Do You Know How to Ensure the Leakproofness of the Valve?

The grinding of valves includes:

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. The fine cracks that are difficult to determine with the naked eye can be carried out by color inspection. After cleaning, the tightness of the disc or gate valve and the sealing surface of the seat should be checked with red and pencil. Test red with red lead, check the sealing surface printing, determine the sealing surface close; Or use a pencil to draw a few concentric circles on the disc and seat sealing surface, and then rotate the disc and seat close, check the pencil circle erase, and determine the close sealing surface. If the tight fit is not good, the standard plate can be used to inspect the disc or gate sealing surface and the valve body sealing surface respectively to determine the grinding position.

2. Grinding Process

The grinding process is essentially a cutting process without a lathe, and the pitting or hole depth on the valve head or seat is generally within 0.5mm, which can be repaired by grinding method. The grinding process is divided into coarse grinding, medium grinding and fine grinding.

Rough grinding is to eliminate the abrasion, indentation, corrosion spot and other defects on the sealing surface, so that the sealing surface can get a high flatness and a certain finish, and lay the foundation for the grinding of the sealing surface. Rough grinding The use of grinding head or grinding seat tool, using coarse grit sandpaper or coarse grit grinding paste, its particle size 80#-280#, coarse particle size, large cutting amount, high efficiency, but the cutting lines are deeper, the surface of the sealing surface is rough. Therefore, the rough grinding only needs to remove the pitting point of the valve head or seat smoothly.

Medium grinding is to eliminate the rough lines on the sealing surface and further improve the flatness and finish of the sealing surface. Using fine grit sandpaper or fine grit abrasive paste, the particle size is 280#-W5, fine particle size, small cutting amount, is conducive to reducing roughness. At the same time, the corresponding lashing tool should be replaced, and the lashing tool should be clean. After grinding, the contact plane of the valve should be bright. If you use a pencil to mark a few lines on the valve head or seat, turn the valve head or seat gently around, 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 fine grinding, W5 or finer fractions can be diluted with oil, kerosene, etc., and the valve head of the valve is ground against the valve seat of the valve, without playing, which is more conducive to the close of the sealing surface. When grinding, generally turn about 60-100° clockwise, and then turn about 40-90° in the opposite direction, gently grind for a while, must be checked once, to be polished to shine, and can see a circle of very fine line on the valve head and seat, when the color reaches black and bright, then gently grind with oil several times, wipe clean with clean gauze. After grinding, the other defects are eliminated, that is, it should be assembled as soon as possible to avoid damaging a well-ground valve head.

Manual grinding, regardless of coarse or fine grinding, is always through lifting and lowering; Rotate and reciprocate; A grinding process that combines tapping, reversing and other operations. The purpose is to avoid the repetition of the abrasive track, so that the lapping tool and the sealing surface can be evenly ground, and the flatness and finish of the sealing surface can be improved.

3. Inspection Stage

In the grinding process has always been through the inspection stage, the purpose is to grasp the grinding situation at any time, so that the grinding quality to meet the technical requirements. It should be noted that different valve grinding should be used to adapt to various sealing surface forms of grinding tools to improve grinding efficiency and ensure grinding quality.

Valve grinding is a very detailed work, need to constantly experience in practice, explore, improve, sometimes grinding very well, but after installation or leakage of steam water, this is because in the grinding process there is a grinding imagination, the hand grinding rod is not vertical, skewed, or the size Angle of the research tool is caused by deviation.

Because the abrasive is a mixture of abrasive and abrasive liquid, and abrasive liquid is only general kerosene and oil. Therefore, the most critical part of the correct selection of abrasive is the correct selection of abrasive. How to choose valve abrasive correctly?

Alumina: Alumina, also known as corundum, has a high hardness and is widely used, generally used to grind iron, copper, steel and stainless steel and other materials of the workpiece.

Silicon Carbide: Silicon carbide has two kinds of green and black, and its hardness is higher than alumina. Green silicon carbide is suitable for grinding carbide; black silicon carbide is used to grind brittle materials and soft materials of the workpiece, such as cast iron, brass, etc.

Boron Carbide: Hardness is second only to diamond powder and harder than silicon carbide, mainly used to replace diamond powder grinding carbide, grinding hard chrome plated surface.

Chromium Oxide: Chromium oxide is a high hardness and extremely fine abrasive, chromium oxide is often used in hardening steel polishing, and it is generally used to polish.

Iron Oxide: Iron oxide is also a very fine valve abrasive, but the hardness and grinding effect are worse than chromium oxide, and the use is the same as chromium oxide.

Diamond Powder: It is the hardest abrasive, cutting performance is good, especially suitable for grinding cemented carbide.