A complete hydraulic system consists of five major parts, namely power components, executive components, control components, auxiliary components (auxiliaries), and working medium (hydraulic oil). The power element mainly refers to the oil pump in the hydraulic system, which can convert the mechanical energy of the prime mover into the pressure energy of the liquid, and thus provide power to the entire hydraulic system.
As the power source of the hydraulic system, the hydraulic pump station is a whole composed of various components and auxiliary parts. It can store working medium with a certain degree of cleanliness, output hydraulic power with a certain pressure and flow to supply one or several systems, and also serve as an integral device for installing the hydraulic valve block base of an integral hydraulic station.
The hydraulic pump station is one of the most important components of the entire hydraulic system or hydraulic station. The quality of its design and the rationality of its use and maintenance will have a great impact on the performance of hydraulic equipment.
The hydraulic pump station is usually composed of five components in the independent form: hydraulic pump group, fuel tank component, temperature control component, filter component, and accumulator. In order to meet the characteristics of the working conditions of the machine and the rationality of the specific requirements of use, these accessories will have designers form specific components in a more reasonable form, such as the liquid temperature gauge and filter components in the temperature control components as fuel tank accessories. Combined into a hydraulic tank.
From the perspective of composition, the hydraulic pump group can be divided into the hydraulic pump, prime mover (electric motor or internal combustion engine), coupling, and transmission base. The hydraulic pump is used to convert the mechanical energy of the prime mover into hydraulic energy, the prime mover is used to drive the hydraulic pump, the coupling is used to connect the prime mover and the hydraulic pump, and the transmission base is used to install and fix the hydraulic pump and the prime mover.
The fuel tank assembly can be divided into the fuel tank, level gauge, breather filter, and drain plug. The oil tank is used for storing oil, dissipating oil heat, escaping air, removing foam, installing components, liquid level gauge for displaying and observing liquid level, breather filter for filling oil and filtering air, and oil drain plug for cleaning Drain the oil tank or when changing the oil.
The temperature control components can be divided into oil temperature gauges, temperature sensors, heaters, and coolers. The oil thermometer is used to display and observe the oil temperature, the temperature sensor is used to detect and control the oil temperature, the heater is used for local heating of the oil, and the pit cooler is used to cool the oil.
The accumulator assembly can be divided into accumulator and support stand. The accumulator is used to store energy, absorb hydraulic pulsation and shock, and the support stand is used to install the accumulator. In addition, filter assemblies are mainly used to separate solid particles in the oil to prevent clogging of small cross-section passages and maintain oil cleanliness.
Due to the wide range of uses of the hydraulic pump station, its classification also has a lot of attention, which can generally be concentrated in three categories: according to the layout method, the driving method, and the output pressure and flow characteristics.
Classification according to the arrangement of hydraulic pump sets: top-mounted hydraulic pump station, non-top-mounted hydraulic pump station, cabinet type, and portable hydraulic pump station
Classification according to the driving mode of the hydraulic pump group: electric type, motor type, manual type
According to the output pressure of the hydraulic pump group: low pressure, medium pressure, medium-high pressure, high pressure, and ultra-high pressure.
Top-mounted pump set
Install the hydraulic pump and other devices on the upper cover of the fuel tank. It has a compact structure and is widely used, especially on equipment that needs to be moved frequently. This installation method requires that the oil tank body, especially the upper cover plate, must have good rigidity.
Under-mounted pump set
In the design, the fuel tank is often elevated to the extent that people can pass under the fuel tank to facilitate the installation and maintenance of the hydraulic pump. The under-mounted pump group is to place the hydraulic pump under the oil tank. This installation method can increase the installation area of the equipment and improve the oil absorption capacity of the hydraulic pump.
Side-mounted pump set
The hydraulic device is designed next to the fuel tank, and the height of the pump station is low, which is convenient for maintenance, but it occupies a large area. This method is often used when the flow rate of the system and the capacity of the fuel tank are large.
For the latter two arrangements, a manual shut-off valve should be set on the pipeline between the oil suction port of the pump and the oil tank, which is convenient for the maintenance or assembly of the hydraulic pump to prevent the oil from flowing out of the oil tank.
This type of hydraulic pump station uses an electric motor as the prime mover and is suitable for stationary mechanical equipment with a stable power supply. Low noise during operation, so it is the most common application;
This type of hydraulic pump station uses a diesel engine or a gasoline engine as the prime mover and does not require a power supply, which is convenient for use in remote areas with no power supply or circuit shortage, as well as various construction equipment for field operations. However, it is noisy when working, and the usage rate is low;
This type of hydraulic pump station is mainly operated by manpower, which can actually be regarded as a kind of hand pump. Although its work efficiency is low, it can supply oil to small stroke hydraulic cylinders through simple piping, so it is often used in conjunction with small presses, testing machines, pipe benders, emergency rescue and demolition equipment, hydraulic shears, and other manual tools and equipment, and can be used as a portable mobile source for motor vehicles.
Output pressure level and flow characteristics
According to the output pressure of the hydraulic pump group, the hydraulic pump station can be divided into low pressure, medium pressure, medium high pressure, high pressure and ultra-high pressure. The pressure values are as follows: Low-pressure pumping station p≤2.5MPa, Medium pressure pump station p =2.5 ~ 8MPa, The medium and high-pressure pump station p=8～16MPa, High-pressure pumping station p=16～32MPa, The ultra-high pressure pumping station p>32MPa.
According to the characteristics of the output flow of the hydraulic pump group, the hydraulic pump station can be divided into two types: quantitative hydraulic pump station and variable hydraulic pump station. If a quantitative pump hydraulic pump station is used, according to the demand for the flow of the hydraulic system, either a single quantitative pump or multiple quantitative pumps can be configured. If a variable type hydraulic pump station is used, it can be further divided into constant power type, constant pressure type, constant flow type, pressure limiting type, and pressure cut-off type according to the adjustment characteristics of pressure-flow. Different output pressure and flow characteristics can be applied to the different host operating conditions and work requirements.
In the actual use of the project, the pressure-compensated variable displacement pump is often selected for oil supply. When the hydraulic system reaches a predetermined pressure, the hydraulic oil does not overflow from the relief valve at high pressure but achieves safety protection by reducing the flow output of the pump.