Valve after long-term use, the valve and seat sealing surface will be worn, tightness reduced. Repairing the sealing surface is a large and important task. The main method of repair is grinding. The seal surface of serious wear is first welded by turning to process and then grinding.
Abrasive materials
Commonly used grinding materials are abrasive cloth and abrasive paste. Abrasive cloth is a fabric backing with grit glued on top. The abrasive paste is made of lubricant and an abrasive blend. The lubricant can be used as machine oil, kerosene, butter, glycerin, oleic acid, stearic acid and paraffin wax, etc.
Abrasive tools
Valve and seat sealing surface due to different degrees of damage, can not be directly on the research. Rather, a certain number and specifications of the specialist prior to the fake valve flap (i.e., grinding head), fake valve seat (i.e., grinding seat), respectively, the valve seat, valve grinding. The grinding head and grinding seat are made of ordinary carbon steel or cast iron. Size and angle should be placed on the valve, valve seat equal.
If the grinding is carried out manually, it is necessary to configure various grinding rods. The grinding rod and research tool should be properly assembled, can not be skewed. To reduce human labor intensity, speed up the grinding speed, often using an electric grinder or vibration grinder grinding.
Valve grinding
Valve and seat sealing surface pockmarks, scoring, when the depth of 0.5mm or less, can be repaired using grinding methods. The grinding process is carried out in three steps: coarse grinding, medium grinding, and fine grinding.
Coarse grinding generally uses 240~W40 abrasive or No.2 abrasive cloth, and uses larger grinding pressure, mainly for grinding away the pockmarks and scratches. The middle grinding uses W28~W14 abrasive or No.1 or No.0 abrasive cloth, the grinding pressure is smaller, and the grinding tool should be replaced with a new one before grinding.
After the middle grinding, the sealing surface basically meets the requirements, and the surface is flat and bright. Fine grinding is done by hand, the valve and valve seat on the valve directly to the grinding. Choose a fine grinding paste (abrasive particle size W14~W5), and a little oil dilution, first clockwise and then counterclockwise, gently grinding back and forth. Grind for a while to check once, until grinding shiny, and can be seen in the valve and valve seat sealing surface of a circle of the black bright closed belt. Finally, gently grind several times with machine oil and dry with clean cotton yarn. When using abrasive cloth grinding, the abrasive cloth should be fixed on the grinding tool made according to the shape and size of the valve flap and valve seat. For large gate valve gates, usually use the scraping method to repair. When scraping and grinding the gate plate on the grinding plate with the coloring method, scraping the uneven parts until every 25px2 contact point reaches more than two points. Then scrape the good gate coloring scraping valve seat, the contact point should also reach every 25px2 contact point to reach more than two points. Welded-in the pipeline gate valve and shut-off valve, it is necessary to special research gate machine grinding repair.
After the valve overhaul, the hydraulic test should be carried out to check its tightness. Hydraulic test pressure is 1.25 times the working pressure, the test pressure is maintained for 5 min. and then the pressure is reduced to the working pressure for inspection. If a leak is found, it should be overhauled again until qualified.
Know about the best valve grinding machines
Metals Kingdom offers both portable and benchtop valve grinders. Portable is suitable for in-line repair of valves that are inconvenient to disassemble and site valve repair. The benchtop type is suitable for site valve repair.
We also provide different models of valve grinders for different valve grinding. M-100 and MJ series are mainly used for repairing globe valves and safety valves. M and MZ series are mainly used for repairing gate valves. Finally, let us help you if you have any questions in shopping for the right valve grinding machine for your task!
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