How to Prevent Corrosion in Vacuum Pumps Used in Chemical Industries【EDWARDS VACUUMA】

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This post was last edited by Kim He on 2022-5-7 15:55. Edwards is a global leader in vacuum products, exhaust treatment systems, and related value-added services. Our products are indispensable in the manufacturing processes of semiconductors, flat panel displays, LEDs, and solar cells. They are also widely used in a growing number of industrial sectors, including freeze-drying, coating, steel and other metallurgy, pharmaceuticals and chemicals, power generation, as well as in scientific instruments and various research and development applications. As part of Atlas Copco, Edward Vacuum has, in recent years, seen its success grow rapidly in the Chinese market. Thanks to its excellent quality products, superior after-sales service, and professional optimization solutions, it has earned high praise from customers in industries such as semiconductors and related fields, lithium plating, and the chemical and pharmaceutical sectors. This is one of the main reasons for the rapid expansion of Edward Vacuum’s business. Currently, Edward Vacuum employs over 700 people in China. Behind this continuous growth, the brand’s value becomes increasingly evident, enabling it to serve society and the manufacturing industry better. In the Greater China region, Edwards has Shanghai Zhangjiang as its service center, the Shanghai Free Trade Zone as its R&D center, Qingdao and Tianjin as its manufacturing centers, and cities such as Dongguan, Beijing, and Xi’an as its after-sales service centers. This is combined with a systematic service network formed through Edwards’ exclusively authorized agents. In the pharmaceutical and chemical industry, Edward offers a full range of vacuum pump products, including rotary vane pumps, liquid ring pumps, oil pumps, fourth-generation dry screw pumps, dry claw pumps, and hydrocoupled Roots pumps. It provides gas handling solutions and corresponding products covering capacities from dozens of cubic meters to tens of thousands of cubic meters, thus enabling true coverage of all product needs and requirements. Today, let’s discuss the issue of corrosion prevention in dry vacuum pumps. First, we need to understand the causes of corrosion: corrosion occurs as a result of electron transfer processes that alter the original physical properties of a material, leading to the formation of new chemical substances that do not meet the requirements regarding physical properties under operating conditions; essentially, it is a redox reaction. The most common type of corrosion is acid corrosion. In the pharmaceutical and fine chemical industries, corrosive substances such as HF, acetic acid (haloacetic acids), HCl, and fatty acids are inevitably present. Since a reaction system is usually very complex, corrosion tends to occur easily in these equipment units. So how does this corrosion arise? The main reasons include the following: 1. These molecules generate corrosive hydrogen ions in liquid water ； For example, condensation occurs during operation ； 2. Water vapor from the air is introduced when starting and stopping pump equipment, resulting in acidic corrosion ； 3. When the design is unreasonable, for example, if the pumping speed is too high, it can draw out a large amount of reactants from the reaction vessels or reaction towers, causing abnormalities and leading to their accumulation inside the pump ； 4. Water vapor and oxygen are introduced after starting and stopping the pump, leading to rust and corrosion ； The common anti-corrosion strategies currently available on the market include: 1. Coating the pump chamber; the materials used for such coatings are similar to paints, and they work by preventing corrosive substances from coming into contact with the core components of the pump. These materials include F-containing substances such as PFTE, as well as Ni-based coatings. These treatment methods can achieve a certain degree of anti-corrosion protection in a short period of time. However, over time, within a vacuum pump, there is a process of gas compression that leads to temperature increases; uneven temperature changes and large temperature gradients cause the coatings to expand differently when heated, resulting in their peeling off. There are two serious consequences: first, the coating peels off, which not only fails to achieve the purpose of corrosion protection but also leads to severe electrochemical corrosion ； Secondly, the flaked coating remains stuck to the pump body and is difficult to remove, causing severe jamming ； 2. Choose the rotor material; for example, 316SS stainless steel can be used, but this material is expensive, has high elasticity, and requires specific temperature conditions for the process medium ； 3. Addressing the root cause of corrosion: For instance, Edward employs effective heat exchange strategies to ensure that the process medium within the pump undergoes continuous compression and a continuous rise in temperature during transportation and compression. Through software-based calculations of heat and saturation pressure data, the substance is kept in a stable unsaturated state, maintaining its gaseous form. Under these conditions, no ions or electrons are generated from molecular crystals, thereby achieving the goal of corrosion prevention by eliminating the root cause of corrosion ； 4. For batch operations (especially in the pharmaceutical industry), Edwards has well-defined standard operating procedures: it ensures thorough preheating when starting the pump, so that the physical conditions of the pump chamber are similar to those during operation; and it carries out solvent cleaning and inert gas purging when stopping the pump, thereby removing any process medium remaining in the pump chamber ； It features a strict and comprehensive logical control program ； In handling materials in the presence of corrosive media, we possess experience spanning only 30–40 years worldwide, with numerous successful application cases both domestically and internationally. In the next issue, we will explain what explosion protection is, how it is defined, the classification of explosion protection, and how to achieve explosion protection. Everyone is welcome to discuss