The device and the principle of operation of the hydraulic mandrel. The principles of hydraulics as simple as possible. What is pressure

TO Manager:

Cranes-pipe-layers

Principle of operation of the hydraulic system of attachments

General. The hydraulic system of attachments is designed to extend and pull up the control, as well as to control brakes and couplings. It consists of a hydraulic pump, hydraulic cylinders, hydraulic distributors, safety hydrocalapanis, hydraulic pipelines, hydrobobacles, measuring instruments (pressure gauges), hydrolynes, filter.

In the pipelayer under consideration, the schemes of the hydraulic system of attachments, despite the use of unified assembly units and elements, have some differences due to the difference in the principle of incorporating couplings of the drum drums and the presence special devices Load control.

Pipe layer T-3560m. From the tank (Fig. 85) the pump serves the working fluid over the line A to the distributor. In the neutral position of the arms of spools, the working fluid through the holes in the casing of the distributor enters the tank over the line. The distributor consists of three sections, two of which are directed by the flow of working fluid to the cylinders of control of clutches of lifting and lowering the cargo and the arrow control, and the third section serves the control cylinder control. In the case of lifting or lowering the handle (and with its spool), the working fluid from the distributor through chokes will flow into the right or left cylinder cavity, respectively, nominating or tightening the control.

Fig. 85. Hydraulic diagram of attachment of the T-3560L1 pipe layer1:
1 - gear pump, 2 - safety valve, 3 - pressure gauge, 4 - three-rod distributor, 5 - Cylinder control control, b, 12, 13 - knobs of spools, 7 and 8 - Cylinders of control of clutches of lifting and lowering hook and arrows, 9 - Breaker, 10 - tank, 11 - chokes

When installing the handle to the neutral position (shown in the figure), the cylinder piston will be fixed in the position in which it was at the time of the transfer of the handle.

When raised (shown in the figure), the handle, the working fluid from the distributor enters the left cylinder, which includes the load clutch clutch and turns off the brake - the rise of the load. When this handle is returned to the neutral position, the working fluid from the cylinder is sent back to the tank along the line and the clutch clutch turns off, and the brake slows down the drum. To lower the cargo, the handle is lowered, including the dummy coupling.

When climbing the handle, the oil from the distributor enters the cylinder, which includes the arrows lift clutch in turns off the brake.

Fig. 86. Hydraulic diagram of attachment of the TT-20I pipelayer:
1 - control panel, 2 - Cylinder-sensor, 3 - Cylinder automatic switching on »Dispenser, 4 7, 8, 10 - cylinders control couplings and lifting kuyuka and arrows; 5, B, 12 - Single-Zolotnikovy Distributors, 9 - Breaker, 11- Cylinder Control Service, 13 - Gears Pump, 14 - Tank, 15, 19 - Safety Valves Direct Action, 16 - Filter, P - Safety Valve Differential Action, 18 - check valve, 20 - load instrument setting panel, 21 - choke; 22 - Load Index

When the boom reaches the vertical position, the buffer device will press the arrow's cam lift to stop, as the oil through the cylinder interrupter on the winch will go to the tank along the additional drain line e. In this case, the coupling turns off and the brake will delay. When lowering (shown in the figure), the arrow handles) will be descended.

The safety valve provides the pressure of the working fluid in the system -Oc-7800 kPa needed to control the winch and control, and the liquid from the pump into the tank along the line is exceeded in the dispenser of this pressure.

Trubaschik TG-201. The working fluid, injected from the tank (Fig. 86) by the pump, comes along the line A to the spool distributor. With the neutral position of the spool, the working fluid flows through the distributor simultaneously along the lines B and to one-rod distributors, and also reaches a fuse valve of a differential action having a remote unloading with the line of the city along this line, as well as the line d, moving from the distributor, the liquid merges In the tank with not shut-off distributors, consistently passing through them.

When the distributor of the distributor is moving to the right or left, the working fluid under pressure enters the rod or piston cavity of the hydraulic cylinder, providing a motion or leakage of the control. As soon as the control will reach the extreme position, the pressure will increase in the hydraulic system to the value of which the direct action safety valve is configured, and the valve will work, starting to cover the liquid into the tank along. The fluid supply and its drain will stop after switching off the distributor.

To turn on the cargo drum, the winch requires a distributor's spool to move to the left or right. The range of remote unloading will be blocked in the distributor and the working fluid will go to the inclusion cylinders from the line in. The pressure of the fluid when it is supplied to the cylinders will be limited to the adjustment of the fuse of the differential action, which, when the setproof pressure exceeds, will work and connect the line B with an additional drain line with a filter.

The inclusion of the boraner is carried out by moving. The distributor value. The working fluid will flow tc cylinders of inclusion of the arrow drum clutch, and the cylinder cohesive the boom clutch is through the breaker dispenser. When the boom is suitable for a vertical position, it will prescribe a distributor of the interrupter, will stop supplying the working fluid to the cylinder and automatically stop the arrow.

The pressure (4500 kPa), which is adjusted to the differential valve, less pressure (9500 kPa) of the direct action valve, since the cylinder and the control unit interacting with the valve and the distributor requires greater pressure than cylinders interacting with the valve and distributors.

All distributors and valves of the pipelayer hydraulic system are concentrated in the driver's cabin in the form of a single block console, which also includes a load control device setting panel. This device includes a sensor cylinder controlling the load on the pipelayer hook, and the cylinder of automatic switching on the load drum control of the winch load drum associated with the sensor cylinder.

Fig. 87. Hydraulic scheme of attachments of pipe-layer TO-1224g:
1 - Filter, 2 - Interrupter, 3 and 4 - Cylinders of controlling a friction clutch drive "Winch and control, 5 and 6 - two- and three-position distributors, 7 - Pressure gauge, 8 - Safety valve, 9 - gear pump, 10 - Crane, 11 - tank

The increase in the pipelayer load leads to an increase in pressure in the rod cavity of the sensor cylinder, the line to and the piston cavity of the automatic power cylinder. Under the action of this pressure, the cylinder rod moves to the right. If, when moving, the left of the two stops fixed on the stem will reach the dispenser handle, the distributor will turn on and the working fluid flow to the cylinder will begin, which will ensure the operation of the cargo drum to the pipeline descent. It is used feature The elastic state of the pipeline: with the growth of his deflection up the load from it increases, and with a decrease in the deflection - falls. As soon as the loading of the pipeline, as a result of the work of the drum, the winch will decrease, the pressure in the cylinders will decrease to normal, the contact between the left stop of the cylinder rod and the handle of the distributor under the action of the cylinder spring will stop and the distributor will turn off, and the winch drum will stop.

If the pressure in the sensor cylinder due to a small external load will fall below the norm, then the spring cylinder and the right focus reinforced on its rod will turn on the distributor to the lifting rotation of the freight drum of the winch.

The load control device configuration panel includes a check valve, an adjustable safety valve, adjustable choke and load index.

Trubaschik TO-1224g. The hydraulic system works as follows. With a pipe-layer engine running and the power selection included, the working fluid from the tank (Fig. 87) along the line and the pump is supplied to the three-position distributor. With a neutral position of the spool of the distributor, the working fluid comes from it through the distributor goes to the draining.

When the spools of the distributor is moved into one of the extreme positions, the working fluid begins to flow through the lines D or E into one of the cavities of the cylinder, providing the movement or demolition of the control. From another cavity, the working fluid is displaced along the opposite lines E or D, and then comes along the lines, to drain into the tank through the filter.

