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The Valve Has Been Used for a Long Time, What To Do?

Sep. 01, 2020

Portable valve grinded machine,After long-term use, the sealing surface of the valve disc and the valve 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 grinding. For the severely worn sealing surface, the surfacing is firstly welded and then ground.

The grinding of the valve includes:

Cleaning and inspection process;

Grinding process

Inspection process.

Cleaning and inspection process

Clean the sealing surface in the oil pan, use a professional cleaning agent, and check the damage of the sealing surface while washing. The fine cracks that are difficult to identify with the naked eye can be carried out by staining flaw detection.

After cleaning, check the tightness of the disc or gate valve and the sealing surface of the valve seat. Use red and pencil when checking. Use red lead to test the red, check the seal of the sealing surface to determine the tightness of the sealing surface; or use a pencil to draw several concentric circles on the sealing surface of the valve disc and the valve seat, and then rotate the valve disc and the valve seat tightly, and check the pencil circle Wipes off the condition to confirm the tightness of the sealing surface.

If the tightness is not good, a standard flat plate can be used to test the sealing surface of the disc or gate and the sealing surface of the valve body respectively to determine the grinding position.

Grinding process

The grinding process is essentially a cutting process without a lathe. The depth of the pits or small holes on the valve head or valve seat is generally within 0.5mm, and the grinding method can be used for maintenance.  The grinding process is divided into coarse grinding, middle grinding and fine grinding.

Rough grinding is to eliminate defects such as scratches, indentations, and corrosion points on the sealing surface, so that the sealing surface can obtain a higher flatness and a certain degree of smoothness, and lay the foundation for the middle grinding of the sealing surface.

Coarse grinding uses grinding head or grinding seat tools, using coarse-grained sandpaper or coarse-grained grinding paste, with a particle size of 80#-280#, coarse particle size, large cutting volume, high efficiency, but deep cutting lines and rough sealing surface.  Therefore, rough grinding only needs to smoothly remove the pitting of the valve head or valve seat.

Middle grinding is to eliminate rough lines on the sealing surface and further improve the flatness and smoothness of the sealing surface. Use fine-grained sandpaper or fine-grained abrasive paste, the particle size is 280#-W5, the particle size is fine, the cutting amount is small, which is beneficial to reduce the roughness; at the same time, the corresponding grinding tool should be replaced, and the grinding tool should be clean.

Portable Valve Grinded Machine

Portable Valve Grinded Machine

After the middle grinding, the contact surface of the valve should be bright. If you draw a few strokes on the valve head or valve seat with a pencil, turn the valve head or valve seat lightly, and erase the pencil line.

Fine grinding is the last process of valve grinding, mainly to improve the smoothness of the sealing surface. For fine grinding, it can be diluted with engine oil, kerosene, etc. with W5 or finer fractions, and then the valve head is used to grind the valve seat instead of drama, which is more conducive to the tightness of the sealing surface.

When grinding, turn it clockwise about 60-100°, and then turn it about 40-90° in the opposite direction. Gently grind for a while. It must be checked once, and it can be seen on the valve head and valve seat after the grinding is shiny. When there is a very thin line and the color is black and bright, lightly rub it with engine oil several times and wipe it with clean gauze.

After grinding, other defects should be eliminated, that is, assembling as soon as possible, so as not to damage a ground valve head.

Manual grinding, regardless of rough grinding or fine grinding, always runs through the grinding process of lifting, lowering, rotating, reciprocating, tapping, and reversing operations. Its purpose is to avoid the repetition of the abrasive grain track so that the grinding tool and the sealing surface can be uniformly ground, and the flatness and smoothness of the sealing surface can be improved.

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