Differences between chemical pumps and ordinary centrifugal pumps

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This post was last edited by Reichter-Li Zongsheng on 2022-11-1 at 16:00 (1). In chemical production, it is necessary to meet the requirements of the chemical processes: not only must liquid materials be transported, but the required pressure for those processes must also be provided, along with ensuring the correct volume of material is delivered. During the operation of certain chemical processing units, the flow rate and head of the pump must remain stable, and its efficient and reliable operation needs to be maintained. (2) The media transported by corrosion-resistant chemical pumps, including raw materials and reaction intermediates, are often corrosive. This requires a proper selection of pump materials to ensure its safe, stable, and long-lasting operation. (3) High-temperature-resistant chemical pumps capable of transporting high-temperature media, including process liquid materials and heat-carrying liquids generated during reaction processes. For example: condensate pumps, boiler feed water pumps, heat transfer oil pumps. Chemical pumps are used to transport a wide variety of low-temperature media, such as liquid oxygen, liquid nitrogen, methane, etc. The operating temperature range of these pumps in low-temperature conditions is usually between 20 and 110°C. Whether it is a chemical pump for transporting high-temperature or low-temperature fluids, the material selection and structure must be appropriate, with sufficient strength. The pump components designed and manufactured can resist thermal shock, thermal expansion, cold deformation at low temperatures, and cold brittleness. (4) Wear and erosion resistance: Since the fluid handled by chemical pumps contains suspended solid particles, and the pump impellers and chambers operate under high pressure and high flow rates, the protective layer on the surface of the pump components is damaged, resulting in a short service life. It is therefore necessary to improve the wear and erosion resistance of chemical pumps; for this purpose, pump materials such as wear-resistant manganese steel, ceramics, cast iron, erosion-resistant titanium, and manganese steel should be used. (5) Reliable operation of chemical pumps implies two things: first, fault-free operation over a long period of time; second, stable values of various parameters during operation. Reliability is crucial for chemical production. If pumps fail frequently, it not only leads to frequent shutdowns, affecting production and economic efficiency, but can sometimes also cause accidents in chemical processing systems. Fluctuations in the speed of chemical process pumps can cause variations in the flow rate and pressure at the pump outlet, which in turn affects the normal progress of chemical production or the reactions taking place within the system. This leads to an imbalance in the materials used, resulting not only in waste but also in a decrease in product quality or even defective products. (6) The media transported by chemical pumps are mostly flammable, explosive, toxic, and harmful liquids. Once it leaks, it will severely pollute the environment, pose a threat to human safety and the physical and mental health of employees, and fail to meet the requirements of a leak-free factory and a clean and civilized factory. Therefore, it is necessary to ensure that chemical pumps do not leak during operation. The pump seals utilize new technologies and materials; they are operated in accordance with regulations and maintained to a high standard. (7) Critical liquids that can transport critical fluids tend to vaporize when the temperature rises or the pressure decreases. Chemical pumps sometimes transport critical liquids; if these liquids evaporate inside the pump, cavitation damage can easily occur, which requires the pump to have high resistance to cavitation. At the same time, the evaporation of liquid may cause frictional bonding between the moving and stationary parts inside the pump, which requires a larger clearance. To prevent mechanical seals, packing seals, labyrinth seals, etc. from being damaged by dry friction due to liquid evaporation, such chemical pumps must have a structure that controls the gas inside them. The shaft seal materials for pumps used to transport critical liquids can be materials with good self-lubricating properties such as polytetrafluoroethylene and graphite. In addition to packing seals, shaft seal configurations can also employ double-end mechanical seals or labyrinth seals. When a double-end face mechanical seal is used, the space between the two end faces is filled with external sealing fluid; in the case of a labyrinth seal, sealing gas at a certain pressure can be introduced from the outside. When a sealing liquid or gas leaks into the pump, the pumping medium should be harmless, and it should also be harmless if it leaks into the atmosphere. When transporting critical liquid helium, methanol can be used as the sealing fluid in the double-end face mechanical seal chamber; when transporting volatile liquid hydrocarbons, nitrogen can be introduced into the labyrinth seal.