When the driver presses a two-position distributor to the armless circulation through it, the working fluid is stopped and the liquid comes along the line to the frying clutch cylinder of the winch drive, ensuring the drive turning on the drive. When the load boom is stopped into the buffer device of the upper frame and triggering the interrupter dispenser, the supply of working fluid to the cylinder is interrupted, since the working fluid begins to come from the line to the drain line G and then to the tank.

In the case of excessive increase in pressure in the hydraulic system, a safety valve and working fluid on line and enters the tank.

Etc.).

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Subtitles

Hydraulus functions

The main function of the hydraulic drive, as well as mechanical transmission, is the transformation of the mechanical characteristics of the drive motor in accordance with the requirements of the load (conversion of the type of motion of the output engine, its parameters, as well as regulation, overload protection, etc.). Another hydraulic function is the transmission of power from the drive motor to the working bodies of the machine (for example, in the single-bonding excavator - power transmission from the internal combustion engine to the ladle or to the hydraulic motors of the boom drive, to the hydrodic motories of the tower rotation, etc.).

In general terms, power transmission in the hydraulic equipment is as follows:

1. The drive motor transmits the torque on the pump shaft, which reports the energy of the working fluid.
2. The working fluid on hydrolynes through regulatory equipment enters the hydraulic motor, where hydraulic energy is converted to mechanical.
3. After that, the working fluid on hydrolynes is returned either to the tank or directly to the pump.

Types of hydraulic drives

Hydrauls can be two types: hydrodynamic and volumetric.

• In the hydrodynamic drives, the kinetic energy of the fluid flow (and, accordingly, the velocity of the fluid movement in hydrodynamic drives is large in comparison with the speeds of movement in the volume hydraulic drive).
• In volumetric hydraulic materials, the potential energy of the working fluid pressure is used (in the volume hydroprys of the speed of movement of the fluid movement is small - about 0.5-6 m / s).

Hydraulic drive with open circulation system

in which the working fluid is constantly reported with a hydraulicular or atmosphere.

Advantages of such a scheme - good conditions For cooling and cleaning the working fluid. However, such hydraulic drives are cumbersome and have a large mass, and the rotational speed of the pump rotor is limited to permissible (from the conditions of adverse operation of the pump) speeds of movement of the working fluid in the suction pipeline.

By source of working fluid

Pump hydraulic drive

In the pumping hydraulic engine, which received the largest distribution in the technique, the mechanical energy is converted by the pump into the hydraulic, the energy carrier is the working fluid, injected through the pressure line to the hydraulic motor, where the energy of the fluid flow is converted into mechanical. Working fluid, giving out its energy to the hydrational, returns either back to the pump (closed diagram of hydraulic), or to the tank (open or open scheme hydraulic). In the general case, the composition of the pump hydraulic drive includes hydraulic frames, hydraulic apparatus, working fluid, hydroevitability and hydrolynes.

Axial-piston, radial-piston, lamellar and gear pumps obtained the greatest use in the hydraulic industry.

Main hydraulic drive

In the main hydraulic engineering, the working fluid is injected with pumping stations to the pressure line, to which hydraulic energy users are connected. Unlike the pumping hydraulic line, in which, as a rule, there is one (less often 2-3) hydraulic energy generator (pump), in the main hydraulic drive of such generators can be a large amount, and consumers of hydraulic energy can also be quite a lot.

Rechargeable hydraulic drive

In the battery hydraulic drive, the liquid is supplied to hydrolyna from a predetermined hydroaccumulator. This type of hydraulic drive is mainly used in machines and mechanisms with short-term operation modes.

By type leading engine

Critical for hydraulic line (primarily volume) is the purification of the working fluid from the abrasive particles contained in it (and constantly generated during operation). Therefore, hydraulic system systems necessarily contain filtering devices (for example, oil filters), although fundamentally hydraulic can work for some time without them.

Since the working parameters of the hydraulic nature are significantly dependent on the temperature of the working fluid, then in the hydraulic systems in some cases, but not always, the temperature control systems (heating and / or cooling devices) are installed.

The number of degrees of freedom of hydraulic system

Application area

Volumetric hydraulic equipment is used in mountain and construction and road machines. Currently, more than 50% of the total fleet of mobile construction and road machines (bulldozers, excavators, automotive drivers, etc.) is a hydrainized. This is significantly different from the situation of the 30s - 40s of the 20th century, when the mechanical transmission was mainly used in this area.

Wide distribution received hydraulic engineering in aviation. The saturation of modern aircraft with hydraulic system systems is such that the total length of pipelines of the modern passenger airliner can reach several kilometers.

In the automotive industry, the wider use of the power steering was found, significantly improving the convenience of car control. These devices are a kind of monitoring hydraulic drivers. Hydraulicers are used in many other areas of technology (aviation, tractor construction, industrial equipment, etc.).

In some tanks, for example, in the Japanese tank type 10, a hydrostatic transmission is used, which is, in fact, the system of volumetric hydraulic drive drives. The same type of transmission is installed in some modern bulldozers.

In general, the boundaries of the area of \u200b\u200bhydraulic use are determined by its advantages and disadvantages.

Benefits

The main advantages of the hydraulic nature include:

• the possibility of universal transformation of the mechanical characteristics of the drive motor in accordance with the requirements of the load;
• easy control and automation;
• easy to protect the drive motor and executive bodies of machines from overload; For example, if the force on the rod of the hydraulic cylinder becomes too large (this is possible, in particular, when the rod, connected to the working body, meets the obstacle on its path), then the pressure in the hydraulic system reaches large values \u200b\u200b- then the safety valve is triggered in the hydraulic system, and after that The liquid goes to the drain into the tank, and pressure decreases;
• reliability of operation;
• a wide range of stepless regulation of the speed of the output link; For example, the range of speed control of the hydraulic rotation can be from 2500 rpm to 30-40 rpm, and in some cases, hydromotors of special design reaches 1-4 rpm, which is difficult for electric motors;
• large power transmitted per unit mass of the drive; In particular, the mass of hydraulic machines is about 10-15 times less than the mass of electrical machines of the same power;
• self-inflammability of rubbing surfaces when using mineral and synthetic oils as working fluids; It should be noted that with maintenance, for example, mobile construction and road machines on lubricant takes up to 50% of the total time maintenance of the machine, therefore the self-mixability of the hydraulic industry is a serious advantage;
• the possibility of obtaining large forces and capacities for small sizes and weight of the transfer mechanism;
• easy exercise different species movements - progressive, rotational, turning;
• the possibility of frequent and rapid switching when reciprocating and rotational direct and reversing movements;
• the possibility of uniform distribution of effort while simultaneously transmitting several drives;
• simplifies the layout of the main hypreen nodes inside the machines and aggregates, in comparison with other types of drives.

disadvantages

The disadvantages of the hydraulic nature include:

• leakage of the working fluid through seals and clearances, especially at high pressure values \u200b\u200bin the hydraulic system, which requires high accuracy of the manufacture of hydraulic equipment;
• heating the working fluid during operation, which leads to a decrease in the viscosity of the working fluid and an increase in leaks, so in some cases it is necessary to use special cooling devices and thermal protection products;
• lower efficiency than in comparable mechanical gears;
• the need to provide in the process of operating the purity of the working fluid, since the presence of large number abrasive particles in the working fluid leads to a rapid wear of the parts of the hydraulic equipment, an increase in gaps and leaks through them, and, as a result, to a decrease in the volume efficiency;
• the need to protect the hydraulic system from air penetration, the presence of which leads to unstable hydraulic operation, large hydraulic losses and heating of the working fluid;
• fire hazard in the case of the use of combustible working fluids, which imposes limitations, for example, to apply hydraulic drive in hot shops;
• the dependence of the viscosity of the working fluid, and therefore the working parameters of the hydraulic line, on the ambient temperature;
• compared to pneumatic and electric drive - the impossibility of effective transmission of hydraulic energy over long distances due to large pressure losses in hydrolynes per unit length.

