Chemical valve material selection2016-11-15
All along, the chemical equipment is one of the most headaches of chemical equipment, a little careless, ranging from damage to equipment, while causing accidents and even lead to disaster. According to statistics, about 70% of the damage to chemical equipment is caused by corrosion, so the selection of chemical valves in the first choice should pay attention to the scientific nature of the selection. There is usually a misunderstanding that stainless steel is "omnipotent material", no matter what the media and environmental conditions are holding out the stainless steel valve, which is very dangerous.
The following for some commonly used chemical media to talk about the selection of the main points:
sulfuric acid
As one of the strong corrosive media, sulfuric acid is a very wide range of important industrial raw materials. Different concentrations and temperatures of sulfuric acid on the corrosion of the material is quite different for the concentration of 80% or more, the temperature is less than 80 ℃ concentrated sulfuric acid, carbon steel and cast iron has good corrosion resistance, but it is not suitable for high-speed flow of sulfuric acid, Not suitable for the valve material; ordinary stainless steel such as 304 (0Cr18Ni9), 316 (0Cr18Ni12Mo2Ti) on the use of sulfuric acid medium is also limited. Therefore, the delivery of sulfuric acid pump is usually made of high silicon cast iron (casting and processing difficult), high alloy stainless steel (20 alloy) manufacturing. Fluorine plastic has a better resistance to sulfuric acid, the use of fluoride valve is a more economical choice.
hydrochloric acid
Most of the metal materials are not resistant to hydrochloric acid corrosion (including a variety of stainless steel), molybdenum high ferrosilicon can only be used for 50 ℃, 30% hydrochloric acid. And the opposite of metal materials, the vast majority of non-metallic materials have good corrosion resistance to hydrochloric acid, so lined with rubber valves and plastic valves (such as polypropylene, fluorine plastic, etc.) is the best choice for the transmission of hydrochloric acid.
Nitric acid
Most of the metal in the nitric acid was quickly corrosion damage, stainless steel is the most widely used nitric acid resistant materials, nitric acid at room temperature all have good corrosion resistance, it is worth mentioning that the molybdenum containing stainless steel (such as 316,316 L) The corrosion resistance to nitric acid is not only better than ordinary stainless steel (such as 304,321), and sometimes even worse. For high temperature nitric acid, titanium and titanium alloy materials are usually used.
acetic acid
It is one of the most corrosive substances in organic acids. Ordinary steel is severely corroded in all concentrations and temperatures of acetic acid. Stainless steel is an excellent acetic acid resistant material. Molybdenum 316 stainless steel is also suitable for high temperature and dilute acetic acid steam The For high temperature and high concentration of acetic acid or other corrosive media and other demanding requirements, the choice of high alloy stainless steel valve or fluorine plastic valve.
