Manifold Block hydraulic valve manufacturers explain the method of cleaning the pollution of hydraulic pipeline
Manifold Block hydraulic valve manufacturers: The pollutants in the hydraulic system generally include solid particles, air, water, chemical substances and microorganisms, etc. The sources of pollutants mainly come from three aspects:
1) Inherent pollutants in the system, such as residual pollutants in the process of processing, assembly, packaging and storage of system components;
2) Internal pollutants are generated, such as the wear debris generated by the wear of system components, the rust and spalling in the pipeline and the particles generated by the oxidation and decomposition of oil;
3) External intrusions, such as pollutants brought through the breathing hole of the oil tank, the piston seal of the hydraulic cylinder and the process of oil supplement, etc. Manifold Block hydraulic valve
Solid particles are the most common and the most harmful among all kinds of pollutants in Manifold Block hydraulic system. Among the hydraulic system failures caused by pollution, except 30 are caused by corrosion, and the remaining 70 are caused by mechanical wear on the surface of hydraulic components caused by the existence of solid particles. Solid particles not only accelerate the wear of hydraulic components, but also plug the clearance and orifice of components, so that the control components action failure and cause system failure.
Because the pollution of Manifold Block hydraulic system is harmful, new hydraulic system or modified hydraulic system should be washed through the system to make the cleanliness of hydraulic medium meet the requirements. The hydraulic equipment test station of Wuhan Iron and Steel Co., Ltd. needs to be relocated due to the water station project of cold rolling plant. After the relocation, the hydraulic pipe is reinstalled. Manifold Block hydraulic valve
1 hydraulic system flushing principle
1.1 Influence of system flow rate on flushing
According to hydrodynamics, the flow state of liquid in a pipe is divided into laminar flow and turbulent flow. The ability of liquid to wash particles from a surface and carry them downstream is proportional to the energy of liquid at the surface of the element.
In laminar flow, there is a liquid steady state layer on the surface of the element, and the force exerted on the surface of the element is very small. The solid particles adhering to the inner wall of the hydraulic pipe are difficult to be washed clean. Therefore, to improve the flushing efficiency, the flow state of the hydraulic medium in the pipe must be turbulent during flushing. Manifold Block hydraulic valve
Turbulence degree is determined by Reynolds number:
Re=VDv=4QDV (1) where V is liquid velocity; Q is the flow rate of pipe (application and improvement of plastic pipe); D is pipe diameter; V is the kinematic viscosity of hydraulic oil.
When the washing oil flows turbulent in the tube, the whole section is not turbulent. Due to the limitation of the pipe wall and the effect of adhesion, there is still a layer of liquid near the pipe wall to maintain laminar flow state, that is, the near wall laminar flow layer. When the thickness is greater than the particle size D attached to the tube wall, the washing effect on particles will be affected. Therefore, good flushing efficiency must be achieved by d.
In turbulent flow, the thickness of the near-wall laminar layer in a circular tube can be calculated using the following empirical formula. Manifold Block hydraulic valve
In equation (2), is the drag coefficient of turbulent flow along the path. When 3×103< Re <105, the drag coefficient is 0.3164re-0.25. < p=”” style=”margin: 0px; padding: 0px;” >
According to Equations (1) and (2), the relationship between the kinematic viscosity of hydraulic oil, flow rate, pipe diameter and thickness of near-wall laminar flow layer can be obtained as follows: Q= 73.93DVD87
1.2 Influence of system temperature on flushing
In pipe flushing, the temperature of hydraulic oil has an important effect on flushing. Firstly, the temperature of hydraulic oil can affect the viscosity of hydraulic oil. According to the viscosity-temperature diagram of hydraulic oil, the viscosity of hydraulic oil decreases with the increase of temperature. Reynolds number is inversely proportional to the viscosity of hydraulic oil. Therefore, increasing the temperature of hydraulic oil during flushing can increase Reynolds number and thus enhance turbulence. In addition, the diameter of micro particles in the oil is widely distributed, as small as 0.005! M. Pollutant particle density, shape and size distribution vary with temperature, electric field and other factors. Rising temperatures and the presence of an electric field accelerate the transition from small particles to larger ones, making them easier to filter out. In practical application, good flushing effect can be achieved by controlling the temperature of flushing hydraulic oil between 60 and 80. Too high oil temperature will accelerate the aging of hydraulic oil. Manifold Block hydraulic valve
1.3 Influence of system pressure on flushing
In order to ensure that the hydraulic oil in the pipeline to maintain turbulent state also consider the hydraulic oil in the pipeline pressure loss, the output pressure of the pump must be greater than the hydraulic oil in the pipeline to maintain turbulent loss of pressure, the loss of pressure P calculated by Formula (4). The output pressure of the pump is set by the relief valve of the system, so the pressure set by the relief valve must be greater than the pressure loss of the system, otherwise the flow rate of the system can not meet the requirements of turbulence.
P =lDV2 (4), where L is the length of hydraulic pipe; P is the density of hydraulic medium.