History of the development of hydropryrys

Hydraulic technical devices are known with deep antiquity. For example, the pumps for extinguishing fires existed during the times of ancient Greece.

However, as a holistic system, which includes the pump, and the hydraulic motor, and the liquid distribution devices, the hydraulic drive began to develop in the last 200-250 years.

One of the first devices that became the type of hydraulic drive is a hydraulic press. In 1795, a patent for such a device received Joseph Brama (Eng. Joseph Bramah), which Henry model helped, and in 1797 the first hydraulic press was built in history.

At the end of the XVIII century, the first lifting devices with hydraulic drives appeared in which

How the hydraulic system works. The system contains 4 basic elements and many other elements intended for certain purposes. Here is a description of these 4 basic elements.

• Fluid tank. This is a tank or another vessel, which contains a liquid that feeds the system.
• Liquid circuit. These are pipes by which the fluid passes from one system element to another.
• Hydraulic pump. This device pumps fluid through the contour, creating energy for the production of work.
• Hydraulic motor or cylinder. This element produces a "movement", getting energy from the pump.
  • Auxiliary elements, control or fluid controlling, such as valves that remove excess liquid, regulators, batteries, pressure switches, pressure meters.

Determine the type of energy source required for your system. It can be an electric motor, an internal combustion engine, steam energy, wind or water. The most important condition is the availability and ability to create sufficient torque.

Examine simple, casual hydraulic systems to better understand the principle. The hydraulic lifter allows an ordinary person to raise more than 20 tons. The power steering in the car reduces the amount of power to turn the steering wheel, and the hydraulic wood cutter allows you to split the hardst tree.

Create a plan for your hydraulic system using the necessary parameters. Determine which source of energy you are going to use to create pressure, as well as the type of control valves, the type of pump and pipes. You need to choose a way to deliver the energy to perform the task for which you create a hydraulic system, for example, to raise a heavy load or split the tree.

Determine the amount of work that the system should perform to correctly populate the size of the components. The system with a large capacity you will need a large volume pump. The volume is calculated in liters per minute, and the pressure is in kilograms per square centimeter. All this also belongs to the hydraulic motor or cylinder, which will cause a device in motion. For example, the cylinder used in the loaders. It requires the "X" oil liters under pressure "Y" to raise "___" kilograms on "___" meters.

Choose a suitable liquid tank. Suitable steel or plastic tank with hermetic clips for hoses. Remember that the tank is not under pressure during system operation, however, you will need a valve in case an excessive fluid go back to the tank.

Choose suitable material To create contour. Fortified rubber hoses with O-shaped seals will be the most simple decisionBut high strength steel tubes Much stronger and require less repairs.

Select a suitable valve system. A simple liquid valve suitable for pressure on your system will completely come down as a control valve, but for more complex actions, a spool will need to control the non-stationary stream, as well as change the flow direction in the system.

Select the type and capacity of the pump. There are two types of hydraulic pumps. The first is the "generator" - the pushing liquid through two and more linked gears in hermetic casing. The second is "roller" - using several cylindrical rollers around the chamber in a hermetically casing. Each has its advantages and disadvantages, so choose the most suitable.

Connect a suitable motor to the pump. Pumps can operate from direct drive, through lower transmission, chain, belts and an asterisk. The selection depends on the purpose of the device.

Purpose and flow assignment.

When studying the basics of hydraulics, the following terms were used: power, energy transfer, operation and power. These terms are used in describing the relationship of pressure and flow. Pressure and flow - two basic parameters of each hydraulic system. Pressure and flow are interrelated, but perform different work. Pressure compresses or applies a force. The stream moves the items of the water gun is a good example of pressure and flow in application. Pressing on the trigger creates pressure inside the water pistol. Water under pressure flies out of the water pistol and thus knocks the wooden soldier.

What is pressure?

Let's think about how and why pressure is created. The fluid (gas and liquid) seeks to expand or resistance occurs during their compression. This is pressure. When you pumped the bus, you create pressure in the tire. You download the air in the tire more and more. When the tire is completely filled with air, pressing the tire walls. Such a press is a type of pressure. Air is a gas type and can be compressed. Compressed air presses on the walls of the tire with the same force at every point. Liquid is under pressure. The main difference is that gases can be compressed in bolsters.

The same force at every point

Pressure in compressed liquid

If you click on a compressed liquid, pressure will occur. As in the case of a tire, the pressure is equally at each point of the barrel containing the liquid. If the pressure is too large, the barrel may break. Barrel will break in weak place, not where there is more pressure, because the pressure is equally at every point.

Liquid is almost not compressed

Compressed liquid is convenient when transferring power through pipes, on bending, up, down, because liquids are almost incompressible and energy transmission occurs immediately.

Many hydraulic systems use oil. This is because the oil is almost not compressed. At the same time, the oil can use as a lubricant.

Pascal Law:The pressure produced by external forces on the surface of the liquid or gas is transmitted in all directions unchanged.

Section 2.

Pressure and power ratio

According to the law of Pascal, the relationship between pressure and strength is expressed by the formulas:

F \u003d p / s, where p - pressure, F - Power, S - Area

Hydraulic lever

On the model of the piston shown in the figure below, you can see an example of balancing various weights through the hydraulic lever. Pascal discovered, as can be seen on this example, that the small weight of the small piston balances the large weight of a large piston, proving that the piston area is proportional to the weight. This discovery is applied to the compressible fluid. The reason why this is possible, this is that the liquid always acts with equal power on an equal area.

The figure shows a load of 2 kg and a load of 100 kg. Area of \u200b\u200bsingle cargo, weighing 2 kg - 1cm?, Pressure is 2 kg / cm?. Square for the otherogogrous, weighing 100 kg - 50 cm? The pressure is 2 kg / cm?. Two weights balancing each other.

Mechanical lever

The same situation can be illustrated by the example of a mechanical lever in the figure below.

A cat weighing 1 kg sits at a distance of 5 meters from the center of gravity of the lever and balances the cat weighing 5 kg at a distance of 1 meter from the center of gravity, like cargo on the example of the hydraulic lever.

Energy conversion of hydraulic lever

It is important to remember that the liquid acts equal to the power on an equal area. When working it helps a lot.

There are two cylinders of the same size. When we press one piston with an effort 10 kg, another piston is extruded with a force of 10 kg, because the area of \u200b\u200beach cylinder is the same. If there are different squares, the forces are also different.

For example, let's say that a large piston has an area of \u200b\u200b50 cm?, And a small piston has an area of \u200b\u200b1 cm?, At an effort of 10 kg to a small piston, an exposure is 10 kg / cm? For each part of a large valve according to the law of Pascal, so a large piston receives a common force of 500 kg. We use pressure to transmit energy and perform work.

There is an important point when converting energy, namely, the relationship between force and distance. Remember, on a mechanical lever, low weight requires a long lever to achieve equilibrium. In order to raise the cat weighing 5 kg per 10 cm, the cat weighing 1 kg should lower the lever 50 cm down.

