Maintenance of hydraulic equipment. Adjustment and maintenance of hydraulic systems. Causes of hydraulic system breakdowns
TO Category:
Maintenance of road machines
Maintenance of hydraulic equipment of machines
The main maintenance works of the hydraulic equipment are: checking the tightness of the system, refilling the working fluid in the tanks and oil in the gearboxes of the pump drive, tightening the fasteners, tensioning the coolant drive belt, cleaning the tank breather and the filter elements of the filters, regulating the safety valves, replacing the working fluid and flushing the tanks.
Hydraulic systems are not as complicated as you think. Thanks to regular maintenance, you will become familiar with the components and will be able to diagnose potential problems. Components of hydraulic systems closely interact. As a result, damage to one component can cause additional damage to others. For example, a superheated oil caused by a hermetic cylinder seal may collapse and damage other cylinders or a pump. That's why he pays for regular maintenance and preventive checks to fix problems before they occur.
Checking the tightness - one of the important maintenance work of hydraulic equipment. Even small leaks of the working fluid can lead to a significant reduction in its level in the tank, as a result of which the machine may be inoperable. Therefore, the tightness of the hydraulic system should be checked daily before starting the machine into operation, during the shift and at its end.
Causes of hydraulic system breakdowns
Most hydraulic systems consist of pumps, hoses and pipelines, cylinders and engines, valves, cooling device, tank, filters and hydraulic fluid. The system is based on a pump. It uses energy from the engine to pump the fluid and creates a hydraulic flow and pressure. Valves control the flow of a fluid, limiting or redirecting it. Cylinders and engines are the "muscles" of hydraulic systems. Cylinders have a direct push action, while engines use energy from the fluid to rotate the shaft.
One of the indicators of leakage is a decrease in the level of working fluid in the tank. If the level is lowered compared to the previous test, the connection points of the pipelines and hoses, the seals between the covers and the pump body, the filter, the distributor, the rods of the hydraulic cylinders and the control levers of the distributor's gold valves must be carefully inspected. The detected leaks are immediately eliminated.
The speed at which these components work is determined by the flow rate of the hydraulic oil, and the hydraulic pressure determines the force that they exert. The cooling unit acts to cool the liquid after it has passed through the system, and the reservoir pumps the pump. Connect all these components - hoses, lines and fittings.
The main requirement for hydraulic maintenance is prevention. If you remove contaminants from hydraulic systems, you will avoid almost all common problems and failures. However, some contaminants inevitably enter the system and scratch the tightly adhering surfaces in the components. Therefore, follow these recommendations to maintain the hydraulic fluid in the upper state.
If the test shows that the level of the working fluid in the tank has dropped below the lower mark on the measuring ruler (DT-75M), or below the middle of the lower sight eye (T-130M), or below the lower eye of the sight glass (EO-3322D, EO-4124 ), the tanks are required to refuel with the sort of working fluid that the system is primed with.
Tanks of cars refuel, as a rule, from the sealed container. If it is necessary to top up the working liquid from the open container, then before testing, analyze it, during which the mark is clarified and filtered through a three-layer batiste or centrifugal filter.
Clean the area around the probes, fill the plugs and hydraulic filters before removing them to check or replace the hydraulic fluid. Keep all liquid containers tightly closed when stored and pour them directly from the container into the system. Often the manufacturing process allows contaminants to enter the hydraulic system. A change in the liquid after 50 hours eliminates these particles. After this, regularly change the hydraulic fluid and filters, as recommended in the user's manual. Check oil before each use. Make sure that the liquid level is sufficient and that the liquid is in good condition. Insufficient oil can cause serious damage to pumps. If your oil looks frothy or milky, a leak may occur, due to which air enters the system. Air will cause a sharp and slow operation of the hydraulics. Find and seal the source of any leakage.
- Remove contaminants from your hydraulic system.
- Change the liquid and filter after the first 50 hours of use.
It is forbidden to use working fluids that were in use, containing mechanical impurities and water, as well as mixtures of various types of liquid.
