Answer: The repair of the safety valve is mainly to repair the sealing surface of the safety valve, so there are high requirements for the material of the safety valve sealing surface. The basic requirements are: high strength, can withstand high sealing pressure ratio; have a certain impact toughness, can withstand the impact of the valve core jumping back to the seat quickly; have high hardness, can withstand the erosion of the medium; cannot rust, otherwise it will leak quickly; must be resistant to high temperature and not soften at high temperature; must be corrosion-resistant and can withstand acid and alkali erosion.
The main forms of safety valve hard seals include plane seals, conical seals, spherical seals, etc., and the most commonly used is plane seals.
(1) Repair of safety valve sealing surface. Safety valve sealing surfaces are of two types: metal and non-metal. Non-metallic seals are generally used for normal temperature media, and metal seals are mostly used for high temperature and high pressure media. When the sealing surface of non-metallic material is damaged, the insert (sealing ring) is generally removed and replaced. If it cannot be removed or there is no spare part, it can only be processed by turning. When the damage of metal sealing surface is not too serious, it is ground. Grinding is divided into coarse grinding and fine grinding. The valve seat and valve core must be ground separately with a flat grinding tool. They cannot be ground in the same direction, because grooves will appear after grinding, which will cause leakage once the valve is opened and the valve seat is returned.
(2) Grinding tools and materials.
1) Grinding tool. Grinding plate: ① cast iron (for rough grinding); ② carbide (for fine grinding). Grinding head (for grinding valve seat).
2) Abrasives. Chromium oxide, white corundum, No. 280, No. 360, No. 600, W4, W2.5, W1.5.
3) Abrasives. Oleic acid, motor oil, rapeseed oil, lard.