Let's look at the drawing of the hydraulic lever again and think about the progress of the small piston. 50 cm small piston stroke is needed to transmit sufficient liquid to move the large cylinder piston by 1 cm.

Section 3.

Flow creates motion

What is a stream?

When the pressure difference at two points of the hydraulic system, the liquid tends to the point with the lowest pressure. Such a fluid movement is called a stream.

Here are some examples of the stream. Water in urban water supply creates pressure. When we turn the crane, then water flows water due to the pressure difference from the crane.

In the hydraulic system, the stream creates a pump. The pump creates a continuous stream.

Speed \u200b\u200band stream value

The speed and value of the stream are used to measure the stream.

Speed \u200b\u200bshows the distance traveled during a certain period of time.

The value of the flow shows how much fluid flows through a certain point for this moment time.

Flow value, lit. / min.

Flood value and speed

In the hydraulic cylinder it is easy to consider the ratio between the amount of flow and speed.

First, we must think about the size of the cylinder, which we must fill out and then think about the progress of the piston.

The figure shows a cylinder and a long 2 meter long and a volume of 10 liters and a cylinder in a long 1 meter and a volume of 10 liters. If you download 10 liters of fluid per minute to each cylinder, the complete move of both pistons lasts 1 minute. The cylinder piston is twice as fast as the cylinder V. This happens because the piston must pass the distance twice as much over the same period of time.

This means that a cylinder with a smaller diameter moves faster than a cylinder with a large diameter at the same flow rate for both cylinders. If we increase the flow rate of up to 20 l / min, both cylinder chambers will be filled twice as fast. The speed of the piston should increase twice.

Thus, we have two ways to increase the cylinder speed. One way to reduce the size of the cylinder and the other by increasing the flow rate.

The speed of the cylinder is thus proportional to the flow rate and inversely proportional to the piston area.

Pressure and power

Creating pressure

If you press the cork in a barrel filled with liquid, the plug will be stopped with liquid. When pressing, the pressure fluid presses on the walls of the barrel. With excessive pressing it is possible to break the barrel.

The path of least resistance

If there is a barrel with water and hole. When you press the lid from above, the water follows from the hole. Water, passing through the hole, does not meet resistance.

When the force is applied to a compressed liquid, the liquid searches for the path of least resistance.

Equipment faults using oil pressure.

The above characteristics of hydraulic fluids are useful for hydraulic equipment, but are also a source of many faults. For example, if there was a flow in the system, the hydraulic fluid will flow, as it seeks the path of the least resistance. Typical examples are leaky compounds and seals.

Natural pressure

We talked about pressure and stream, but often the pressure exists without a stream.

Gravity is a good example. If we have three interrelated reservoirs of different levels, as shown in the figure, gravity strength retains fluids in all tanks on the same level. This is another principle that we can use in the hydraulic system.

Liquid mass

The mass of the liquid also creates pressure. Diver, who dives into the sea, will say that he cannot dive too deep. If the diver falls too deep, the pressure will give it away. This pressure is created by a mass of water. Thus, we have a type of pressure that appears on your own water weight.

The pressure increases in proportion to the depth and we can accurately measure the pressure at depth. The figure shows a square column with water with a height of 10 meters. It is known that one cubic meter of water weighs 1000 kg. With an increase in the height of the column to 10 meters, the weight of the column will increase to 10,000 kg. On the bottom is formed one square meter. Thus, the weight is distributed per 10,000 square centimeters. If we split 10,000 kg per 10,000 square centimeters, it turns out that the pressure at this depth is 1 kg per 1 square centimeter

The value of gravity

Under the action of gravity, the oil hits the tank to the pump. The oil is not absorbed by the pump, as many people think. The pump serves to supply the oil. What is usually understood under the suction of the pump, denotes the supply of oil to the pump under the action of gravity.

Oil to the pump enters the action of gravity.

What causes pressure?

When the pressure is mixed with the stream, we have hydraulic power. Where does the pressure in the hydraulic system comes from. Part is the result of gravity, but where the rest of the pressure comes from.

Most of the pressure appears from the impact of the load. In the figure below, the pump serves continuously. The oil from the pump finds the path of the smallest resistance and heads through the hose to the working cylinder. The weight of the load creates pressure, the value of which depends on the weight.

Hydraulic strength of the working cylinder

(1) The law of inertia suggests that the body property to maintain their rest of the peace or straight uniform movement until any external force declines it from this state. This is one reason why the piston of the working cylinder does not move

(2) Another reason why the piston does not move is the location on it.

Flow

Earlier, we said that the flow makes work and moves objects. There is another key point - how does the flow rate refers to the operation of the hydraulic system?

The answer is that the flow rate is constant,

The growing flow rate creates high speed

Many people think that increasing pressure increases speed, but it is not true. You can't make the piston move faster, raising pressure. If you want to make the piston move faster, you must increase the flow rate.

Parallel compound

There are three different cargo connected in parallel in one hydraulic system, as shown in the figure below. Oil, as usual, looking for the path of least resistance. This means that the easiest cargo will rise first, because the cylinder will need the smallest pressure. When the easiest cargo rises, the pressure will increase in order to raise the next cargo from the remaining. When the cylinder and reaches the end of the stroke, the pressure will increase to raise the worst cargo. The cylinder with will rise last.

(3) When the pump begins to put pressure on the cylinder, the working piston and the goods have resistance to the oil flow. Thus, the pressure increases. When this pressure overcomes the piston resistance, the piston begins to move.

(4) When the piston moves up, it raises the cargo. Pressure and stream are used together to perform work. This is a hydraulic force in action.

When closing the safety valve, the speed does not increase

Here is one common error when searching for a malfunction in the hydraulic system. When the speed of the cylinder drops, some mechanics are immediately sent to the safety valve, because they think that the pressure increase will increase the operating speed. They try to reduce the settings of the safety valve, which is supposed to increase the maximum pressure in the system. Such changes do not lead to an increase in the speed. Safety valve is used to protect the hydraulic system from excessive pressure. Pressure parameters should never be higher than magnitude pressed pressure. Instead of increasing pressure settings, mechanics should look for other causes of system malfunction.

Conclusion

Now you have knowledge of the foundations of the theory of hydraulics. You know that the Pascal law suggests that the pressure produced by external forces on the surface of the liquid or gas is transmitted in all directions unchanged.

You also learned that the hydraulic fluid under pressure seeks the path of the least resistance. It is good when it works for us and bad when it causes to flow in the system. You have seen how we can use low weight on one cylinder for the movement of big weight on another cylinder. In this case, the course of small cargo piston is greater. You also received a clear understanding of the relationship of pressure and strength, flow rates and speed and of course pressure and flow.

Hydraulic mechanisms

Hydraulic systems

Hydraulic systems are used to transmit mechanical energy from one place to another. This occurs through the use of pressure energy. The hydraulic pump is driven by mechanical energy. Mechanical energy is converted into the pressure energy and the kinetic energy of the hydraulic fluid and then again converted into mechanical energy to perform work.

Meaning of energy conversion

The energy that is transmitted to the hydraulic system is converted from the mechanical energy of the engine, which drives the hydraulic pump. The pump converts mechanical energy into a fluid flow, transforming mechanical energy into pressure and kinetic energy. The fluid flow is transmitted through the hydraulic system and is sent to the drives of cylinders and motors. The pressure of the pressure and the kinetic energy of the fluid causes the drive movement. At the same time, another conversion into mechanical energy occurs.

