Valve sealing surface wear, how to repair valve water pressure test safe operation procedures

Valve sealing surface wear, how to repair valve water pressure test safe operation procedures

After long-term use of the valve, the sealing surface of the disc and seat will be worn and the tightness will be reduced. Repairing the sealing surface is a large and important task. The main method of repair is grinding. For the heavily worn sealing surface, it is first surfacing after turning processing and then grinding. Valve grinding includes: cleaning and inspection process; The grinding process
After long-term use of the valve, the sealing surface of the disc and seat will be worn and the tightness will be reduced. Repairing the sealing surface is a large and important task. The main method of repair is grinding. For the heavily worn sealing surface, it is first surfacing after turning processing and then grinding.
Grinding of valves includes:
Cleaning and inspection process;
Grinding process;
The inspection process.
Cleaning and inspection process
Cleaning sealing surface in the oil pan, use professional cleaning agent, wash while checking the damage of sealing surface. Microscopic cracks that are difficult to be determined by the naked eye can be carried out by tint detection.
After cleaning, the disc or gate valve should be checked for the tightness of the sealing surface of the seat, using red and pencil when checking. Use red lead to test the red, check the sealing surface, determine the sealing surface of the sealing surface; Or with a pencil on the valve disc and seat sealing surface draw a few concentric circles, and then the valve disc and seat close rotation, check the pencil circle erased, determine the sealing surface close.
If THE SEAL IS NOT GOOD, THE DISC OR GATE SEAL FACE AND THE VALVE BODY SEAL FACE CAN BE INSPECTED BY STANDARD PLATE TO DETERMINE THE GRINDING SITE.
The grinding process
The grinding process is essentially the cutting process of the lathe, the pitting or hole depth on the valve head or seat is generally within 0.5mm, and the method of grinding can be used for maintenance. The grinding process is divided into coarse grinding, medium grinding and fine grinding.
Rough grinding is to eliminate the abrasion, indentation, corrosion point and other defects on the sealing surface, so that the sealing surface can get higher flatness and a certain degree of finish, and lay a foundation for the grinding of the sealing surface.
Coarse grinding using grinding head or grinding seat tools, the use of coarse sand paper or coarse grinding paste, its particle size 80#-280#, coarse particle size, large cutting amount, high efficiency, but the cutting grain is deeper, the sealing surface surface is rough. Therefore, coarse grinding as long as the flat to remove the valve head or seat pitting.
Medium grinding is to eliminate the rough grain on the sealing surface and further improve the flatness and finish of the sealing surface. The use of fine sand paper or fine abrasive paste, its particle size is 280#-W5, fine particle size, small cutting amount, is conducive to reduce the roughness; At the same time, the corresponding grinding tool should be replaced, and the grinding tool should be clean.
After grinding, the contact plane of the valve should be bright. If you use a pencil to draw a few lines on the valve head or seat, turn the valve head or seat to the light circle, the pencil line should be erased.
Fine grinding is a process of valve grinding, mainly to improve the sealing surface finish. Fine grinding can be used in W5 or smaller micro fraction diluted with oil, kerosene and so on, with the valve head against the valve seat for grinding, without drama, which is more conducive to the sealing surface of the close.
Generally when turn clockwise around 60-100 °, about 40-90 ° to turn in the opposite direction again, gently for a while, you have to check once, stay bright shine, and on the valve head and valve seat can see a very fine line, color to black black, gently with the oil mill again several times, with a clean cloth to wipe clean can.
After grinding, then eliminate other defects, that is, should be assembled as soon as possible, so as not to damage a good grinding valve head.
Manual grinding whether coarse or fine, are always through the lifting, putting down; Rotation, reciprocation; A grinding process that combines tapping, reversing and other operations. The purpose is to avoid the repetition of abrasive tracks, make the grinding tool and sealing surface get uniform grinding, and improve the flatness and finish of sealing surface.
Inspection stage
In THE grinding process, the inspection stage is always running through, its purpose is to grasp the grinding situation at any time, do know, make 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, in order to improve grinding efficiency and ensure grinding quality.
