Maintenance of excavator

The purpose of regular maintenance of excavators is to reduce machine failures, prolong machine service life, shorten machine downtime, improve work efficiency and reduce operating costs.

As long as the fuel, lubricating oil, water and air are well managed, 70% of failures can be reduced. In fact, about 70% of failures are caused by poor management.

Check regularly.

Visual inspection: Visual inspection shall be carried out before the starter. Thoroughly inspect the surrounding environment and the bottom of the locomotive in the following order:

1, whether there is oil, fuel and coolant leakage.

2. Whether there are loose bolts and nuts.

3. Whether the electrical circuit is broken, short-circuited and the battery connector is loose.

4. Whether there is oil pollution.

5. Whether there are people piling up.

Matters needing attention in daily maintenance

Daily inspection is an important link to ensure the long-term and efficient operation of hydraulic excavators, especially for self-employed, doing a good job of daily inspection can effectively reduce maintenance costs. First, turn the machine twice to check whether the appearance and chassis of the machine are abnormal, and whether there is grease flowing out of the slewing support. Then, check the bolts and fasteners of the retarder and the crawler. If it is a wheeled excavator, it is necessary to check whether the tires are abnormal and the stability of air pressure. Check the bucket teeth of the excavator for serious wear. It is understood that the wear of bucket teeth will greatly increase the resistance in the construction process, which will seriously affect the work efficiency and increase the wear of equipment parts. Check the stick and cylinder for cracks or oil leakage. Check the battery electrolyte to avoid falling below the low level. The air filter is an important part to prevent a large amount of dusty air from entering the excavator, so it should be checked and cleaned frequently. Check fuel, lubricating oil, hydraulic oil, coolant, etc. frequently. Need to add, it is best to choose oil according to the requirements of the manual and keep it clean.

Post-startup inspection

1, the horn and all instruments are in good condition.

2. Engine starting state, noise and tail gas color.

3, whether there is oil, fuel and coolant leakage.

Fuel oil management

Choose different brands of diesel oil according to different ambient temperatures (see table1); Diesel oil cannot be mixed with impurities, lime soil and water, otherwise it will make the fuel pump wear prematurely; High paraffin and sulfur content in inferior fuel will damage the engine; After daily operation, the fuel tank should be filled with fuel to prevent water droplets from forming on the inner wall of the fuel tank; Before daily operation, open the drain valve at the bottom of the oil tank to drain water; After the engine runs out of fuel or the filter element is replaced, the air in the road must be exhausted.

The lowest ambient temperature is 0℃-10℃ -20℃ -30℃

Diesel brand 0#-10# -20# -35#

Management of other oils

Other oils include engine oil, hydraulic oil and gear oil; Different brands and grades of oils cannot be mixed; Different kinds of excavator oil have different chemical or physical additives in the production process; Ensure that the oil is clean and prevent impurities (water, dust, particles, etc.) from entering. ) from mixing; Select the oil label according to the ambient temperature and use. When the ambient temperature is high, the engine oil with high viscosity should be selected; when the ambient temperature is low, the engine oil with low viscosity should be selected; The viscosity of gear oil is relatively large to adapt to large transmission load, and the viscosity of hydraulic oil is relatively small to reduce the flow resistance of liquid.

Selection of Oil for Excavators

External temperature of container℃ Oil type change cycle h Change quantity l

Engine oil pan -35-20 CD SAE 5W-30 250 24

-20- 10 CD SAE 10W

-20-40 CD SAE 10W-30

- 15-50 CD SAE 15W-40

0-40 CD SAE 30

Rotating mechanism box -20-40 CD SAE 30 1000 5.5

Shock absorber housing CD SAE 30 6.8

Hydraulic oil tank CD SAE 10W 5000 PC200 Model: 239

Type PC220: 246

CD SAE 10W-30

CD SAE 15W-40

Final drive CD SAE90 1000 5.4

1), and reasonable selection of hydraulic oil.

1. Viscosity of hydraulic oil

The principle of determining the viscosity of hydraulic oil is to make the viscosity of hydraulic oil (used for pumps and motors) in the best range (16-36x 10-6mm 2/s) on the premise of considering the working temperature and efficiency of the hydraulic circuit. The short-time cold start viscosity corresponding to the lowest ambient temperature is ≤1000x10-6mm 2/s; The viscosity at 90℃ corresponding to the maximum allowable oil leakage temperature in a short time is ≥10x10-6mm 2/s.

