Safety valve repair
Safety valve repair is mainly on the safety valve sealing surface repair, so the valve sealing surface materials have higher requirements, basic requirements are: have higher strength and can withstand high sealing pressure ratio: have a certain impact toughness, can withstand the impact of the valve core quickly jump back to the seat, has high hardness, can withstand the erosion of medium: can't rust, or leak soon: high temperature resistant, can be applicable to steam medium, such as: from high temperature to soften to corrosion resistance and can bear acid and alkali erosion, etc.
The main forms of hard seal of safety valve are: plane seal, conical seal, ball seal, etc., the most commonly used is plane seal.
(1) repair of safety valve sealing surface
There are two types of safety valve sealing surface: metal and non-metal. Non-metal sealing is generally used in normal temperature media.After the non-metal sealing surface is damaged, the insert ring (seal ring) is usually removed and replaced.Metal sealing surface in the case of less serious damage, the use of grinding.Grinding is divided into coarse grinding and fine grinding.The seat and the valve core must be ground separately with a flat abrasive tool, not against the grinding, because after grinding the groove cavities, once open the back seat leakage.
(2) grinding tools and materials
Grinding tool: grinding plate: a, cast iron (for rough grinding) b, hard alloy (for fine grinding) grinding head (for grinding seat)
Abrasive: chromium oxide, white fused alumina, 280#, 360#, 600#, W4, W2.5, W1.5
Grinding agent: oleic acid, machine oil, vegetable oil, pork oil
(3) grinding of sealing surface
Grinding is the application of grinding tools and grinding agents, after the grinding agents bear certain pressure of the grinding tools, the working surface is slightly grinding, so that the surface of the workpiece is polished off a very thin layer of metal, so that the workpiece surface obtains a high flatness and a high level of surface finish. This process is called grinding.
The principle of grinding;When grinding, the grinding agent added to the grinding tool is under certain pressure from the workpiece and the grinding tool.When the grinding tool and the workpiece are in complex relative motion, the abrasive will slide and roll between the workpiece and the grinding tool, resulting in cutting and agent pressure, which will remove a layer of convex peaks from the workpiece surface. Meanwhile, the grinding agent will play a chemical role and form an oxide film quickly.
(4) safety valve metal nameplate should contain contents
1) model, specification (pass diameter) 2) pressure grade 3) runner diameter 4) nominal pressure 5) operating temperature, medium 6) rated displacement coefficient 7) manufacturer, manufacturing approval number 8) date of manufacture 9) product number 10) inspection mark 11) opening pressure
(5) features and precautions of high voltage calibration
1) high pressure safety valve opens with loud sound, especially large bore
2) the high pressure safety valve has a large vibration when opened
3) high recoil force when opening, so the material of flange joint is good
4) the spring can not be adjusted very much, only fine tuning (the spring of the high pressure safety valve is thicker)
5) the high pressure safety valve is usually high temperature and high pressure, and there is an error between normal temperature check and working condition (the spring is soft at high temperature).
6) the calibrated airflow and water flow must be filtered