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The electric valve has been used for a long time. How to ensure the tightness of the valve?
2022-11-11
After the electric valve is used for a long time, the sealing surfaces of the valve disc and valve seat will be worn and the tightness will be reduced. Repairing the sealing surface is a large and important work. The main method of repair is grinding. For seriously worn sealing surfaces, surfacing welding shall be carried out first and then grinding shall be carried out after turning. Grinding of valves 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. Tiny cracks that are difficult to determine by naked eyes can be detected by dye penetrant method. After cleaning, check the tightness of the valve clack or gate valve and the sealing surface of the valve seat with red and pencil. Test the red with red lead, check the seal surface print, and determine the sealing surface tightness; Or use a pencil to draw several concentric circles on the sealing surface of the valve clack and the valve seat, then rotate the valve clack and the valve seat tightly, check the erasure of the pencil circle, and determine the tightness of the sealing surface. If the sealing is not good, the standard flat plate can be used to inspect the sealing surface of the valve disc or gate and the sealing surface of the valve body to determine the grinding position.
Rough grinding is to eliminate the scratch, indentation, corrosion spot and other defects on the sealing surface, so that the sealing surface can get a higher flatness and a certain degree of finish, laying a foundation for the intermediate grinding of the sealing surface. Rough grinding uses grinding head or grinding seat tools, and uses coarse abrasive paper or coarse abrasive paste. Its particle size is 80 # - 280 #, with coarse particle size, large cutting amount and high efficiency, but the cutting pattern is deep and the sealing surface surface is rough. Therefore, rough grinding is only required to remove the pitting on the valve head or valve seat smoothly.
The intermediate grinding is to eliminate the rough lines on the sealing surface and further improve the flatness and smoothness of the sealing surface. Use fine abrasive paper or fine abrasive paste, the particle size is 280 # - W5, the particle size is fine, the cutting amount is small, which is conducive to reducing the roughness; At the same time, the corresponding lapping tool shall be replaced, and the lapping tool shall be clean. After intermediate grinding, the contact surface of the valve shall be bright. If you use a pencil to draw several lines on the valve head or valve seat, gently turn the valve head or valve seat against each other for a circle, and erase the pencil line.
Fine grinding is the last process of valve grinding, mainly to improve the smoothness of the sealing surface. During fine grinding, W5 or finer fractions can be diluted with engine oil, kerosene, etc., and then the valve head of the valve is used to grind against the valve seat instead of acting, which is more conducive to the sealing surface sealing. When grinding, it is generally turned about 60-100 ° clockwise, and then about 40-90 ° in the opposite direction. After a little grinding, it must be checked once. When the grinding is bright, and a circle of fine lines can be seen on the valve head and valve seat, when the color reaches black light, it can be lightly polished several times with engine oil and wiped with clean gauze. After grinding, remove other defects, that is, assemble as soon as possible to avoid damaging the ground valve head.
Manual grinding, no matter coarse grinding or fine grinding, is always lifting and laying down; Rotation and reciprocating; Grinding process combining tapping, reversing and other operations. The purpose is to avoid the repetition of abrasive track, make the lapping tool and sealing surface evenly ground, and improve the flatness and finish of the sealing surface.
3. Inspection stage
During the grinding process, the inspection stage is always carried out to keep abreast of the grinding situation and make sure that the grinding quality meets 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.
The valve grinding is a very meticulous work, which requires constant experience, exploration and improvement in practice. Sometimes the grinding is very good, but after installation, there is still steam leakage and water leakage. This is due to the imagination of eccentric grinding during the grinding process, and the grinding rod is not vertical or oblique when holding it, or the size angle of the grinding tool is deviated.
Aluminum oxide (AL2O3), also known as corundum, is widely used because of its high hardness. It is generally used to grind workpieces made of cast iron, copper, steel and stainless steel.
Silicon carbide (SiC) is green and black, and its hardness is higher than that of alumina. Green silicon carbide is suitable for grinding cemented carbide; Black silicon carbide is used for grinding brittle materials and workpieces made of soft materials, such as cast iron, brass, etc.
The hardness of boron carbide (B4C) is only inferior to that of diamond powder but harder than that of silicon carbide. It is mainly used to replace diamond powder to grind cemented carbide and grind hard chromium plated surface.
Chromium oxide (Cr2O3) Chromium oxide is a kind of abrasive with high hardness and extremely fine. Chromium oxide is often used for fine grinding of hardened steel, and is generally used for polishing.
