Valve grinding includes cleaning and inspection process, grinding process and inspection process.
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. Fine cracks that are difficult to determine with the naked eye can be detected by color flaw detection.
After cleaning, the close fit of the valve disc or gate valve and the valve seat sealing surface should be checked, and red and pencil should be used for inspection. Use red lead to test red, check the sealing surface imprint, and determine the close fit of the sealing surface; or use a pencil to draw several concentric circles on the valve disc and valve seat sealing surface, and then rotate the valve disc and valve seat to check the pencil circle wiping situation to determine the close fit of the sealing surface. If the close fit is not good, the valve disc or gate sealing surface and the valve body sealing surface 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 grinding 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 has a higher flatness and a certain degree of finish, laying the foundation for the medium grinding of the sealing surface. Coarse grinding uses a grinding head or a grinding seat tool, and uses coarse sandpaper or coarse grinding paste with a particle size of 80#-280#, coarse particle size, large cutting amount, high efficiency, but deep cutting lines, and rough sealing surface. Therefore, coarse grinding only needs to remove the pitting of the valve head or valve seat smoothly.
Medium grinding is to eliminate the coarse lines on the sealing surface and further improve the flatness and finish of the sealing surface. Use fine sandpaper or fine grinding paste with a particle size of 280#-W5, fine particle size, small cutting amount, which is conducive to reducing roughness; at the same time, the corresponding grinding tool should be replaced, and the grinding tool should be clean. After medium grinding, the contact surface 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 in a circle, and the pencil lines should be erased.
Fine grinding is the last process of valve grinding, which is mainly to improve the smoothness of the sealing surface. When fine grinding, you can use W5 or finer micro-portions and dilute them with engine oil, kerosene, etc., and use the valve head of the valve to grind the valve seat of the valve without acting, which is more conducive to the close fit of the sealing surface. When grinding, generally turn clockwise about 60-100°, and then turn in the opposite direction about 40-90°, and grind gently for a while. It must be checked once. When it is shiny and a circle of very fine lines can be seen on the valve head and valve seat, and the color reaches black and shiny, use engine oil to gently grind several times, and wipe it clean with clean gauze. After grinding, eliminate other defects, that is, it should be assembled as soon as possible to avoid damaging the polished valve head.
Whether it is rough grinding or fine grinding, manual grinding is a grinding process that combines lifting, putting down, rotating, reciprocating, tapping, reversing and other operations. The purpose is to avoid repeated abrasive track, so that the grinding tool and the sealing surface are evenly ground, and the flatness and finish of the sealing surface are improved.
3. Inspection stage
The inspection stage is always carried out during the grinding process. Its purpose is to grasp the grinding situation at any time, to have a clear mind, and to make the grinding quality meet the technical requirements. It should be noted that different valves should be ground with grinding tools suitable for various sealing surface forms to improve grinding efficiency and ensure grinding quality.
Valve grinding is a very delicate job, which requires continuous experience, exploration and improvement in practice. Sometimes the grinding is very good, but there is still steam and water leakage after installation. This is because there is an imagination of grinding deviation during the grinding process, the hand-held grinding rod is not vertical or skewed, or the size and angle of the grinding tool are deviated.buy Valve Grinding Machine
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