As we all know, the main factor of damage to the sealing element is the working fluid impurities. These contaminants grind between sealing elements, causing the valve to leak. Therefore, foreign countries have put forward the corresponding level of hydraulic components, the filter should be the appropriate accuracy. They think of a 5 μM pump seal, with a filter life of 3 / μM, a 10-fold improvement in lifetime over a 10 μM. But the hydraulic support valve, the working environment is very poor. In coal mining face, the total length of tubing more than 1,000 meters, up to more than 4,000 connector socket, tank no special dust measures. Emulsion has a large number of floating impurities in the cylinder bottom and the valve cavity, leaving more coal, rock and iron filings. Intake valve plug and seat, because the opening and closing more frequently, the liquid flow rate is high, the seal will soon fail. Practice has proved that reducing the hydraulic impurities of the stent hydraulic system is very difficult problem, it was envisaged in the emulsion pump station using high-pressure filter, while the entrance of each bracket to add a small filter. However, it was quickly blocked up at work, resulting in a stoppage. On the other hand, follow the development of hydraulic support technology. The use of valve performance and valve life put forward higher requirements. Currently, with a 120-mesh filter and a magnetic filtration device, the life of the hydraulic valve is measured by the total flow of the emulsion through the valve being tested and the number of valve opening and closing. But in fact the indoor type test and the actual results of underground work vary greatly. Now many countries in the form of experiments, increased anti-pollution requirements, some in the emulsion mixed with appropriate pulverized coal, some added mechanical impurities. To this end, the need to use the new, anti-pollution ability, suitable for working conditions underground seal vice. Hydraulic support hydraulic valve life is very low, foreign solutions and ways to improve the system's filtration accuracy and improve the quality of emulsion, but with little success.
ALUMINUM MOULD The cast aluminum mold is generally placed above the sealed crucible or the holding furnace, and compressed air is introduced into the crucible or the holding furnace to cause a low pressure (0.06-0.15 MPa) on the surface of the molten metal, so that the aluminum liquid is filled up by the riser tube.
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