2. Viscosity index (VI)

This index directly reflects the property that the viscosity of oil changes with the change of temperature (that is, the viscosity-temperature characteristics of oil). The high viscosity index of oil shows that the viscosity of this oil changes little with the change of temperature. On the contrary, it is bigger. The viscosity index of anti-wear hydraulic oil of well-known foreign manufacturers (such as Mobil and Shell) is all VI≥ 1 10, and the viscosity index of domestic advanced anti-wear hydraulic oil is about VI=95. The viscosity indexes of high viscosity index hydraulic oil (HV) and multi-grade engine oil produced abroad are all VI; 140。 Users who use large imported hydraulic excavators and use domestic hydraulic oil (or use engine oil as hydraulic oil) should pay special attention to this point. The decrease of viscosity index will reduce the environmental temperature range that oil can adapt to. If you don't need to use it, you should consult the oil manufacturer for relevant information, adjust the use range of oil appropriately, and change the relevant setting values of the equipment (such as the limit temperature, etc.). ) If necessary.

3. Other comprehensive performance

Due to the high working pressure (≥32 MPa) of the hydraulic system of modern large-scale hydraulic excavators, the allowable working oil temperature is high (about 90℃). In order to ensure that the hydraulic system can work normally during the normal oil change cycle, the oil selected by the system is required to have good quality in lubricity, oxidation stability, wear resistance, rust prevention and corrosion resistance, emulsification resistance, foam resistance, shear stability and extreme pressure load.

2) Good hydraulic oil cooling system

For the improvement of the hydraulic oil cooling system (more precisely, the hydraulic oil temperature control system) of large hydraulic excavators, although the specific methods adopted by various manufacturers are different, the basic idea is the same, that is, not only can the hydraulic oil temperature be balanced within the ideal range during continuous operation, but also the hydraulic system can be quickly heated up when it is put into operation in cold state (reaching the normal working temperature range of oil). On the premise of using qualified hydraulic oil, when the hydraulic oil is overheated, the inspection steps of the hydraulic oil cooling temperature control system are as follows:

1. Whether the hydraulic oil radiator is blocked by dirt, which leads to the decrease of heat dissipation efficiency, and clean the radiator if necessary.

2. Detect the actual working pressure of the fan speed system under extreme conditions, so as to determine whether the hydraulic components of the loop are faulty and whether the oil temperature sensor or the control loop is working normally. At this point, the fan speed and system working pressure should be the maximum; Otherwise, the corresponding parameters of the system should be adjusted or the damaged parts should be replaced.

3) Inspection of relevant hydraulic parameters in the system

There are two main control modes for the working pump of a large hydraulic excavator: limit load regulation (GLR) with pressure cut-off function and load sensing regulation (LS). When the working pressure of the system reaches the set value, the deflection angle of the swash plate of the variable displacement pump is reduced, so that the pump can only be kept in the "residual" flow state needed to maintain the pressure, so as to avoid overheating caused by overflow of the overflow valve. In order to achieve this goal, according to the technical requirements, the system parameters are matched to make the set value of the cut-off valve in the loop lower than the set value of the primary pressure valve; Otherwise, the opening of the main pressure valve will cause the overflow to overheat.

At the same time, check whether the secondary valve works normally. This work must be carried out in strict accordance with the technical requirements, and the relevant parameters of the system should be restored if necessary.

4), eliminate abnormal internal leakage

Mainly refers to the abnormal internal leakage caused by the locking of reversing valve and pressure valve caused by the pollution of hydraulic oil in the system. Inspection method: measure the pressure, check the function, or listen to abnormal noise ("throttle flushing sound" is caused by lax valve opening) or touch to check whether the temperature is too high locally.

5), prevent the component volume efficiency decline.

Attention should be paid to both abnormal wear and normal wear. The former may happen in a short time, and can be judged by checking the quality of oil and combining the functions of the system (such as whether the actuator moves normally and whether the speed drops, etc.). ); The latter should follow certain laws, conduct a comprehensive investigation and take timely measures.

Lubricating oil management

Using lubricating oil (butter) can reduce the wear of moving surfaces and prevent noise. When storing grease, dust, sand, water and other impurities should not be mixed; It is suggested to choose lithium-based grease G2-L 1, which has good wear resistance and is suitable for heavy load conditions. When filling, try to squeeze out all the old oil and wipe it clean to prevent sand sticking.

