Hydraulic drive system consists of the following five components:
- as in hydraulic power units. It is the role of the prime mover (engine, motor or motors, etc.) of mechanical energy into fluid pressure energy, oil pressure to the hydraulic system, is the power source of the hydraulic system. The general structure of the hydraulic pump gear pumps, vane pumps and piston pumps.
- actuator means all types of hydraulic cylinders, hydraulic motors. Its role is to fluid pressure energy into mechanical energy, the output of a certain force (or torque) and speed to drive the load.
- adjusting the control element refers to the various types of hydraulic control valves, such as relief valve, throttle valve and the like. Their role is to control the oil in the hydraulic system pressure, flow and flow direction, so as to ensure the implementation of components capable of driving a load, in the direction of movement provisions, access to the required velocity.
- assist device means fuel tanks, filters, pipes, fittings, seals, pressure gauge, oil temperature oil level gauge and so on. They ensure the hydraulic system is reliable, stable and lasting work, play an important role.
- the fluid medium is a fluid medium in the hydraulic system energy transfer working medium, there are petroleum based hydraulic oil, fire resistant hydraulic fluid (aqueous hydraulic fluids, synthetic hydraulic fluid). Commonly used mainly refers to all types of hydraulic oil.
Classification of the hydraulic system
There are two types of hydraulic system based systems, namely open and closed systems
Open systems: Variable Pressure
When the control switch is in the off position tools, hydraulic equipment, hydraulic oil through the original bypass switch, and back to the hydraulic tank, in such a system, hydraulic fluid continuously through the bypass switch tools, non-pressure hydraulic oil flow back to the tank. When the utility control valve is opened, the hydraulic oil into the working circuit, power tool, and then flows back to the tank. In this case, the external resistance spread through the tool hydraulic systems, hydraulic systems provide pressure oil to the tool to overcome the external load. Under the safety relief pressure, the pressure of the hydraulic
Closed system: Variable Flow
When the tool switch is in the off position, the hydraulic oil valve stuck in the position switch, the system established retention pressure, hydraulic oil does not flow back into the tank. When the control switch is open, the hydraulic oil into the working circuit tool, and then flow back into the hydraulic tank. This system, the working pressure of the hydraulic system is constant, if the need to increase the working pressure to the hydraulic system pressure set in advance. If the pressure is greater than the set pressure of the hydraulic system security, the system will cause damage, but also reduce the hydraulic flow (part of the overflow away)
The hydraulic system works
Hydraulic transmission is the use of fluid pressure energy to deliver power, the use of hydrostatic transmission
Delivery principle to achieve.
Hydrostatic transfer principle (Pascal’s principle): Add the liquid in a sealed pressure can be transmitted by the same size of the liquid in all directions.
Power units hydraulic oil from the reservoir to generate high pressure oil, high-pressure hydraulic fluid to pass through a closed hydraulic lines to the actuator, then the oil back into the tank through the implementation of components, to achieve recycling; intermediate pressure control valve can change the oil , flow and transmission direction.
When the hydraulic pump the greater the flow of oil, actuators work faster (such as hammers impact velocity); when the larger external load (such as the hard work of hammers ground), the system pressure will higher.
The role and selection of hydraulic oil
Hydraulic oil is equivalent to the body’s blood in the hydraulic system, its main role:
- transmit motion and power: the pump mechanical energy into fluid pressure energy and spread everywhere because the oil itself has a viscosity in the transfer process will produce a certain amount of power loss.
- Lubricate: each of the mobile parts of the hydraulic components, can be sufficiently lubricated by the hydraulic oil, thereby reducing component wear.
- Seal: viscous oil itself slightest gap sealing effect.
- Cool: loss of energy of the system will become hot, the oil out. Use hydraulic oil, based on the temperature of the environment to determine:
- When the ambient temperature at -25 ℃ ~ -10 ℃, the selection HV46 hydraulic oil temperature;
- When the ambient temperature is -10 ℃ ~ 10 ℃, the selection HM32 anti-wear hydraulic oil;
- When the ambient temperature is 10 ℃ ~ 40 ℃, the choice of HM46 anti-wear hydraulic oil;
- When the ambient temperature is above 40 ℃, the selection HM68 anti-wear hydraulic oil;
- When the temperature changes with the seasons larger areas (such as the Northeast), summer should use HM46 anti-wear hydraulic oil, winter use HM32 anti-wear hydraulic oil; or use a wide temperature hydraulic oil, but the cost is relatively high.
- Different manufacturers, different models of hydraulic oil is best not to mix; such as when you want to mix, the need for qualified and then use the relevant tests in advance; when hydraulic oil is changed, the need to exhaust all the oil tank, and clean.
The hydraulic control system temperature
Hydraulic control system operating temperature is generally between 30 ~ 80 ℃ appropriate.
Oil hydraulic system too high can lead to: reduce the viscosity of the hydraulic oil, prone to leakage, reduced efficiency; reduce lubricant film strength, accelerated machine wear; generate carbide and silt ballast; accelerate oil oxidation, oil deterioration; Seal , high pressure hose premature aging.
To avoid overheating; do not long-term overload; do not use an excessively high viscosity of hydraulic oil; note radiator fins do not be oil pollution, to prevent dust adhesion affect the cooling effect; to maintain sufficient oil in order to facilitate the circulation of hydraulic oil cooling; hot summer day do not work, to avoid the midday heat time.
When the oil temperature is too low, its viscosity, poor mobility, resistance, low work efficiency; when the oil temperature is below 20 ℃, intense maneuvering easily damaged hydraulic motors, valves, pipes and so on. Which requires a warm-up operation, no-load operation of the system for 3 to 5 minutes, is again working after the hydraulic oil temperature.
Why use hydraulic tools?
- Durability and easy to maintain: There are less work for daily maintain ce because the hydraulic oil can keep them lubricated. It’s not a rare thi ng to use a hydraulic device more than 15 years.
- Low noise: Quieter operation than air tools and internal combustion tools.
- Increased power: Compressed oil transfers more energy than compressed air, meaning more power in a smaller package.
- Low tempreture operation: hydraulic tools allow for work in sub-zero conditions
- Wet operation: hydraulic tools allow for high performance in wet conditions. They are more safe and reliable than electric tools when work UNDEWATER .
- The closed operation space: The hydraulic system is totally enclosed. No exhaust gas or dust from hydraulic tool as with gas or air tools.
- Cost effective: High efficiency and environment protection. Closed operation space makes the hydraulic tools less fuel reductions compared with some other tools. Kept in a closed space , the oil can not be polluted. So it can be used recycling.
- Lightweight, small size and powerful, the hydraulic tools can be widely used Hydraulic tools are largely used to cutting concrete and rock, transferring liquids. Internal components are continually bathed in hydraulic oil, providing long tool life with minimal maintenance. Since the hydraulic system is totally enclosed, there is no tool exhaust or oil atomization.