After a long period of use, the sealing surface of the valve flap and seat will be worn and the tightness will be reduced. Repairing the sealing surface is a large and very important task. The main method of repair is to use a valve grinding machine for grinding. For the sealing surface with serious wear, it is first overlay welding by turning to process and then grinding.

Grinding of valves includes

• Cleaning and inspection process.

• Grinding process.

• Inspection process.

Cleaning and inspection process

Cleaning the sealing surface in the oil pan, using a professional cleaning agent, while washing to check the damage of the sealing surface. Fine cracks that are difficult to determine with the naked eye can be carried out by the coloring detection method.

After cleaning, the valve flap or gate valve should be checked with the sealing surface of the valve seat tightness, check with red and pencil. Use red Dan test red, check the seal surface impression, to determine the seal surface sealing situation. Or use a pencil to draw a few concentric circles on the valve flap and seat sealing surface, and then rotate the valve flap and seat tightly. Check the pencil circle erased to determine the sealing surface fit.

If the fit is not good, the standard plate can be used to test the valve or gate sealing surface and valve body sealing surface, respectively, to determine the grinding parts.

Grinding process

The grinding process with a portable valve grinding machine is essentially a cutting process without a lathe, and the depth of the pockmark or small hole on the valve head or seat is generally within 0.5mm. The grinding process is divided into coarse grinding, medium grinding, and fine grinding.

Coarse grinding

Rough grinding is to eliminate the sealing surface of the abrasion, indentation, corrosion points, and other defects, so that the sealing surface gets a high degree of flatness and a certain degree of finish, to lay the foundation for the sealing surface of the medium grinding.

Rough grinding using grinding head or grinding seat tools, using coarse sandpaper or coarse grinding paste, its particle size 80#-280#, coarse particle size, cutting volume, high efficiency, but the cutting pattern is deeper, the sealing surface is rougher. Therefore, coarse grinding is enough to remove the pockmarks on the valve head or valve seat as long as they are flat.

Medium grinding

Medium grinding is to eliminate the coarse grain on the sealing surface and further improve the flatness and finish of the sealing surface. The use of fine-grained sandpaper or fine-grained grinding paste, the particle size of 280 # - W5, fine particle size, small cutting volume, which is conducive to reducing the roughness; at the same time should be replaced with the corresponding research tools, research tools should be clean and clean.

After the middle grinding, the contact plane of the valve should reach brightness. If you use a pencil on the valve head or seat a few lines, the valve head or seat against a light turn, the pencil line should be erased.

Fine grinding

Fine grinding is the last process of grinding the valve with a valve grinding machine, mainly to improve the finish of the sealing surface. Fine grinding can be used W5 or finer micro-part with machine oil, kerosene, etc. after dilution, with the valve head against the valve seat for grinding, without acting drama, which is more conducive to the sealing surface of the close.

Grinding inspection process

In the process of grinding the valve with a portable valve grinding machine always throughout the inspection stage, the purpose is to grasp the grinding situation at any time, so as to have a good idea of the quality of grinding to meet the technical requirements. It should be noted that different valves should be ground using grinding tools adapted to various forms of sealing surfaces to improve grinding efficiency and ensure grinding quality.

Grinding generally clockwise turn about 60-100 °, and then the opposite direction turn about 40-90 °, gently grinding for a while, just check once, to be ground to shine, and in the valve head and valve seat can be seen on a very thin line, the color reaches the black bright, and then gently grinding a few times with machine oil, wipe clean with clean gauze can be.

After grinding, and then eliminating other defects, that is, should be assembled as soon as possible, so as not to destroy a good grinding of the valve head.

Manual grinding regardless of coarse or fine grinding, is always throughout the lifting, put down; rotation, reciprocation; light knock, change direction and other operations combined grinding process. The purpose is to avoid repetition of abrasive trajectory so that the grinding tool and sealing surface get uniform grinding, improving the flatness and smoothness of the sealing surface.

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