Before topping up the tank with working fluid, the filler neck and its lid should be thoroughly cleaned of contaminants. Pour liquid into the tank through the hose and the dispensing valve of the fuel oil or oil dispenser. In exceptional cases, it is allowed to add the working liquid to the tank from the bucket or the measuring cup through the funnel, putting a cambric cloth in it, after thoroughly cleaning them from the contaminants.
When the system cools after operation, the humidity can condense and mix with the hydraulic fluid. Water in a hydraulic fluid is similar to a milky appearance, resulting from air pollution. If you hear a pop-up or crackle, then there is water in the liquid, and you must immediately change it.
Perhaps your cooling system does not work properly, or you may run into problems with pressure. Remove dirt or other debris that obstructs the air flow around them. If the liquid remains hot for a long time, it can deteriorate and lose the ability to lubricate properly.
- Regularly check the temperature of the working fluid during operation.
- Too hot liquid?
- Check the hydraulic oil cooler or tank.
A number of machines (EO-4124 and others) have a special pump for refilling their working fluid. It is driven manually or from the engine of the machine. In this case, before refueling, it is necessary to clean and rinse thoroughly the contamination of the intake hose, lower it into the barrel with the working fluid, activate the pump and, when its level in the tank reaches the upper risks on the measuring ruler or the glazed eye, turn off the filling pump.
This occurs when the pump does not receive sufficient fluid from the reservoir. Perform the following steps every 50 hours to check cavitation. If it rattles or sounds as if it is filled with marbles or stones, cavitation occurs and the system must be immediately disconnected. Check the fluid level and filter to determine if they can limit or restrict the flow. Then determine if any previous changes in the tank, inlet lines or pump have been made. If any of the components are changed, this can affect the pump input flow. Check the input lines for leaks, bends, jams or other breaks that can limit the flow. In addition, many systems have inlet filters that act as a second filter to prevent contaminants from entering the pump. If your system has a filter, clean it regularly to maintain the required input flow. Listen to the pump when the hydraulic system is running. . Most importantly, maintain a clean fluid and filters.
In addition to external leakage of the working fluid, there are internal, due to wear of the piston seals of hydraulic cylinders and distributor valves. In this case, the cylinders fluid flows from one cavity to another, and at the distributors - from the discharge line to the suction, which increases the duration of the working cycle of machines.
Pumps have check valves, blades, pistons and gears, which can be cleaned and damaged by contaminants. This will result in inefficient pumping and wear on other parts of the equipment. Cylinders have seals and rings that can be damaged by excessive pressure and contaminants in the liquid. Check the points at which the cylinder rod moves and exits the cylinder housing for leakage. Check the length of the cylinder rods for any vibrations, dents or other damage that can lead to liquid and pressure exiting. Once again, make sure that your hydraulic fluid is clean. . The cylinder is designed to load loads on its axis.
Fig. 64. Checking the condition of the hydraulic cylinder with the device KI-5473: 1 - pump, 2 - device, 3 - tee, 4 - plugs, 5 - distributor, 6 - locking device, 7 - ruler, 8-hydraulic cylinder, 9-tank, 10 - filter
The tightness of the hydraulic cylinders is checked with the KI-5473 instrument, connecting it with one pipeline to the distributor, and the other by lowering it into the tank (Figure 64). Instead of the pipeline connecting the over-piston cavity of the hydraulic cylinder with the distributor, the technological sleeves with the clutches of the locking device are installed.
Side loads can shorten the life of the cylinder, causing excessive wear on the seals and the rod. With hydraulic motors, as with pumps, your main focus on maintenance is clean hydraulic oil. Gears, blades and pistons can be cleaned with contaminants, which leads to loss of pressure. Before each use, check the engine drive shaft for damage or leakage.
- Make sure that the engines are running and working at the correct speed.
- This manual will provide a user's guide.
After that, start the engine, warm up the working liquid to 45-55 ° C, fill it with cavities of the hydraulic cylinder by moving the piston. Then set the minimum stable engine speed at idling speed. Transfer the handle of the spool, which controls the supply of liquid to the tested hydraulic cylinder, to the "Lifting" position. When the piston of the hydraulic cylinder occupies the middle position, the couplings of the locking device are separated and with the aid of the device the pressure in the rod cavity is increased to 10 MPa.