How it works in the hydraulic excavator.

In hydraulic excavators, the primary mechanical engine power drives the hydraulic pump. The pump sends the oil flow into the hydraulic system. When the drive is moving under the action of oil pressure, convert to mechanical energy is once again. The excavator boom can rise or descend, the bucket movement is made, etc.

Hydraulics and work

Three elements of work

When there is any job, then for the performance of this work requires certain conditions. It is necessary to know what power will need. You need to decide how quickly it is necessary to work and you must determine the direction of work. These are three working conditions: force, speed and direction are used in hydraulic terms, as shown below.

Components of the hydraulic system

Main components

The hydraulic system consists of many parts. The main details are the pump and the drive. The pump serves oil, transforming mechanical energy into pressure and kinetic energy. The actuator is part of the system that converts hydraulic energy back to mechanical energy to perform work. Other details, besides the pump and drive, are necessary for the complete operation of the hydraulic system.

Tank: Oil Storage

Valves: Control over the direction and value of the stream or pressure limit

Pipeline lines: Connecting system parts

Let's look at two simple hydraulic systems.

Example 1, hydraulic jack

What you see in the picture is called a hydraulic jack. When you make an effort to the lever, the hand pump serves oil into the cylinder. The pressure of this oil presses the piston and raises the cargo. The hydraulic jack is largely reminiscent of Pascal's hydraulic lever. A hydraulic tank has been added here. The check valve is set to keep the oil in the tank and the cylinder between the piston stroke.

On the top figure, the pressure is retained, the check valve is closed. When the pump handle stretches up, the intake check valve opens and the oil falls out of the tank into the pump chamber.

Bottom drawing shows open stop valve To connect the tank and cylinder, allowing the oil to flow into the tank, while the piston moves down.

Example 2, Hydraulic Cylinder

1. First, there is a hydraulic tank filled with oil and connected to the pump.

3. The pump works and shakes oil. It is important to understand that the pump moves only the volume. Volume Sets the hydraulic speed. Pressure is created by load and is not created by the pump.

4. The hose from the pump is connected to the camshaft. The oil comes from the pump to the valve. The operation of this valve consists in the direction of flow or to the cylinder, or to the tank.

5. The next step is the cylinder that performs the actual work. Two hoses from the camshaft are connected to the cylinder.

6. The pump oil is directed to the lower piston cavity through the switch valve. The load causes a stream resistance, which in turn creates pressure.

7. The system looks finished, but it is not. Still needed very necessary important detail. We need to know how to protect all components from damage in case of sudden overload or other incident. The pump continues to work and serve oil into the system, even if the system has occurred.

If the pump serves oil and there is no possibility for oil output, the pressure increases until anyone breaks down. We set the safety valve to prevent it. It is usually closed, but when the pressure reaches the installed value, the safety valve opens and the oil flows into the tank.

8. Tank, pump, camshaft, cylinder, compound hoses and safety valve are the basis of the hydraulic system. All these details are necessary.

Now we have a clear idea how the hydraulic system works.

Classification of pumps

What is the pump?

Like your heart that pumps blood according to your body, the pump is the heart of the hydraulic system. The pump is part of the system that shakes oil to perform work. As we wrote before, the hydraulic pump converts mechanical energy into the pressure energy and the kinetic energy of the liquid.

What is a hydraulic pump?

Each pump creates stream. The liquid moves from one place to another.

There are two types of displacement pumps.

Forced action pump

No enforcement pump

Water circle in the figure is an example of a not forced pump. The circle raises the liquid and moves it.

Another enforcement pump. It is called forced action, since the pump is injected with a liquid and prevents it back to return it. If the pump can not do it, there will be no sufficient pressure in the system. Today, all hydraulic systems use high pressure, and thus need for compulsory pumps.

Types of hydraulic pumps

Today, many machines installed one of the three pumps:

• Gear pump
• Bandal pump
• Piston pump

All pumps operate on a rotary piston type, the liquid is activated by the rotation of the part inside the pump.

Piston pumps are divided into two types:

Axially piston type

Radial piston type

The pumps are an axially piston type called so because the pistons of the pump are located parallel to the axis of the pump.

The pumps of radially piston type are called so, because the pistons are perpendicular to the (radial) axis of the pump. The pumps of both types make reciprocating movement. Pistons move forward and forth and use a rotary piston movement.

Hydraulic pump

The working volume, which means the volume of oil, which the pump can pump or move in each cylinder. Hydraulic pumps are divided into two types:

Fixed working volume

Changeable working volume

Pumps of fixed working volume pump the same amount of oil for each cycle. To change the volume of such a pump, you need to change the pump speed.

NSOSs with a modified working volume can change the volume of oil depending on the cycle. This can be done without changing speed. Such pumps have an internal mechanism that adjusts the output amount of oil. When the pressure in the system drops, the volume increases when the pressure in the system increases, the volume decreases automatically.

Power

Pump fixed working volume pump of a variable working volume

Design

Driving classification

What is the drive?

The drive is part of a hydraulic system that produces energy. The drive converts hydraulic energy into mechanical energy to perform work. There are linear and rotary drives. The hydraulic cylinder is a linear drive. The hydraulic cylinder force is directed straight. The hydraulic motor is a rotary drive. The output force is torque and rotary action.

Rotary drive

Linear drive

Hydraulic cylinders

Hydraulic cylinders like lever. There are two types of cylinders.

Single-action cylinders.

The hydraulic fluid can only move in one end of the cylinder. The return of the piston at the initial position is achieved by the action of gravity.

Double-acting cylinders.

The hydraulic fluid can move to both end of the cylinder, so the piston can move in both directions.

In both types of cylinders, the piston moves in the cylinder in the direction in which the fluid presses on the piston. Different seal types are used in pistons to prevent leaks.

Single-action cylinder

Dual-action cylinder

Hydraulic motor

Like a cylinder, the hydraulic motor is a drive, only a rotary drive.

The principle of operation of the hydraulic motor is directly opposite to the operation of the hydraulic pump. The pump is injected fluid and the hydraulic motor runs from this fluid. As we wrote before, the hydraulic pump converts mechanical energy into the pressure energy and the kinetic energy of the liquid. The hydraulic motor converts hydraulic energy into mechanical energy.

With hydraulic drive, pumps and motors work together. Pumps are powered by mechanically and injected fluid into hydraulic motors.

Motors are powered by a liquid from the pump and this movement in turn rotates mechanical parts.

Types of hydraulic motors

There are three types of hydraulic motors and all of them have internal moving parts, which are powered by the incoming stream, their name:

• Gear motor
• Bad motor
• Piston Motor.

Operating volume and torque

Working motor is called torque. This is the power of rotation of the motor shaft. Torque This is the value of measuring force per unit length, it does not include speed. The torque of the motor is determined by the maximum pressure and the volume of the fluid that can move during each cycle. The speed of the motor is determined by the flow of the stream. More flow magnitude, faster speed.

Torque is the power of the motor shaft rotation

Torque is equal to strength

Valve classification

What valves come?

Valves are controls in the hydraulic system. The valves regulate the pressure, the direction of flow and the value of the stream in the hydraulic system.

Three types of valves are distinguished:

In the figure below, you can see how the valves work.

Pressure control valves

These valves are used to limit pressure in the hydraulic system, unloading the pump or setting the chain pressure. There are several types of pressure control valves, some of which are safety, pressure reduction valves and discharge valves.