Valve grinding is a very detailed work, need to experience, explore, improve in practice, sometimes grinding very well, but after the installation or leakage water leakage, this is because in the grinding process there is a grinding deviation imagination, hand grinding rod is not vertical, skew, or grinding tool size Angle deviation.
Because the abrasive agent is a mixture of abrasive and abrasive liquid, and the abrasive liquid is the general kerosene and oil. Therefore, the correct selection of abrasive agents ** the key link is the correct selection of abrasive.
How to choose valve abrasive correctly?
Aluminum oxide (>
Silicon carbide (SiC) Silicon carbide is green and black, its hardness is higher than alumina. Green silicon carbide is suitable for grinding hard alloy; Black silicon carbide is used for grinding brittle materials and soft materials, such as cast iron, brass, etc.
Boron carbide (B4C) hardness is inferior to diamond powder and harder than silicon carbide, mainly used to replace diamond powder grinding hard alloy, grinding hard chrome-plated surface.
Chromium oxide (Cr2O3) chromium oxide is a high hardness and very fine abrasive, quenched steel is often used in finishing chromium oxide, generally also used in polishing.
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 use and chromium oxide.
Diamond powder The crystallization 磮 C, it is a * * hard abrasive, cutting performance is good, especially suitable for grinding hard alloy.
In addition, the abrasive particle size (abrasive particle size) has a *** influence on grinding efficiency and surface roughness. Coarse grinding, the valve workpiece surface roughness requirements are not high, in order to improve the grinding efficiency should choose coarse abrasive; When finishing, the grinding allowance is small, the requirement of workpiece surface roughness is high, and fine-grained abrasive can be used.
Sealing surface coarse grinding abrasive particle size is generally 120 # ~ 240 #; The precision is W40 ~ 14.
The valve modulates the abrasive, usually by adding kerosene and motor oil directly to the abrasive. Abrasives prepared with 1/3 kerosene plus 2/3 oil and abrasive are suitable for coarse grinding; The abrasives made of 2/3 kerosene plus 1/3 oil and abrasive can be used for finishing.
When grinding the workpiece with high hardness, the effect of using the abrasive agent is not ideal. At this moment, the lard THAT CAN USE 3 abrassERS TO ADD A HEATING TO adjust TOGETHER rise, FORM PASTE AFTER COOLING, ADD SOME KEROSENE APPROPRIATELY AGAIN WHEN USING OR GASOLINE TO adjust EVENLY.
Choice of grinding tool
Valve disc and valve seat sealing surface due to different degrees of damage, can not be directly studied, but with a certain number and specifications of the false valve disc (namely grinding head), false valve seat (namely grinding seat) respectively on the valve seat, valve disc grinding.
Grinding HEAD AND GRINDING SEAT SHALL BE MADE OF COMMON CARBON STEEL OR CAST IRON AND SHALL BE OF THE SAME SIZE AND Angle AS THE disc AND SEAT placed ON THE VALVE.
If the grinding is performed manually, various grinding rods are required. The grinding rod and grinding tool should be properly assembled and should not be skewed. In order to reduce the labor intensity and speed up the grinding speed, electric grinding machine or vibration grinding machine is often used.
Safety practice for hydraulic test of valves
1. The valve sent into the hydraulic test is not allowed to have cracks, pores, dents, valve stem adjustment is not allowed to have stuck phenomenon.
2. Used and spare bolts and nuts must be calculated for strength and marked to prevent confusion.
3. The test workpiece must be fastened to the device and not allowed to be placed freely. Haofm.com.q2G  B  V5vJ
4. Rubber bands or other elastic pads used for testing should not be bumpy, layered, loose, or lose elasticity.
5. Perform pressure test in accordance with product process rules. When the pressure is raised above the working pressure, it is not allowed to twist the nut, clamp the device and other parts on the component.
6. The end cover must meet the requirements of the technical documents and pass the test before it can be used. When the test pressure exceeds 25% of the calculated pressure, it is not allowed to be used.