The principle of selecting pump material

how selection, how to choose the pump materials become the important problem of the chemical industry. Usually there is a misunderstanding that universal material is stainless steel, no matter what medium and environmental conditions could be stainless steel. Is taking a risk, light cause trade disputes, or cause a serious accident. Several common chemical medium and the following list of materials

1, hydrochloric acid. Most metal materials don't resist the corrosion of acid salt, salt, acid concentration is higher when including all kinds of stainless steel materials, have to bear the corrosion, high silicon molybdenum and only can be used in 50 ℃ and below 30% acid salt. And metal materials contrary, the vast majority of non-metallic materials on sodium acid have good corrosion resistance, so the lining rubber and plastic pump ( Such as polypropylene, fluorine plastic, etc. ) Is a good choice for conveying acid salt.

2, sulfuric acid. As one of strong corrosive medium, sulfuric acid is an important industrial raw material is very versatile. Corrosion of different concentration and temperature of sulfuric acid on the material difference is bigger, the concentration is above 80%, 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, so the pump valve material is unfavorable use carbon steel and cast iron; Even the ordinary stainless steel such as 304 and 316 also limited use for sulphuric acid medium. So transport of sulfuric acid pump valve usually adopts the high silicon cast iron or 20 high alloy stainless steel or alloy, but they are casting and machining difficulty is very big. Fluorine plastic has good acid resistance, the use of lining fluoride water pump is a kind of more economical choice.

3, nitric acid. As a kind of has a strong oxidizing acid, general metal corrosion and damage, mostly in nitric acid was quickly under room temperature, fluorine plastic and stainless steel materials for nitric acid has strong corrosion resistance, it is worth noting that the molybdenum stainless steel ( Such as 316, 316 l) For nitric acid corrosion resistance not only no better than ordinary stainless steel ( Such as 304, 321) And sometimes not. For the high-temperature nitric acid, usually with titanium and titanium alloy materials.

4, acetic acid it is machine in one of corrosive strong material, ordinary steel in all concentration and temperature of severe corrosion of acetic acid, acetic acid proof material is stainless steel, 316 stainless steel containing molybdenum can also apply to high temperature and dilute acetic acid steam. For high temperature and high concentration of acetic acid or contain other corrosive medium such as strict requirements, can choose high alloy stainless steel or fluorine plastic pump.

5, alkali. Common chemical alkali for sodium hydroxide. Below 80 ℃, 30% concentration of sodium hydroxide solution can use steel material, there are also many factory under 100 ℃, 75% still USES the ordinary steel, although the corrosion increases, but the economy better. Ordinary stainless steel for corrosion resistance of lye no significant advantages compared to cast iron, as long as the medium for allowing a small amount of iron added to stainless steel is not recommended. For high temperature and alkali liquor with titanium and titanium alloy or high alloy stainless steel. General cast iron pumps can be used for low concentration of alkali liquor under normal temperature, special requirements can use all kinds of chemical glass fiber reinforced plastic pump, stainless steel pump, magnetic pump four fluorine chemical industry plastic magnetic pump, fluorine plastic magnetic water pump, high temperature resistant magnetic pump and so on.

6, ammonia ( Ammonia hydroxide) Most metals and non-metallic liquid ammonia and ammonia ( Ammonia hydroxide) The corrosion is very slight, only copper and copper alloy should not be used.

7, esters, alcohols, ketones, and so on. Alcohols common such as methanol, ethanol, ethylene glycol, propylene glycol, etc. ; Such as acetone, butanone, etc; Esters such as methyl ester, ethyl ester, etc. , their basic no corrosive, general common material, but in order to clean better choose stainless steel material; In addition it is worth noting that the ketone, esters are solubility to a variety of rubber, when choosing machine sealing materials should pay attention to.

8, salt water and sea water. Such as seawater medium, ordinary steel in sodium chloride solution and sea water, salt water corrosion rate is not too high, the coating should be used in general protection; All kinds of stainless steel has a very low uniform corrosion rate, but may be localized corrosion caused by chloride ion, usually adopts 316 stainless steel material with good