Pressure control valves

The pressure control valve is used for the following purposes:

Pressure limits inside the system

Reducing pressure

Setting the incoming chain pressure

Discharge pump

Safety valve is sometimes called a protective valve, because it reduces excessive pressure when it reaches extremely values. Safety valve prevents the details of the overload system.

There are two types of safety valve:

Safety valve direct actionwhich simply open and closes.

Pilot Line Safety Valvewhich has a pilot line to control the main safety valve.

The direct action safety valve is usually used in places where the stream volume is small and the work is rarely repeated. The pilot line safety valve is required in places where the large oil volume should be reduced.

Valve direction control

This valve controls the selection of the flow direction of the hydraulic system. A typical directional control valve is a camshaft and a spool.

Valve of adjustment value

This valve controls the speed of the hydraulic oil flow rate. The control occurs due to the limitation of the flow or the assignment it. Several different types of valve valve valve are a flow control valve and a flow division valve.

These valves are managed different ways: manually, hydraulically, electrically, pneumatically.

Directional control valves

This valve sets the oil flow, as the adjustor controls the traffic. Such valves:

Check valve

Spool valve

Are used different types Direction management design.

Check valve uses a plate valve and a spring for the direction of flow in one direction. The spool valve uses a movable cylindrical spool. The spool moves forward and backward, opening and closing channels for passing the flow.

Check valve

Check valve is easy. It is called a valve of one stream. This means that it is open to the passage of flow in one direction, but is closed to leakage oil in the opposite direction.

In the picture below, you can see the operation of the check valve. This is the check valve that is arranged for through stream on the same line. A plate valve opens when the intake pressure is larger than the outlet pressure. When the valve is open, the oil freely flows. The plate valve closes when the inlet pressure drops. The valve interrupts the flow in the opposite direction and stops the flow under the action of the exhaust pressure.

Spool valve

The spool valve is a typical camshaft, which is used to control the operation of the drive. What is usually called the camshaft and is a spool valve. The spool valve sends the oil flow to start, conducting and ending work.

When the spool moves from the neutral position to the right or left, the opening of some channels and the closure of other channels occurs. In this way, the oil is supplied to and from the drive. The spool bin close the incoming and outgoing oil streams.

The spool is made of durable material and has a smooth, precision, strong surface. It is even covered with chrome to prevent wear, rust and damage.

The spool valve in the figure shows three positions, neutral, left and right. We call it a four-position, because it has four possible directions that are directed in both cavities of the cylinder, to the tank and in the pump.

When we move the spool to the left, the oil flow is directed from the pump to the left cavity of the cylinder and the stream from the right cavity of the cylinder is directed to the tank. As a result, the piston moves to the right.

If we shift the spool to the right, the actions are directly opposite, respectively, the piston moves to the right.

In the central position, neutral, oil is sent to the tank. Channels in the wallpaper of the cylinder cavity are closed.

neutral

Valves of regulatory valves

As we wrote before, the valve of regulating the size works in one of two directions. He or overlaps the flow, or changes its direction.

Flow control valve Used to control the drive speed by means of flow measurement. Measurement involves measuring or regulating the flow rate to or from the drive. The flow separation valve adjusts the stream volume, but also separates the streams between two or more chains.

Flexible flex valve Controls the amount of stream, but also separates the streams between two or more chains.

Proportional flow divider

Purpose of this valve - flow dividing from one source.

The flow divider in the figure below divides the streams in the ratio of 75-25 at the output. This is possible because the entry number 1 is more input number 2.

Hydraulic circuit

Earlier, the text contains pictures to help understand the principles of the hydraulic system and its component parts. We tried to show the design on various examples and used various types of drawings.

Drawings that we use are called graphic scheme.

Each part of the system and each line is depicted by a graphic symbol.

Below are examples of a graphic chart.

It is important to understand that the assignment of the graphic diagram does not show the device details. The graphic diagram is used only to display functions and connectors.

Classification of lines

All components of the hydraulic system are connected by lines. Each line has its own name and performs its function. Main lines:

Work lines: Pressure line, suction line, drain line

Do not working lines: drainage line, pilot line

Oil the working line involved in the conversion of energy. The suction line delivers oil from a tank to the pump. The pressure line delivers oil from the pump to the drive under pressure to perform work and the drain line returns the oil from the drive back to the tank.

No work lines are additional lines that are not used in the basic functions of the system. The drainage line is used to return to the exhaust oil or pilot line oil. The pilot line is used to manage the working bodies.

Advantages and disadvantages of the hydraulic system

We studied the basic principles of the hydraulic system.

Before completing, look at the advantages and disadvantages of the hydraulic system before other systems.

Benefits

1. Flexibility - a limited amount of fluid is a more flexible source of energy and has good energy transmission properties. Using sleeves high pressure and hoses instead of mechanical parts allows you to eliminate many problems.

2. Increase in force - low power can control a lot of power.

3. Smoothness - the work of the hydraulic system smooth and quiet. Vibration is minimized.

4.Surestate - there are several moving parts and a small number of hydraulic system connections, as well as self-lubricant.

5. Compactness - the device of component parts is very simple compared to mechanical devices. For example, the size of the hydraulic motor is significantly less than an electric motor that produces the same energy.

6. Savings - simplicity and compactness ensures the economy of the system with small power losses.

7. Security - Safety valve protects the system from overloads.

disadvantages

The need for timely maintenance - components of the hydraulic system are precision details and operate under high pressure. Timely maintenance is necessary to protect against rust, oil pollution, increased wear, so the use and replacement of the appropriate oil is a necessity.

A little more about hydraulics

Energy loss (pressure)

Another important point for understanding the basics of hydraulics is the loss of energy (pressure) in the hydraulic system.

For example, some resistance of the stream causes a reduction in flow pressure, resulting in a loss of energy.

Now I will study some details.

Oil viscosity.

Oil has viscosity. The viscosity of the oil independently creates stream resistance.

Flow resistance due to friction.

During the passage of oil on pipes, pressure drops due to friction.

Such a reduction in pressure increases in the following cases:

1) when using a long pipe

2) Using a small diameter pipe

3) with a sharp increase in flow

4) with high viscosity

Pressure reduction for other reasons

In addition to lower pressure due to friction, losses can occur due to changes in the direction of flow and changing the oil flow channels.

Leakage of oil through choke

As we said earlier, the pressure decrease occurs when the oil flow is restricted.

The throttle is a limit view that is often installed in the hydraulic system to create a pressure difference in the system.

However, if we stop the flow of the throttle, the law of Pascal and the pressure is aligned on both sides.

Loss of energy

As you know well, there are many pipes, fittings (connections) and valves included in the hydraulic system.

A certain amount of energy (pressure) is used only to move oil from one place to another, before performing the work.

Lost energy is converted to heat

The loss of energy due to the reduction in pressure is converted to heat. Increase the oil flow, an increase in oil viscosity, an increase in the length of the pipe or hose, as well as similar changes, cause an increase in resistance and causes overheating.

To avoid this problem, use spare parts identical to the original.

Efficiency of the pump

As we said earlier in the preceding text, the hydraulic pump converts mechanical energy into hydraulic energy. The efficiency of the pump is checked by its performance and is one of the items when checking the performance. The effectiveness of the pump means how well the pump copes with its work.

There are three approaches in determining the performance of the pump.

Feed efficiency

Torque efficiency (mechanical)

Full efficiency

The effectiveness of torque

The effectiveness of the torque is the ratio of the actual output torque of the pump to the incoming torque of the pump.