They can be worn and leak, resulting in low hydraulic pressure. Pollutants can be placed in valves and restrict flow. Again, maintain a clean hydraulic fluid to keep the valves in good working order.
The next aspect of routine maintenance is checking hoses, lines, fittings and couplers. Check these components to determine if they were damaged and make sure they are in good condition and are in the right place. Metal lines may be crumpled from falling tools, contact with other equipment, or a variety of other reasons. Inspect lines for cracks, incisions or dents that limit flow or cause pressure leaks. Sludge can be damaged in the same way, as well as from overheating, prolonged wear and defective manufacturing. The hose can be damaged from the inside, causing the hose parts to enter the hydraulic system and contaminate them. Check the direction of the hose. Sometimes brackets break, and hoses and lines end where they should not be. They can be jammed, bent, drawn or worn. Inspect the hoses at flexible points. Operate the hydraulic system and observe the bend point for bending or stretching. Check all hose fittings to make sure they are tight. If you notice a leak on the fitting, tighten it. Be careful not to overtighten or damage the thread. Check the couplings. Always keep these points clean, they are the main source of contamination. Make sure that the caps are installed when the couplings are not in use, and replace the covers that are not snug. Before connecting any lines, carefully clean each coupling. Regularly keep the hoses clean by washing machines. This will also help reduce the temperature of the hydraulic fluid.
- Check hoses and lines.
- Look at the crimp or collapsed hoses, which can limit the flow.
Measure the distance between the stem head and the hydraulic cylinder cover with a ruler and count the number of drops of fluid leaks on the rod. After 3 minutes, the measurement is repeated. If the movement of the rod during this time exceeds 7.5 mm, and the leakage of 15 drops, replace the sealing rings of the hydraulic cylinder.
When checking the tightness of the valves, the KI-5473 device is connected to the distributor (Figure 65), as well as when checking the cylinders. Start the engine, warm up the working fluid, move the control lever spool into the "Lift" position, install the device at a pressure of 10 MPa and determine the supply of liquid with the distributor switched on. The difference between the actual pump flow, bypassing the distributor, and the flow measured with the distributor on, is the amount of leakage in the distributor. For the hydraulic distributor of the tractor T-130M, it should not exceed 36, T-IOMM-31, and DT-75M-16 l / min. If these leakage sizes are exceeded, the distributor is replaced.
Regular preventive examination
Refer to the service manual for specifications. Check the hydraulic system carefully before and after each use. However, most hydraulic systems are not checked until the operator complains about low productivity. By this time it may be too late to prevent major repairs. In addition to the regular maintenance described in the user manual, follow these basic procedures every 50 hours or so to determine the health of your system and to prevent costly failures.
The actual pump feed is measured by the KI-5473 in this order. By connecting it with one hose to the pump and the other to the tank, the working fluid is heated, the nominal engine speed is set and the pressure in the system is 10 MPa and the pump is determined by the mark on the scale of the device.
In the hydraulic system with pumps with a flow rate of more than 90 liters / minute, the distributor leaks and the supply of hydraulic fluid are determined at a lower engine speed of the crankshaft.
Checking a Limited Flow
After you have encountered a problem, contact a professional hydraulic specialist to perform most repairs. They can ensure the preservation of all specifications and tolerances in the system. A slow hydraulic system is the result of a limited flow. Possible causes are low oil level, limited hoses and lines, as well as damaged valves, pumps, cylinders and engines.
Check for weak hydraulics
Activate the hydraulic system and determine which individual components of the system are running slowly. If, for example, the bucket on your forklift does not rise or fall at a normal speed, but other hydraulic attachments, this restriction applies to lines and components serving the bucket. Large pollutants can block the valve or enter the cylinder or motor. If you can not isolate the obstacle, and the whole system is running slowly, check the pump. If you hear a cavitation sound, the pump does not receive sufficient flow. Determine that fluid levels are sufficient and all filters and filters are clean. If the problem persists, check the input line to make sure that there is no blockage or kinks. Also make sure that the pump shaft is running and is not damaged.
- Visually inspect these components for leaks.
- Pay special attention to the connection points.
- If the external constraint is not obvious, then the obstacle may be internal.
For the T-130M tractor pump, the admissible supply is not less than 90 l / min.
