MODERN VACUUM PUMPS FOR THE VACUUM DEGASSING OF STEEL IN SMALL AND LARGE VACUUM-DEGASSING UNITS

摘要

This article discusses a new design for Roots pumps and screw pumps which uses hermetically sealed motors. The new pump is easy to maintain, alleviates wear, and increases safety, which makes it more reliable than traditional Roots pumps. The screw vacuum pumps operate within a wide range of pressures. Thanks to the absence of friction in the vacuum chamber and the use of special coatings on the working elements, these units can be used in place of water-ring and rotary vane pumps for the high-vacuum evacuation of gases and vapors of liquids (including aggressive liquids). In this case, the gas being pumped is not contaminated by water vapor or oil. The absence of friction elements in the vacuum chamber means that the unit requires almost no maintenance. The use of standardized pre-equipped modular building blocks reduces fabrication and installation/startup costs, makes the equipment more compact, and saves power, oil, and water compared to other systems. The small size of both types of pumps — which can be used in any configuration - not only shortens delivery times and simplifies spare-parts management but also facilitates equipment assembly or (if necessary) replacement. Attainment of the pumps' rated productivity is assured by parallel connection of several compact modules. The mechanical pumps can be used for VID, VIM, VD, RH, VIT (vacuum ingot teeming), and VAR (vacuum-arc remelting) units, including units that perform vacuum-oxygen decarburization. The pumps' design incorporates measures to protect against dust and water-vapor condensation, which can lead to the formation of acidic liquids. The pumps can be used in all types of vacuum processes - including processes that involve the injection of oxygen — while observing existing safety standards. The low inertial mass of the pumps helps them respond rapidly to frequency control, which facilitates the evacuation process. Redundant operation is provided for in all the pumping-unit configurations.