After the valve is used for a long period of time, the sealing surfaces of the valve disc and the valve seat will wear out and the tightness will be reduced. Repair sealing surface is a large and important work. The main method of repair is grinding. On the serious sealing surface, is the first surfacing after grinding and then grinding.
Valve grinding including cleaning and inspection process, grinding process and inspection process.
1, cleaning and inspection process
Clean the sealing surface in the oil pan, the use of professional cleaning agents, while washing the surface to check the sealing surface damage. Subtle cracks with the naked eye can be determined by color inspection. After cleaning, should check the valve flap or valve seat sealing surface of the close contact, check with red and pencil. Reddish red test, check the sealing surface printing shadow, to determine the sealing surface close situation; or pencil and valve seat seal surface draw a few concentric circles, and then close the valve disc and valve seat rotation, check the pencil circle Erase the situation, to determine the sealing surface of the close. If the fit is not good, the standard plate can be used to test valve flap or gate sealing surface and valve sealing surface, to determine the grinding site.
2, grinding process
Grinding process is essentially no lathe cutting process, the valve head or seat on the pitch or hole depth are generally within 0.5mm, you can use the grinding method for maintenance. Grinding process is divided into coarse grinding, grinding and fine grinding.
Rough grinding is to eliminate the sealing surface of the scratch, indentation, etching points and other defects, so that the sealing surface to obtain a high degree of smoothness and a certain degree of finish for the sealing surface grinding lay the foundation. Coarse grinding using grinding head or grinding tools, using coarse abrasive paper or coarse abrasive paste, the particle size of 80 # -280 #, coarse size, large amount of cutting, high efficiency, but the cutting lines deep, rough sealing surface. Therefore, rough grinding as long as the flat head or seat can be removed from the pock.
In the mill is to eliminate the rough surface of the sealing surface, to further improve the sealing surface of the flatness and finish. The use of fine abrasive paper or fine abrasive paste, the particle size of 280 # -W5, fine size, cutting a small amount, help to reduce the roughness; the same time should be replaced with the corresponding research tools, research tools should be clean. After grinding, the valve contact surface should reach the light. Such as pencil or valve seat in the draw a few Road, the valve head or seat against the light turn around, pencil line should be erased.
Fine grinding is the last step of the valve grinding, mainly to improve the finish of the sealing surface. Fine grinding can be W5 or finer micro and oil, kerosene and other dilution, with the valve head against the valve seat grinding, without a show, it is more conducive to the sealing surface of the close. Grinding generally clockwise to 60-100 ° or so, and then turn the opposite direction 40-90 ° or so, gently grinding for a while, you must check once to be polished shiny and shiny, and the valve head and seat can be seen To a very thin line of the circle, the color to black and black when the oil and then gently rub several times, wipe with a clean gauze can. After grinding, and then eliminate other defects, that assembly should be as soon as possible, so as not to damage a polished valve head.
Manual grinding regardless of rough or fine study, are always throughout the lift, down; rotation, reciprocating; tapping, reversing and other operations combined with the grinding process. Its purpose is to avoid abrasive track repetition, the grinding tool and sealing surface to be uniform grinding, improve the sealing surface of the flatness and finish. 3, inspection phase
In the grinding process has always run through the inspection phase, the purpose is to keep abreast of the situation, be aware of, so that grinding quality to meet the technical requirements. It should be noted that different valve grinding should be used to adapt to a variety of sealing surface in the form of grinding tools to improve grinding efficiency and ensure grinding quality.
Valve grinding is a very meticulous work, you need to continue to experience in practice, explore, improve, and sometimes very well ground, but after the leakage or leakage is installed, it is because the grinding process in the partial bias of the imagination, The grinding rod is not vertical, skewed, or the angle of the dimension of the research tool is deviated.
Since the abrasive is a mixture of abrasive and abrasive fluid, the abrasive fluid is only normal kerosene and engine oil. Therefore, the correct choice of abrasive the most crucial part is the correct choice of abrasive. How to choose the correct valve abrasive?
Alumina (AL2O3) Alumina, also known as corundum, its hardness is high, the use is very common. Generally used to grind cast iron, copper, steel and stainless steel and other materials of the workpiece.
Silicon carbide (SiC) Silicon carbide has two kinds of green and black, the hardness is higher than alumina. Green silicon carbide for grinding cemented carbide; black silicon carbide for grinding brittle materials and soft materials, such as cast iron, brass and so on.
Boron carbide (B4C) hardness second only to diamond powder and silicon carbide than hard, mainly used to replace diamond powder grinding cemented carbide, polished chrome-plated hard surface.
Chromium oxide (Cr2O3) Chromium oxide is a high hardness and very fine abrasive, hardened steel often use chromium oxide grinding, it is also used to polish it.
Iron oxide (Fe2O3) Iron oxide is also a very fine valve abrasive, but the hardness and grinding effect are worse than chromium oxide, the same purpose and chromium oxide.
Diamond powder that is crystalline C, it is the hardest abrasive, cutting performance is better, especially for grinding cemented carbide.
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