When selecting the model of the nitrous acid transfer pump, correctly determining the material of the nitrous acid transfer pump is an important factor to ensure the safe operation of the centrifugal pump and prolong the service life of the pump. When choosing a material, it is necessary to comprehensively consider the influence of various factors from many aspects, so as to select the most suitable material.
①The nature of the nitrous acid delivery pump and the operating conditions of the pump, such as temperature, pressure, corrosivity, viscosity, whether it contains solid particles, etc. In addition, we have to consider whether there are other special circumstances, such as the medical and food industries that require the delivery of media to be particularly clean to prevent metal ion contamination, and pumps that transport media containing solid particles require good wear resistance.
②The mechanical properties of the material should meet the requirements of the pump. There are many indicators that reflect the mechanical properties of materials. For the materials used in the pump, the main consideration is the strength, stiffness, hardness, plasticity, impact toughness and fatigue resistance of the material.
③The processing performance of the material is directly related to the manufacture, installation and maintenance of the pump. Most of the parts of the centrifugal blade, such as the impeller, the shell, and the balance disc, are cast from metal materials, and then undergo a machining process, and some parts need to be heat treated. The performance of the material processing technology also directly affects the use of materials and the cost of the pump.
④The quality of corrosion resistance is an important issue that cannot be ignored in the selection of pump materials. For the petrochemical industry, the corrosion resistance of pumps is particularly important.
Selection of corrosion-resistant materials for commonly used nitrous acid transfer pumps
In petrochemical production, acids, bases and other liquid materials that are corrosive to metal materials are often encountered. The centrifugal pumps used to transport these materials are collectively called corrosion-resistant centrifugal pumps. The models of these pumps are denoted by F. The working principle is similar to that of a centrifugal clean water pump, and its corrosion resistance is mainly determined by the nature of the material used to make this type of pump. The following table is the commonly used materials for the manufacture of nitrous acid delivery pumps.
The corrosion resistance of most corrosion-resistant nitrous acid delivery pumps mainly depends on the material of the flow parts of the pump. For corrosion-resistant pumps, the material of the flow parts of the pump should be selected according to the different conveying medium. The materials in Table 3-1 are only suitable for certain specific corrosive media. For example, Cr18Ni9Ti can be used for low-concentration nitric acid at room temperature and other oxidizing acids, lyes and weak corrosive media. OCr18Ni12M02Ti is suitable for conveying high-concentration nitric acid at room temperature. It can transport reducing media such as sulfuric acid and organic acid. Gray cast iron HT200 is suitable for concentrated sulfuric acid. It has a wide range of plastic applications. Various materials such as polytetrafluoroethylene and polyperfluoroethylene propylene have been reasonably formulated, molded, and processed. Plastic The corrosion-resistant pump combines the advantages of a variety of plastics, has strong corrosion resistance, and has the characteristics of high mechanical strength, no aging, and no toxin decomposition. It is an ideal equipment for conveying various strong and weak acids. Among them, PTFE is One of the good corrosion-resistant materials, which can basically resist the corrosion of any acid or alkali medium, is called the king of plastics. Plastics have a wide range of applications. Various materials such as polytetrafluoroethylene and polyperfluoroethylene have been reasonably formulated, molded, and processed. Plastic corrosion-resistant pumps have strong corrosion resistance, and have high mechanical strength, no aging, No decomposition and other advantages, chemical pumps are ideal equipment for conveying various strong and weak acids. Among them, polytetrafluoroethylene is one of the corrosion-resistant materials. Pipeline chemical pumps can basically resist the corrosion of any acid or alkali medium and are self-priming. The chemical pump is called the plastic king. Ceramics, enamel, glass, etc. are also used to make the flow parts of corrosion-resistant pumps on certain occasions.
High-purity aluminum has excellent corrosion resistance to concentrated nitric acid at room temperature, but the welding seam of its equipment is prone to problems, which is a problem that many nitric acid users often encounter. Special high-silicon stainless steel has the best comprehensive corrosion resistance of concentrated nitric acid among these materials. Its corrosion resistance is better than high-purity aluminum and similar to high-silicon iron, and its mechanical strength and machining performance are high-purity aluminum and high-quality aluminum. Ferrosilicon is incomparable. This material is more expensive, and the investment is relatively high, but it has good corrosion resistance and long service life. It has good mechanical performance, high safety factor in use, convenient maintenance, etc. It can achieve less or no parking during production, which improves the production efficiency of the entire production line.