Maintenance of filter element

The filter element plays the role of filtering impurities in the oil circuit or gas circuit to prevent impurities from invading the system and causing failures; All kinds of filter elements should be replaced regularly according to the requirements of the operation and maintenance manual; When replacing the filter element, check whether there is metal adhesion on the old filter element, and diagnose and take improvement measures in time if metal particles are found; Use pure filter elements that meet the requirements of the machine. The filtering ability of fake and inferior filter elements is poor, and the quality of filter layers and materials does not meet the requirements, which will seriously affect the normal use of the machine.

Contents of regular maintenance

① Replace the fuel filter and additional fuel filter after the new machine works for 250 hours; Check the clearance of the engine valve.

② Daily maintenance; Check, clean or replace the air filter element; Clean the inside of the cooling system; Check and tighten the track shoe bolts; Check and adjust the back tension of the track; Check the air inlet heater; Replace the bucket teeth; Adjust the bucket clearance; Check the liquid level of the front window cleaning solution; Check and adjust the air conditioner; Clean the floor in the cab; Replace the crusher filter element (optional). When cleaning the inside of the cooling system, after the engine is completely cooled, slowly loosen the water filler cap to release the internal pressure of the water tank, and then discharge the water; Don't clean the engine when it is working, the high-speed rotating fan will cause danger; When cleaning or replacing coolant, the machine should be parked on a level ground; Replace the coolant and corrosion inhibitor according to Table 3. The ratio of antifreeze to water is as required in Table 4.

Type of internal cleaning and replacement cycle of coolant for corrosion inhibitor replacement cycle of cooling system

Use AF-ACL antifreeze (super antifreeze) every 2 years or every 4000 hours, every 1000 hours or when changing coolant.

AF-PTL antifreeze (long-acting antifreeze) every year or 2000 hours.

Add AF-PT antifreeze (winter type) every 6 months (only in autumn).

Table 4 Mixing ratio of antifreeze and water

Ambient temperature℃/capacity l-5-10-15-20-25-30

Antifreeze PC 200 5.16.7 8.09.110.211.

PC 220 5.4 7.0 8.4 9.6 10.7 1 1.65

Water pc20017.115.514.213.12.01.

PC 220 17.9 16.3 14.9 13.7 12.6 1 1.65

③ Check items before starting the engine. Check the coolant level (add water); Check the engine oil level and add oil; Check the fuel level (add fuel); Check the hydraulic oil level (add hydraulic oil); Check whether the air filter element is blocked; Check the wires; Check whether the horn is normal; Check the lubrication of the bucket; Check the water and sediment in the oil-water separator.

④ Every 100 maintenance items. Boom cylinder head pin shaft; Boom pin; Rod end of boom cylinder; Pin shaft of bucket cylinder head; Connecting pin of boom and bucket arm; The cylinder rod end of the stick cylinder; Bucket cylinder head pin shaft; Half-bar connecting rod connecting pin; Rod ends of bucket rod and bucket cylinder; Bucket cylinder head pin shaft; Connecting pin of connecting rod; Check the oil level in the slewing mechanism box (refueling); Drain water and sediment from the fuel tank.

⑤ Check the oil level in the main reducer box every 250 hours for maintenance items (add gear oil); Check the battery electrolyte; Change the oil in the engine oil pan and engine filter; Lubricate the slewing bearing (2 places); Check the tension of fan belt, check the tension of air conditioner compressor belt and adjust it.

⑥ Maintenance items every 500 hours and maintenance items every 100 and 250H at the same time; Replace the fuel filter element; Check the height of the grease for the slewing pinion (add grease); Check and clean radiator fins, oil cooler fins and cold sensor fins; Replace the hydraulic oil filter element; Change the oil in the final drive box (only at the first 500 hours, and then at 1000 hours); Clean the air filter inside and outside the air conditioning system; Replace the hydraulic oil exhaust element.

⑦ Maintenance items every 1000 hours. At the same time, carry out maintenance projects every 100, 250 and 500h; Replace the oil in the slewing mechanism box; Check the oil level (oil return) of the shock absorber housing; Check all fasteners of turbocharger; Check the clearance of turbocharger rotor; Inspection and replacement of generator belt tension; Replace the anti-corrosion filter element; Change the oil in the final drive box.

⑧ Maintenance items every 2000 hours First, complete the maintenance items every 100, 250, 500 and 1000 hours; Clean the filter screen of the hydraulic oil tank; Clean and check the turbocharger; Check the generator and start the motor; Check the engine valve clearance (and adjust it); Check shock absorber.