Iron oxide (Fe2O3) Iron oxide is also a very fine valve abrasive, but its hardness and grinding effect are worse than chromium oxide, and its use is the same as chromium oxide.
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 determine by naked eyes can be detected by dye penetrant method. After cleaning, check the tightness of the valve clack or gate valve and the sealing surface of the valve seat with red and pencil. Test the red with red lead, check the seal surface print, and determine the sealing surface tightness; Or use a pencil to draw several concentric circles on the sealing surface of the valve clack and the valve seat, then rotate the valve clack and the valve seat tightly, check the erasure of the pencil circle, and determine the tightness of the sealing surface. If the sealing is not good, the standard flat plate can be used to inspect the sealing surface of the valve disc or gate and the sealing surface of the valve body to determine the grinding position.
2. Grinding process
Rough grinding is to eliminate the scratch, indentation, corrosion spot and other defects on the sealing surface, so that the sealing surface can get a higher flatness and a certain degree of finish, laying a foundation for the intermediate grinding of the sealing surface. Rough grinding uses grinding head or grinding seat tools, and uses coarse abrasive paper or coarse abrasive paste. Its particle size is 80 # - 280 #, with coarse particle size, large cutting amount and high efficiency, but the cutting pattern is deep and the sealing surface surface is rough. Therefore, rough grinding is only required to remove the pitting on the valve head or valve seat smoothly.
The intermediate grinding is to eliminate the rough lines on the sealing surface and further improve the flatness and smoothness of the sealing surface. Use fine abrasive paper or fine abrasive paste, the particle size is 280 # - W5, the particle size is fine, the cutting amount is small, which is conducive to reducing the roughness; At the same time, the corresponding lapping tool shall be replaced, and the lapping tool shall be clean. After intermediate grinding, the contact surface of the valve shall be bright. If you use a pencil to draw several lines on the valve head or valve seat, gently turn the valve head or valve seat against each other for a circle, and erase the pencil line.
Fine grinding is the last process of valve grinding, mainly to improve the smoothness of the sealing surface. During fine grinding, W5 or finer fractions can be diluted with engine oil, kerosene, etc., and then the valve head of the valve is used to grind against the valve seat instead of acting, which is more conducive to the sealing surface sealing. When grinding, it is generally turned about 60-100 ° clockwise, and then about 40-90 ° in the opposite direction. After a little grinding, it must be checked once. When the grinding is bright, and a circle of fine lines can be seen on the valve head and valve seat, when the color reaches black light, it can be lightly polished several times with engine oil and wiped with clean gauze. After grinding, remove other defects, that is, assemble as soon as possible to avoid damaging the ground valve head.
Manual grinding, no matter coarse grinding or fine grinding, is always lifting and laying down; Rotation and reciprocating; Grinding process combining tapping, reversing and other operations. The purpose is to avoid the repetition of abrasive track, make the lapping tool and sealing surface evenly ground, and improve the flatness and finish of the sealing surface.
3. Inspection stage
During the grinding process, the inspection stage is always carried out to keep abreast of the grinding situation and make sure that the grinding quality meets 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.
The valve grinding is a very meticulous work, which requires constant experience, exploration and improvement in practice. Sometimes the grinding is very good, but after installation, there is still steam leakage and water leakage. This is due to the imagination of eccentric grinding during the grinding process, and the grinding rod is not vertical or oblique when holding it, or the size angle of the grinding tool is deviated.
Aluminum oxide (AL2O3), also known as corundum, is widely used because of its high hardness. It is generally used to grind workpieces made of cast iron, copper, steel and stainless steel.
Silicon carbide (SiC) is green and black, and its hardness is higher than that of alumina. Green silicon carbide is suitable for grinding cemented carbide; Black silicon carbide is used for grinding brittle materials and workpieces made of soft materials, such as cast iron, brass, etc.
The hardness of boron carbide (B4C) is only inferior to that of diamond powder but harder than that of silicon carbide. It is mainly used to replace diamond powder to grind cemented carbide and grind hard chromium plated surface.
Chromium oxide (Cr2O3) Chromium oxide is a kind of abrasive with high hardness and extremely fine. Chromium oxide is often used for fine grinding of hardened steel, and is generally used for polishing.
Iron oxide (Fe2O3) Iron oxide is also a very fine valve abrasive, but its hardness and grinding effect are worse than chromium oxide, and its use is the same as chromium oxide.
Diamond powder, namely crystalline C, is the hardest abrasive with good cutting performance, especially suitable for grinding cemented carbide.
