Do you know how to ensure the tightness of the valve after it has been used for a long time

After long-term use of the valve, the sealing surface of the disc and seat will wear and reduce the tightness. Repairing sealing surface is a large and important work. The main method of repair is grinding. For the sealing surface with serious wear, it is first surfacing after turning and then grinding.
Valve grinding includes the cleaning and inspection process, the grinding process and the inspection process.
1. Cleaning and inspection process
Clean the sealing surface in the oil pan, using professional cleaning agent, while washing and check the damage of the sealing surface. Fine cracks that are difficult to determine with the naked eye can be detected by staining. After cleaning, should check the disc or gate valve and seat sealing surface of the case, check with red and pencil. Test red with red red, check the sealing surface printing shadow, determine the sealing surface close situation; Or with a pencil in the valve disc and seat sealing surface of a few concentric circles, and then the valve disc and seat close rotation, check the pencil circle erase, determine the sealing surface close. If the sealing is not good, check the disc or gate sealing face and body sealing face separately with a standard plate to determine the grinding site.
2. Grinding process
The grinding process is essentially the cutting process without a lathe. The pitting or small hole depth on the valve head or seat is generally within 0.5mm, which can be repaired by grinding. The grinding process is divided into coarse grinding, medium grinding and fine grinding.
Rough grinding is to eliminate the abrasion, indentation, corrosion point and other defects on the sealing surface, so that the sealing surface can get a higher flatness and a certain degree of finish, and lay a foundation for the middle grinding of the sealing surface. Rough grinding the use of grinding head or grinding seat tools, the use of coarse sand paper or coarse grinding paste, the particle size of 80#-280#, coarse particle size, large cutting, high efficiency, but the cutting lines are deep, the surface of the sealing surface is rough. Therefore, rough grinding as long as the valve head or seat smooth pitting can be removed.
Middle grinding is to eliminate the rough lines on the sealing surface and further improve the flatness and finish of the sealing surface. The use of fine sand paper or fine abrasive paste, its particle size of 280#-W5, fine particle size, small cutting, is conducive to reduce roughness; At the same time, the corresponding grinding tools should be replaced, and the grinding tools should be clean. After grinding, the contact plane of the valve should be bright. If the valve head or seat with a pencil on a few lines, the valve head or seat to a light turn, the pencil line should be erased.
Fine grinding is the last process of valve grinding, mainly to improve the finish of the sealing surface. When grinding, W5 or finer fraction can be diluted with oil, kerosene and so on, and the valve head of the valve seat is grinded without drama, which is more conducive to the sealing surface. Generally when turn clockwise around 60-100 °, about 40-90 ° to turn in the opposite direction again, gently for a while, you have to check once, stay bright shine, and on the valve head and valve seat can see a very fine line, color to black black, gently with the oil mill again several times, with a clean cloth to wipe clean can. After grinding, to eliminate other defects, that is, should be assembled as soon as possible, so as not to destroy a good grinding valve head.