The lap and valve sealing surfaces are pressed together, and the grinding motion is then performed along the surface. There should be an abrasive between them, and as the grinding begins, the abrasive particles start rolling back and forth between the two, cutting off a thin layer of metal on the sealing surface. 1. Cleaning and inspection process Clean the sealing surface in the oil pan, use professional cleaning agent, and check the damage of the sealing surface while washing. Tiny cracks that are difficult to identify with the naked eye can be detected by coloring. After cleaning, check the tightness of the disc or gate valve
and the sealing surface of the valve seat with red and pencil. Use red red to test the red, check the printing of the sealing surface to determine the tightness of the sealing surface; or use a pencil to draw several concentric circles on the sealing surface of the valve disc and the valve seat, and then rotate the valve disc and the valve seat tightly to check the pencil circle Wipe off the condition to confirm the tightness of the sealing surface. If the sealing is not good, the sealing surface of the disc or gate and the sealing surface of the valve body can be inspected with a standard flat plate to determine the grinding position. 2. Grinding process The grinding process is essentially a cutting process without a lathe. The depth of pits or small holes on the valve head or valve seat is generally within 0.5mm, and the grinding method can be used for maintenance. The grinding process is divided into coarse grinding, medium grinding and fine grinding. Coarse grinding is to eliminate defects such as scratches, indentations, and pits on the sealing surface, so that the sealing surface can obtain a higher flatness and a certain smoothness, and lay the foundation for the intermediate grinding of the sealing surface. Coarse grinding uses a grinding head or grinding seat tool, and uses coarse-grained sandpaper or coarse-grained abrasive paste. Therefore, rough grinding only needs to remove the pitting of the valve head or valve seat flatly. Intermediate grinding is to eliminate the rough lines on the sealing surface and further improve the flatness and finish of the sealing surface. Use fine-grained sandpaper or fine-grained abrasive paste with a particle size of 280#-W5, with fine particle size and small cutting amount, which is conducive to reducing the roughness; at the same time, the corresponding grinding tools should be replaced, and the grinding tools should be clean. After the middle grinding, the contact plane of the valve should be bright. If you use a pencil to draw a few lines on the valve head or valve seat, turn the valve head or valve seat slightly toward each other, and the pencil line should be erased. Fine grinding is the last process of valve grinding, mainly to improve the smoothness of the sealing surface. When fine grinding, it can be diluted with oil, kerosene, etc. with W5 or finer fractions, and then use the valve head of the valve to grind against the valve seat of the valve without drama, which is more conducive to the tightness of the sealing surface. When grinding, generally turn clockwise about 60-100°, and then turn in the opposite direction for about 40-90°, and grind gently for a while. It must be checked once. After grinding, it is shiny and can be seen on the valve head and valve seat When a very thin line is reached, and the color reaches black and bright, then gently grind it with oil a few times, and wipe it off with a clean gauze. After grinding, other defects should be eliminated, that is, it should be assembled as soon as possible to avoid damaging a ground valve head. Manual grinding, regardless of rough grinding or fine grinding, is always a grinding process that combines lifting and lowering; rotation, reciprocation; tapping, reversing and other operations. The purpose is to avoid the repetition of the abrasive particle trajectory, so that the grinding tool and the sealing surface can be ground evenly, and the flatness and smoothness of the sealing surface can be improved. 3. Inspection stage The inspection stage runs through the grinding process. The purpose is to keep abreast of the grinding situation at any time, so that the grinding quality can meet the technical requirements. It should be noted that grinding tools suitable for various sealing surfaces should be used when grinding different valves to improve grinding efficiency and ensure grinding quality. Valve grinding is a very meticulous work, which requires continuous experience, exploration and improvement in practice. Sometimes the grinding is very good, but after installation, it still leaks steam and water. This is because there is an imagination of grinding deviation during the grinding process. The grinding rod in hand is not vertical, skewed, or the size and angle of the grinding tool are deviated. The grinding of the valve is to obtain a closer geometric pattern and to make the sealing surface tighter. In this way, its service life can be better increased. During the grinding process, the valve is overhauled at the same time, so that the valve can be used better.
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