with a new one. The standard of the tightness of the transmission belt is to press the middle point of the transmission belt with your thumb with all your strength, and its deflection is mm, which is the best

three fan noise. If the motor bearing of the air conditioner blower is worn or even damaged, the fan will make a lot of noise as the speed increases; At this time, the bearing must be replaced

3 the air conditioner system is faulty due to the construction machinery itself

insufficient cooling water in the engine radiator causes overheating, resulting in an increase in the temperature at the high pressure side and a decrease in the cooling effect of the air conditioner

the second engine cooling fan tape is too loose, causing slipping and high water temperature

three engine radiator or hydraulic oil radiator is blocked by dirt, and poor ventilation causes poor cooling of the condenser

after the thermostat of the fourth engine was damaged, it was not replaced in time, which led to the working water temperature of the engine not rising in winter, resulting in insufficient heating; It is necessary to reset the thermostat in time

v. the battery current is overloaded, and the failure of the alternator causes insufficient charging of the battery or the failure of the voltage regulator; At this time, repair or replace it