The petrochemical industry occupies a very important position in the national economy, and the chemical process pump as a key supporting equipment has attracted more and more attention. Due to the complex characteristics of chemical media, and the increasing requirements of users, as a manufacturer, how should we choose? What should we pay attention to And so on. Based on the characteristics of the company's related products and personal superficial knowledge, this paper makes a brief comment on the selection of commonly used chemical pumps, hoping to be helpful for colleagues to better carry out their work in this field.

Corrosion resistance

For a long time, corrosion is one of the most headache hazards of chemical equipment. Slight carelessness may damage the equipment, or even cause accidents or even disasters. According to relevant statistics, about 60% of the damage of chemical equipment is caused by corrosion. Therefore, the scientific selection of chemical pump should be paid attention to first. There is usually a misunderstanding that stainless steel is a "universal material". It is very dangerous to produce stainless steel no matter what medium and environmental conditions. The key points of material selection are as follows:

1. Sulfuric acid is one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. The corrosion resistance of carbon steel and cast iron is good for concentrated sulfuric acid with concentration above 80% and temperature less than 80 ℃, but it is not suitable for high-speed flow of sulfuric acid, and it is not suitable for pump valve material; ordinary stainless steel such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) are also limited in the use of sulfuric acid medium. Therefore, high silicon cast iron (casting and processing is difficult) and high alloy stainless steel (No.20 alloy) are usually used to transport sulfuric acid. Fluoroplastics have good sulfuric acid resistance, so it is a more economical choice to use fluorine lined pump (F46). The company's applicable products are: IHF fluorine lining pump, PF (FS) strong corrosion-resistant centrifugal pump, cqb-f fluoroplastic magnetic pump, etc.

2. Most of the metal materials in hydrochloric acid are not resistant to hydrochloric acid corrosion (including all kinds of stainless steel materials). High silicon iron containing molybdenum can only be used in hydrochloric acid below 50 ℃ and 30%. On the contrary, most nonmetal materials have good corrosion resistance to hydrochloric acid. Therefore, lined rubber pump and plastic pump (such as polypropylene, fluoroplastics, etc.) are the best choice for transporting hydrochloric acid. The company's applicable products are: IHF lining fluorine pump, PF (FS) strong corrosion-resistant centrifugal pump, CQ polypropylene magnetic pump (or fluoroplastic magnetic pump), etc.

3. Most metals in nitric acid are rapidly corroded and destroyed in nitric acid. Stainless steel is the most widely used nitric acid resistant material. It has good corrosion resistance to all concentrations of nitric acid at room temperature. It is worth mentioning that the corrosion resistance of stainless steel containing molybdenum (such as 316, 316L) is not better than that of ordinary stainless steel (such as 304, 321), sometimes even worse. For high temperature nitric acid, titanium and titanium alloy are usually used. The company's applicable products are: DFL (W) H chemical pump, DFL (W) pH shielded chemical pump, dfcz process pump, dflzp self-priming chemical pump, IH chemical pump, CQB magnetic pump, etc., with material of 304.

4. Acetic acid is one of the most corrosive substances in organic acids. Ordinary steel will be seriously corroded in acetic acid of all concentrations and temperatures. Stainless steel is an excellent acetic acid resistant material, and molybdenum containing 316 stainless steel can also be used for high temperature and dilute acetic acid steam. High alloy stainless steel or fluoroplastic pump can be selected when high temperature and high concentration acetic acid or other corrosive media are involved.

5. Alkali (sodium hydroxide) steel is widely used in sodium hydroxide solution below 80 ℃ and within 30% concentration. Many factories still use ordinary steel at 100 ℃ and below 75%. Although the corrosion increases, the economy is good. The corrosion resistance of ordinary stainless steel to alkaline solution has no obvious advantage compared with cast iron. So long as a small amount of iron is allowed in the medium, stainless steel is not recommended. For high temperature alkaline liquor, titanium and titanium alloy or high alloy stainless steel are used. The general cast iron pump of the company can be used for normal temperature and low concentration alkali liquor, and all kinds of stainless steel pump or fluoroplastic pump can be used for special requirements.

6. Ammonia (ammonia hydroxide) the corrosion of most metals and nonmetals in liquid ammonia and ammonia water (ammonia hydroxide) is very slight, only copper and copper alloy are not suitable for use. Most of the company's products are suitable for the transportation of ammonia and ammonia water.

7. The corrosion rate of common steel in salt water (sea water) is not too high in sodium chloride solution, sea water and salt water, so it is generally necessary to adopt coating protection; various stainless steels also have very low uniform corrosion rate, but local corrosion may be caused by chloride ion, and 316 stainless steel is generally better. All kinds of chemical pumps have 316 material configuration.

8. Alcohols, ketones, esters, ethers Common alcohol media include methanol, ethanol, ethylene glycol, propanol, etc., ketone media include acetone, butanone, etc., ester media include various methyl esters, ethyl esters, etc., ether media include methyl ether, ether, butyl ether, etc., they are basically non corrosive, and common materials can be applied, and reasonable selection should be made according to the properties and relevant requirements of the media. In addition, it should be noted that ketone, ester and ether have solubility to a variety of rubber, so mistakes can be avoided when selecting sealing materials.

There are many other media can not be introduced here one by one. In short, we must not be random and blind in the selection of materials. We should consult more relevant information or learn from mature experience.

Cooling problem

The transportation of high-temperature medium puts forward higher requirements for the structure, materials and auxiliary system of the pump. The following is about the cooling requirements of different temperature changes and the pump types applicable to the company

1. For media with temperature lower than 120 ℃, no special cooling is usually set