The actual outlet torque of the pump is always less than the incoming torque of the pump. The loss of torque occurs due to the friction of the movable parts of the pump.

Full efficiency

Complete efficiency is the ratio of the existing hydraulic power to the incoming mechanical power of the pump.

This is the magnitude of both: the effectiveness of the feed and efficiency of the torque. In other words, complete efficiency can be expressed as the outgoing power separated by incoming power. The output power is less than the incoming power due to losses in the pump due to friction and internal leaks.

In general, the effectiveness of six and piston pumps is 75 - 95%.

The piston pump is usually estimated above than the gear pump.

Feed efficiency

The feed efficiency is the ratio of the actual pump feed to the theoretical pump feed. In fact, the actual pump feed is less than the theoretical feed of the pump.

This is usually expressed as a percentage.

The difference is usually expressed in the internal flow in the pump at the expense of the holes in the working parts of the pump.

Some holes are made in all parts for lubrication.

Internal leak happens when wearing the pump parts produced with a low tolerance.

We consider increased internal flow as loss of efficiency.

Power required for pump operation

For reasons given earlier, the power required for the pump operation should be greater than the outgoing power.

Here is an example of a pump with a capacity of 100 hp.

If the effectiveness of the pump is 80%, then it is necessary to supply the power of 125 hp.

Required power \u003d output power / efficiency \u003d 100/80

In other words, the engine capacity of 125 hp We are necessary for the operation of the pump with a capacity of 100 hp with an efficiency of 80%.

Fault pump

What reduces the efficiency of the pump?

Dirty oil is the main reason for the breakage of the pump.

Sliding particles of dirt, sand, etc. In oil used in the pump as an abrasive material.

This causes intensive wear of parts and increases the internal flow, thereby lowering the efficiency of the pump.

Drainage canal

A channel that is used to drain the oil into the tank is called a drainage channel.

Cavitation pump

When is cavitation?

Cavitation happens when oil does not fully fill the space intended for filling in the pump.

This contributes to the appearance of air bubbles that are harmful to the pump.

Imagine that the intake line of the pump is narrow, it causes a drop in incoming pressure.

When the pressure is low, the oil cannot enter the pump as quickly as to leave it.

The result is that air bubbles are formed in the incoming oil.

Air in oil

Such a reduction in pressure leads to the appearance of a certain amount of dissolved air in oil and the air fills the cavities.

Air in oil in the form of bubbles, also fills the cavities.

When air filled with air, which are formed at low pressure, enter the high pressure pump area, they are destroyed.

This creates an action, an equivalent explosion that splits or makes small pump particles and causes excessive noise and vibration of the pump.

Consequences of the explosion

Destruction that happens constantly cause an explosion.

The strength of this explosion reaches 1000 kg / cm² and small metal particles are taken out of the pump. If the pump works at cavitation for a long time, it may be seriously damaged.

Hydraulic motor

The motor operates in the reverse order, if compared with the pump.

The pump serves oil, while the motor runs from this oil.

Motor converts hydraulic energy into mechanical energy to perform work.

Motor efficiency

Like the hydraulic pump, the efficiency of the motor is determined by its performance.

Flow efficiency is one of the indicators when determining the performance of the motor.

Internal leaks occurs because of the holes in the working parts of the motor. Some holes are available in all parts for lubrication. The increase in the leaks is associated with the wear of parts with a small tolerance.

We consider increased internal flow as loss of efficiency.

Verification of motor work

As we said earlier, the canal, through which the oil enters the tank, is called the drainage canal.

This gives us one method to check the operation of the motor, comparing the actual amount of the engine fused to the oil tank with a fixed value. The greater the amount of fused oil into the tank, the more loss Energy and, accordingly, reducing the performance of the motor.

Hydraulic cylinder

Leak cylinder - outdoor leak

During the drawing of the cylinder rod, dirt and other material is possible. Then, when the rod retracts, the dirt in the cylinder and damage to the seals occurs.

There is a protective seal on the cylinder stock, which prevents dirt getting into the cylinder during the rod retracting. If leak occurs from the cylinder rod, it is necessary to replace all stem seals.

Cylinder leak - internal flow

To flow inside the cylinder can cause slow motion or stop under load.

Piston leak can be caused by faulty piston seal, rings or scratched surface inside the cylinder.

The latter may be caused by the fall of dirt and the presence of sand in oil.

Slow motion

The presence of air in the cylinder is the main cause of slow motion, especially when installing a new cylinder. The entire air caught in the cylinder should be bleed.

Lowering the cylinder

If the cylinder descends when stopping, check for internal flow. Other causes of malfunction can be a faulty distribution valve or a safety valve breakdown.

Irregularity or rust rod cylinder

An unprotected cylinder rod may be damaged by a blow to a solid object. If a smooth surface The rod is damaged, stock seals can be destroyed.

Irregularities on stock can be corrected special tool.

Another problem is rust on stock.

When storing a cylinder, pull the stock to protect it from rust.

Valves

The preceding text revealed the basic knowledge of the valves and their differences when working.

It is necessary to study several technical terms associated with the camshaft valves.

Claking Pressure and Pressure Full Flow

Claking Pressure is the pressure at which the safety valve opens.

The full stream pressure is the pressure at which the most complete stream passes through the safety valve.

Full stream pressure is slightly higher than Cracing pressure. Adjusting the safety valve is set to the full flow pressure value.

Craketing pressure and pressure adjustment

In the preceding text, we studied the fact that there are two types of safety valves: a direct action safety valve and a safety valve controlled by a pilot line.

Let's consider adjusting the pressure of these valves.

The safety valve controlled by the pilot line has a smaller adjustment pressure than a direct action valve.

The figure shows the comparison of these two types of valves.

While the direct action safety valve in the figure opens at half the pressure of the full stream, the safety valve, the pilot line controlled by 90% of its full flow pressure.

Adjusting pressure

As we said earlier, the pressure of the full stream is slightly higher than the cr stock pressure.

This is because the springs tension is adjusted to the opening of the valves. This condition is called as pressure adjustment and this is one of the disadvantages of a simple safety valve.

What's better?

A safety valve controlled by a pilot line is better for a high-pressure system and with great performance.

Because these valves do not open until the full stream is reached, occurs. effective protection Systems - oil is saved in the system.

Although slower work than a direct action valve, a safety valve, controlled by a pilot line supports more constant pressure in the system.

Reduction valve

What it is?

The reduction valve is used in the hydraulic motor circuit to create a back pressure for control during operation and to stop the motor when the chain is neutral.

Crane reducing valve

The reduction valve is usually closed together with the pressure control valve with an internal check valve.

When the pump serves oil on the wind turret Motor, the motor works on inertia under the action of gravity of the load, in other words, when the motor exceeds the permissible speed, the reducing valve supplies the opposite pressure, thus preventing free drop in cargo.

Internal check valve gives permission to feed reverse flux To rotate the motor in the opposite direction, to raise the cargo.

Reduction valve for excavators.

The equivattor reduction valve provides a soft start and increase the speed / turn, and also prevents the motor cavitation.

The pressure in the pump pressure line is always higher than the pressure of the motor line.

An attempt to exceed the installed inertia motor velocity causes a pressure reduction in the pressure line and the valve immediately overlaps the motor line until the pressure of the pressure line is recovered.

Valve maintenance

Support a good valve status

As you know well, the valves are precision products and should take accurate testimony of pressure, direction and volume of hydraulic oil oil.

Therefore, the valves must be properly installed and in the normal state.

