Considerations for the proper selection of chemical pumps

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The chemical industry holds a very important position in the national economy, and chemical process pumps, as key supporting equipment, are attracting increasing attention. Choosing the right chemical pump is therefore of utmost importance to users. Due to the complexity of chemical media, the correct choice by users becomes crucial. The common media transported by chemical process pumps include acids, alkalis, salts, etc. Acetic acid: It is one of the organic acids with the strongest corrosive properties; ordinary steel corrodes severely in acetic acid. For high-concentration acetic acid, high-alloy stainless steel chemical pumps or fluoroplastic pumps can be used. Alkalis: For high-temperature alkaline solutions, titanium and titanium alloys or highly alloyed stainless steels are commonly used. Ordinary cast-iron chemical pumps can be used for alkaline solutions at normal temperature and low concentration; for special requirements, various stainless steel pumps or fluoroplastic pumps can be employed. Hydrochloric acid: The vast majority of metals are not resistant to hydrochloric acid (including various stainless steel materials); therefore, rubber-lined pumps and plastic pumps (such as polypropylene, fluoroplastics, etc.) are the best choices for transporting hydrochloric acid. Products used: IHF fluorinated lining pumps, highly corrosion-resistant centrifugal pumps, fluoroplastic magnetic pumps. Nitric acid: Most metals corrode and are damaged rapidly in nitric acid, while stainless steel is the most widely used material resistant to nitric acid; it exhibits good corrosion resistance against all types of nitric acid at room temperature. Products that utilize this material include chemical pumps, corrosion-resistant centrifugal pumps, IH chemical pumps, and magnetic pumps. Sulfuric acid: An important industrial raw material with a wide range of uses. Sulfuric acid at different concentrations and temperatures causes varying degrees of corrosion to the material; therefore, chemical pumps used for transporting sulfuric acid are typically made of high-silicon cast iron (which is difficult to cast and process) or high-alloy stainless steel (grade 20 alloy). It is more economical to use fluorine-lined pumps (F46). Suitable products include IHF fluorine-lined pumps, highly corrosion-resistant centrifugal pumps, and fluoroplastic magnetic pumps. Care must be taken when selecting seals for the transportation of chemical products; leaks of toxic and explosive substances can lead to serious disasters. Leakage-free operation is the goal pursued by chemical processing equipment, and it is precisely this requirement that has led to the increased use of magnetic pumps and shielded pumps. However, there is still a long way to go before true leakage-free operation can be achieved; issues such as the lifespan of the isolation sleeves in magnetic pumps and shielded pumps, pitting corrosion of materials, and the reliability of static seals remain challenges to be overcome. Static sealing: In chemical pumps, gaskets and seals are commonly used. Gaskets are mainly flat gaskets; through repeated experiments, our company has found that adding two semi-circles at each end of the two sealing surfaces of the flat gasket improves its sealing performance. O-rings are the most widely used type of sealing ring. Dynamic sealing: It is mainly used in mechanical seals, which are further divided into single-face and double-face types, as well as packing seals, balanced and unbalanced types. Double-end face mechanical seals are primarily used for high-temperature, crystallizable, viscous, and toxic media ； Packing seals are suitable for media containing small solid particles ； The balanced type is suitable for sealing high-pressure media. For the selection of materials for the static seals of chemical pumps, fluororubber is generally used; in special cases, polytetrafluoroethylene materials are employed (such as in the presence of organic solvents) ； The material selection for the static and dynamic rings of a mechanical seal is quite important. It’s not true that cemented carbide paired with cemented carbide is always the best option; such a combination is expensive, and it’s also unreasonable when there is no difference in hardness between the two materials. Therefore, the choice should be made based on the characteristics of the medium being handled.