The condition of the filter elements of the filters of the hydraulic system of the tractors T-130M and DT-75M is checked with the device KI-13936. It is connected to the distributor in the place of fixing the hose of the remote hydraulic cylinder, put the spool handle in a floating position, start the engine, shift the handle of the control valve of the main hydraulic cylinder to the "Lift" position, warm the working fluid to 45-55 ° С, set the rated speed of the crankshaft and The manometer of the device determines the pressure of the working fluid on the drain. If it is below 0.1 MPa, then the filter is defective, and if above 0.25 - it is dirty and requires cleaning.
On single-bucket excavators, the degree of contamination of the filter elements is checked according to the readings of the pressure gauge installed on the discharge line. When the pressure is increased from 0.25 MPa, it is necessary to remove and clean the filter elements.
Before removing the filter elements, clean their body and lids from dirt, remove the bolts that secure the lid, remove the filter elements, rinse them in a kerosene bath, purge with air supplied from the compressor inside the cell. After this, the mesh lenticular-shaped elements (hydraulic systems of tractors) are cleaned of contamination with a hair brush in kerosene.
The washed filter elements are collected in the reverse order. In this case, each element is inspected and discarded. They also ensure that their quantity does not decrease, since the leakage between them will be broken and the liquid will flow into the tank uncleaned.
Paper filter elements of hydrosystems of single-bucket excavators after rinsing in pure kerosene are blown again with air. Its pressure should not exceed 0.2 MPa, since at higher pressure the cardboard from which the elements are made can be damaged.
The correct tension of the coolant drive belt is checked for the size of its deflection. If it exceeds 15 mm, the belt is pulled by moving the motor along the frame (EO-4124). Normal is the belt tension at its deflection of 8-10 mm.
To test the pressure in the hydraulic system of tractors T-100MZ and T-130M, connect a manometer to the pipeline, which supplies the working fluid from the pump to the distributor with adapters and a high-pressure hose. Start the engine, heat the working fluid and when its temperature is 45-55 ° C, turn the non-working distributor lever to the "Lift" or "Forced lowering" position and note the pressure in the system by the manometer. The normal pressure at the T-100MZ tractor is 9-11, and the T-130M-11 is 12 MPa. To regulate the pressure in the hydraulic system, remove the seal from the adjusting screw on the distributor, unscrew the cap nut and set the required pressure by turning the adjusting screw.
In the same manner, the pressure in the hydraulic system of the tractor DT-75 and its modifications is checked and regulated. The normal pressure in their hydraulic system is 13-13.5 MPa.
In the hydraulic system of the tractors, the pressure can be checked and adjusted by the KI-5473 instrument during the pump flow check. To do this, turn the handle of the device until the safety valve is activated and notice on the scale of the device at what pressure it opened. If it is less than the required one, set the device to normal pressure and turn the adjusting bolt to open the valve at this pressure.
On one-bucket excavators, the manometer is mounted on the instrument panel in the cab. It is activated by special valves. With the engine running, at the rated speed of the crankshaft and heated working fluid, move one of the distributor arms until the rod of the corresponding hydraulic cylinder has shifted to failure. At that moment, the valve is opened and the pressure is determined from the manometer. If it is not within 21.5-22.5 MPa for the EO-4124 excavator, it is adjusted with an adjusting bolt. After adjustment, the valve is rolled up to failure. In the same manner, the safety valves of the other distributor of the excavator are adjusted.
The replacement of hydraulic fluid in the hydraulic system of machines is carried out in the following order. With the engine running, the cylinder rods are fully retracted and immediately drained of the working fluid, opening the plugs of the drain holes of the tank. The spent liquid is collected in barrels and put into storage of fuel-lubricating materials for its subsequent regeneration. Attach a tag to the barrel, which indicates which liquid is in it.
The tank is filled with clean diesel fuel, the engine is started and, with the hydraulic pump running, the control levers of the control valves are moved for 3-5 minutes. After that, retract the rods, muffle the engine and drain the washing diesel fuel from the tanks and pipelines, disconnecting them in the lowest places by turning off the air valves of the hydraulic cylinders. The fused contaminated diesel fuel is collected in barrels and put into storage of fuel-lubricating materials.