Causes of valve faults

Pollution, such as dirt, fluff, corrosion and sucks can cause incorrect operation and damage to the valve parts.

Such pollution causes the valve jamming, incomplete opening or ripping the pairing surface until flowing.

Such malfunctions are excluded when equipped with cleanliness.

Checkpoints

While finding faults or repair, check the following details.

Pressure Distribution Valve - Safety Valve

Check the valve seat (valve seat and valve plate) for leaks and jams.

Check for a plunger jam in the housing.

Check out rubber rings.

Check if the choke is clogged.

Distribution valve flow

• Check the spool and channels for irregularities and scratches.
• Check the seals to flow
• Check for root irregularities.
• Check for scratches on the spool.

Flow switch valve spools are installed in the case in the calculated locations.

This is done to provide the smallest gap between the case and the spool to prevent internal leaks and the maximum assembly quality. Therefore, install spools into the appropriate holes.

Hydraulic pump - equipment by which mechanical energy is converted into hydraulic: either pressure is formed from the torque generated by the engine. There are many types of such aggregates, but they work according to the similar principle, the essence of which is the displacement of the fluid between the hydraulic pump cameras.

This article will consider the high-pressure hydraulic pump and its manual analogue. We study the device and the principle of action of such equipment, read it with its species and we will recommend the recommendations on the installation and repair of such equipment.

1 Classification and varieties of hydraulic pumps

The principle of operation of any hydraulic pump is quite simple - when working inside the design, two isolated cavities (absorption and discharge chamber) are formed, between which the hydraulic fluid moves. After filling in the discharge chamber, the liquid begins to put pressure on the piston and displaces it, thereby becoming a feeding movement in the working tool.

Operating parameters Any hydraulic pump displays the following characteristics:

• rotation frequency (rpm);
• operating pressure (bar);
• working volume (CM3 / OB) - the amount of fluid that pump displaces in one turn.

Pumps that we will be considered in the future possess individual operational features, so when choosing them, first of all, it is necessary to take into account the characteristics of the existing hydraulic system - the pressure range, the viscosity of the pumped fluid, the cost of construction and the nuances of its maintenance.

Consider the main varieties of hydraulic pumps, settling in detail their advantages and disadvantages.

1.1 Manual hydraulic pump

Manual hydraulic pump is the simplest equipment in which the principle of displacement of the fluid is used. Such units are widespread in the field of automotive industry, where they are used as additional or emergency mechanisms to provide hydraulic engine motors.

Handmade hydraulic pump of the NWG type (series, most common in the domestic industry) can develop pressure house 50 bar, but most models are designed for pressure up to 15 bar. There is a direct ratio - the lower the working volume of the unit (the amount of fluid displaced for the full course of the handle) large pressure He develops.

The image presents a scheme of work that manual pumps possess. When pressing the handle, the piston moves up, as a result of which the power is created and through the CO2 valve in the case there is a fluid that is supplied when picked up the handle. Pump manual hydraulic NWG can be bilateral ( lower scheme), in it suction and displacement of the fluid occurs simultaneously, both when pressed on the lever and when it is raised.

The advantages of such hydraulic pumps are simplicity of their design (the repair of manual type hydraulic pumps is fairly simple), reliability and low cost. Weak Party is performance, incomparable with drive equipment.

1.2 Radial-piston

Radial-piston structures are able to develop the highest possible pressure (up to 100 bar) with long work. There are two types of radial piston pumps:

• rotary;
• with an eccentric shaft.

The device of rotary units is shown in the diagram. In them, the entire piston group is placed inside the rotor, when rotating which the pistons make reciprocating movements and alternately jerk with holes for draining hydraulic fluid.

The high-pressure hydraulic pump with an eccentric shaft is distinguished by the fact that the piston group is installed inside the stator, with such pumps have a valve distribution of the fluid, and rotary - spool.

The benefits of such equipment will be highly reliable, the possibility of working in high pressure mode (100 MPa), the minimum noise level during operation. To disadvantages - high level Pulsation when flowing fluid and considerable weight.

1.3 axial-piston

The most common type of equipment in modern hydraulic drives is an axial-piston pump. There is also an axial-piston technique, which is characterized in that instead of pistons, plungers are used to displace liquid.

Pumps with axial-piston drive, depending on the axis of rotation piston groupcan be divided into two types - inclined and straight. The principle of operation they are identical - the rotation of the pump shaft leads to the rotation of the cylinder block, in parallel, which the pistons begin the return-transit movement. With the coincidence of the axis of the cylinder and the suction opening, the piston squeezes the liquid from the chamber, then the cylinder is filled and the cycle is repeated.

By the ratio of the mass-duty characteristics, the axial-piston pump is optimal option. It is capable of developing pressure up to 40 MPa at a frequency of 5000 rpm, highly specialized installations operate at a frequency of 15-20 thousand rpm. The advantages of axial-piston pumps are the maximum efficiency and performance. The key disadvantage is the high cost.

As an example, such equipment can be considered popular in domestic engineering hydraulic pump 310. There are several modifications of this model designed for a working volume from 12 to 250 cm 3 / about. The price of the 310th model varies within 15-30 thousand rubles, depending on performance. A more affordable analogue is hydraulic pump 210 (the price of 10-15 thousand), characterized by a lower frequency of revolutions.

1.4 Gear hydraulic pumps

Gears aggregates refer to the category of rotary equipment. The hydraulic part of the pump is represented in two rotating gears whose teeth are displaced with a liquid from the cylinder. There are two types of gear pumps - with external and internal engagement, which are characterized by the location of the gears inside the case.

Gear units are used in low-level systems - up to 20 MPa. They are widespread in agricultural and construction machinery, feed systems lubricants and mobile hydraulics.

The popularity of gear hydraulic pumps is caused by the simplicity of their design, in small sizes and weight for which you have to pay a small efficiency (up to 85%), low turns and short operational resources.

1.5 We designate in the device of hydraulic pumps (video)

2 Features of the repair of hydraulic pumps

Almost all malfunctions that may occur during the operation of hydraulic pumps of any type are a consequence of the following factors:

• incorrect hydraulic pump control and disregard maintenance - late replacement of oil and filters, lack of removing leaks;
• incorrectly selected hydraulic fluid (oil);
• the use of third-party components that do not correspond to the pump operation mode (filters, seals, hoses);
• incorrect setting of hydraulic pump.

Consider the most common faults Equipment and methods of their liquidation:

1. Emergency stop. The reason may be the break of the sleeve from excessive pressure, the insufficient level of the working fluid or blocking the pumping nozzle. In the latter case, you need to remove fragments from the camera with your own hands and replace the deformed filters.
2. No pressure set. Most likely, the plunger's nest jack, which requires cleaning, or the valve spring is deformed (it is necessary to replace).
3. Uneven pace of piston movement. Check the system for air penetration, can also overly thicken the working fluid or score the filter. Serious repair of hydraulic pumps may be required only when the rotation shaft fails.
4. Unusually high level of vibration. Cause - Incorrect balancing of rotation shaft with a drive, requires checking the coincidence of the axes of the shafts and their centering.

The small repair of the hydraulic pump will not become a serious problem if there is a repair kit, which includes spare filters, rubber bands and sealing sleeves - the most wear-in design elements. Most manufacturers deliver full kits for each pump model at a price of 500 to 1000 rubles, but the kit can be assembled and in accordance with the diameter of the equipment nozzles. In this case, the hydraulic pump repair kit will cost you much cheaper.