2. Flushing scheme of test system in Hydraulic station of Wisco
A variety of solid particles are attached to the inner wall of the new or modified hydraulic system pipe, and it is necessary to remove the solid particles by washing to avoid the formation of pollution to the hydraulic system. According to the above hydraulic flushing principle, whether the pollutants in the pipeline can be effectively removed, so that the cleanliness level of the hydraulic system reaches the required level, the flow rate, pressure and temperature during flushing are the key. [Shandong hydraulic valve]
2.1 Determine the flushing flow rate
In order to ensure that the thickness of the near-wall laminar flow layer is less than the particle size d attached to the tube wall, =δ5um should be taken. When washing, the oil temperature is 60. The hydraulic medium used by Wisco hydraulic station is Mobil DTE26 anti-wear hydraulic oil and TSA32 turbine oil. According to relevant information, the motion viscosity of Mobil DTE26 anti-wear hydraulic oil is 71.2mm2/s and 8.5mm2/s respectively at 40 and 100 hours. The kinematic viscosity of TSA32 turbine oil at 40 and 100 is 31.26mm2/s and 5.43mm2/s, respectively. The viscosities and temperature curves of hydraulic media are close to straight lines. According to the proportional relationship, the kinematic viscosity of Mobil DTE26 anti-wear hydraulic oil at 60 can be estimated to be 50.3mm2/s. The movement viscosity of TSA32 turbine oil at 60 is 22.65mm2/s. The required flush flow rate can be obtained by replacing, V and the maximum pipe diameter in the system, D, into (3).
2.2 Determine the flushing pressure
Determines the test-bed system required flow must also determine the pressure of irrigation system, after flushing of the circulation medium in the process through hydraulic pipeline pressure loss can be created, must ensure that the flushing system relief valve set pressure is greater than the loss of pressure, otherwise will flow through the overflow valve for the hydraulic medium tank back, short of flushing effect. Especially in large hydraulic system, the pressure loss of the system must be calculated through Equation (4) to ensure that the flushing system pressure is greater than the loss pressure because the pipe is longer. Because the hydraulic system of Wuhan Iron and Steel Hydraulic station belongs to small hydraulic system, the pipe is short, so the pressure loss is small. The pressure loss of the test bed system of Wuhan Iron and Steel Hydraulic station is as shown by calculation. Considering other factors such as shitter and elbow, the flushing pressure of each system should be set to be more than 1.5 times of the calculated pressure loss. Manifold Block hydraulic valve
2.3 Determine the flushing loop
There are usually two options for the construction of a circulating flushing pump station.
First, off-line washing is to establish a temporary washing pump station independent of the hydraulic system. Crude filter is used for oil intake and fine filter is used for oil return, because the oil return pressure is low and the pulsation is not large. Its advantage is that the flushing pump station is independent of the hydraulic system, and the safety of the equipment itself will not be affected. In addition, a heater can be added to the flushing equipment to improve the flushing effect.
The second is to use the hydraulic system’s own working pump station as a flushing pump station, including the use of the pump filter, including random filter element heater and other equipment, usually called online flushing. It can save a lot of equipment and labor costs, suitable for small hydraulic systems with fewer pipelines, but to give full consideration to the technical parameters of hydraulic equipment itself, to ensure the safety of the system equipment, construction technology requirements are high.
The selection principle of the washing scheme is to consider the first use of the pump under the principle of ensuring safety. In the case that the pump can achieve the required flow and pressure of the washing, the pump can be used to wash, otherwise it is necessary to use offline washing. Manifold Block hydraulic valve
All this pump test-bed system of the hydraulic pressure station of wisco is able to provide maximum flow, and flushing system of the calculation of minimum flow cylinder motor test bench, we can know that the oil pump test rig and hydraulic valve test rig of hydraulic pipe must adopt the way of offline flush, and the servo valve test-bed and large flow servo valve test-bed is just can be completed by the pump irrigation irrigation requirement.
2.4 Flushing Procedure
First, choose offline or online washing, and then determine the flushing loop, in order to ensure that the test bench without any pollution of the premise of the hydraulic components are short-circuiting to form a flushing loop. Offline washing needs to rent a professional flushing pump station from an equipment leasing company. Pay attention to the appropriate size of the oil tank and the flow of the pump. Generally, the washing can be completed in 3 to 4 days. Note the following during the operation:
1) Carefully clean the oil tank before washing, and use dough to clean up the residues inside the oil tank if necessary. The tank breathing hole should be equipped with a filter, and the oil tank should be closed to reduce the particles in the air on site into the oil;
2) When refueling into the oil tank, a refueling trolley with a filter should be used to filter out the pollutants in the barrel oil; Manifold Block hydraulic valve
3) If the pipe mouth that is separated from the hydraulic cylinder or valve table is not connected to the flushing circuit in time or not restored in time after washing, it must be wrapped with clean plastic cloth;
4) Knock the pipe from upstream to downstream to enhance the flushing effect.
The hydraulic equipment test station of Wisco requires that the servo system is NAS6 level and the non-servo system is NAS7 level. The above scheme was used for flushing. Through the efforts of all parties involved in the construction, both online and offline methods were adopted respectively. The hydraulic pipe flushing of each test bed was qualified and reached the required cleanliness level.
A new or modified hydraulic system must be piping flushed. Before selecting a flushing system, the flow and pressure required for flushing must be calculated, and the temperature factor should be taken into account, and then the appropriate flushing scheme should be selected.