Pet-name ruby more than 4000 h maintenance. Increase the inspection of the water pump every 4000 hours; Add the item of changing hydraulic oil every 5000 hours.

Attending long-term storage. When the machine is stored for a long time, the working device should be placed on the ground to prevent the piston rod of the hydraulic cylinder from rusting; The whole machine is cleaned and dried and stored in an indoor dry environment; If it can only be stored outdoors due to conditions, the machine should be parked on a well-drained cement floor; Before storage, please fill the oil tank, lubricate all parts, replace hydraulic oil and engine oil, coat a thin layer of butter on the exposed metal surface of the piston rod of the hydraulic cylinder, and remove the negative terminal of the battery, or remove the battery and store it separately; According to the lowest ambient temperature, an appropriate proportion of antifreeze is added to the cooling water; Start the engine once a month, and operate the machine to lubricate the moving parts, while charging the battery; Turn on the air conditioner and refrigerate for 5- 10 minutes.

Wear of hydraulic pump of excavator

The serious wear and tear of hydraulic pump of excavator has a fatal impact on excavator, so it is necessary to solve such problems of excavator in time. When repairing the excavator hydraulic pump, find out the cause of the failure from the following three points:

(1) Check the internal leakage of the boom cylinder.

The easiest way is to raise the boom and see if it has obvious free fall. If the drop is obvious, remove the oil cylinder for inspection; if the sealing ring is worn, replace the sealing ring.

② Check the control valve

First, clean the safety valve and check whether the valve core is worn. If it is worn, it should be replaced. If the safety valve has not changed after installation, check the wear of the control valve spool. The clearance limit is generally 0.06 mm, and it should be replaced if it is seriously worn.

③ Measure the pressure of hydraulic pump.

If the pressure is low, adjust the pressure. If the pressure is still not adjusted well, it means that the hydraulic pump is seriously worn.

First of all, the main reasons why the boom can't be lifted with load are:

1. The hydraulic pump of excavator is badly worn.

When running at low speed, the pump leaks seriously; When running at high speed, the pump pressure rises slightly, but due to the wear and leakage of the pump, the volumetric efficiency is obviously reduced and it is difficult to reach the rated pressure. Long-term work of hydraulic pump intensifies wear and oil temperature rise, which leads to wear and tear of hydraulic components and aging damage of seals, loss of sealing ability, deterioration of hydraulic oil and final failure.

2. The choice of hydraulic components is unreasonable.

The specification of the boom cylinder is 70/40 non-standard series, and the seal is also non-standard, which leads to high manufacturing cost and inconvenient replacement of the seal. The diameter of the boom cylinder is small, which will inevitably make the system set pressure higher.

3. The design of hydraulic system is unreasonable.

The control valve and the full hydraulic steering gear are connected in series with a single pump, the setting pressure of the safety valve is 16MPA, and the rated working pressure of the hydraulic pump is 16MPA. The hydraulic pump often works under full load or long-term overload (high pressure), the system has hydraulic shock, and the oil is not changed for a long time, so the hydraulic oil is polluted, which aggravates the wear of the hydraulic pump and leads to the bursting of the pump shell (this fault was discovered later).

Second, the improvement and effect

(1) Improve the design of hydraulic system.

After many arguments, the advanced priority valve and load sensing full hydraulic steering gear are finally adopted. The new system can give priority to the flow distribution according to the steering requirements, and can ensure sufficient oil supply regardless of the load size and steering wheel speed, and the rest can be supplied to the working device loop, thus eliminating the power loss caused by excessive oil supply in the steering loop, improving the system efficiency and reducing the working pressure of the hydraulic pump. Reduce the serious wear of hydraulic pump of excavator.

(2) Optimize the design of boom cylinder and hydraulic pump.

Reduce the working pressure of the system. Through optimization calculation, the standard series 80/4 is adopted for the boom cylinder. The displacement of hydraulic pump is increased from 10ML/R to 14ML/R, and the system set pressure is 14MPA, which meets the requirements of lifting force and lifting speed of boom cylinder.

(3) Strengthen daily inspection and maintenance.

We should also pay attention to the correct use and maintenance of loaders, add or replace hydraulic oil regularly, keep the cleanliness of hydraulic oil, and strengthen daily inspection and maintenance. Only in this way can serious wear and tear of hydraulic pump of excavator be avoided.