After that, flush the drain plugs, clean and flush the tank filler cap filter, the breather filler, the filter elements of the hydraulic filters, connect the pipelines and wind the air valves. Then, fresh working fluid is poured into the tank. Hydraulic systems of single-bucket excavators operating in cold and temperate climates use working fluid MG-15-B (the old designation of the VMGZ liquid). In the hot climate zone and in the summer in the temperate zone for mass-produced cars, the MG-46-B fluid (the old designation of MG-30 liquid) is used for upgrading them, and in the same conditions for newly manufactured and upgraded machines - MG- 46-B (old designation of liquid MGE-46E).
In the hydraulic systems of tractors, diesel oil of the sorts that are poured into engine carts is used as a working fluid.
After filling the system with the working fluid, the engine is started and, by moving the control levers of the gilders, fill the entire system with a working liquid. For more complete removal of air from the system, air valves are opened on the hydraulic cylinders.
By removing air, close the valves, muffle the engine, inspect all the components of the hydraulic system, whether or not the working fluid leaks. The detected leakage is eliminated, the level of working fluid in the tank is checked and, if necessary, it is added to the set level.
Hydraulic tanks are washed with seasonal maintenance once a year, using a special device for this, or removing the tank from the machine.
TO Category: - Maintenance of road machines
Every day before and after the work, it is necessary to perform an external inspection of the hydraulic system, its elements (pump, hydraulic cylinders, hydraulic equipment, distribution equipment, etc.). Ensure that there is no leakage at the junction of the hydraulic lines and connecting them to the pump, hydraulic distributor, hydraulic actuators, as well as at the junctions of the pump parts, the hydraulic distributor, the hydraulic cylinders between each other and the pump with the drive flanges.
Ensure the cleanliness of the working fluid, as contaminated fluid leads to rapid wear of the working surfaces of the hydraulic system components and seals.
It must be remembered that the durability of the hydraulic system depends to a large extent on the purity of the filter elements. The first cleaning of filters or the replacement of filter elements is made after running in, checking and adjusting the hydraulic system. In the future, the filters must be cleaned from clogging according to the instructions on the machine.
It should be borne in mind that because of untimely cleaning of the filter elements of the tank, contaminants fall into the gaps between the working surfaces of spool valves, valves, pumps and other hydraulic units, causing abrasive wear and the appearance of scratches, scoring on the working surfaces. In addition, contaminants, falling into the gaps, can cause seizure of the valves, which can lead to rupture of the hulls of hydraulic units.
Observe the level of the working fluid in the tank. In the event of a drop in the liquid level below the lower mark, it is necessary to stop work and add oil to the top mark of the hydraulic system.
It should be ensured that the temperature of the hydraulic fluid in the hydraulic system does not exceed 70-80 ° C.
After every 240 hours of operation, the air filter of the tank breather must be cleaned of dust and thoroughly washed (according to the instructions on the machine).
Replace the oil in the hydraulic system according to the maintenance schedule for the machine.
The tank must be opened in a dust-free room, equipped with shelves, covered with a clean, non-fleecy cloth or paper. To clean the tank parts, you need to prepare clean dishes. The external surface of the tank must be thoroughly cleaned of dirt and dust, after which the places to be disassembled should be cleaned with clean kerosene (DT) and dryed. It is strictly forbidden to open the tank system in the field or in a dusty room.
Replace worn seals, gaskets and wipers in a timely manner. Change seals only in a clean indoor area.
All the parts must be thoroughly washed before assembly, in aviation gasoline, clean kerosene or diesel fuel.
To prevent corrosion, the hydraulic system components must always be filled with working fluid.
The external surfaces of hydraulic units and pipelines must be kept clean and free of corrosion. All bolt and socket connections must be fully tightened.
Do not allow the appearance of leaks in the places of hinged and fixed joints. If a leak is detected, it must be immediately removed by tightening the connection or replacing the seal.
Make sure that during work, there is no twisting and pinching of the hoses between the moving parts of the vehicle, as this leads to premature failure of the hoses.
Timely maintenance of hydraulic systems repeatedly prolongs the service life of tractor equipment.
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